CHO-induced Blunting of Cortisol Response to Weightlifting Exercise in Resistance-Trained Older Men

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1 European Journal of Sport Science, vol. 3, issue 2 Modification of Cortisol Response / by Human Kinetics Publishers and the European College of Sport Science CHO-induced Blunting of Cortisol Response to Weightlifting Exercise in Resistance-Trained Older Men Kyle M. Tarpenning, Steven A. Hawkins, and Robert A. Wiswell With weightlifting exercise, the attenuation of the cortisol response is a major factor by which an increase in muscle mass occurs. A reduction in the exerciseinduced cortisol response has been observed in younger but not older men, suggesting that under normal circumstances older men may lack the mechanism(s) to down-regulate cortisol activity. The purpose of this study was to determine if CHO consumption during a weightlifting exercise bout could modify the cortisol response to exercise. Five resistance-trained older men (62.8 ± 1.5 y) completed (on 2 occasions) a 9-station weightlifting protocol (3 sets, 10 repetitions, 75% of 1RM). One session included the ingestion of a placebo beverage, and the other, a CHO solution. Blood samples were collected prior to, during, and after the exercise bout. With the placebo, plasma glucose levels remained unchanged, while plasma cortisol levels were significantly elevated (from 284 ± 49.7 nmol/l to 474 ± 130 nmol/l). In contrast, CHO consumption resulted in significantly higher plasma glucose levels (from 5.55 ±.48 to 7.63 ± 0.53 mmol) and a blunted cortisol response. These findings indicate that the stimulatory effect of exercise on cortisol secretion can be overcome by CHO administration. Key Words: aging, hormonal response, plasma glucose, sarcopenia, growth factors Key Points: As with younger men, the stimulatory effect of exercise on cortisol secretion can be overcome by CHO administration in older men. Previous research from our laboratory has observed a correlation between the attenuation of the cortisol response and gains in muscle size. K.M. Tarpenning is with the Human Movement Studies Unit at Charles Sturt University, Bathurst NSW, 2795, Australia, and the Department of Exercise Sciences at the University of Southern California, Los Angeles, CA. S.A. Hawkins is with the Department of Kinesiology and Nutritional Science at California State University Los Angeles, Los Angeles, CA. R.A. Wiswell is with the Department Biokinesiology and Physical Therapy at the University of Southern California. 1

2 2 / Tarpenning, Hawkins, and Wiswell Introduction In response to a moderately high intensity weightlifting exercise bout for younger men (20 30 y), insulin secretion is normally unchanged (7, 16) while serum testosterone (12, 16), growth hormone (12, 18), and insulin-like growth factor (IGF)-I concentrations (16) increase above resting levels. In addition, the cortisol concentration (12, 14) has been shown to rise above that occurring at rest. Yet, these hormonal responses are associated with an acute decrease in protein synthesis (6, 25), an increase in protein degradation (4, 24), and a transient negative nitrogen balance (19) during and, for several hours, after an exercise bout. This would suggest that at least during the early stages of recovery from weightlifting exercise, catabolic events predominate in determining the net protein turnover status. Research (10, 19) has also demonstrated that formerly sedentary individuals show a negative nitrogen balance during the first several weeks after initiating a weight-training program. This negative balance is primarily due to an increase in protein degradation rather than a decrease in protein synthesis (4, 13, 24). It has been reported that elevated cortisol levels are the primary factor for stimulating the exercise-induced increases in muscle protein degradation (9). However, Kraemer et al. (17) reported that with younger men, the cortisol response to weightlifting exercise tends to increase less as training progresses, while testosterone, growth hormone, and IGF-I responses remain unchanged. Yet, this group experienced a 10.1 ± 3.7% increase in thigh muscle cross-sectional area. This finding would suggest that the modification of the cortisol response that is to say, the attenuation of cortisol release is a major factor by which the physiological adaptations in muscle occur: that of enhancing nitrogen retention and promoting muscle growth. Previous research (29) from our laboratory has demonstrated that carbohydrate (CHO) administration during weightlifting exercise can modify the acute cortisol response to exercise in younger men. Weightlifting with CHO ingestion resulted in a non-significant change in plasma cortisol concentration both during and after the exercise bout. This response is in contrast to significantly elevated cortisol levels (99%) occurring with weightlifting exercise alone. This finding demonstrated that the stimulatory effect of weightlifting exercise on cortisol can be overcome by CHO consumption. Additional research on this phenomenon showed that progressive resistance weight training performed with CHO consumption continued to blunt the cortisol response to exercise throughout 12 weeks of training. This altered response was associated with significantly greater gains in both type I (r = 0.86, p <.01) and type II (r = 0.72, p <.05) muscle fiber cross-sectional area compared to progressive resistance weight training exercise alone. These findings indicate that with weight training exercise, the chronic modification of the acute cortisol response associated with CHO ingestion can positively impact the skeletal muscle hypertrophic adaptation to training. Normal aging is accompanied by numerous alterations in neuroendocrine function (for review, see 27). Aging is also associated with reductions in muscle mass (i.e., sarcopenia), and subsequent decrements in strength and functional ability (11). Although a number of investigations (1, 8, 23) have reported the ability of older men to gain strength and increase muscle size consequent to a resistance training regimen, the extent of these adaptations appear to be less than those reported for younger men (20, 28). In a study examining the effects of heavy-resistance training on hormonal response patterns in younger and older men, Kraemer et al.

