Testosterone: Practical Applications From the Laboratory to the Weight Room
by Robbie J. Durand, MS, CSCS
???True knowledge exists in knowing that you know nothing.?????? Socrates
TESTOSTERONE PHYSIOLOGY
Testosterone (T) is loosely bound to sex hormone binding globulin (SHBG) after excretion from the testis and circulates in the blood for about 30 minutes to one hour. Approximately five to six milligrams of testosterone is secreted into plasma daily in men. In men, LH and testosterone are secreted in a pulsatile manner every 60 to 90 minutes in a diurnal rhythm, with peak levels occurring in the morning.
T has many functions in the body which include: development of adult primary and secondary sexual characteristics, bone growth, increased calcium retention, red blood cell production, muscular development, fat lipolysis and protein synthesis.
Testosterone and Protein Synthesis
A number of studies have documented the effects of testosterone on protein synthesis. Testosterone transcriptional activation by androgens leads to the production of specific mRNA???s and subsequent increased protein synthesis.31 Growth factors (e.g., IGF-1) are an important class of proteins secreted by cells upon stimulation by testosterone. The mechanism by which testosterone increases protein synthesis isn???t completely understood. It???s debated whether testosterone increases protein synthesis through the androgen receptor, or whether the effects of testosterone on protein synthesis are mediated through the GH/IGF-1 axis or other systems. Testosterone effects on protein synthesis can cause anabolic actions on skeletal muscle. Testosterone administration has been reported to increase skeletal muscle protein synthesis and strength in the elderly, as well as increased mixed protein synthesis rates in normal subjects. The protein accretion from testosterone can result in muscle hypertrophy. Mauras et al.,48 administered Lupron (a drug that suppresses natural testosterone production) to six 23-year-old healthy men (with reduced circulating testosterone levels) to those of prepubertal boys and found testosterone deficiency caused decreased rates of whole body protein turnover and protein synthesis, decreased fat-free muscle, decreased strength and increased adiposity. Interestingly, there were no decreases in GH and IGF-1 production but there was a decrease in gene expression for IGF-1 in muscle.
Additionally, Urban et. al.,49 reported that testosterone increases muscle protein synthesis by stimulating serum IGF-1 and a down regulation of its binding protein IGFBP-4. Testosterone influences muscle hypertrophy through a variety of mechanisms such as increased satellite cell activation, increased protein synthesis rates, enhanced growth factor activity (e.g., GH, IGF-1, etc.), enhanced myonuclear number and new myofiber formation. Satellite cell activation seems to be a necessity for hypertrophy; without satellite cell activation, hypertrophy won???t occur.50 Satellite cells are located between the sarcolemma and the basal lamina of the myofibers. In vivo rat studies have reported that at the onset of puberty, the increase in testosterone production causes hypertrophy with an increase in muscle cell diameter, a transient increase in satellite cell number and an increase in myonuclear number. Testosterone is thought to be the predominant factor producing greater hypertrophy in men than women when placed on identical training regimens.
Testosterone and Muscle Tissue Hypertrophy
The importance of testosterone on muscle tissue hypertrophy can be demonstrated in a study of hypogonadal men (i.e., men with low testosterone levels) who were sedentary and received testosterone replacement for 10 weeks. The men gained an average of 5.7 kilograms (one kilogram equals 2.2 pounds) of bodyweight and strength increased in both the bench press and parallel bar squat. The amazing aspect of this study was the men were not exercising during the 10-week study, yet strength and lean body mass were improved.47 Testosterone has been shown to increase circulating levels of both GH and IGF-1 concentrations.32
Kadi et al.,33 measured the effects of anabolic steroids for nine months on muscle tissue hypertrophy in five elite trained powerlifters and compared steroid users to drug-free powerlifters who were the same weight and trained the same amount of years. Testosterone injections in the steroid group induced a significant increase in muscle size by both hypertrophy and the formation of new muscle fibers via satellite cell activation. The anabolic steroid group had increased DNA content, which likely facilitated an increase in muscle protein synthesis and greater muscle tissue hypertrophy than the non-steroid group.
How Do Testosterone Levels Increase During Exercise?
