Acute Hormonal Responses Research Articles

The effect of time of day on hormonal responses to resistance exercise

The aim of this study was to examine the acute hormonal responses to resistance training performed in the morning or in the evening. Eighteen active men underwent two lower body resistance exercise (RE) sessions (3 × 10 repetitions, maximum of four exercises) on two occasions (07:00 and 17:00 h). Blood samples were collected in the morning and evening before (BT), after (AT), and 60 min after (60-AT) the RE training session for the determination of testosterone (T) and cortisol (C) concentrations. The Δ-changes of T and C concentrations were calculated as the difference between AT and BT, the difference between 60-AT and BT, as well as the difference between 60-AT and AT. The results showed that T increased from BT to AT and decreased from AT to 60-AT at the two times of testing. However, T was higher in the evening and lower in morning at 60-AT compared with BT. C increased from BT to AT and 60-AT in the evening, and decreased from AT to 60-AT at the two times of testing. Likewise, Δ-changes of T and C concentrations between AT and BT and between 60-AT and BT were higher in the evening than in the morning. In conclusion, training-induced hormonal responses are observed to be greater in the evening than in the morning, which potentially provides a more favorable profile for anabolism.

Acute hormonal responses following different velocities of eccentric exercise

The aim of this study was to compare the acute hormonal responses following two different eccentric exercise velocities. Seventeen healthy, untrained, young women were randomly placed into two groups to perform five sets of six maximal isokinetic eccentric actions at slow (30°s(-1) ) and fast (210°s(-1) ) velocities with 60-s rest between sets. Growth hormone, cortisol, free and total testosterone were assessed by blood samples collected at baseline, immediately postexercise, 5, 15 and 30min following eccentric exercise. Changes in hormonal responses over time were compared between groups, using a mixed model followed by a Tukey's post hoc test. The main findings of the present study were that the slow group showed higher growth hormone values immediately (5·08±2·85ng ml(-1) , P=0·011), 5 (5·54±3·01ng ml(-1) , P=0·004) and 15min (4·30±2·87ng ml(-1) , P=0·021) posteccentric exercise compared with the fast group (1·39±2·41ng ml(-1) , 1·34±1·97ng ml(-1) and 1·24±1·87ng ml(-1) , respectively), and other hormonal responses were not different between groups (P>0·05). In conclusion, slow eccentric exercise velocity enhances more the growth hormone(GH) response than fast eccentric exercise velocity without cortisol and testosterone increases.

Exercise-Induced Insulin-Like Growth Factor I System Concentrations after Training in Women

This study examined the effects of short-term physical training on the acute hormonal response (i.e., growth hormone, total and free insulin-like growth factor I [IGF-I], and IGF binding proteins [IGFBP]-1, IGFBP-2, and IGFBP-3) to resistance exercise (RE) in women. Forty-six women (20.3 ± 0.3 yr, mass = 64.1 ± 7.3 kg, height = 165.7 ± 1.0 cm) were randomly assigned to an endurance training (E), resistance training (R), combined training (R + E), or control (C) group for 8wk. Subjects completed a standardized bout of RE (six sets of back squats at 10 repetition maximum) before and after training. Blood samples were obtained at rest (PRE), after the third set, immediately postexercise (POST), and at 15 min and 30 min after exercise. Acute RE significantly increased (P < 0.05) serum growth hormone (mean ± SD; change from PRE to POST = +10.9 ± 7.5 μg·L-1), total IGF-I (+66.1 ± 25.4 μg·L-1), IGFBP-1 (+2.5 ± 3.1 μg·L-1), IGFBP-2 (+86.0 ± 86.8 μg·L-1), and IGFBP-3 (+0.69 ± 0.25 mg·L-1) concentrations and decreased free IGF-I concentrations (-0.14 ± 0.21 μg·L-1). After 8 wk of training, total IGF-I concentrations were significantly increased (change in POST concentrations from week 0 to week 8 = +82.5 ± 120.8 μg·L-1), and IGFBP-1 concentrations were significantly decreased (-6.7 ± 13.6 μg·L-1) during exercise in groups that participated in resistance training (R and R + E); no significant changes were seen after E or C. Participation in resistance training increased total IGF-I and reduced IGFBP-1 concentrations during acute RE, indicating exercise mode-specific adaptations in the circulating IGF-I system.

