Squats… is there another exercise that throws on slabs of muscle quite like heavy squats? Subjectively speaking, outside of maybe deadlifts, I’m guessing probably not. Although Romanian deadlifts are my favorite lift, they are closely followed by squats. After a good squat workout, especially an intensive one that brings about a good muscle pump, I feel like the Incredible Hulk, waiting to burst out of my “suddenly too small” gym attire! {To save a few eyebrows from being raised, when I say “suddenly too small”, I’m referring to the fact that I mentally feel as if my muscles are bursting through my clothes (a la Incredible Hulk); not that I work out in clothes purchased at GAP Kids ® as I sometimes feel other “muscular” resistance trained individuals do!!!}. Within the past year, there have been some interesting studies published on the biomechanics of squats. Although some of these studies simply confirm what power athletes may already know, others serve as good reminders on how to properly execute the lift. Without any further digressions, I’d like to share with you recently published research regarding squat mechanics …

Recently Published Research Regarding the Squat Exercise.

Study #1

Miletello et al. examined how squat mechanics differed between individuals with various experience performing the back squat¹. Their study compared 9 collegiate competitive lifters (most of whom placed at the 2006 U.S. Collegiate National Championships; mean age- 20 years), 9 competitive high school lifters (most of whom placed at the 2006 Louisiana State High School Powerlifting Championships; mean age- 17) and 11 novice powerlifters (mean age-20) who had < 6 months of training experience. Each lifter performed their approximate 1 rep max without the use of wraps or squat suits. The main difference noted between groups was that collegiate lifters had a much faster acceleration out of the bottom squat position (ie-firing out of the hole) vs. both the high school and novice lifters.

From a practical standpoint, many individuals (including myself from time to time), often forget to consciously “explode” out of the hole while squatting. This has implications for all individuals, especially those competing in sport. The greater acceleration one has coming out of the bottom position in a squat exercise, the more momentum they have to help carry them through the “sticking point” during the exercise. Thus, one is able to lift more weight. Regardless of the weight (1RM, 5RM, etc), one’s goal should always move the weight as fast as possible. As mentioned by Dr. Digby Sale, one of the foremost authorities on neuromuscular influences on resistance training…

“When the intent is to contract the muscle as fast as possible with the maximum rate of force development, motor units begin firing at a very high frequency…”² which leads to, “an increase in rate of force development”²

In layman’s terms, when you consciously try to move fast (even if you’re physically not moving fast), your muscles contract more powerfully. Indeed, a few studies have shown that following a resistance training program (where relative training intensity was held constant between fast and slow training groups), the intention to lift as fast as possible led to greater rate of force development/power [3]⁴. One caveat worth mentioning with those studies is that one was completed in an elderly population³ and the other was completed in novice resistance trained athletes⁴. Despite these study drawbacks, my personal experience while training athletes seems to agree with the results obtained in those studies.

Study #2

Paoli et al. studied the effects of stance width and foot position on 8 muscles of the thigh (including ones composing the quadriceps, hamstring, butt muscles)⁵. Experienced weightlifters completed back squats (3X10) with a narrow stance feet even with greater trochanter (feet pointed straight ahead), intermediate stance (150% greater trochanter distance), and a wide stance (200% greater trochanter; feet angled outward at 45º angle). See Figure 1 for picture. All squats were completed at 70% of single rep max (1RM) as the researchers stated that “this is often selected in training programs.” After completing all trials, it was found that only the gluteus maximus (main muscle in butt) was affected by stance width. In comparison to a narrow stance, wider stances increased muscle activity of the gluteus maximus. Paoli et al.also found foot placement (straight in narrow stance vs. outward angled in wide stance), did not selectively activate specific muscles of the quadriceps (vastus lateralis, rectus femoris, vastus medialis). See Figure 2

Figure 1 Location of greater trochanter. Basically, if they squat at greater trochanter distance, feet are straight below these structures.

Figure 2 Individual muscles of the Quadriceps. The vastus lateralis is labeled #2 and has a pinkish color. The rectus femoris is labeled #1 and has a red color. The vastus medialis is labeled #4 and has a dark yellow color.

From a practical standpoint, if you want to increase gluteus activation/strength, go with a wider stance. In my opinion, the most interesting finding of this study was that no difference was observed in quadriceps activation between the narrow and wide stances. Additionally, the angle with which ones feet were pointed did not influence activation of various quadriceps muscles. Various bodybuilding magazines/books often claim that different stance widths/foot placements influence how hard the individual quadriceps muscles are worked. In particular, one popular book claimed that narrow stance squats, feet straight ahead, increase activation of the outer, vastus lateralis aspect of the quadriceps⁶. Furthermore, this same piece of literature indicates that wide stance squats (with feet pointed out) preferentially works the inner, vastus medialis portion of the quadriceps. This popular body building myth is clearly contradicted by the work of Paoli et al.⁵ Other studies have found similar results⁷.

One could play a devil’s advocate and point out that Paoli et al had individuals complete this lift at 70% 1RM. Maybe, differential quadriceps activation only occurs at higher training intensities such as 85-95% 1RM. However, as explained by McCaw & Melrose⁷, differential activation of the individual muscles of the quadriceps muscles doesn’t make sense from an anatomical perspective….

“The results of this study suggest the three components of the quadriceps perform as a group regardless of concentric or eccentric activation during varied stance and load conditions. Because the vastus medialis and vastus lateralis are uniarticular muscles, crossing only the knee joint, varying stance width by altering thigh position in the frontal plane would not affect the length of the muscles, a factor that could influence recruitment patterns and magnitudes. The lack of a significant stance width effect on IEMG values for the rectus femoris suggests limited physiological implications of any change in the length of this biarticular muscle that may occur when hip position varies within the altered stance widths used in this study”⁷.

For reference, uniarticular simply means a muscle extends over a single joint. For this study, the vastus lateralis & medius start on the femur bone, cross the knee joint, and attach into the tibia (main lower leg bone). Biarticular refers to the fact that a muscle crosses 2 joints. In this case, the rectus femoris starts on the pelvis, crosses hip joint and then passes over the knee joint before connecting into tibia.

Study #3

The front and back squat are probably the two most common squat variations used by ball/speed sport athletes. Recently, Gullet et al examined the biomechanical differences between these 2 lifts⁸. The study included 15 experienced lifters (9 men, 6 women) who had been training with each lift at least 1x/week for a > 1 year. During separate trial days, each lift was completed at the same relative training intensty (70% 1RM). After analyzing the data, it was found that front squats, vs. back squats, had lower compressive stresses, but equal shear stresses on the knee joint. In the knee joint, one’s cruciate ligaments (ie-anterior cruciate ligament which is commonly referred to simply as the ACL ) are responsible for “handling” this stress. In contrast, the hyaline cartilage and meniscus tissue are responsible for absorbing compressive forces. Please refer to Figure 3 for explanation on these forces. Despite lifting more weight with the back squat, muscle activation was the same for the hamstring (biceps femoris, semitendinosus), quadriceps (rectus femoris, vastus lateralis, & vastus medialis) and spine (erector spinae) muscles. It should be noted that the butt muscles (gluteus maximus, etc) were never tested.

Figure 3 Various types of Stress. The bottom box represents shear stress. This type of stress occurs when two objects are rubbing past each other. An example of shear stress would be rubbing your hands together when you are cold. The box on the right is compressive stress. This type of force occurs when an object is being squeezed together. An example of compressive stress would be squeezing toothpaste out of its container.

This study provides an interesting look at squat mechanics. At 70% of 1RM, no differences were found in muscle activity⁸. {Again I want to stress that the gluteus/butt muscles were not tested in the trial. I hypothesize that if these muscles were tested, it would show far greater activation levels during the back squat}. Although squat variation did not appear to affect stress on structures such as the ACL, higher compressive forces were found while performing the back squat. As a result, more stress would have been put on the meniscus and hyaline cartilage. This has large implications for someone with a medical history of problems associated with these structures. With similar muscle activation between exercises (excluding the gluteus maximus), and lower stresses on the knee, individuals may be better off including more front vs. back squats into their exercise routine.