Testosterone levels are positively correlated with fitness levels and levels of fatigue in weightlifters .34 Resistance training has also been shown to increase circulating testosterone concentration in men during exercise. Testosterone responses to exercise are stimulated to varying degrees depending on many factors including, the rest periods between sets, volume of training, age and amount of muscle mass activated. So here???s the million dollar question: What???s the mechanism or how does intense exercise stimulate testosterone production? Testosterone levels under resting conditions are influenced by leutinizing hormone (LH), which stimulates Leydig cells to secrete testosterone. However, during brief intense resistance exercise, testosterone levels have been reported to increase despite no increases in LH.39
Nindl et al.,25 had subjects perform a high volume resistance training protocol which consisted of 50 total sets of upper and lower body exercise with repetitions of five and 10 1-RM loads with 90-second rest periods between sets. The suspected research hypothesis was that there would be huge increases in testosterone with such a high-intensity, high volume training protocol mediated by some increases in LH. The high-volume resistance training protocol resulted in just the opposite. There was no change in testosterone and LH during exercise and immediately after exercise; shockingly there was a concomitant lower LH secretion and suppressed total and free testosterone for up to 13 hours after exercise.
The results of this study can be extrapolated to the bodybuilder who thinks spending hours in the gym performing countless sets is the key to stimulating anabolic hormones. In another study, which documented what excessive training volume can do to your testosterone levels, Hakkinen et al.,51 monitored elite Olympic lifters??? testosterone concentrations to twice daily training for one week. Elite Olympic weightlifters trained twice a day using similar volume (greater than 90 percent of a 1-RM) but different exercises. The morning session (9:00 a.m. to 11:00 a.m.) consisted of Olympic snatches, clean & jerks, and front squats, while the afternoon session (3:00 p.m. to 5:00 p.m.) consisted of power snatches, power cleans and back squats. Testosterone started to decrease after the first training day and continued to systematically decrease over the course of the training period. When the training stress was reduced to one training session a day, serum testosterone concentrations started to increase, and after one full day of rest, values returned to the pre-training level. Strength levels of the elite athletes did not decline over the course of the week despite a decline in testosterone concentrations.
The absent response of LH to an acute bout of resistance exercise despite an increase in testosterone has led researchers to speculate other mediators are influencing testosterone production. Possible mechanisms for increasing testosterone levels during high intensity exercise are due to increased circulating lactic acid levels, which are being produced from anaerobic glycolysis. Lactic acid has been shown to stimulate testosterone release in vitro (i.e. ,which means in the test tube).35 So this is one of those research studies where you don???t think your job is that bad after all, at least you???re not in a lab removing rat testicles all day long. Researchers exposed the testosterone-producing portion of the cell (i.e., Leydig cells) to lactic acid and found administration of lactate at five to 20 mM dose-dependently increased the basal testosterone production by 63 to 187 percent. Remember, that anaerobic threshold is four mM and it???s not uncommon for high-intensity weight training sessions to exceed 15mM, but remember this was done with rat testes so let???s not jump to conclusions too fast. More research needs to be conducted, so before you start injecting lactic acid into your ???family jewels??? wait till more research is available on the subject.
A second mechanism that has been proposed for increased testosterone levels during exercise is what is called, plasma volume shifts,36 which concludes that during high-intensity resistance exercise as you muscles become engorged with blood, water or plasma is displaced from your circulatory system. As a result, your blood becomes more concentrated with active metabolites (in this case testosterone). Kraemer et al.,36 reported that a resistance training protocol of three sets of bench press, lat-pulldowns, leg extension and leg curls performed at a 10-RM load for 10 repetitions or until muscular failure resulted in a significant increase in testosterone levels. But when he corrected for the plasma volume shifts or the amount of fluid lost from blood, he found that there was no change in testosterone. Interesting!!