Effects of Strongman Training on Salivary Testosterone Levels in a Sample of Trained Men

Strongman exercises consist of multi-joint movements that incorporate large muscle mass groups and impose a substantial amount of neuromuscular stress. The purpose of this study was to examine salivary testosterone responses from 2 novel strongman training (ST) protocols in comparison with an established hypertrophic (H) protocol reported to acutely elevate testosterone levels. Sixteen men (24 ± 4.4 years, 181.2 ± 6.8 cm, and 95.3 ± 20.3 kg) volunteered to participate in this study. Subjects completed 3 protocols designed to ensure equal total volume (sets and repetitions), rest period, and intensity between the groups. Exercise sets were performed to failure. Exercise selection and intensity (3 sets × 10 repetitions at 75% 1 repetition maximum) were chosen as they reflected commonly prescribed resistance exercise protocols recognized to elicit a large acute hormonal response. In each of the protocols, subjects were required to perform 3 sets to muscle failure of 5 different exercises (tire flip, chain drag, farmers walk, keg carry, and atlas stone lift) with a 2-minute rest interval between sets and a 3-minute rest interval between exercises. Saliva samples were collected pre-exercise (PRE), immediate postexercise (PST), and 30 minutes postexercise (30PST). Delta scores indicated a significant difference between PRE and PST testosterone level within each group (p ≤ 0.05), with no significant difference between the groups. Testosterone levels spiked 136% (225.23 ± 148.01 pg·ml(-1)) for the H group, 74% (132.04 ± 98.09 pg·ml(-1)) for the ST group, and 54% (122.10 ± 140.67 pg·ml) for the mixed strongman/hypertrophy (XST) group. A significant difference for testosterone level occurred over time (PST to 30PST) for the H group p ≤ 0.05. In conclusion, ST elicits an acute endocrine response similar to a recognized H protocol when equated for duration and exercise intensity.

Acute Hormonal and Force Responses to Combined Strength and Endurance Loadings in Men and Women: The “Order Effect”

PurposeTo examine acute responses and recovery of serum hormones and muscle force following combined strength (S) and endurance (E) loading sessions in which the order of exercises is reversed (ES vs. SE).MethodsThis cross-over study design included recreationally endurance trained men and women (age 21–45 years, n = 12 men n = 10 women) who performed both loadings. Maximal bilateral isometric strength (MVC), isometric rate of force development (RFD) and serum concentrations of testosterone (T), cortisol (C), growth hormone (GH), insulin-like growth factor 1 (IGF-1), binding protein 3 (IGFBP3) and sex hormone binding globulin (SHBG) were measured during and after both loadings.ResultsBoth of the present combined (ES and SE) loadings led to a greater acute decrease in MVC in men than in women, while RFD was slightly affected only in men. Recovery of MVC and RFD to baseline was complete at 24 h regardless of the order of exercises. In men, neuromuscular fatigue was accompanied by increased C concentrations observed post SE. This was followed by decreased concentrations of T at 24 h and 48 h that were significantly lower than those observed following ES. GH response in men also differed significantly post loadings. In women, only a significant difference in T between ES and SE loadings was observed at post.ConclusionThese observed differences in hormonal responses despite similarities in neuromuscular fatigue in men indicate the presence of an order effect as the body was not fully recovered at 48 h following SE. These findings may be applicable in training prescription in order to optimize specific training adaptations.

Influence of upper-body exercise order on hormonal responses in trained men

The aim of this study was to examine acute hormonal responses after different sequences of an upper-body resistance-exercise session. Twenty men completed 2 sessions (3 sets; 70% 1-repetition maximum; 2 min passive rest between sets) of the same exercises in opposite sequences (larger to smaller vs. smaller to larger muscle-group exercises). Total testosterone (TT), free testosterone (FT), testosterone/cortisol (T/C) ratio, sex-hormone-binding globulin (SHBG), growth hormone (GH), and cortisol (C) concentrations were measured before and immediately after each sequence. The results indicate that the GH concentration increased after both sessions, but the increase was significantly greater (p < 0.05) after the sequence in which larger muscle-group exercises were performed prior to the smaller muscle-group exercises. No differences were observed between sessions for TT, FT, SHBG, C, or the T/C ratio at baseline or immediately after resistance exercise. These results indicate that performing larger muscle-group exercises first in an upper-body resistance-exercise session leads to a significantly greater GH response. This may have been due to the significantly greater exercise volume accomplished. In summary, the findings of this investigation support the common prescriptive recommendation to perform larger-muscle group exercises first during a resistance-exercise session.