Regarding front squats… Many individuals struggle with this exercise due to limited shoulder and/or wrist mobility. If you find yourself in this category, work on stretching the large latissimus dorsi (a.k.a.- “lats”) muscles of your back. Also, look into using wrist straps. As a FYI, I have no financial or career related connection with the website that comes up if you click on “wrist straps” in the previous sentence. Rather, it was the first good link I could find with good example pictures of an individual using wrist straps.

Study #4

While coaching the squat, many instructors commonly use the phrase, “don’t let your knees go over the toes.” In fact, while in high school, I used to give this cue to my fellow football teammates while spotting them during the squat. Why did I say this? Quite frankly, I used this phrase simply because I was told that one would be develop knee problems if they squatted in this fashion. However, my stance on the knee issue has changed during the past 8-10 years as I obtained more experience working and began to further examine the biomechanics of the squat. In a study completed by Fry et al., researchers examined the effects of limiting knee movement (in the anterior direction) during back squats⁹. Participants squatted under the following 2 conditions:

• Normal Squat

• Restricted squat- vertical board placed anterior edge of food, preventing knees from drifting beyond toes

Torque on the knee decreased during the restricted vs. normal squat. However, during the restricted squat, torque increased on hips and an exaggerated forward lean with the upper torso. Thus,

“It thus becomes a trade-off between optimal knee positioning and optimal hip and back positioning. While it is critical to protect the knees from unnecessary forces, it is also important to avoid unnecessary forces acting at the hips. These hip forces will ultimately be transferred through the lower back and therefore must be carefully applied. The net result is that proper lifting technique must create the most optimal kinetic environment for all the joints involved.”⁹

In applying this information, I’m not quite as adamant as I once was regarding the knees going over the toes during squats. Please don’t misunderstand my comment, I’m not saying that one’s knee should extend WAY past their toes during the exercise!!! I’m simply saying that in order to optimize hip/low back mechanics, allowing one’s knees to drift over their toes is necessary for some athletes depending on their anthropometrics. This is especially true for tall, long limbed athletes. Yes, you could force them to keep their lower leg (tibia) relatively perpendicular to the ground, but you’ll usually find 1 of 2 things- A) They lose their balance or B) their backs get sore.

When coaching the squat, my primary concern is not how far their knees travel over their toes. Rather, I’m focused on how the weight is distributed on their foot. One should always have the weight distributed from the balls of their feet back through their heel. For those who learn best via mental images, think of a “power triangle” with the base at the balls of your foot and pointing towards your heal. When this triangle is pointed the opposite way, knee problems occur as the weight shifts towards one’s toes.

In attempting to squat to parallel, many individuals shift the weight over the front (anterior) end of the foot. As aforementioned, this increases stress on the knees. What can one do to prevent this from happening? First, work on ankle mobility. If one has stiff ankles, they’re limited in their ability to dorsiflex their ankle. In turn, one often compensates by shifting the weight onto their toes or rounding their back.

Figure 4 Movements at Ankle. Ankle plantarflexion occurs when the angle between your foot and tibia gets longer. This occurs when you jump into their air or stand on your toes. In contrast, dorsiflexion occurs when the angle between their ankles and tibia gets smaller.

For those struggling with weight distribution there are a few things to work on….

• #1: Work on ankle mobility. I can’t stress this enough. If you’re stiff in the ankles (especially dorsiflexion) you’ll compensate for this stiffness by either shifting the weight towards your toes or rounding the back.

• #2: Focus on lowering your body by pushing your hips behind you vs. bending the knees. Speaking from experience, one’s first movement should be at the hips. If your first movement is at the knees, its dang near impossible to maintain the biomechanics necessary to preserve the knees.

• #3: Put weight plates (2 ½ or 5 lb plates usually work well) under your heels. Due to the biomechanics of the squat, this allows you to squat near parallel while still pushing through the preferred “power triangle.”

• #4. Curl your toes upward during your warm up sets to get the kinesthetic feel of how the weight should be distributed on your foot. I’ve found this to be very effective as it “primes” your motor program prior to competing heavier sets.

Bottom Line

These studies provide interesting commentary on squat mechanics. The take home points I gathered from each of the above studies are as follows:

1). Explode out of the bottom “hole” position during the squat. Even if the weight is heavy, attempt to move it as fast as possible.

2). Don’t get caught up in old body building myths which claim that narrow vs. wide squat stances preferentially affect certain muscles of the quadriceps. Human anatomy prevents this claim from even making sense!!!

3). Save your knees by performing more front squats.

4). Within reason, it’s “OK” to let your knees extend over your toes while squatting. Focus your attention on weight distribution on your foot Just make sure that you’re focusing on lowering your body by pushing your hips behind you (vs bending at the knees).

Good luck as you continue to develop into a squatting machine.

GapKids ® is a trademark or registered trademark of Gap Inc.

References

¹ Miletello WM, Beam JR, Cooper ZC. A biomechanical analysis of the squat between competitive collegiate, competitive high school, and novice powerlifters. J Strength Cond Res. 2009 Aug;23(5):1611-7.

² Sale D. “Neural Adaptation to Strength Training.” Strength and Power in sport. 2nd ed. Komi P.V. Blackwell Publishing Company. Malden MA. 2003. 282-283. Print.

³ Fielding RA, LeBrasseur NK, Cuoco A, Bean J, Mizer K, Fiatarone Singh MA. High-velocity resistance training increases skeletal muscle peak power in older women. J Am Geriatr Soc. 2002 Apr;50(4):655-62.

⁴ Young, W.B., Bilby. GB. The effect of voluntary effort to influence speed of contraction on strength, muscular power, and hypertrophy development. J. Strength. Cond. Res. 7:172– 178. 1993.

⁵ Paoli A, Marcolin G, Petrone N. The effect of stance width on the electromyographical activity of eight superficial thigh muscles during back squat with different bar loads. J Strength Cond Res. 2009 Jan;23(1):246-50.

⁶ Schwarzenegger, A and Dobbins, B. The Arnold Schwarzenegger Encyclopedia of Modern Bodybuilding. New York: Simon and Schuster, Inc., 1985.

⁷ McCaw ST, Melrose DR.. Stance width and bar load effects on leg muscle activity during the parallel squat. Med Sci Sports Exerc. 1999 Mar;31(3):428-36.

⁸ Gullett JC, Tillman MD, Gutierrez GM, Chow JW. A biomechanical comparison of back and front squats in healthy trained individuals.J Strength Cond Res. 2009 Jan;23(1):284-92.

⁹ Fry AC, Smith JC, Schilling BK. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 2003 Nov;17(4):629-33.

In the first part of this article, we observed a lack of evidence supporting the use of popular amino acids purported to stimulate HGH secretion. Furthermore, it was noted that exercise induced HGH secretions failed to enhance myofibrillar protein synthesis (MPS) (the proteins which are responsible for generating force in the muscle during muscular contraction), muscle strength, and/or muscle size. I know what you’re thinking right now… The studies reviewed in Part I of this article examined the effects of exercise induced or HGH secretagogues on increases in HGH. Individuals who take HGH injections to increase muscle size and strength often take supraphysiological doses far larger than those induced by these methods. Furthermore, HGH injections clearly benefit individuals clinically deficient in the hormone¹ So, the question still exists, “Do HGH injections benefit physical performance?”