The training-induced rise in testosterone has also been thought to be stimulated by catecholamines (i.e., adrenaline). Schwab et al.,7 investigated the effect of heavy weightlifting and moderate weightlifting on concentrations of serum testosterone in males. The heavy weightlifting consisted of four sets of six squats at 90 to 95 percent of a six-repetition maximum (RM), while the moderate weightlifting consisted of four sets of nine or 10 repetitions at 60 to 65 percent of a 1-RM. The weight and number of repetitions were manipulated such that the total weight lifted for the two sessions was equal. Testosterone levels were measured after each set to determine when a rise in testosterone occurred. Testosterone levels didn???t rise until the fourth set for both groups. Schwab hypothesized that because the exercise bout was brief, possibly epinephrine and nor-epinephrine, which have been shown to increase during exercise to the magnitude of the intensity of the exercise, could have significantly increased testosterone levels in response to the exercise bouts. Regardless of which mechanism is causing these acute increases in testosterone during exercise, androgen skeletal muscle receptors are actively binding to a higher concentration of testosterone.
Testosterone and Resistance Training Intensity
Resistance training routines, which incorporate short rest periods between sets, produce higher testosterone concentrations than training protocols using the same workload and prolonged rest periods. Hakkinen et al.,38 subjected 10 male strength athletes to two different training intensities while maintaining similar rest periods (three minutes). The first session consisted of maximum loads (20 sets x 1-RM x 100 percent), while one week later they performed sub-maximum training (10 sets x 10-RM x 70 percent). Testosterone levels with maximum training (20 sets x 1-RM) didn???t change immediately and one hour post-exercise, however testosterone and cortisol responses to sub-maximum training (10 sets x 10-RM) increased significantly after and one hour post-exercise with the sub-maximum training loads. Hakkinen concluded that heavy resistance exercises can stimulate varying endocrine responses of anabolic hormones, which differ in duration, and magnitude depending on the degree of stress of the exercise protocol. W.J. Kraemer 52 compared bodybuilders and powerlifters of the same age, size and experience to an intense resistance training protocol, which shorted rest periods. The experimental sessions consisted of three sets of 10 repetitions for 10 exercises with 10-second rest periods between sets and 30 to 60 second rest periods between exercises. There was no significant difference between the groups as peak plasma lactate levels five minutes post-exercise was 21 mmol/L( talk about high intensity training session! Remember lactate threshold starts to increase at 4 mmol/L) for both groups. Testosterone increased significantly for both groups, but regardless of previous training experience, both bodybuilders and powerlifters had similar increases in testosterone concentrations.
Testosterone responses to resistance training in men are less with low-intensity resistance training protocols than those using high intensity. Raastad et al.,39 compared testosterone responses to two protocols, which utilized different intensities of squats, front squats and leg extensions yet workload remained constant. One protocol was a moderate intensity (70 percent of a 1-RM) and the other protocol was a high-intensity workload (100 percent of a 6-RM). Rest periods between sets were four to six minutes for both workouts. Testosterone responses were higher during, and one hour after, the 70 percent protocol compared to the 100 percent protocol. Training intensity should be at least 70 percent or more to stimulate sufficient rises in testosterone production. So now that you understand that powerlifting type protocols which incorporate high training percent (90> and above) and long rest periods aren???t conducive for increasing GH and testosterone during exercise, however using a high training percent should be incorporated into your routines for increasing muscular strength.
Testosterone levels are also influenced by the amount of muscle mass activated in response to exercise. Craig et al.40 reported that testosterone levels did not increase from pre- to post-exercise for younger and older men to upper and lower body isolation-type resistance exercise on a Nautilus machine consisting of three sets of 10 repetitions. Contrary to these finding, W.J. Kraemer 41 reported significant increases in testosterone responses of older and younger men in response to a high-intensity squat protocol.
Kraemer speculated the greater testosterone produced in his study compared to the study by Craig et al.,38 was due to his protocol using large muscle mass and higher training intensity.
Fahey et al.,56 reported significant increases in testosterone after deadlifts in college-age men; however, maximum and sub-maximum efforts in the bench press resulted in no increases in testosterone in experienced weightlifters.8 The disparities in results between the studies is probably due to large amounts of muscle groups activated during the deadlift (i.e., legs, back, arms, abdominals),whereas a much smaller amount of muscle mass is activated during the bench press (i.e., pectoralis major, triceps brachii and anterior deltoid).