The Effects of Soy and Whey Protein Supplementation on Acute Hormonal Responses to Resistance Exercise in Men

Objective: For many resistance-trained men concerns exist regarding the production of estrogen with the consumption of soy protein when training for muscle strength and size. Thus, the purpose of this investigation was to examine the effects of soy and whey protein supplementation on sex hormones following an acute bout of heavy resistance exercise in resistance trained men. Methods: Ten resistance-trained men (age 21.7 ± 2.8 [SD] years; height 175.0 ± 5.4 cm; weight 84.2 ± 9.1 kg) volunteered to participate in an investigation. Utilizing a within subject randomized crossover balanced placebo design, all subjects completed 3 experimental treatment conditions supplementing with whey protein isolate (WPI), soy protein isolate (SPI), and maltodextrin placebo control for 14 days with participants ingesting 20 g of their assigned supplement each morning at approximately the same time each day. Following supplementation, subjects performed an acute heavy resistance exercise test consisting of 6 sets of 10 repetitions in the squat exercise at 80% of the subject's one repetition maximum. Results: This investigation observed lower testosterone responses following supplementation with soy protein in addition to a positive blunted cortisol response with the use of whey protein at some recovery time points. Although sex hormone binding globulin (SHBG) was proposed as a possible mechanism for understanding changes in androgen content, SHBG did not differ between experimental treatments. Importantly, there were no significant differences between groups in changes in estradiol concentrations. Conclusion: Our main findings demonstrate that 14 days of supplementation with soy protein does appear to partially blunt serum testosterone. In addition, whey influences the response of cortisol following an acute bout of resistance exercise by blunting its increase during recovery. Protein supplementation alters the physiological responses to a commonly used exercise modality with some differences due to the type of protein utilized.

Responses of Angiogenic Growth Factors to Exercise, to Hypoxia and to Exercise under Hypoxic Conditions

The purpose of the present study was to compare the acute hormonal response of angiogenic regulators to a short-term hypoxic exposure at different altitudes with and without exercise. 7 subjects participated in 5 experimental trials. 2 times subjects stayed in a sedentary position for 90 min at 2000 m or 4000 m, respectively. The same was carried out again in combination with exercise at the same relative intensity (2 mmol∙L(-1) of lactate). The fifth trial consisted of 90 min exercise at sea level. Venous blood samples were taken under resting conditions, 0 and 180 min after each condition to determine VEGF, EPO, IL-6, IL-8 and IGF-1 serum concentrations. EPO, VEGF, and IL-8 showed increases only, when hypoxia was combined with exercise. IL-6 was increased after exercise, independent of altitude. IGF-1 showed no changes in any intervention. The present study suggests that short term hypoxic exposure combined with low intensity exercise is able to up-regulate angiogenic regulators, which might be beneficial to induce angiogenesis and to improve endurance performance. However, in some cases high altitudes are needed, or it can be speculated that exercise intensity needs to be increased.

Effect of exercise order on endocrine and metabolic responses to concurrent exercise

Despite its popularity, few studies characterize the acute hormonal and metabolic responses to combined endurance and resistance exercise (concurrent exercise, CE). Since exercise order might influence training adaptations, elucidating these acute responses might contribute to optimizing program design. The purpose of this study was to examine the effects of CE order on endocrine and metabolic responses. Nine healthy, concurrently trained males (age = 22.7 ± 1.7 y; mass = 84.8 ± 11.9 kg; height = 176.1 ± 7.4 cm) performed two CE trials: resistance exercise (squat, bench press, lat pulldown: 60% 1‐RM, 4 sets × 10 reps, 90‐s rest intervals) followed by endurance exercise (RE‐EE) and EE (cycling: 80% ventilatory threshold for 30‐min) followed by RE (EE‐RE). Growth hormone, testosterone, cortisol, glucose, lactate (Lac) and free fatty acids were measured prior to CE, between exercise bouts, following CE, and 15, 30, and 60 minutes post‐CE. [Lac] was significantly greater at all post‐CE time points in EE‐RE (AUC = 909 ± 123 mmol•min/L) than RE‐EE (AUC = 777 ± 93 mmol•min/L). Plausibly, enhanced lactate metabolism during EE reduced [Lac] in RE‐EE. No differences were observed between trials for any other variable. Thus, differences in concurrent training adaptations predicated on CE order might not derive from humoral variations. Funding provided by California State University, Fullerton.

Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training

The purpose of this study was to investigate associations between acute exercise-induced hormone responses and adaptations to high intensity resistance training in a large cohort (n = 56) of young men. Acute post-exercise serum growth hormone (GH), free testosterone (fT), insulin-like growth factor (IGF-1) and cortisol responses were determined following an acute intense leg resistance exercise routine at the midpoint of a 12-week resistance exercise training study. Acute hormonal responses were correlated with gains in lean body mass (LBM), muscle fibre cross-sectional area (CSA) and leg press strength. There were no significant correlations between the exercise-induced elevations (area under the curve—AUC) of GH, fT and IGF-1 and gains in LBM or leg press strength. Significant correlations were found for cortisol, usually assumed to be a hormone indicative of catabolic drive, AUC with change in LBM (r = 0.29, P < 0.05) and type II fibre CSA (r = 0.35, P < 0.01) as well as GH AUC and gain in fibre area (type I: r = 0.36, P = 0.006; type II: r = 0.28, P = 0.04, but not lean mass). No correlations with strength were observed. We report that the acute exercise-induced systemic hormonal responses of cortisol and GH are weakly correlated with resistance training-induced changes in fibre CSA and LBM (cortisol only), but not with changes in strength.Electronic supplementary materialThe online version of this article (doi:10.1007/s00421-011-2246-z) contains supplementary material, which is available to authorized users.

Retrospective Analysis Of Resistance Training-induced Strength And Hypertrophy: Separating The Wheat From The Hormone Chaff

PURPOSE: To investigate associations between purportedly anabolic acute exercise-induced hormone responses and adaptations to resistance training in a cohort with normally distributed training-induced adaptations. METHODS: Acute post-exercise serum growth hormone (GH), free testosterone (fT), cortisol, and insulin-like growth factor (IGF-1) responses were determined at the midpoint of a 12-wk resistance exercise program conducted previously. Correlations of hormonal responses with gains in lean body mass (LBM), muscle fiber cross-sectional area (CSA) and leg press strength were investigated. Dietary factors were combined with hormonal responses as independent variables in multiple regression analysis of adaptations to resistance training. RESULTS: There were no significant correlations between the exercise-induced elevation (area under the curve_AUC) of GH, fT and IGF-1 and gains in LBM or leg press strength. Significant correlations were found for cortisol AUC with change in LBM (r = 0.29, P < 0.05) and type II fiber CSA (r = 0.35, P < 0.01) as well as GH AUC and gain in fiber area (type I: r=0.36, P=0.006; type II: r= 0.28, P=0.04). Multiple regression analysis showed that increments in daily dietary protein intake and the daily consumption of dairy, but no acute hormonal response, were significant predictors in a model of change in LBM and type II fiber area. CONCLUSION: A significant association existed between GH and cortisol and fiber hypertrophy, but there was no association between any hormones and strength gains. Multiple regression analysis revealed an important role of increasing dietary protein and servings of dairy in promoting training-induced gains in LBM and fiber hypertrophy. In contrast, post-exercise elevations in endogenous hormones were relatively impotent in their predictive value for resistance training-induced hypertrophy calling into question persistent referrals, which are frequently erroneously based on pharmacological intervention studies, to their anabolic capacity. Supported by NSERC and CIHR

Effects of Variable External Resistance Exercises on Acute Neuromuscular and Hormonal Responses

Effects of Variable External Resistance Exercises on Acute Neuromuscular and Hormonal Responses

Differential Effect of Aging on Acute Hormonal Response to Low-Volume Resistance Exercise

Age associated decrease in skeletal muscle mass and function (sarcopenia) leads to an increased risk of fall, fracture, and bedridden. Resistance exercise has been shown to be a useful intervention to increase skeletal muscle mass and strength; however, aging seems to blunt the acute hormonal response to high-intensity, high-volume resistance exercise. PURPOSE: To investigate the acute effect of a traditional resistance exercise protocol (i.e. low-volume and high-intensity) on hormonal responses in healthy young and older men. METHODS: Fourteen old men (68 ± 6.8 yrs, 64 ± 4kg) and eight young men (23 ± 1.3 yrs, 68 ± 8kg) were recruited for the study. Before the study, all subjects were assessed for muscle cross sectional area at mid-thigh, maximal knee extension and flexion strength. After taking a baseline blood sample, each subject performed a bout of resistance exercise consisting of bilateral knee extension and flexion at 70% 1-RM (3 sets of 10 reps, 3 min rest between sets). Blood samples were drawn immediately after and following exercise up to 3 hours. Blood samples were analyzed for metabolites and hormones. RESULTS: Although muscle CSA of knee extensor and flexor muscles as well as maximal isometric knee extension and flexion strength were significantly higher in young men as compared to older men(P<0.05), no significant difference in specific strength was observed between young and older subjects (3.24 ± 0.14 and 3.09 ± 0.15 Nm/cm2, P>0.1). In response to a bout of resistance exercise, GH increased significantly in young men, whereas no significant change was observed for older men (11.4 ± 6.0 and 1.7 ± 0.6 ng/ml for young and old; P<0.05). Although no significant change in testosterone or cortisol concentration was observed in either group in response to resistance exercise (P>0.1), hormonal concentrations were significantly suppressed in older men throughout the experiment (P<0.05). CONCLUSION: Although specific strength was well matched, hormonal responses to conventional low-volume, high-intensity resistance exercise protocol were significantly suppressed in older men as compared to those of young men. Further training study is warranted to investigate the relationship between age associated decline in hormonal response and capacity of muscle hypertrophy in older individuals.