The Effects of Human Growth Hormone Injections on Muscle Hypertrophy and Strength

Yarasheski et al. studied the effects of HGH injections on changes in strength and body composition amongst 16 previously untrained men (mean age- 27 years) following a 12 week resistance training program². Each participant was randomly assigned to either a placebo or the experimental group which received 40 μg rHGH/kg/day. Prior to initiating the 12 week training program, no significant differences were present between groups with respect to body composition (total body weight, fat mass, fat free mass). At study’s end, it was found that HGH injections did not significantly increase muscle strength gains (9 common exercises tested including shoulder, bench and leg presses) or size between the 2 groups. This happened despite significantly increasing circulating HGH (6x) and IGF-1 (4x) levels vs. placebo treatment (See below for explanation of IGF-1). Both groups experienced similar gains in total body weight. Although not quite statistically significant (p= 0.056) the HGH group tended to experience losses in fat mass. Those receiving HGH did experience significantly greater gains in fat free mass (which includes lean muscle tissue, connective tissue, body fluid, etc) vs. placebo. However, as pointed out by Yarasheski et al., no significant differences in muscle protein synthesis were found between groups. Furthermore, greater water retention was found in those given HGH. Thus, the research team concluded that chronic HGH injections do not augment muscle gains commonly observed following a 12 week resistance training program. Finally, it should be noted that the study originally included 18 individuals. However, 2 of the individuals receiving HGH had to drop out due to symptoms of carpel tunnel.

—————————————-
Insulin-like growth factor (IGF-1) is another hormone produced by the body that has anabolic effects on muscle tissue³. As seen in Figure 1, HGH stimulates the release of IGF-1, which is then believed to stimulate growth of muscle tissue. Few published studies have examined the effects of administering only IGF-1 on muscle growth. A study completed by Friedlander et al. indicated that receiving IGF-1 had no benefit on body composition or muscle strength in postmenopausal women⁴.

Figure 1 Effects of growth hormone (GH) and circulating IGF-I (IGF-I) on cultured myotubes. Both GH and IGF-I induce myotube hypertrophy. IGF-I increases protein synthesis and inhibits protein degradation. In addition, it induces fusion of myoblasts by upregulating synthesis of interleukin (IL)-13. It is possible that the IL-13 response is secondary to protein synthesis, with new nuclei being recruited only when required to maximize growth. Indeed treatment of cultures with rapamycin, inhibitor of mTOR, inhibits both hypertrophy and increase in fusion index of IGF-I-treated myotubes (Jacquemin et al., 2007⁵). Cotreatment of cultures with GH and IGF-I induces greater hypertrophic gains than either treatment alone. Thus, the hormones have distinct and overlapping effects on cells.³

For reference, myotubes are muscle cells in skeletal muscle.

Similar to HGH, current literature does not support the use of exogenous (of external origin) IGF-1 in already healthy individuals³. A more in-depth look at IGF-1 is beyond the scope of this article. For those interested in further discussion on it, I highly recommend reading _Regulation of muscle mass by growth hormone and IGF-I_. If you click on the title, this peer reviewed literature review can be obtained for free.
—————————————-

In contrast to Yarasheski et al.² who examined the effects of HGH in previously untrained individuals, Deyssig et al. studied its effects in 18 male, lean, power trained athletes (mean age-23.4; 10% body fat)⁶. Over the course of a 6 week period, individuals received a placebo or 30 μg rHGH/kg/day. Despite significantly increasing circulating HGH and IGF-1 levels over this time period, HGH injections did not significantly alter gains in muscle strength, total body weight and fat mass. With respect to adverse effects, a case of carpel tunnel like symptoms developed in one participant using HGH. In closing, Deyssig et al. stated…

“We conclude that the anabolic, lipolytic effect of GH therapy in adults depends on the degree of fat mass and GH deficiency. In highly trained power athletes with low fat mass there were no effects of GH treatment on strength and body composition”⁶

In a large meta-analysis, Liu et al reviewed all evidence to date (2008) that examined the effects of HGH injections on athletic performance or body composition changes in active, physically fit populations⁷. When combining the results of all 27 studies reviewed, it was found that lean body mass increased and there was a tendency for body fat to decrease. However, performance measurements such as muscular strength and aerobic capacity (VO2max) were not altered. Similar to Yarasheski et al², Liu et al concluded that gains in lean body mass could be attributed to fluid retention rather than increases in contractile muscle proteins⁷. For reference, the 27 studies included 440 participants with the following characteristics: lean (BMI-24), young (mean age- 27 years), physically fit and received a mean dose of 36 μg HGH/kg/day. If you’re interested in reading the full paper (vs. my cliff-not version), it can be found by CLICKING HERE

The question as to if HGH injections have anabolic effects in non-clinical populations may have finally been put to rest by Doessing et al⁸. In their study, 10 healthy, untrained men (mean age- 30 years) received HGH shots for 14 consecutive days (33 μg rHGH/kg/days 1-7; 50 μg rHGH/kg/days 8-14) after which they completed unilateral (single leg) leg extensions. 5 months later, the process was repeated except those who received HGH previously now received a placebo. Despite increasing circulating HGH levels by ~850% and insulin like growth factor (IGF-1) by ~320%, the rate of MPS was not significantly altered while receiving HGH injections vs. placebo treatment. Although MPS did not increase, HGH injections did increase collagen protein syntheses. For those unfamiliar with collagen, this protein serves as “guy wires” in the connective tissue of the musculoskeletal system. It’s found in tendons, bone, ligaments, muscles and cartilage. In contrast to myofibrillar proteins, collagen does not have any contractile properties. Rather it provides structural/connective support. In this study, the HGH injections increased collagen synthesis 1.3-fold in tendon tissue and 6-fold in muscle tissue. This led the authors of the study to conclude that:

“… rather than causing muscle fibre growth, GH/IGF-I appear to stimulate the supporting connective tissue that would help force transmission from the contracting muscle fibres to the bone.”⁸

Simply put, HGH does not appear to directly increase the size or strength of muscle tissue. It may indirectly increase muscular force capabilities (via strengthening support tissue), but to my knowledge, this has yet to be shown in exercise based research.

What About HGH Injections for Acting as “The Fountain of Youth”?

Does HGH stem off the physical decline seen with normal, healthy aging? That appears to be the popular question amongst the aging baby boomer population. Many anecdotal stories indicate that HGH can greatly enhance personal well-being and physical function as you age. Current scientific research to support these anecdotal stories is inconclusive and highly debated. In a recent review of the literature (completed in 2007), Liu et al. examined the effects of HGH injections in elderly individuals without any known health problems (ie- free of cancer, heart disease, diabetes, osteoporosis, etc)⁹. Their meta-analysis included results of 21 studies, consisting of 220 older, overweight individuals (mean age- 69 years; 33% women; BMI-28). Although great variation existed, the mean duration of each study was 27 weeks and average starting dose was 14 μg rHGH/kg/days. On one hand, results indicated that receiving HGH injections (vs. placebo treatment) > 26 significantly increased lean body mass (3.6 lbs) and decreased fat mass (5.1 lbs). On the other hand, those treated with HGH experienced significantly more “adverse events” such as carpel tunnel, edema, and arthralgias (joint pain). No significant differences were seen in bone density or blood lipid levels between groups.

Unfortunately, as noted be Liu et al., there was not enough information presented on physical function variables (ie- grip strength, 30 second sit-to-stand muscular endurance test, etc) and well-being measurements (mood profile, etc) to statistically analyze all of the purported benefits associated with HGH. However, in the small number of studies that did examine performance gains, HGH + exercise did not appear to increase muscular strength in trained¹⁰ or untrained¹¹¹² older individuals vs. exercise alone (see Figure 1). Thus, looking only at the scientific data available to them, they concluded…

“Although GH has been widely publicized as an antiaging therapy and initial studies suggested that it might be clinically beneficial and safe in the healthy elderly, we find little evidence to support these claims. The scant clinical experience of GH in the healthy elderly suggests that although GH may minimally alter body composition, it does not improve other clinically relevant outcomes. Substantial evidence suggests that GH use in the healthy elderly is associated with high rates of adverse events. On the basis of available evidence, GH cannot be recommended for use among the healthy elderly.”⁹

For those interested in reading the full review completed by Liu et al, CLICK HERE

Figure 2 Strength assessment of right knee extension as measured by the percentage change of 1RM. Increases in 1RM were statistically significant (P < .0005). Each bar represents the mean ± SD of determinations in each group, from left to right, Group 1 (n = 8), 2 (n = 7), 3 (n = 8), 4 (n = 8). 1RM = 1 repetition maximum; SD = standard deviation; GH = growth hormone; EX = exercise; PBO = placebo.¹²

Part of Figure 2 was cut off. Looking at the bars from left to right, the groups are: HGH + Exercise, HGH, Exercise + Placebo, Placebo.