Effects of Training Experience on Testosterone Levels
Training experience could also influence the degree in which testosterone is produced in response to an intense resistance-training protocol. W.J. Kraemer42 investigated adolescent Olympic weightlifters??? (17-18 years old) testosterone concentrations in response to an a intense weightlifting session consisting of 10 maximum effort vertical jumps and high-intensity, low-volume resistance training with the Olympic snatch and snatch pull. Subjects were separated into two experimental groups: 1) less than two years lifting experience, and 2) greater than two years lifting experience. Exercise-induced increases in testosterone occurred only in the weightlifters training for greater than two years, while weightlifters with less than two years experience did not see a significant exercise-induced increase in testosterone. W.J. Kraemer hypothesized the experienced weightlifters had enhanced hypopituitary-gonadal axis (HPG) from training and testicular function that was remodeled to promote enhanced release of testosterone. A most intriguing aspect of the study was lactate levels were similar in both groups post-exercise; these data suggest that in adolescent boys, blood lactate is not a strong activator of the HPG axis.
In conclusion, GH and testosterone have synergistic effects on muscle and lead to increases in intramuscular growth factors that may work on similar molecular pathways or may work completely independent of each other. GH has potent effects on fat lipolysis, yet GH effects on muscle hypertrophy are less well documented and are mild at best. Testosterone has potent effects on increasing muscular hypertrophy and is a potent stimulator of satellite cell activation, which is essential for muscle hypertrophy. High intensity exercise with short rest periods seems to lead to dual rises in both GH and testosterone though one, or possibly many, mechanisms.
References
12.Kraemer, W.J., Marchitelli, L.J., Gordon, S.E., Harman, E., Dziados, J.E., Mello, R., Frykman, P., McCurry, D., and Fleck, S.J. Hormonal and growth factors responses to heavy-resistance exercise protocols. J Appl Physiol, 69:1442-1450, 1990.
by Robbie J. Durand, MS, CSCS
???True knowledge exists in knowing that you know nothing.?????? Socrates
TESTOSTERONE PHYSIOLOGY
Testosterone (T) is loosely bound to sex hormone binding globulin (SHBG) after excretion from the testis and circulates in the blood for about 30 minutes to one hour. Approximately five to six milligrams of testosterone is secreted into plasma daily in men. In men, LH and testosterone are secreted in a pulsatile manner every 60 to 90 minutes in a diurnal rhythm, with peak levels occurring in the morning.
T has many functions in the body which include: development of adult primary and secondary sexual characteristics, bone growth, increased calcium retention, red blood cell production, muscular development, fat lipolysis and protein synthesis.
Testosterone and Protein Synthesis
A number of studies have documented the effects of testosterone on protein synthesis. Testosterone transcriptional activation by androgens leads to the production of specific mRNA???s and subsequent increased protein synthesis.31 Growth factors (e.g., IGF-1) are an important class of proteins secreted by cells upon stimulation by testosterone. The mechanism by which testosterone increases protein synthesis isn???t completely understood. It???s debated whether testosterone increases protein synthesis through the androgen receptor, or whether the effects of testosterone on protein synthesis are mediated through the GH/IGF-1 axis or other systems. Testosterone effects on protein synthesis can cause anabolic actions on skeletal muscle. Testosterone administration has been reported to increase skeletal muscle protein synthesis and strength in the elderly, as well as increased mixed protein synthesis rates in normal subjects. The protein accretion from testosterone can result in muscle hypertrophy. Mauras et al.,48 administered Lupron (a drug that suppresses natural testosterone production) to six 23-year-old healthy men (with reduced circulating testosterone levels) to those of prepubertal boys and found testosterone deficiency caused decreased rates of whole body protein turnover and protein synthesis, decreased fat-free muscle, decreased strength and increased adiposity. Interestingly, there were no decreases in GH and IGF-1 production but there was a decrease in gene expression for IGF-1 in muscle.