Acute Hormone Responses to a Bouldering Workout in Young Men

Acute Hormone Responses to a Bouldering Workout in Young Men

Resistance Exercise Induced Acute Hormonal Responses and Chronic Adaptations: A Null Field?

Resistance Exercise Induced Acute Hormonal Responses and Chronic Adaptations: A Null Field?

Acute Endocrine Responses to Maximal Velocity Barbell Squats with Three Different Loads

Acute Endocrine Responses to Maximal Velocity Barbell Squats with Three Different Loads

Hormonal response to lipid and carbohydrate meals during the acute postprandial period

BackgroundOptimizing the hormonal environment during the postprandial period in favor of increased anabolism is of interest to many active individuals. Data are conflicting regarding the acute hormonal response to high fat and high carbohydrate feedings. Moreover, to our knowledge, no studies have compared the acute hormonal response to ingestion of lipid and carbohydrate meals of different size.MethodsWe compared the hormonal response to lipid and carbohydrate meals of different caloric content during the acute postprandial period. Nine healthy men (22 ± 2 years) consumed in a random order, cross-over design one of four meals/beverages during the morning hours in a rested and fasted state: dextrose at 75 g (300 kcals), dextrose at 150 g (600 kcals), lipid at 33 g (300 kcals), lipid at 66 g (600 kcals). Blood samples were collected Pre meal, and at 0.5 hr, 1 hr, 2 hr, and 3 hr post meal. Samples were assayed for testosterone, cortisol, and insulin using ELISA techniques. Area under the curve (AUC) was calculated for each variable, and a 4 × 5 ANOVA was used to further analyze data.ResultsA meal × time effect (p = 0.0003) was noted for insulin, with values highest for the dextrose meals at the 0.5 hr and 1 hr times, and relatively unaffected by the lipid meals. No interaction (p = 0.98) or meal (p = 0.39) effect was noted for testosterone, nor was an interaction (p = 0.99) or meal (p = 0.65) effect noted for cortisol. However, a time effect was noted for both testosterone (p = 0.04) and cortisol (p < 0.0001), with values decreasing during the postprandial period. An AUC effect was noted for insulin (p = 0.001), with values higher for the dextrose meals compared to the lipid meals (p < 0.05). No AUC effect was noted for testosterone (p = 0.85) or cortisol (p = 0.84).ConclusionsThese data indicate that 1) little difference is noted in serum testosterone or cortisol during the acute postprandial period when healthy men consume lipid and dextrose meals of different size; 2) Both testosterone and cortisol experience a drop during the acute postprandial period, which is similar to what is expected based on the normal diurnal variation--feeding with lipid or dextrose meals does not appear to alter this pattern; 3) dextrose meals of either 75 g or 150 g result in a significant increase in serum insulin, in particular at 0.5 hr and 1 hr post-ingestion; 4) lipid meals have little impact on serum insulin.