3 Modification of Cortisol Response / 3 (17) reported that even though the exercise stimulus was identical, a reduction in the exercise-induced cortisol response (with training) was observed in younger but not older men. No changes in the testosterone or growth hormone response were noted. This would suggest that under normal circumstances, older men may lack the mechanism(s) to down-regulate cortisol activity. Older individuals may not be able to modulate the hormonal system to respond in the same manner as younger individuals and therefore may not be able to evoke the same hormone-mediated adjustments. At present, it is not known whether these differences are due to insurmountable sarcopenia of the musculature due to prolonged disuse or deconditioning, changes in muscle tissue functional properties that limit its ability to stimulate growth, changes in hormonal action, and/or sensitivity that diminishes the tissue s ability to respond and adapt to an exercise stimulus, or some other age-related constraint. Therefore, the purpose of this study was to examine the influence of ingesting a CHO solution during weightlifting exercise on the acute hormonal response in a group of resistance-trained, older men. Specifically, the aim of this study was to determine if CHO consumption during a bout of weightlifting exercise could attenuate the acute cortisol response to exercise as is reported to occur in younger individuals (29). The intent was to bring about a hormonal environment associated with a reduction in protein degradation (5), and greater gains in muscle size and strength than weightlifting exercise alone (29), as reported to occur in younger men. Subjects Methods With approval from the Institutional Review Board of the University of Southern California, 5 apparently healthy older men (62.8 ± 1.5 y) volunteered to participate in the study. The anthropometric characteristics of the subjects are displayed in Table 1. After explanation of the study protocol and requirements, written informed consent was obtained before testing began. All subjects had some recreational weightlifting experience (having participated in a regular weight-training program for a minimum of 1 year prior to testing), but none were competitive lifters. All subjects were reported to be non-steroid users and had no history of any endocrine disorders, glucose intolerance, or chronic disease that might influence their responsiveness to strenuous exercise. Exercise Conditions On an initial visit to the laboratory, each subject was tested for maximal strength on Universal (Universal Gym Equipment, Inc.) equipment for the nine exercises utilized in the protocol. These exercises included: bench press, seated rows, shoulder press, lat pull downs, triceps extensions, biceps curls, leg press, leg extensions, and leg curls. One repetition maximum (1RM) was determined as the maximal amount of weight the individual could move through the full range of motion only one time without change in body position, other than that dictated by the specific exercise motion. No less than 1 week later, the subjects returned to the laboratory for the first of two exercise sessions. Following a 4-hour fast, the subjects completed (on two occasions separated by 1 week) the weightlifting routine (in the order previously