Although HGH alone does not appear beneficial, Sattler et al. demonstrated that HGH + testosterone was more beneficial than testosterone alone¹³. Their study involved 122 older, slightly overweight, men (mean age- 70.8 years; BMI- 27.4) with testosterone and IGF-1 levels “typical” for their age group. Over the course of 4 months, individuals were randomly assigned to receive various low dose testosterone and /or HGH combinations (Please see Table 1).

Table 1 Daily testosterone and HGH doses. Doses were chosen to reflect normal physiological level of these hormones vs. supra-physiological levels seen in other studies.

After 4 months, it was found that increasingly greater hormone doses enhanced changes in body composition (Figure 3); this seemed to be augmented with HGH co-administration¹³. There was a small to moderate positive correlation between increased lean body mass and strength levels. Aerobic capacity increased in all groups vs. baseline measurements. With respect to cardiometabolic risk factors, insulin resistance, total and LDL cholesterol remained unchanged during the 4 month trial. Additionally, HDL cholesterol increased whereas triglyceride levels decreased. Outside of a small increase in fasting blood glucose, the only significant cardiometabolic risk factor negatively affected was blood pressure (systolic and diastolic blood pressure increased by 12 mmHG and 8mmHG).

Figure 3 DEXA-derived changes (mean + 1 SE) in LBM and fat mass for each treatment group from baseline to wk 17. A, Increases in total LBM (solid bars) and appendicular lean mass (hatched bars). Changes across groups are significant for linear trend for total lean mass (P < 0.0002) and appendicular lean (P < 0.0002). B, Decreases in total body fat mass (solid bars) and trunk fat (hatched bars). Changes across groups are significant for linear trend for total fat mass (P < 0.0004) and trunk fat (P < 0.0003). *, Bonferoni adjusted within group changes (P < 0.008). Pairs of treatment groups with different letters (e.g. a vs. b) are significantly different by one-way ANCOVA with pairwise comparison (Tukey adjusted; P < 0.05).

Other Possible Benefits of HGH

From an orthopedic standpoint, HGH injections may be useful to those who have muscle-tendon, ligament, bone fractures or cartilage injuries. As seen in the study by Doessing et al., HGH does significantly increase collagen protein synthesis⁵. Studies completed by Raschke et al.¹⁴ and Van der Lely et al.¹⁵ provide some support to this possible use for HGH injections. However, more research is needed in this area before a definitive conclusion can be drawn.

Bottom Line

Strong evidence exists indicating that HGH administration does not increase muscle strength or size in healthy populations. Rather, it appears to increase collagen (the main protein in connective tissue such as bones, tendons, ligament, cartilage) and may be useful to those coming off injuries.

HGH injections have been shown to significantly decrease fat mass and increase lean body mass. However, improvements in lean body tissue are likely the result of increased water retention and non contractile tissues vs. actual gains in muscle mass.

Current, peer reviewed, scientific research does not support the “anti-aging” use of HGH in older populations. Although positive changes in body composition are observed, these benefits do not appear to increase strength or aerobic capacity. Resistance training has been shown to be just as effective as HGH + resistance training protocols with respect to increasing strength. Finally. HGH does not appear beneficial when taken alone. On the other hand, one recent study indicated HGH + testosterone does increase lean body mass. This increase was modestly correlated with increases in total body strength. Long term studies must still be carried out to further define potential quality of life/health benefits HGH + testosterone combinations may have in older adults.

References

¹ Rennie MJ. Claims for the anabolic effects of growth hormone: a case of the emperor’s new clothes? Br J Sports Med. 2003 Apr;37(2):100-5.

² Yarasheski KE, Campbell JA, Smith K, et al. Effect of growth hormone and resistance exercise on muscle growth in young men. Am J Physiol 1992;262:E261–7.

³ Velloso CP.Regulation of muscle mass by growth hormone and IGF-I. Br J Pharmacol. 2008 Jun;154(3):557-68.

⁴ Friedlander AL, Butterfield GE, Moynihan S, Grillo J, Pollack M, Holloway L, et al. One year of insulin-like growth factor I treatment does not affect bone density, body composition, or psychological measures in postmenopausal women. J Clin Endocrinol Metab. 2001;86:1496–1503.

⁵ Jacquemin V, Butler-Browne GS, Furling D, Mouly V. IL-13 mediates the recruitment of reserve cells for fusion during IGF-1-induced hypertrophy of human myotubes. J Cell Sci. 2007;120:670–681.

⁶ Deyssig R, Frisch H, Blum WF, et al. Effect of growth hormone treatment on hormonal parameters, body composition and strength in athletes. Acta Endocrinol (Copenh) 1993;128:313–18.

⁷ Liu H, Bravata DM, Olkin I, Friedlander A, Liu V, Roberts B, Bendavid E, Saynina O, Salpeter SR, Garber AM, Hoffman AR. Systematic review: the effects of growth hormone on athletic performance.Ann Intern Med. 2008 May 20;148(10):747-58. Epub 2008 Mar 17.

⁸ Doessing S, Heinemeier KM, Holm L, Mackey AL, Schjerling P, Rennie MJ, Smith K, Reitelseder S, Kappelgaard AM, Rasmussen MH, Flyvbjerg A & Kjaer M (2010). Growth hormone stimulates the collagen synthesis in human tendon and skeletal muscle without affecting myofibrillar protein synthesis. J Physiol 588, 341–351.

⁹ Liu H, Bravata DM, Olkin I, Nayak S, Roberts B, Garber AM, Hoffman AR. Systematic review: the safety and efficacy of growth hormone in the healthy elderly.
Ann Intern Med. 2007 Jan 16;146(2):104-15.

¹⁰ Taaffe DR, Pruitt L, Reim J, Hintz RL, Butterfield G, Hoffman AR, Marcus R. Effect of recombinant human growth hormone on the muscle strength response to resistance exercise in elderly men. J Clin Endocrinol Metab. 1994 Nov;79(5):1361-6.

¹¹ Yarasheski KE, Zachwieja JJ, Campbell JA, Bier DM. Effect of growth hormone and resistance exercise on muscle growth and strength in older men. Am J Physiol. 1995 Feb;268(2 Pt 1):E268-76.

¹² Hennessey JV, Chromiak JA, DellaVentura S, Reinert SE, Puhl J, Kiel DP, et al. Growth hormone administration and exercise effects on muscle fiber type and diameter in moderately frail older people. J Am Geriatr Soc. 2001;49:852–858.

¹³ Sattler FR, Castaneda-Sceppa C, Binder EF, Schroeder ET, Wang Y, Bhasin S, Kawakubo M, Stewart Y, Yarasheski KE, Ulloor J, Colletti P, Roubenoff R, Azen SP. Testosterone and growth hormone improve body composition and muscle performance in older men. J Clin Endocrinol Metab. 2009 Jun;94(6):1991-2001. Epub 2009 Mar 17.

¹⁴ Raschke M, Rasmussen MH, Govender S, Segal D, Suntum M & Christiansen JS (2007). Effects of growth hormone in patients with tibial fracture: a randomised, double-blind, placebo-controlled clinical trial. Eur J Endocrinol 156, 341–351.

¹⁵ Van der Lely AJ, Lamberts SW, Jauch KW, Swierstra BA, Hertlein H, Danielle De Vries D, Birkett MA, Bates PC, Blum WF, Attanasio AF. Use of human GH in elderly patients with accidental hip fracture. Eur J Endocrinol. 2000 Nov;143(5):585-92.