Neuromuscular and Hormonal Responses to Constant and Variable Resistance Loadings

The purpose of this study was to investigate the acute effects of constant and variable resistance exercise on neuromuscular and endocrine responses during maximal strength and hypertrophic loadings. Thirteen young men (age = 28.4 ± 3.7 yr) took part in four loadings (maximal strength and hypertrophic loadings using both constant and variable resistance) in a counterbalanced order. Maximal strength loadings consisted of 15 sets of one repetition at 100% one-repetition maximum, and hypertrophic loadings consisted of five sets of 10 repetitions (initial load of 80% one-repetition maximum). Preloading, immediately postloading, 15 min postloading, and 30 min postloading tests consisted of maximal bilateral isometric leg press, venous blood samples (analyzed for total testosterone, growth hormone, and cortisol), and fingertip blood lactate samples. Concentric force and vastus lateralis, vastus medialis, rectus femoris, and biceps femoris EMG was recorded throughout each loading protocol and analyzed over 20° segments. Force and quadriceps EMG was greater from 120° to 180° knee angle (P < 0.05) during variable resistance hypertrophic loadings. Larger increases in concentric quadriceps muscle activation and slower recovery in isometric force and muscle activation were observed during variable resistance hypertrophic loadings. Preloading to postloading serum total testosterone, growth hormone, and cortisol concentration increased during variable resistance hypertrophic loading, whereas during constant resistance loadings, only growth hormone increased (P = 0.051). During 30 min postloading, growth hormone and cortisol concentrations remained elevated after both hypertrophic loadings. A greater level of neuromuscular fatigue and larger responses in serum hormone concentrations occurred after hypertrophic variable resistance loading. These findings indicate greater fatigability during variable resistance loading and that this fatigability influences acute hormonal responses.

Effects of acid–base balance and high or low intensity exercise on VEGF and bFGF

The purpose of the present study was to compare the acute hormonal response to a short-term high-intensity training (HIT) versus a high-volume endurance training (HVT) and to investigate the effects of acid-base status on cytokines involved in angiogenesis (VEGF and bFGF). Eleven subjects participated in three experimental trials. Two times subjects performed four 30-s "all-out" exercise bouts on a cycle ergometer separated by 5-min rest each, at which subjects either received bicarbonate (HIT (B)) or a placebo (HIT (P)) before the exercise. The third exercise trail consisted of a constant load exercise for 1 h at 50% peak power output (PPO). Venous blood samples were taken under resting conditions, 10, 60, and 240 min after each exercise condition to determine VEGF and bFGF serum concentrations. Capillary blood samples were taken to determine lactate concentrations and blood gas parameters. Mean pH values were significantly higher during HIT (B) compared to HIT (P). Serum VEGF concentration was significantly increased 10-min post-exercise in both HIT interventions. HVT showed no significant effects on VEGF levels. The diminished acidosis during HIT (B) had no effects on the VEGF response. There were no significant changes in bFGF in response to HIT or HVT. The present study suggests that HIT is a stimulus for exercise-induced VEGF secretion. These findings might be relevant for the arrangement of training, due to the fact that most of the training is often performed at low intensities possibly leading to an insufficient stimulus for VEGF secretion and angiogenesis.

Testosterone Physiology in Resistance Exercise and Training

Testosterone is one of the most potent naturally secreted androgenic-anabolic hormones, and its biological effects include promotion of muscle growth. In muscle, testosterone stimulates protein synthesis (anabolic effect) and inhibits protein degradation (anti-catabolic effect); combined, these effects account for the promotion of muscle hypertrophy by testosterone. These physiological signals from testosterone are modulated through the interaction of testosterone with the intracellular androgen receptor (AR). Testosterone is important for the desired adaptations to resistance exercise and training; in fact, testosterone is considered the major promoter of muscle growth and subsequent increase in muscle strength in response to resistance training in men. The acute endocrine response to a bout of heavy resistance exercise generally includes increased secretion of various catabolic (breakdown-related) and anabolic (growth-related) hormones including testosterone. The response of testosterone and AR to resistance exercise is largely determined by upper regulatory elements including the acute exercise programme variable domains, sex and age. In general, testosterone concentration is elevated directly following heavy resistance exercise in men. Findings on the testosterone response in women are equivocal with both increases and no changes observed in response to a bout of heavy resistance exercise. Age also significantly affects circulating testosterone concentrations. Until puberty, children do not experience an acute increase in testosterone from a bout of resistance exercise; after puberty some acute increases in testosterone from resistance exercise can be found in boys but not in girls. Aging beyond 35-40 years is associated with a 1-3% decline per year in circulating testosterone concentration in men; this decline eventually results in the condition known as andropause. Similarly, aging results in a reduced acute testosterone response to resistance exercise in men. In women, circulating testosterone concentration also gradually declines until menopause, after which a drastic reduction is found. In summary, testosterone is an important modulator of muscle mass in both men and women and acute increases in testosterone can be induced by resistance exercise. In general, the variables within the acute programme variable domains must be selected such that the resistance exercise session contains high volume and metabolic demand in order to induce an acute testosterone response.