Additionally, Urban et. al.,49 reported that testosterone increases muscle protein synthesis by stimulating serum IGF-1 and a down regulation of its binding protein IGFBP-4. Testosterone influences muscle hypertrophy through a variety of mechanisms such as increased satellite cell activation, increased protein synthesis rates, enhanced growth factor activity (e.g., GH, IGF-1, etc.), enhanced myonuclear number and new myofiber formation. Satellite cell activation seems to be a necessity for hypertrophy; without satellite cell activation, hypertrophy won???t occur.50 Satellite cells are located between the sarcolemma and the basal lamina of the myofibers. In vivo rat studies have reported that at the onset of puberty, the increase in testosterone production causes hypertrophy with an increase in muscle cell diameter, a transient increase in satellite cell number and an increase in myonuclear number. Testosterone is thought to be the predominant factor producing greater hypertrophy in men than women when placed on identical training regimens.
Testosterone and Muscle Tissue Hypertrophy
The importance of testosterone on muscle tissue hypertrophy can be demonstrated in a study of hypogonadal men (i.e., men with low testosterone levels) who were sedentary and received testosterone replacement for 10 weeks. The men gained an average of 5.7 kilograms (one kilogram equals 2.2 pounds) of bodyweight and strength increased in both the bench press and parallel bar squat. The amazing aspect of this study was the men were not exercising during the 10-week study, yet strength and lean body mass were improved.47 Testosterone has been shown to increase circulating levels of both GH and IGF-1 concentrations.32
Kadi et al.,33 measured the effects of anabolic steroids for nine months on muscle tissue hypertrophy in five elite trained powerlifters and compared steroid users to drug-free powerlifters who were the same weight and trained the same amount of years. Testosterone injections in the steroid group induced a significant increase in muscle size by both hypertrophy and the formation of new muscle fibers via satellite cell activation. The anabolic steroid group had increased DNA content, which likely facilitated an increase in muscle protein synthesis and greater muscle tissue hypertrophy than the non-steroid group.
How Do Testosterone Levels Increase During Exercise?
Testosterone levels are positively correlated with fitness levels and levels of fatigue in weightlifters .34 Resistance training has also been shown to increase circulating testosterone concentration in men during exercise. Testosterone responses to exercise are stimulated to varying degrees depending on many factors including, the rest periods between sets, volume of training, age and amount of muscle mass activated. So here???s the million dollar question: What???s the mechanism or how does intense exercise stimulate testosterone production? Testosterone levels under resting conditions are influenced by leutinizing hormone (LH), which stimulates Leydig cells to secrete testosterone. However, during brief intense resistance exercise, testosterone levels have been reported to increase despite no increases in LH.39
Nindl et al.,25 had subjects perform a high volume resistance training protocol which consisted of 50 total sets of upper and lower body exercise with repetitions of five and 10 1-RM loads with 90-second rest periods between sets. The suspected research hypothesis was that there would be huge increases in testosterone with such a high-intensity, high volume training protocol mediated by some increases in LH. The high-volume resistance training protocol resulted in just the opposite. There was no change in testosterone and LH during exercise and immediately after exercise; shockingly there was a concomitant lower LH secretion and suppressed total and free testosterone for up to 13 hours after exercise.
The results of this study can be extrapolated to the bodybuilder who thinks spending hours in the gym performing countless sets is the key to stimulating anabolic hormones. In another study, which documented what excessive training volume can do to your testosterone levels, Hakkinen et al.,51 monitored elite Olympic lifters??? testosterone concentrations to twice daily training for one week. Elite Olympic weightlifters trained twice a day using similar volume (greater than 90 percent of a 1-RM) but different exercises. The morning session (9:00 a.m. to 11:00 a.m.) consisted of Olympic snatches, clean & jerks, and front squats, while the afternoon session (3:00 p.m. to 5:00 p.m.) consisted of power snatches, power cleans and back squats. Testosterone started to decrease after the first training day and continued to systematically decrease over the course of the training period. When the training stress was reduced to one training session a day, serum testosterone concentrations started to increase, and after one full day of rest, values returned to the pre-training level. Strength levels of the elite athletes did not decline over the course of the week despite a decline in testosterone concentrations.