This past Friday, February 19th, I had the opportunity to appear along with Mike Nelson as a guest on Iron Radio and discuss my thoughts on Nutrition/Exercise Blogging. Mike Nelson is currently finishing up his PhD work in Kinesiology at University of Minnesota and writes an excellent blog which can be found on his website Extreme Human Performance

CLICK HERE

During the week of February 21st (2010), my interviews/discussion is the featured broadcast. After this week, it will be placed in the Iron Radio archives (episode #44) which can be found in the middle of their homepage, just underneath the “Staley Training”, “Experiments vs. Experience” and “Academic Talks” archives. As a forewarning, my first response sounds a little rough….someone called into my phone during that time period and it got me a little distracted. There are also some pauses in my conversation (later in the interview) due to the phone beeping from that missed call.

For those not familiar with Iron Radio it is a…

“FREE repository of more sports nutrition, weight training and bodybuilding talk than you can shake a stick at! It’s purpose is to preserve a ton of highly-rated content and allow it to be distributed for the benefit of the power sport public…Our mission is to provide free athletic education to all those who recognize a connection between knowledge, health and performance. We strive to clearly indicate which parts of the sites are ads and to make sure our podcast guests know our stance in advance. Visitors are under no obligation to patronize ANY entity shown on this site. Beyond site maintenance, a portion of all advertising dollars goes to charitable causes.”¹

The shows are hosted by the following nationally recognized names:

Dr. Lonnie Lowery, a man who holds graduate degrees in both Kinesiology and Nutritional Science. Additionally, he has written for many major health, fitness and nutrition publications. Dr. Lowery is a noted lecturer who routinely travels the globe, giving presentations on how to enhance physical performance via nutritional interventions. In my opinion, Dr. Lowery is the best in the business with respect to applied sports nutrition.

Phil Stevens, is a competitive powerlifter and strong man competitor. He holds many powerlifting records. Last year he performed a 700 lb raw deadlift (raw refers to the fact that he wasn’t wearing any special attire to increase his performance.) In addition, Mr. Stevens is the director of operations at Staley Training Systems and founder of the Lift For Hope charitable organization.

Charles Staley is a highly recognized strength coach and creator of the Energy Density Training System and author of Muscle Logic. He has appeared on NBC’s The TODAY Show and The CBS Early Show. Coach Staley is also an avid Olympic style weightlifter, currently competing on the masters circuit.

Robert “Fortress” Fortney is a journalist in the fitness industry, a former competitive body builder and now competes in powerlifting. His writings are characterized by their “no-nonsense” attitude.

References

¹ Iron Radio Listeners. Facebook. 2010. Accessed February 22, 2010 from: http://www.facebook.com/group.php?gid=56270951924#.

Human growth hormone… is there a hormone over the past 10 years that has gained more attention in main stream media? During this time period, it has gone from a word generally reserved for the scientific community to a common household term. Much of this can be attributed to well known athletes such as Barry Bonds, Roger Clemens, Marion Jones and others who have been linked to this performance enhancing drug. Even non athlete celebrities, such as Sylvester Stallone, swear by it. Due to its name, many individuals commonly believe that human growth hormone (HGH) will improve muscle size and strength. Furthermore, HGH has been shown to improve body composition (ie- lean body mass, % body fat) in those clinically deficient in the hormone¹. For these reasons, HGH has piqued the interest of both competitive athletes and exercise enthusiast.

The Effects of Exercise Induced Human Growth Hormone on Muscle Hypertrophy and Strength

HGH is naturally produced by the body in response to intense workouts that are characterized by high rep sets and short rest intervals (ie- the same type of workouts that create a “burning” sensation in your muscles due to lactic acid buildup)². These workouts have been shown to significantly increase circulating HGH concentrations for up to 30 minutes post-exercise in both men and women. Recently, West et al. analyzed the relationship between exercise induced HGH elevations and muscle growth. In the first of their 2 studies, 8 healthy, untrained males (mean age- 20 years) completed 2 separate resistance training sessions; one was a high hormone (HH) session that significantly increased HGH release (single arm preacher curls followed by intense leg training) and the other was a low hormone (LH) session which failed to increase circulating HGH levels (preacher curls only; completed on the arm opposite of the one used in the HH session)³. Following each session, researchers measured the rate of myofibrillar protein synthesis (MPS) in the bicep of the respectively trained arm. {For reference, myofibrillar proteins are the proteins which are responsible for generating force in the muscle during muscular contraction. Via resistance training, one increases the synthesis of myofibrillar proteins, leading to gains in both muscle strength and size.}. Results indicated that despite increasing circulating HGH levels, the hormone stimulating workout failed to significantly improve MPS vs. the arm only training session (determined via muscle biopsies obtained from bicep brachii muscle following each respective workout). In other words, the exercise induced increase in HGH failed to enhance muscle growth vs. the LH training session.

Figure 1 Rate of myofibrillar protein synthesis in the fed state at rest and following LH and HH exercise protocols ∗Significantly different from rest, P < 0.05. Values are means ± S.E.M.³

As seen in figure 1, both exercise sessions (HH= high hormone stimulating; LH= low hormone stimulating) increased the rate of protein synthesis. Yet, despite the presence of elevated HGH levels, the HH failed to enhance muscle growth vs. the LH training session.

The aforementioned study only looked at how a single session influenced the rate of muscle protein synthesis. One may naturally wonder what would happen if this protocol was repeated over an extended time period. Maybe, the cumulative effects of elevating HGH levels would influence MPS. Thankfully for us, this very question was answered in a 2nd study completed by West et al⁴. The design and exercise routine of this study was similar to their previously mentioned study except participants (12 untrained males; mean age 21.8 years) completed 15 weeks of training using the following routine:

• Weeks 1-6: exercised 3x/week alternating between HH (single arm preacher curls and LH routines every other training day.

• Weeks 7-15: exercised 4x/week alternating routines every other training day.

Pre- and post- workout protein shakes have been shown to influence muscle growth⁵ and are commonly used by athletes. Thus, each participant received 18 grams of whey protein just prior and again 90 minutes following each session to mimic real life training⁴. At the completion of the 15 week training period, West et al. examined increases in muscle size and strength of each arm. Both biceps, regardless of if it was trained under the HH or LH conditions, experienced similar increases in both muscle size (Figure 2) and strength gains (Figure 3).

Figure 2. Type I (A) and II fiber (B) cross-sectional area (CSA) of the biceps brachii before (Pre) and after (Post) training in LH and HH; main effect of training, *P < 0.01, {dagger}P < 0.001. Elbow flexor CSA before and after training ( C ) in LH and HH; main effect of training, {dagger}P < 0.001. Elbow flexor CSA as a function of distance from the elbow joint line before and after training (D) in LH and HH; main effect of training, {dagger}P < 0.001. There were no interactions (training x condition) for either fiber or whole muscle CSA (type I, P = 66; type II, P = 0.55; CSA, P = 0.27). Values are means ± SE⁴

Figure 3. Maximal voluntary contraction (MVC; A), one-repetition maximum (1 RM; B), and 10-repetition maximum (10 RM; C) before and after training in LH and HH. *Main effect of training, P < 0.001; there were no interactions (training x condition) for any strength measure (P = 0.65, 0.43, 0.63 for MVC, 1 RM and 10 RM, respectively). Values are means ± SE.⁴

The Effects of Exercise Induced Human Growth Hormone on Fat Loss

Although exercise induced HGH workouts will not enhance muscle growth, they may be useful for decreasing body fat. One of the physiological functions of HGH is to increase lipoloysis (breakdown of fat for energy purposes)⁶. There has been some evidence that intense exercise, which stimulates HGH, may decrease total abdominal fat. This was demonstrated in a study completed by Irving et al. in which 27 middle aged women (mean age – 51 years) were assigned to a control, low intensity or high intensity aerobic training program for a total of 16 weeks⁷. Duration of each exercise session was adjusted such that individuals in the high and low intensity training groups burned equal kcal/session. At the conclusion of the study, those participating in the high intensity training group saw significantly greater losses in visceral and total abdominal fat vs. those in the low intensity group. Study authors hypothesized that results were due to greater release of lipolytic hormones (such as HGH). On the other hand, when men of a similar background were added to the study results, (exercise conditions held exactly the same) no differences were present between groups⁸.

