Resistance exercise has been shown to elicit a significant acute hormonal response. It appears that this acute response is more critical to tissue growth and remodelling than chronic changes in resting hormonal concentrations, as many studies have not shown a significant change during resistance training despite increases in muscle strength and hypertrophy. Anabolic hormones such as testosterone and the superfamily of growth hormones (GH) have been shown to be elevated during 15-30 minutes of post-resistance exercise providing an adequate stimulus is present. Protocols high in volume, moderate to high in intensity, using short rest intervals and stressing a large muscle mass, tend to produce the greatest acute hormonal elevations (e.g. testosterone, GH and the catabolic hormone cortisol) compared with low-volume, high-intensity protocols using long rest intervals. Other anabolic hormones such as insulin and insulin-like growth factor-1 (IGF-1) are critical to skeletal muscle growth. Insulin is regulated by blood glucose and amino acid levels. However, circulating IGF-1 elevations have been reported following resistance exercise presumably in response to GH-stimulated hepatic secretion. Recent evidence indicates that muscle isoforms of IGF-1 may play a substantial role in tissue remodelling via up-regulation by mechanical signalling (i.e. increased gene expression resulting from stretch and tension to the muscle cytoskeleton leading to greater protein synthesis rates). Acute elevations in catecholamines are critical to optimal force production and energy liberation during resistance exercise. More recent research has shown the importance of acute hormonal elevations and mechanical stimuli for subsequent up- and down-regulation of cytoplasmic steroid receptors needed to mediate the hormonal effects. Other factors such as nutrition, overtraining, detraining and circadian patterns of hormone secretion are critical to examining the hormonal responses and adaptations to resistance training.

Hormonal Responses and Adaptations to Resistance Exercise and Training

An imbalance between the overall strain experienced during exercise training and the athlete's tolerance of such effort may induce overreaching or overtraining syndrome. Overtraining syndrome is characterised by diminished sport-specific physical performance, accelerated fatiguability and subjective symptoms of stress. Overtraining is feared by athletes yet there is a lack of objective parameters suitable for its diagnosis and prevention. In addition to the determination of substrates (e.g. lactate, ammonia and urea) and enzymes (e.g. creatine kinase), the possibilities for monitoring of training by measuring hormonal levels in blood are currently being investigated. Endogenous hormones are essential for physiological reactions and adaptations during physical work and influence the recovery phase after exercise by modulating anabolic and catabolic processes. Testosterone and cortisol are playing a significant role in metabolism of protein as well as carbohydrate metabolism. Both are competitive agonists at the receptor level of muscular cells. The testosterone/cortisol ratio is used as an indication of the anabolic/catabolic balance. This ratio decreases in relation to the intensity and duration of physical exercise, as well as during periods of intense training or repetitive competition, and can be reversed by regenerative measures. Correlations have been noted with the training-induced changes of strength. However, it seems more likely that the testosterone/cortisol ratio indicates the actual physiological strain in training, rather than overtraining syndrome. The sympatho-adrenergic system might be involved in the pathogenesis of overtraining. Overtraining appears as a disturbed autonomic regulation, which in its parasympathicotonic form shows a diminished maximal secretion of catecholamines, combined with an impaired full mobilisation of anaerobic lactic reserves. This is supposed to lead to decreased maximal blood lactate levels and maximal performance. Free plasma adrenaline (epinephrine) and noradrenaline (norepinephrine) may provide additional information for the monitoring of endurance training. While prolonged aerobic exercise conducted at intensities below the individual anaerobic threshold lead to a moderate rise of sympathetic activity, workloads exceeding this threshold are characterised by a disproportionate increase in the levels of catecholamines. In addition, psychological stress during competitive events is characterised by a higher catecholamines to lactate ratio in comparison with training exercise sessions. Thus, the frequency of training sessions with higher anaerobic lactic demands or of competition, should be carefully limited in order to prevent overtraining syndrome. In the state of overtraining syndrome and overreaching, respectively, an intraindividually decreased maximum rise of pituitary hormones (corticotrophin, growth hormone), cortisol and insulin has been found after a standardised exhaustive exercise test performed with an intensity of 10% above the individual anaerobic threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Hormones as Markers of Training Stress and Overtraining