The absent response of LH to an acute bout of resistance exercise despite an increase in testosterone has led researchers to speculate other mediators are influencing testosterone production. Possible mechanisms for increasing testosterone levels during high intensity exercise are due to increased circulating lactic acid levels, which are being produced from anaerobic glycolysis. Lactic acid has been shown to stimulate testosterone release in vitro (i.e. ,which means in the test tube).35 So this is one of those research studies where you don???t think your job is that bad after all, at least you???re not in a lab removing rat testicles all day long. Researchers exposed the testosterone-producing portion of the cell (i.e., Leydig cells) to lactic acid and found administration of lactate at five to 20 mM dose-dependently increased the basal testosterone production by 63 to 187 percent. Remember, that anaerobic threshold is four mM and it???s not uncommon for high-intensity weight training sessions to exceed 15mM, but remember this was done with rat testes so let???s not jump to conclusions too fast. More research needs to be conducted, so before you start injecting lactic acid into your ???family jewels??? wait till more research is available on the subject.
A second mechanism that has been proposed for increased testosterone levels during exercise is what is called, plasma volume shifts,36 which concludes that during high-intensity resistance exercise as you muscles become engorged with blood, water or plasma is displaced from your circulatory system. As a result, your blood becomes more concentrated with active metabolites (in this case testosterone). Kraemer et al.,36 reported that a resistance training protocol of three sets of bench press, lat-pulldowns, leg extension and leg curls performed at a 10-RM load for 10 repetitions or until muscular failure resulted in a significant increase in testosterone levels. But when he corrected for the plasma volume shifts or the amount of fluid lost from blood, he found that there was no change in testosterone. Interesting!!
The training-induced rise in testosterone has also been thought to be stimulated by catecholamines (i.e., adrenaline). Schwab et al.,7 investigated the effect of heavy weightlifting and moderate weightlifting on concentrations of serum testosterone in males. The heavy weightlifting consisted of four sets of six squats at 90 to 95 percent of a six-repetition maximum (RM), while the moderate weightlifting consisted of four sets of nine or 10 repetitions at 60 to 65 percent of a 1-RM. The weight and number of repetitions were manipulated such that the total weight lifted for the two sessions was equal. Testosterone levels were measured after each set to determine when a rise in testosterone occurred. Testosterone levels didn???t rise until the fourth set for both groups. Schwab hypothesized that because the exercise bout was brief, possibly epinephrine and nor-epinephrine, which have been shown to increase during exercise to the magnitude of the intensity of the exercise, could have significantly increased testosterone levels in response to the exercise bouts. Regardless of which mechanism is causing these acute increases in testosterone during exercise, androgen skeletal muscle receptors are actively binding to a higher concentration of testosterone.
Testosterone and Resistance Training Intensity
Resistance training routines, which incorporate short rest periods between sets, produce higher testosterone concentrations than training protocols using the same workload and prolonged rest periods. Hakkinen et al.,38 subjected 10 male strength athletes to two different training intensities while maintaining similar rest periods (three minutes). The first session consisted of maximum loads (20 sets x 1-RM x 100 percent), while one week later they performed sub-maximum training (10 sets x 10-RM x 70 percent). Testosterone levels with maximum training (20 sets x 1-RM) didn???t change immediately and one hour post-exercise, however testosterone and cortisol responses to sub-maximum training (10 sets x 10-RM) increased significantly after and one hour post-exercise with the sub-maximum training loads. Hakkinen concluded that heavy resistance exercises can stimulate varying endocrine responses of anabolic hormones, which differ in duration, and magnitude depending on the degree of stress of the exercise protocol. W.J. Kraemer 52 compared bodybuilders and powerlifters of the same age, size and experience to an intense resistance training protocol, which shorted rest periods. The experimental sessions consisted of three sets of 10 repetitions for 10 exercises with 10-second rest periods between sets and 30 to 60 second rest periods between exercises. There was no significant difference between the groups as peak plasma lactate levels five minutes post-exercise was 21 mmol/L( talk about high intensity training session! Remember lactate threshold starts to increase at 4 mmol/L) for both groups. Testosterone increased significantly for both groups, but regardless of previous training experience, both bodybuilders and powerlifters had similar increases in testosterone concentrations.