4 4 / Tarpenning, Hawkins, and Wiswell listed), performing 3 sets of 10 repetitions of each exercise at 75% of 1RM. One minute of rest was allowed between each set, and 2 min of rest between exercises. Randomly assigned, one session included the ingestion of a non-caloric placebo beverage, and the other included the ingestion of a 6% CHO solution (Gatorade) each at a quantity of 8.5 ml per kg of body weight. The total volume of fluid was divided by 28 servings, allowing for between 22.5 and 30 ml (1.5 and 2 tbs.) depending on body size, to be ingested between each set of exercise. All exercise sessions were performed between 1500 and 1600 h to minimize the influence of diurnal variations on hormone release. Blood Sampling Prior to the exercise sessions, the subjects had an indwelling angiocatheter (20GA, 1IN) inserted into an antecubital arm vein. Five-milliliter blood samples were drawn just prior to exercising, after the third, sixth, and ninth exercise (approximately every 15 min), and 10 and 30 min post exercise. One milliliter of saline solution was injected into the catheter between draws in order to keep the line patent. Blood samples were collected in Vacutainer tubes containing lithium heparin, gently inverted 5 times, and then centrifuged for 10 min at 3000 rpm. The plasma was decanted into plastic storage containers and frozen at 20 C until analysis. Blood Analysis The plasma was defrosted and mixed gently via inversion. Plasma glucose concentrations were determined spectrophotometrically using a Yellow Springs Instrument (YSI) model 23L analyzer. Plasma cortisol and free testosterone concentrations were determined by radioammunoassay ( 125 I) using commercial kits purchased from Diagnostics Products Corp. (Los Angeles, CA). Statistical Analysis All data were entered into a personal computer, and analysis was performed using the statistical software package Statistical Package for Social Sciences (SPSS 7.0, Chicago, IL, USA). Analysis included standard descriptive statistics and analysis of variance (ANOVA) for repeated measures to examine the characteristics of the two trials at each sampling point. When differences were observed, a Scheffe post hoc analysis was performed to identify the source of differences. Significance was set a priori at p.05 level. Throughout, the values are expressed as mean ± SD. Results Table 1 displays the anthropometric characteristics of the subjects and the 1RM data from the nine exercises used in the protocol. For this group of resistance-trained older men (62.8 ± 1.5 yr), height and body mass measures are consistent with normative standards for persons within their age range (60 65 years). The 1RM values were, on average, about 20% less than the 1RM values recorded for untrained year olds completing an identical protocol (29). With the ingestion of the placebo beverage, the plasma glucose concentration was not significantly (p <.05) changed during exercise, or up to 30 min after, from

5 Modification of Cortisol Response / 5 Table 1 Subject Anthropometric Characteristics, and 1RM Data From the Nine Exercises Used in the Protocol (Mean ± SD; N = 5) Variable Mean SD Age (yr) Height (cm) Body mass (kg) BMI (kg m 1 ) Bench press (kg) Seated row (kg) Shoulder press (kg) Lat pulldowns (kg) Triceps extensions (kg) Biceps curls (kg) Leg press (kg) Leg extension (kg) Leg curl (kg) the pre-exercise baseline value of 5.45 ± 0.24 mmol/l. Conversely, CHO consumption during the exercise bout resulted in significantly higher plasma glucose levels (37%) compared to the baseline concentration. This increase in plasma glucose occurred within 30 min of initiating the exercise period, and peaked approximately 30 min post-exercise (7.63 ± 0.53 mmol/l). Further, CHO ingestion resulted in significantly higher glucose levels than that occurring with the placebo control trial, beginning within 15 min of commencing the exercise and remaining for at least 30 min after (Figure 1). Coinciding with the placebo control trial, plasma cortisol levels were significantly elevated above the baseline level of 284 ± 50 nmol/l. The increase in cortisol concentration occurred within 30 min after the initiation of the exercise bout, peaked approximately 10 min post exercise at 474 ± 130 nmol/l, and remained significantly elevated for at least 30 min during the recovery period. However, consequent to the CHO intervention, the cortisol response was blunted, resulting in a non-significant change from the pre-exercise baseline of 342 ± 97 nmol/l, both during the exercise bout and throughout the recovery period. Further, this blunted response was associated with significantly lower plasma cortisol levels compared to the placebo control trial, beginning within 30 min of the start of exercise and remaining for 30 min after (Figure 2). Neither the placebo control, nor CHO treatment trials, altered the plasma-free testosterone levels. Free testosterone concentration was not significantly changed from the pre-exercise values of 55.8 and 52.0 pmol/l for the placebo and CHO interventions, respectively (Figure 3).