Purpose: The use of anabolic androgenic steroids (AAS) to increase muscle size and strength is widespread. Information regarding self-administered AAS used nonmedically to enhance athletic performance or improve physical appearance is sparse and poorly documented. The purpose of this study is to identify current trends in the drug-taking habits of AAS users. Methods: An anonymous self-administered questionnaire was posted on the message boards of Internet Web sites popular among AAS users. Results: Of the 500 AAS users who participated in the survey, 78.4% (392/500) were noncompetitive bodybuilders and nonathletes; 59.6% (298/500) of the respondents reported using at least 1000 mg of testosterone or its equivalent per week. The majority (99.2%) of AAS users (496/500) self-administer injectable AAS formulations, and up to 13% (65/500) report unsafe injection practices such as reusing needles, sharing needles, and sharing multidose vials. In addition to using AAS, 25% of users admitted to the adjuvant use of growth hormone and insulin for anabolic effect, and 99.2% (496/500) of users reported subjective side effects from AAS use. Conclusions: This survey reveals several trends in the nonmedical use of AAS. Nearly four out of five AAS users are nonathletes who take these drugs for cosmetic reasons. AAS users in this sample are taking larger doses than previously recorded, with more than half of the respondents using a weekly AAS dose in excess of 1000 mg. The majority of steroid users self-administer AAS by intramuscular injection, and approximately 1 in 10 users report hazardous injection techniques. Polypharmacy is practiced by more than 95% of AAS users, with one in four users taking growth hormone and insulin. Nearly 100% of AAS users reported subjective side effects.

Anabolic androgenic steroids: a survey of 500 users.

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.

Testosterone physiology in resistance exercise and training: the up-stream regulatory elements.

Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone. According to surveys and media reports, the legal and illegal use of these drugs is gaining popularity. Testosterone restores sex drive and boosts muscle mass, making it central to 2 of society's rising preoccupations: perfecting the male body and sustaining the male libido. The anabolic effects of AAS have been questioned for decades, but recent scientific investigation of supraphysiologic doses supports the efficacy of these regimens. Testosterone has potent anabolic effects on the musculoskeletal system, including an increase in lean body mass, a dose-related hypertrophy of muscle fibers, and an increase in muscle strength. For athletes requiring speed and strength and men desiring a cosmetic muscle makeover, illegal steroids are a powerful lure, despite the risk of subjective side effects. Recent clinical studies have discovered novel therapeutic uses for physiologic doses of AAS, without any significant adverse effects in the short term. In the wake of important scientific advances during the past decade, the positive and negative effects of AAS warrant reevaluation. Guidelines for the clinical evaluation of AAS users will be presented for sports medicine practitioners.

Current Concepts in Anabolic-Androgenic Steroids

The physiological importance of the increase in androgen receptors in exercise-induced muscle hypertrophy was investigated in rats. Together with training rat gastrocnemius muscles by electrical stimulation every other day for 2 weeks, male rats were administered the androgen receptor antagonist, oxendolone. The androgen receptor antagonist effectively decreased the wet mass of the prostate, an androgen target organ, and did not significantly affect body mass. The increase in muscle mass induced by electrical stimulation was effectively suppressed by the androgen receptor blockade. The mean degree of muscle hypertrophy in the antagonist-treated group was significantly lower than that in the control group (102.30% vs 107.41%, respectively;P=0.006). This result suggests that the androgen pathway has a significant effect in exercise-induced muscle hypertrophy and emphasizes the importance of the increase in the number of androgen receptors in exercised muscle.

Yoshimune Okada

Papers

Androgen receptor antagonist suppresses exercise-induced hypertrophy of skeletal muscle.