There are two caveats worth mentioning regarding the aforementioned studies looking at high intensity aerobic workouts, HGH and fat loss. First, dietary records were not kept. Thus, differences in dietary intake may account for the changes seen. Second, Irving et al. did not present data reflecting HGH levels in the study involving the 27 middle aged women⁷. As such, there is a lack of definitive evidence indicating that exercise induced HGH release leads to greater losses in fat mass vs. exercise of equal kcal expenditure that fails to raise circulatory HGH release. Also, I’m unaware of any study which has looked at this potential benefit in a young, healthy adult population. Thus, with respect to the scientific literature, the jury is still out on the effectiveness of exercise inducing HGH workouts on accelerating fat loss vs. non HGH stimulating aerobic workouts of similar kcal expenditure.

Growth Hormone Secretagogues

If one looks on the internet, he/she can find many products that are alleged to enhance the body’s natural production of HGH. These products, commonly referred to as HGH secretagogues, often consist of the amino acids Gamma-aminobutyric acid (GABA), arginine, ornithine, and lysine.

Gamma-aminobutyric acid

Research has indicated that Gamma-aminobutyric acid (GABA) stimulates HGH secretion in subjects at rest⁹. For this reason, its been advertised to strength athletes as a natural way to “stimulate secretion of growth hormone, decrease body fat levels and increase lean muscle tissue.”¹⁰ Using this as a backdrop, Powers et al examined if 3 grams (g) of GABA would enhance both resting and exercise induced levels of HGH¹¹. On four separate occasions (2 resting sessions, 2 exercise sessions), 11 resistance trained men (mean age- 23.6 years) received either HGH or a placebo treatment. Blood levels of ifGH, which is believed to be the biological active form of HGH, was measured for 90 minutes following ingestion. At rest, GABA supplementation significantly increased mean ifGH levels vs. placebo (>300%). Also, GABA vs. placebo tended to increase ifGH levels during exercise. At 30 minutes post-ingestion ifGH was significantly greater (175%) in the exercise + GABA vs. exercise + placebo. It also tended to be higher over the entire 90 minute observation period.

To my knowledge, the effect of long term GABA supplementation on body composition in active or sedentary individuals has not been studied.

Arginine

Arginine is one of the more popular amino acid HGH secretagogues. Evidence exists indicating that oral doses of 5 and 9 grams of arginine could significantly increase HGH levels in resting individuals¹². In a classic study completed by Collier et al., the effects of arginine on resting and exercise (including post-exercise) HGH levels were examined¹³. Their study involved 8 males (man age- 20.4 years) who participated in the following four sessions:

• Rest + Placebo
• Rest + l-Arginine (7 g)
• Exercise + Placebo
• Exercise + l-Arginine (7 g)

Circulating HGH levels were measured after each exercise or resting session (Figure 4). The greatest HGH levels were found after exercise-placebo session, followed by exercise-arginine session. No statistically significant difference was observed between the rest-arginine and the exercise-arginine trials. Interestingly, as seen in figure 5, the exercise-arginine actually significantly decreased the exercise induced HGH release vs. exercise alone.

Figure 4 Growth hormone (GH) concentrations in subject 7 on all 3 study days.¹³

The authors stated that the response seen in subject 7 was typical response seen amongst participants.

Figure 5 Integrated GH concentrations on each study day. *P < 0.05 vs. placebo. **P < 0.05 vs. exercise. {dagger}P < 0.05 vs. arginine + exercise.¹³

It should be noted that some studies have failed to find any benefit of arginine on HGH levels. This was seen in a study completed by Marcell et al. who gave ~ 4 grams of arginine to both young (mean age-22) and older (mean age- 68.5) participants¹⁴. In contrast to Collier et al.¹³, Marcell et al.¹⁴ failed to find any stimulatory effect for arginine on HGH levels in subjects at rest. Arginine also came up short with respect to enhancing exercising HGH levels. These results were observed in both the older and younger age groups. It should be mentioned that no placebo pill was given in this study. Rather, they just compared HGH levels during and following an exercise only session vs. arginine(4g) + exercise session.

Amino Acid Combinations

L-arginine & L-lysine

Suminski et al. gave 16 men (mean age- 22.4) 1.5 g lysine + 1.5 g arginine under both resting and exercising conditions¹⁵. At rest, HGH was significantly increased (270%) 60 minutes post ingestion, but no significant differences were found at 30 and 90 minutes. During exercise conditions, no significant differences were seen between the amino acid and placebo treatments.

L-arginine, L-ornithine & L-lysine

Fogelholm et al. completed an interesting study in which 11 trained weightlifters (19-35 years of age), took L-arginine, L-ornithine & L-lysine prior to a training session as well as just prior to going to bed¹⁶. 1 g of each amino acid was taken at both time periods for a total daily dose of 6 grams. After four days of this routine, the researches found that “supplementation did not affect the physiological variation of serum hGH concentration.”¹⁶

L-arginine & Aspartate

Abel et al. randomly assigned 30 endurance trained athletes to either a placebo, high supplement (5.7 g arginine and 8.7 g aspartate), or low supplement (2.8 g arginine and 2.2 g aspartate) groups for a duration of 4 weeks¹⁷. At study’s conclusion, Abel et al. found no differences in HGH levels between any of the groups.

What does this all mean?

When an effect is seen with amino acids on circulating HGH levels, it appears to occur only under resting, fasted conditions. The important question one has to ask themselves is, “Do these small transient increases in HGH, induced by amino acids, have any significant effect on body composition or performance?” Exercise induced HGH secretions were shown to have no effect on myofibrillar protein synthesis (MPS), muscle strength or size in the aforementioned study by West et al.³⁴. This lack of effect on MPS occurred despite an 8 fold increase in peak HGH levels⁴, which is greater than the peak increase seen with most of the amino acid supplements¹⁸.

Before I go any further evaluating all of this research on amino acids and HGH, there is one BIG problem that needs to be mentioned. As pointed out by Chromiak and Antonio, HGH secretions are usually stimulated to a greater degree following an overnight fast¹⁸. Thus, if you’re going to take these HGH secretagogues, one should probably do it on an empty stomach. In the above studies that showed a positive effect of GABA¹¹ and arginine¹³ on HGH, the amino acids were given following an overnight fast. In addition, individuals in the GABA and arginine trials waited > 90 minutes before having any food after the amino acid ingestion. When putting this into practice, I feel that it would be very foolish for any exerciser/athlete to follow this type of a fast. After an overnight fast, catabolic forces are at full throttle in your body, destroying your hard earned skeletal muscle²⁰. This metabolic state must be reversed and one of the best ways to accomplish this is by eating anabolic foods… one should not prolong it simply to get a little more benefit from an amino acid HGH secretagogue!!!

Don’t get me wrong. I’m not saying that taking supplements containing these amino acids are bad. In fact some studies have shown a beneficial effect of taking some of the above mentioned amino acids. Elam et al. found that taking 1 gram of both arginine and ornithine in conjunction with a 5 week resistance training program led to significantly greater gains in lean body mass and total strength vs. those taking a placebo¹⁹. However, I feel these gains are completely independent of HGH. As seen in the studies by West et al., HGH does not appear to increase MPS in young, healthy individuals.

Bottom Line

There’s strong evidence that exercise induced HGH secretions have no anabolic effect on the contractile fibers (myofibrillar proteins) of muscle tissue in healthy (ie- not clinically deficient in HGH) populations. With respect to the current scientific literature on fat loss, the jury is still out on if exercise inducing HGH workouts (aerobic) are more effective than non HGH inducing workouts (aerobic) when kcal expenditure is held constant.