6 6 / Tarpenning, Hawkins, and Wiswell Figure 1 Plasma glucose concentration before, during, and after weightlifting exercise. *Significantly different (p <.05) from pre-exercise value. Figure 2 Plasma cortisol concentration before, during, and after weightlifting exercise. *Significantly different (p <.05) from pre-exercise value.

7 Modification of Cortisol Response / 7 Figure 3 Plasma-free testosterone concentration before, during, and after weightlifting exercise. *Significantly different (p <.05) from pre-exercise value. Discussion It has been reported (17, 28) that early-phase adaptations associated with heavyresistance training include a reduction in the exercise-induced cortisol response. However, Kraemer et al. (17) qualified this position, reporting that this occurrence was observed in younger, but not older men. This would suggest that under normal circumstances, older men may lack the mechanism(s) to downregulate cortisol activity. Previous research has demonstrated that with younger subjects (20 30 y), CHO supplementation during protocols utilizing endurance (2, 22) and weightlifting (29) exercise can attenuate the cortisol response throughout the exercise trial. The major finding of the present investigation was that, like that occurring with a companion study using younger men (29), the ingestion of a CHO solution during a weightlifting exercise bout blunted the cortisol response to exercise for this group of older (resistance-trained) men, resulting in a non-significant change. This response is in contrast to significantly elevated cortisol levels occurring with weightlifting exercise alone. This finding indicates that as with younger men, the stimulatory effect of weightlifting exercise on cortisol secretion can be overcome by CHO administration. The finding also suggests that CHO consumption during the exercise bout can modify the acute cortisol response to exercise to promote a hormonal adjustment observed following 10 weeks of training in younger but not older men (17). In response to a moderately high intensity weightlifting exercise bout, free and total serum testosterone concentrations have been shown to be elevated above that occurring at rest (12, 17). In the present investigation, however, the testosterone concentration did not change (with either the placebo control or CHO treatment) during or after the exercise bout from the pre-exercise level. The explanation for this result may be inferred from the findings of Chandler et al. (3), who reported that,

8 8 / Tarpenning, Hawkins, and Wiswell with weightlifting exercise, the exercise-induced elevations in testosterone were overcome by carbohydrate administration that is to say, CHO supplementation caused a significant decline in testosterone concentration. The decline in testosterone, however, was not associated with a reduction in luteinizing hormone. This finding provided indirect evidence that the decrease in plasma testosterone was due to an increased rate of clearance rather than a reduced rate of secretion. Thus, dietary supplementation during exercise can affect the hormonal state of the body including a decrease in circulating levels of testosterone. While the markers that demonstrate this phenomenon were not measured in the present investigation, this mechanism could have theoretically contributed to the response patterns observed. The steroid hormone cortisol is an important hormone that assists in maintaining blood glucose homeostasis. Under the influence of cortisol, blood glucose levels tend to be elevated. Because of this gluco-regulatory action, it was hypothesized that if an individual ingested a CHO solution while exercising, the exogenous glucose load would elevate blood glucose levels. In turn, the elevated blood glucose level would inhibit the stimulus for the adrenal cortex to secrete cortisol to catabolize cellular protein for gluconeogenic purposes. In the present experiment, the cortisol response during and after the exercise bout followed a pattern somewhat counter to that of glucose. When glucose levels remained unchanged, cortisol concentration increased, and when the glucose levels were elevated, the cortisol concentration remained unchanged. Weightlifting exercise alone resulted in a significant increase (67%) in plasma cortisol levels. The time of peak cortisol concentration corresponded with a non-significant increase in plasma glucose levels. This finding is consistent with the companion study completed with younger men (29). Conversely, exercise performed in conjunction with CHO consumption resulted in a blunted cortisol response, resulting in a non-significant change. This occurrence corresponded with a significant increase of 37% in plasma glucose levels. Again, this finding is consistent with the companion results observed with the younger men (29). The results from previous studies suggest that older individuals may not be able to modulate the hormonal system to the same degree as younger individuals and therefore may not be able to elicit the same hormone-mediated adjustments to respond to a physical stress or adapt to a chronic workload. In a study examining the effects of heavy-resistance training on hormonal response patterns in younger and older men, Kraemer et al. (17) reported that the ability of younger men to elicit a greater relative hypertrophic response in 10 weeks of training appears to be associated with the differences in the exercise-induced adaptational patterns of the hormones. This was most evident by the observation that cortisol secretion was downregulated. That is to say, there was an attenuation in the response of cortisol to the exercise stress, while testosterone, growth hormone, and IGF-I responses remained unchanged. A reduction in the cortisol response, and a reduction in cortisol-induced protein degradation is thought to provide a mechanism by which protein accretion occurs that of stimulating muscle growth by suppressing muscle breakdown (5, 15). The results of the present investigation demonstrate that CHO consumption during the exercise bout can modify the acute cortisol response to exercise, thereby mimicking the adaptation to 10 weeks of resistance training observed in younger but not older men (17). While the biochemical evidence identifying the mechanism(s) and kinetics by which this phenomenon regulates skeletal muscle growth are yet to