Testosterone responses to resistance training in men are less with low-intensity resistance training protocols than those using high intensity. Raastad et al.,39 compared testosterone responses to two protocols, which utilized different intensities of squats, front squats and leg extensions yet workload remained constant. One protocol was a moderate intensity (70 percent of a 1-RM) and the other protocol was a high-intensity workload (100 percent of a 6-RM). Rest periods between sets were four to six minutes for both workouts. Testosterone responses were higher during, and one hour after, the 70 percent protocol compared to the 100 percent protocol. Training intensity should be at least 70 percent or more to stimulate sufficient rises in testosterone production. So now that you understand that powerlifting type protocols which incorporate high training percent (90> and above) and long rest periods aren???t conducive for increasing GH and testosterone during exercise, however using a high training percent should be incorporated into your routines for increasing muscular strength.
Testosterone levels are also influenced by the amount of muscle mass activated in response to exercise. Craig et al.40 reported that testosterone levels did not increase from pre- to post-exercise for younger and older men to upper and lower body isolation-type resistance exercise on a Nautilus machine consisting of three sets of 10 repetitions. Contrary to these finding, W.J. Kraemer 41 reported significant increases in testosterone responses of older and younger men in response to a high-intensity squat protocol.
Kraemer speculated the greater testosterone produced in his study compared to the study by Craig et al.,38 was due to his protocol using large muscle mass and higher training intensity.
Fahey et al.,56 reported significant increases in testosterone after deadlifts in college-age men; however, maximum and sub-maximum efforts in the bench press resulted in no increases in testosterone in experienced weightlifters.8 The disparities in results between the studies is probably due to large amounts of muscle groups activated during the deadlift (i.e., legs, back, arms, abdominals),whereas a much smaller amount of muscle mass is activated during the bench press (i.e., pectoralis major, triceps brachii and anterior deltoid).
Effects of Training Experience on Testosterone Levels
Training experience could also influence the degree in which testosterone is produced in response to an intense resistance-training protocol. W.J. Kraemer42 investigated adolescent Olympic weightlifters??? (17-18 years old) testosterone concentrations in response to an a intense weightlifting session consisting of 10 maximum effort vertical jumps and high-intensity, low-volume resistance training with the Olympic snatch and snatch pull. Subjects were separated into two experimental groups: 1) less than two years lifting experience, and 2) greater than two years lifting experience. Exercise-induced increases in testosterone occurred only in the weightlifters training for greater than two years, while weightlifters with less than two years experience did not see a significant exercise-induced increase in testosterone. W.J. Kraemer hypothesized the experienced weightlifters had enhanced hypopituitary-gonadal axis (HPG) from training and testicular function that was remodeled to promote enhanced release of testosterone. A most intriguing aspect of the study was lactate levels were similar in both groups post-exercise; these data suggest that in adolescent boys, blood lactate is not a strong activator of the HPG axis.
In conclusion, GH and testosterone have synergistic effects on muscle and lead to increases in intramuscular growth factors that may work on similar molecular pathways or may work completely independent of each other. GH has potent effects on fat lipolysis, yet GH effects on muscle hypertrophy are less well documented and are mild at best. Testosterone has potent effects on increasing muscular hypertrophy and is a potent stimulator of satellite cell activation, which is essential for muscle hypertrophy. High intensity exercise with short rest periods seems to lead to dual rises in both GH and testosterone though one, or possibly many, mechanisms.
References
- Page, M.D., Dieguez, C., Valcavi, R., Edwards, C., Hall, R., and Scanlon, M.F. Growth Hormone responses to arginine and L-dopa alone and after GHRH pretreatment. Clin Endocrinol, (Oxf) 28:551-558, 1988.
- Murakami, Y., Kato Kabayama, Y., Tojo, K., Inoue, T., and Imura, H. Involvement of growth hormone releasing factor in GH secretion induced by serotoninergic mechanisms in conscious rat. Endocrinology, 119: 1089-1092, 1986.
- Felsing, N.E., Brasel, J.E., and Cooper, D.M. Effect of Low and High Intensity Exercise on Circulating Growth Hormone in Men. J Clin Endocrinol Metab, 75: 157-162, 1992.
