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

Recent advances in human life history theory have provided new insights into the potential selection pressures that were instrumental in the evolution of human and non-human primate males However, gaps remain in our understanding of how primate males regulate and allocate energetic resources between survivorship and reproductive effort Defense against parasitic infection is an important force shaping life history evolution Proper performance of immunological responses against infection is influenced by many physiological systems, including metabolic, reproductive, and stress hormones Because androgens influence and modulate immune, reproductive, and somatic metabolic functions, assessing changes in testosterone and immune factors during infection may yield insight into male physiological ecology In this review, we examine male life history trade-offs between immune and reproductive endocrine functions as well as provide a comprehensive review of testosterone–immunocompetence relationships Emphasis is placed on testosterone because it is a primary hormone shown to be crucial to energy-allocation processes in vertebrates Non-primate species have been used more extensively in this research than humans or non-human primates, and therefore this extensive literature is organized and reviewed in order to better understand potential parallel relationships in primates, especially humans Furthermore, we attempt to reconcile the many inconsistent results obtained from field studies on immune–endocrine interactions as well as detail various methodologies that may be used to forward this research in evolutionary anthropology Am J Hum Biol 17:527–558, 2005 © 2005 Wiley-Liss, Inc

Testosterone-mediated immune functions and male life histories.

Purpose: Soldiers are expected to maintain a high degree of physical readiness as operational demands can severely degrade performance capabilities. This study examined the physiological consequences of U.S. Army Ranger training on strength, power, body composition, and somatotrophic hormones.

Methods: In an intensive 8-wk military training course that included an average daily energy deficit of 1000 kcal·d-1, lower-body power output, maximal lifting strength, body composition, and serum concentrations of several somatotrophic hormones were measured in 50 male soldiers (24.6 ± 4.4 y; 176.1 ± 7.8 cm; 78.4 ± 8.7 kg; 14.7 ± 4.2% body fat) before and after the course.

Results: Vertical jump height (-16%), explosive power output (-21%), maximal lifting strength. (-20%), body mass (-13%), fat-free mass (-6%), and fat mass (-50%) declined (P < 0.05) after the training course. Circulating total testosterone and insulin-like growth factor-I (IGF-I) experienced significant (P < 0.05) declines, and cortisol was significantly increased. Lower-body power output, but not maximal lifting strength, correlated with changes in fat-free mass. IGF-I and cortisol, but not total testosterone, were correlated with losses of tissue mass.

Conclusion: Lower-body power output, estimated from vertical jump height and body mass, is a sensitive and field expedient measure that can be used to assess the influence of caloric deficit on physical performance after 8 wk of U.S. Army Ranger training. With severe weight loss (=13% of body mass), IGF-I and cortisol correlate more closely with soft-tissue tissue adaptations than does testosterone.

Physiological consequences of U.S. Army Ranger training.

Smoking, obesity, alcohol, and physical activity can modulate theendocrine system, and therefore have been hypothesized to play a role in theetiology of prostate cancer. At baseline in 1982, 80 percent (n = 3,673) ofthe noninstitutionalized persons age 65+ in two rural Iowa (United States)counties were enrolled into the Iowa 65+ Rural Health Study. Follow-up formortality was complete through 1993, and cancer experience was determined bylinkage to the State Health Registry of Iowa cancer database for the years1973-93. We analyzed data on 1,050 men aged 65 to 101 years (mean age 73.5)with a full interview in 1982 and with no documented cancer in the 10 yearsprior to baseline. Through 1993 (8,474 person-years of follow-up), there were71 incident cases of prostate cancer. In a multivariate model, age, cigarettesmoking (relative risk [RR] = 2.9 for currently smoking 20 or more cigarettesper day compared with never smoking; P trend = 0.009), greater body massindex (BMI) (wt/ht 2 ) (RR = 1.7 for BMI > 27.8 kg/m 2 compared with <23.6; P trend = 0.1), and greater level of physical activity (RR = 1.9 forhigh activity level cf inactive; P trend = 0.05) were independent predictorsof prostate cancer, and these associations were stronger for regional ordisseminated disease at diagnosis. Percent change in BMI from age 50 tobaseline was associated positively with risk (P trend = 0.01), and thisassociation appeared to be stronger in heavier men. There were no data ondiet. These findings suggest that smoking, overweight, and weight gain inlater life are risk factors for prostate cancer and support a hormonaletiology; the positive association for physical activity confirms someprevious reports, but remains without a credible biologicmechanism.

Association of smoking, body mass, and physical activity with risk of prostate cancer in the Iowa 65+ Rural Health Study (United States)

The effects of a 24-weeks' progressive training of neuromuscular performance capacity on maximal strength and on hormone balance were investigated periodically in 21 male subjects during the course of the training and during a subsequent detraining period of 12 weeks. Great increases in maximal strength were noted during the first 20 weeks, followed by a plateau phase during the last 4 weeks of training. Testosterone/cortisol ratio increased during training. During the last 4 weeks of training changes in maximal strength correlated with the changes in testosterone/cortisol (P less than 0.01) and testosterone/SHBG (P less than 0.05) ratios. During detraining, correlative decreases were found between maximal strength and testosterone/cortisol ratio (P less than 0.05) as well as between the maximal strength and testosterone/SHBG ratio (P less than 0.05). No statistically significant changes were observed in the levels of serum estradiol, lutropin (LH), follitropin (FSH), prolactin, and somatotropin. The results suggest the importance of the balance between androgenic-anabolic activity and catabolizing effects of glucocorticoids during the course of vigorous strength training.

Serum hormones during prolonged training of neuromuscular performance

The endocrine response to severe physical strain including lack of sleep has been investigated in army personnel during a combat course of 5 days' duration. The thyroxine (T4) concentration in serum increased during the first 24 h, and then declined at a rate corresponding to a halflife of 7.6 days and on day 6 reached the lowest level, 55 ng/ml. Triiodothyronine (T3) displayed a similar pattern, although an increase during the first 24 h could not be demonstrated. Within 48 h after the course T4 had returned to normal, whereas the serum level of T3 was significantly below the level before the course (p<0.05). The serum level of TSH was suppressed during the course. The serum level of prolactin was significantly suppressed and growth hormone was markedly elevated during the course with a significant negative correlation (r=−0.6) between the two. In agreement with a previous report, there was a rapid and sustained suppression of the serum level of testosterone to a mean level of 1.1 ng/ml on day 5. Short periods of sleep (3–6 h) were shown to be effective in reversing the changes described in this paper, especially for growth hormone, prolactin, and testosterone.

F. Fonnum

Papers

Hormonal changes in serum in young men during prolonged physical strain.