Various studies provide evidence that amino acids can act as HGH secretagogues in resting individuals¹¹¹²¹³. However, this finding is not universal amongst all studies¹⁴. Additionally, when taken prior to a training session, it appears that taking HGH secretagogues will have no effect or actually reduce the exercise induced levels of HGH. If I wanted to play the devil’s advocate, I could point out that all but 1¹⁴ of the studies showing little to no effect were done on a younger population who normally have high HGH levels. However, research seems to indicate that with increasing age, one is less responsive to a given dose of various HGH secretagogues²¹. A dose of 1.5 g lysine + 1.5 g arginine has been shown to stimulate HGH in young adults (mean age 22.4)¹⁵. Yet, even when this dose is quadrupled (6 g of each amino acid), HGH levels fail to significantly rise in older adult men (mean age- 69)²².

Amino acids are great supplements to use in conjunction to an exercise program due to their ability to directly stimulate protein synthesis²³. I use various amino acid supplements myself. However, the current scientific research just doesn’t support their ergogenic effect via a HGH pathway/mechanism. Rather I think they work via a non-HGH pathway/mechanism to enhance muscle size/performance. For this reason, I feel they are wrongfully promoted as “HGH Secretagogues” since their beneficial effect on body composition/performance is likely through a non-HGH pathway.

And with that, Human Growth Hormone-Part I comes to an end, but stay tuned for Part II of this story when we bring out the big boy… HGH injections!!!

References

¹ Baum HB, Biller BM, Finkelstein JS, Cannistraro KB, Oppenhein DS, Schoenfeld DA, Michel TH, Wittink H, Klibanski A. Effects of physiologic growth hormone therapy on bone density and body composition in patients with adult-onset growth hormone deficiency. A randomized, placebo-controlled trial. Ann Intern Med. 1996 Dec 1;125(11):883-90.

² Kraemer WJ, Ratamess NA. Hormonal responses and adaptations to resistance exercise and training.Sports Med. 2005;35(4):339-61.

³ West DW, Kujbida GW, Moore DR, Atherton P, Burd NA, Padzik JP, De Lisio M, Tang JE, Parise G, Rennie MJ, Baker SK, Phillips SM. Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men. J Physiol. 2009 Nov 1;587(Pt 21):5239-47.

⁴ West DW, Burd NA, Tang JE, Moore DR, Staples AW, Holwerda AM, Baker SK, Phillips SM. Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors. . J Appl Physiol. 2010 Jan;108(1):60-7. Epub 2009 Nov 12.

⁵ Hartman JW, Tang JE, Wilkinson SB, Tarnopolsky MA, Lawrence RL, Fullerton AV, Phillips SM. Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters. Am J Clin Nutr. 2007 Aug;86(2):373-81.

⁶ Moller N, Jørgensen JO. Effects of growth hormone on glucose, lipid, and protein metabolism in human subjects. Endocr Rev. 2009 Apr;30(2):152-77. Epub 2009 Feb 24.

⁷ Irving BA, Davis CK, Brock DW, Weltman JY, Swift D, Barrett EJ, Gaesser GA, Weltman A.Effect of exercise training intensity on abdominal visceral fat and body composition. Med Sci Sports Exerc. 2008 Nov;40(11):1863-72.

⁸ Irving BA, Weltman JY, Patrie JT, Davis CK, Brock DW, Swift D, Barrett EJ, Gaesser GA, Weltman A.Effects of exercise training intensity on nocturnal growth hormone secretion in obese adults with the metabolic syndrome. J Clin Endocrinol Metab. 2009 Jun;94(6):1979-86. Epub 2009 Mar 24.

⁹ Cavagnini F, Benetti G, Invitti C, Ramella G, Pinto M, Lazza M, Dubini A, Marelli A, Müller EE.Effect of gamma-aminobutyric acid on growth hormone and prolactin secretion in man: influence of pimozide and domperidone. J Clin Endocrinol Metab. 1980 Oct;51(4):789-92.

¹⁰ SW Tech Staff.GABA. IronMagazine.com. 2003. Accessed February 20, 2010 from: http://www.ironmagazine.com/review20.html.

¹¹ Powers ME, Yarrow JF, McCoy SC, Borst SE. Growth hormone isoform responses to GABA ingestion at rest and after exercise. Med Sci Sports Exerc. 2008 Jan;40(1):104-10.

¹² Collier SR, Casey DP, Kanaley JA. Growth hormone responses to varying doses of oral arginine. Growth Horm IGF Res. 2005 Apr;15(2):136-9. Epub 2005 Jan 26.

¹³ Collier S, Collins E, Kanaley JA. Oral arginine attenuates the growth hormone response to resistance exercise. J Appl Physiol 2006; 101:848–852.

¹⁴ Marcell TJ, Taaffe DR, Hawkins SA, Tarpenning KM, Pyka G, Kohlmeier L, Wiswell RA, Marcus R. Oral arginine does not stimulate basal or augment exercise-induced GH secretion in either young or old adults. J Gerontol A Biol Sci Med Sci. 1999 Aug;54(8):M395-9.

¹⁵ Suminski RR, Robertson RJ, Goss FL, Arslanian S, Kang J, DaSilva S, Utter AC, Metz KF.Acute effect of amino acid ingestion and resistance exercise on plasma growth hormone concentration in young men. Int J Sport Nutr. 1997 Mar;7(1):48-60.

¹⁶ Fogelholm GM, Näveri HK, Kiilavuori KT, Härkönen MH.Low-dose amino acid supplementation: no effects on serum human growth hormone and insulin in male weightlifters. Int J Sport Nutr. 1993 Sep;3(3):290-7.

¹⁷ Abel T, Knechtle B, Perret C, Eser P, von Arx P, Knecht H. Influence of chronic supplementation of arginine aspartate in endurance athletes on performance and substrate metabolism – a randomized, double-blind, placebo-controlled study. Int J Sports Med. 2005 Jun;26(5):344-9.

¹⁸ Chromiak JA, Antonio J.Use of amino acids as growth hormone-releasing agents by athletes. Nutrition. 2002 Jul-Aug;18(7-8):657-61.

¹⁹ Elam RP, Hardin DH, Sutton RA, Hagen L. Effects of arginine and ornithine on strength, lean body mass and urinary hydroxyproline in adult males. J Sports Med Phys Fitness. 1989;29(1):52-6.

²⁰ Meek SE, Persson M, Ford GC, Nair KS. Differential regulation of amino acid exchange and protein dynamics across splanchnic and skeletal muscle beds by insulin in healthy human subjects. Diabetes. 1998 Dec;47(12):1824-35.

²¹ Tanaka, KS, Inoue J, Shiraki J, et al. Age-related decreases in plasma growth hormone: response to growth hormone-releasing hormone, arginine, and L-dopa in obesity. Metabolism 1991;40:1257.

²² Corpas E, Blackman MR, Roberson R, Schofield D, Harman SM. Oral argininelysine does not increase growth hormone or insulin-like growth factor-I in old men. J Gerontol 1993;48:M128.

²³ Drummond MJ, Rasmussen BB. Leucine-enriched nutrients and the regulation of mammalian target of rapamycin signalling and human skeletal muscle protein synthesis. Curr Opin Clin Nutr Metab Care. 2008 May;11(3):222-6.

In my last WNF, Effect of Caloric Restriction and Exercise on Weight Loss and Heart Health, I discussed how equal weight loss could be achieved via dietary modifications alone or a combination of exercise + dietary changes. Unfortunately, in attempting to drop a few inches from the waistline (ie- decreasing fat mass), collateral damage, in the form of muscle breakdown, often occurs. Furthermore, the lower % body fat you have at baseline, the greater likelihood that muscle will be lost while on a caloric restricted diet¹. For functional and aesthetic purposes, individuals often desire to lose fat while maintaining muscle tissue. Thus, various researchers have examined how weight loss can be maximized while still preserving as much lean muscle mass as possible. One way to offset this decline in lean muscle mass is via resistance training². Additionally, it appears that macronutrient distribution (ie- % protein, % carbohydrates, % fat in diet) may also effect loss of lean muscle mass during times of caloric (kcal) restriction. In 2006, a large meta-analysis, which combined the results from 87 previously conducted studies, suggested that increasing dietary protein intake, in conjunction with a reduced kcal diet, preserved muscle tissue (and other fat free tissue)³. However, most studies examining the influence protein intake has on body composition changes have focused on overweight, obese and/or individuals with preexisting health conditions⁴.