9 Modification of Cortisol Response / 9 be elucidated, previous research from our laboratory (29) has observed a correlation between the attenuation of the cortisol response and gains in muscle size (type I and type II muscle fiber cross-sectional area). In conclusion, the results of the present study demonstrate that the ingestion of a CHO solution during a weightlifting exercise bout can attenuate the cortisol response to exercise in older men. Further, this CHO-induced modification can promote a hormonal adjustment observed in younger but not older men (17) an adjustment associated with greater gains in muscle size and strength than weightlifting exercise alone (29). While normal aging is associated with alterations in neuroendocrine function (27) as well as reductions in muscle mass and subsequent decrements in strength and functional limitations in activities of daily living (11), CHO consumption during weight training exercise may modulate the well-documented decline in neuroendocrine function and may allow older individuals to maintain, or at least partially off-set, the diminishments in physiological capacity normally observed. References 1. Aniansson A, Gustufsson E Physical training in elderly men with special reference to quadriceps strength and morphology. Clin Physiol 1: Burgess WA, Davis JM, Bartoli WP, Woods JA Failure of low dose carbohydrate feeding to attenuate glucoregulatory hormone responses and improve endurance performance. Int J Sport Nutr 1: Chandler RM, Byrne HK, Patterson JG, Ivy JL Dietary supplemts affect the anabolic hormones after weight-training exercise. J Appl Physiol 76: Dohm GL, Kasperek GJ, Tapscott EB, Beecher GR Effect of exercise on synthesis and degradation of muscle protein. Biochem J 188: Doerr P, Pirke KM Cortisol-induced suppression of plasma testosterone in normal adult males. J Clin Endocrin Metabol. 43: Dohm GL, Williams RT, Kasperek GJ, van Rij AM Increased excretion of urea and N-methylhistadine by rats and humans after a bout of exercise. J Appl Physiol 52: Fahey TD, Hoffman K The effects of intermittent liquid meal feeding on selected hormones and substrates during intense exercise. Int J Sports Med 3: Frontera WR, Merideth CN, O Riley KP, Knuttgen HG, Evans W Strength conditioning in older men: skeletal muscle hypertrophy and improved function. J Appl Physiol 64: Goldberg AL, Goodman HM Relationship between cortisone and muscle work in determining muscle size. J Physiol 200: Gontzea I, Sutzescu R, Dumitrache S Influence of adaptation of physical effort on nitrogen balance in man. Nutr Rep Int 11: Hakkinen K, Kraemer WJ, Kallinen M, Linnamo V, Pastinen UM, Newton RU Bilateral and unilateral neuromuscular function and muscle cross-sectional area in middleaged and elderly men and women. J Gerontol Series A-Bio Sci Med Sci 51:B Hakkinen K, Pakarinen A Acute hormonal responses to two different fatiguing heavy-resistance protocols in male athletes. J Appl Physiol 74: Hickson J, Hinkelmann K Exercise and protein intake effects on urinary 3- methylhistadine excretion. Am J Clin Nutr 41:

10 10 / Tarpenning, Hawkins, and Wiswell 14. Kraemer WJ, Dziados JE, Marchitelli LJ, Gordon SE, Harman EA, Mello R, Fleck SJ, Fryman PN, Triplett NT Effects of different heavy-resistance exercise protocols on plasma β-endorphin concentrations. J Appl Physiol 74: Kraemer WJ, Fleck SJ, Evans WJ Strength and power training: physiological mechanisms of adaptation. In: Holloszy JO, editor. Exercise and sport science reviews. Baltimore, MD: Williams & Wilkins. vol. 24, p Kraemer WJ, Gordon SE, Fleck SJ, Marchitelli LJ, Mello R, Dziados JE, Friedl K, Herman E, Maresh C, Fry AC Endogenous anabolic hormonal and growth factor responses to heavy resistance exercise in males and females. Int J Sports Med 12: Kraemer WJ, Hakkinen K, Newton RU, Nindl BC, Volek JS, McCormick M, Gotshalk LA, Gordon SE, Fleck SJ, Campbell WW, Putukian M, Evans WJ Effects of heavy-resistance training on hormonal response patterns in younger vs. older men. J Appl Physiol 87: Kraemer WJ, Marchitelli L, Gordon SE, Harman E, Dziados JE, Mello R, Frykman P, McCurry D, Fleck SJ Hormonal and growth factor responses to heavy resistance exercise protocols. J Appl Physiol 69: Lemon PW, Tarnopolsky MA, MacDougall JD, Atkinson SA Protein requirements and muscle mass/strength changes during intensive training in novice body builders. J Appl Physiol 73: MacDougall JD, Sale DG, Moroz JR, Elder GCB, Sutton JR Howard H Mitochondrial volume density in human skeletal muscle following heavy resistance training. Med Sci Sports 11: Millard DJ, Bates PC, Brown JG, Cox M, Giuglino R, Jepson M, Pell J Role of thyroid, insulin, and corticosteroid hormones in the physiological regulation of proteolysis in muscle. Progress in Clinical and Biological Research 180: Mitchell JB, Pizza FX, Paquet A, Davis BJ, Forrest MB, Braun WA Influence of carbohydrate status on immune responses before and after endurance exercise. J Appl Physiol 84: Moritoni T, DeVries H Neural factors versus hypertrophy in the time course of muscle strength gain. Am J Phys Med 58: Pivarnik JM, Hickson Jr JF, Wolinsky I Urinary 3-methylhistadine excretion increases with repeated weight training exercise. Med Sci Sports Exerc 21: Rennie MJ, Edwards RHT, Davies CTM, Krywawych S, Halliday D, Waterlow JC, Millard DJ Protein and amino acid turnover during and after exercise. Biochem Soc Trans 8: Seene T, Viru A The catabolic effect of glucocorticoids on different types of skeletal muscle fibers and its dependence upon muscle activity and interaction with anabolic steroids. J Steroid Biochem 16: Sonntag WE Hormone secretion and action in aging animals and man. Rev Biol Res Aging 3: Staron RS, Karaponda DL, Kraemer WJ, Fry AC, Gordon SE, Falkel JE, agerman FC, Hikida RS Skeletal muscle adaptations during early phase of heavy-resistance training in men and women. J Appl Physiol 76: Tarpenning KM, Wiswell RA, Hawkins SA Marcell TJ Influence of weight training exercise and modification of hormonal response on skeletal muscle growth. J Sci Med Sport 4:

11 Modification of Cortisol Response / 11 About the Authors Kyle M. Tarpenning earned his PhD in Exercise Physiology from the University of Southern California in His research interests are in identifying the mechanism(s) by which hormonal events and resistance exercise regulate skeletal muscle growth. Tarpenning is currently an Assistant Professor at Charles Sturt University in Bathurst, NSW Australia. Steven A. Hawkins earned his PhD in Exercise Physiology from the University of Southern California in His research interests are in exercise and aging, and exercise and bone. Currently, Hawkins is an Assistant Professor at California State University Los Angeles. Robert A. Wiswell earned his PhD in Exercise Physiology from the University of Southern California in Wiswell is the principle investigator of an ongoing (since 1986) 20-year longitudinal study on over 200 master athletes at USC. Currently, Wiswell is an Associate Professor at the USC Health Science campus.