- Ho, K.Y., Veldhuis, J.D., Johnson, M.L., Furianetto, R., Evans, W.S., Alberti, K.G., and Thorner, M.O. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest, 81: 968-975, 1987.
- Fryburg, D.A. Insulin-Like growth factor exerts growth hormone- and insulin-like actions on human muscle protein metabolism. Am J Physiol, 267 (Endocrinol Metab, 30) E331-E336, 1994.
- Schwab, R., Johnson, G.O., Housh, T.J., Kinder, J.E., and Weir, J.P. Acute effects of different intensities of weightlifting on serum testosterone. Med Sci Sports Exerc, Dec;25(12):1381-5, 1993.
- Pyka, G., Wiswell, R.A., and Marcus, R. Age-Dependent Effect of Resistance Exercise on Growth Hormone Secretion in People. J Clin Endocrinol Metab, 75: 404-407, 1992.
- Shibasaki, T., Hotta, M., Masuda, A., Imaki, T., Obara, N., and Demura, H. Plasma responses to GHRH and insulin-induced hypoglycemia in man. J Clin Endocrinol Metab, 60: 1265-1267, 1998.
- Luger, A., Watschinger, B., Deuster, P., Svoboda, T., Clodi, M., and Chrousos, G.P. Plasma growth hormone and prolactin responses to graded levels of acute exercise and to lactate infusion. Neuroendocrinology, 56: 112-117, 1992.
12.Kraemer, W.J., Marchitelli, L.J., Gordon, S.E., Harman, E., Dziados, J.E., Mello, R., Frykman, P., McCurry, D., and Fleck, S.J. Hormonal and growth factors responses to heavy-resistance exercise protocols. J Appl Physiol, 69:1442-1450, 1990.
- Gotshalk, L.A., Loebel, C.C., Nindl, B.C., Putukian, M., Sebastianelli, W.J., Newton, R.U., Hakkinen, K., and Kraemer, W.J. Hormonal responses of multiset versus single-set heavy-resistance exercise protocols. Can J Appl Physiol, Jun;22(3):244-55, 1997.
- Carroll, P.V., Christ, E.R., Bengtsson, B.A., Carlsson, L., Christiansen, J.S., Clemmons, D., Hintz, R., Ho, K., Laron, Z., Sizonenko, P., Sonksen, P.H., Tanaka, T., and Thorne, M. Growth hormone deficiency in adulthood and the effects of growth hormone replacement: a review. Growth Hormone Research Society Scientific Committee. J Clin Endocrinol Metab, Feb;83(2):382-95, 1983.
- Berneis, K., Ninnis, R., Girard, J., Frey, B. M., and Keller, U. Effects of Insulin-Like Growth Factor I Combined with Growth Hormone on Glucocorticoid-Induced Whole-Body Protein Catabolism in Man. J Clin Endocrinol Metab, 82: 2528-2534, 1997.
- Hoffman, D.M., Pallasser, R., Duncan, M., Nguyen, T.V., and HO, K.K. How is whole body protein turnover perturbed in growth hormone-deficient adults? J Clin Endocrinol Metab, 83: 4344-4349, 1998.
- Valk, N.K., vd Lely, A.J., de Herder, W.W., Lindmans, H.J., and Lamberts, S.W. The effects of human growth hormone (GH) administration in GH-deficient adults: a 20-day metabolic ward study. J Clin Endocrinol Metab, 79: 1070-1076, 1994.
- Yin, D., Clarke, S.D., Peters, J.L. and Etherton, T.D. Somatotropin-dependent decrease in fatty acid synthase mRNA abundance in 3T3-F442A adipocytes is the result of a decrease in both gene transcription and mRNA stability. Biochem J, 331, 815???820, 1998.
- Teglund, S. et al. Stat5a and Stat5b proteins have essential and nonessential, or redundant, roles in cytokine responses. Cell, 93, 841???850, 1998.
- Deyssig, R., Frisch, H., Blum, W.F., and Waldhor, T. Effect of growth hormone treatment on hormonal parameters, body composition and strength in athletes. Acta Endocrinol (Copenh), Apr;128(4):313-8, 1993.
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