Influence of Dietary Protein on Body Composition in Healthy Athletes during Times of Energy Restriction

Few studies have examined the effects of protein on body composition in healthy, athletic populations while on a reduced kcal diet. In a study completed by Walberg et al., researchers placed experienced body builders on kcal restricted diets (51.4% of usual kcal intake) that consisted of either a high protein (0.73g/lb) or moderate protein (0.36g/lb) content⁵. These diets were followed for 1 week. See Table 1 for the complete macronutrient distribution. Based off nitrogen balance tests, it appeared that those in the high protein group maintained lean tissue while on the low energy diets. This was not seen in the moderate protein group. However, those in the high protein group also experienced a 22% loss in muscular endurance in their quadriceps vs. baseline measurements. In contrast, no changes were found in the moderate protein group when comparing pre- and post-diet muscular endurance times. Despite maintaining a positive nitrogen balance, Lambert et al hypothesized that the decrease in muscular endurance of the quadriceps muscle was a result of the extreme reduction in total kcal consumption⁶, which potentially failed to provide enough carbohydrates to supply energy at higher intensities.

Table 1. Energy intake and percent of total energy contributed to each group by various macronutrients⁵. As seen below, dietary carbohydrate levels fluctuated to account for the changes in dietary protein, whereas fat content stayed relatively the same between diets.

In a recently published study, Mettler et al. examined the effects of dietary protein on body composition in 20 trained male athletes (mean age ~25 years; BMI ~23-24) while undergoing a 2 week diet consisting of 60% of usual kcal intake⁷. All participants were healthy (no reported metabolic disorders), participated in at least 2 resistance training sessions/week for >6 months and on average, exercised 4-5 times/week for a total duration of ~330-360 minutes. Participants were separated into 2 separate groups; a high (1.04g/lb) or moderate (0.45g/lb) protein group. Due to the importance of carbohydrates in supplying energy during high intensity training, Mettler et al. did not decrease the overall percentage of carbohydrates in the diet. Rather they altered the contribution that fat made to each diet. This is in contrast to Walberg et al., who varied protein at the expense of carbohydrates⁵. Please see Table 2 for the complete macronutrient distribution in Mettler et al.’s study.

Table 2. Energy intake and percent of total energy contributed to each group by various macronutrients⁷. As seen below, dietary fat levels fluctuated to account for the changes in dietary protein, whereas carbohydrate content stayed relatively the same between diets.

Please note that Mettler et al.⁷ reduced dietary energy intake to 60% of usual intake, vs. Walberg et al. who reduced it to 51.4%⁵. Therefore, despite having somewhat similar macronutrient distributions, those in Mettler et al.’s high protein groupwere consuming more total energy (and thus more protein, carbohydrates, etc) vs those in Walber et al.‘s high protein group.

Normal training routines were maintained during the 2 weeks of kcal restriction. Body composition and athletic/anaerobic performance measurements (squat jump, maximal isometric leg extension, one-repetition maximum (1RM) bench press, muscle endurance bench press, and 30-s Wingate test) were taken at baseline and at the completion of the trial. At the end of the 2 week kcal restricted period, both groups experienced similar fat mass losses. However, individuals in the moderate protein group lost ~2 lbs more fat free mass (which includes lean muscle mass) than those in the high protein group. Athletic performance measurements did not appear to suffer over this 2 week time span. This conflicts with the results of Walberg et al. who found a decrease in muscular endurance of the quadricep muscles⁵. An overall smaller kcal reduction (48.6% vs. 40%) and greater carbohydrate content of the diet employed by Mettler et al. may have accounted for this difference.

A few quick caveats should be mentioned with this study. First, only males participated in this study. Due to physiological differences, similar results may not have been obtained in thin, athletic women. However, studies completed on women, albeit overweight and/or obese, have shown higher protein levels to be protective against loss of lean tissue during times of kcal restriction with⁸ or without⁹ the inclusion of a supervised exercise program. Finally, I must point out that this study was only 2 weeks in duration. Thus, one must be careful in how they extrapolate these results (performance and body composition) out to longer time durations. Despite these limitations, this study provides strong evidence that consuming higher protein levels, during times of caloric restriction (60% of usual intake), minimizes the loss of muscular tissue.

Bottom Line

When losing any significant amount of weight, it’s unrealistic to think that some of the loss won’t be in the form of muscle. This is even truer in thin individuals who have lower initial % body fat prior to weight loss. For non active individuals, losing a 2-3 pounds of lean muscle tissue, along with 8-10 lbs of body fat, may not seem like a large deal. However, for active individuals and/or competitive athlete, maximizing fat loss while minimizing muscle loss is often desired.

No significant differences existed between the groups with respect to performance measurements at anytime during the trial. If I was playing the role of the devil’s advocate, I could argue that the preservation of muscle does not benefit exercise performance. However, as pointed out by the authors, many pertinent athletic tests may have better captured the effects of minimizing muscle loss than those chosen in this study. Furthermore, the duration of energy restriction was only 2 weeks. If this was extended over an entire sport season, I strongly believe that the preservation of muscle mass would have a more significant effect on athletic performance.

I’d also like to point out that neither of the dietary interventions employed in these 2 studies dropped carbohydrate content less than 50% of overall kcal consumption. Individuals in the study by Mettler et al. still consumed ~1.5 grams of carbohydrates/lb once kcal intake was reduced to 60% of usual consumption. On one hand, 1.5 grams of carbohydrates/lb probably wouldn’t be enough to refill glycogen stores and sustain performance in endurance athletes. On the other hand, this amount did not seem to negatively affect any of the athletic/anaerobic performance measurements obtained during the course of this study.

In summary, collateral damage, in the form of muscle breakdown, commonly occurs when reducing one’s weight. When decreasing kcal intake, be sure to still consume ~1 gram of protein/lb of body weight. In turn, this will help minimize potential muscle breakdown, assisting you in developing the body you desire!

References

¹ Forbes GB. Body fat content influences the body composition response to nutrition and exercise. Ann N Y Acad Sci. 2000 May;904:359-65.

² Stiegler P, Cunliffe A.The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss. Sports Med. 2006;36(3):239-62.

³ Krieger JW, Sitren HS, Daniels MJ, Langkamp-Henken B. Effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction: a meta-regression 1. Am J Clin Nutr. 2006 Feb;83(2):260-74.

⁴ Stiegler P, Cunliffe A.The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss. Sports Med. 2006;36(3):239-62.

⁵ Walberg JL, Leidy MK, Sturgill DJ, Hinkle DE, Ritchey SJ,Sebolt DR. Macronutrient content of a hypoenergy diet affects nitrogen retention and muscle function in weight lifters. Int J Sports Med. 1988;9(4):261–6.

⁶ Lambert CP, Frank LL, Evans WJ. Macronutrient considerations for the sport of bodybuilding. Sports Med. 2004;34(5):317-27.

⁷ Mettler S, Mitchell N, Tipton KD. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010 Feb;42(2):326-37.

⁸ Layman DK, Evans E, Baum JI, Seyler J, Erickson DJ, Boileau RA Dietary protein and exercise have additive effects on body composition during weight loss in adult women. J Nutr. 2005 Aug;135(8):1903-10.

⁹ Layman DK, Boileau RA, Erickson DJ, Painter JE, Shiue H, Sather C, Christou DD. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr. 2003 Feb;133(2):411-7.