Multifactorial monitoring of training load in elite rugby sevens players: cortisol/cortisone ratio as a valid tool of training load monitoring.

The effectiveness of selected physiological and perceptual measures for monitoring training load and fatigue was studied in 16 male elite rugby sevens players during a 6-week intense training block (IT) and 2-week tapering (TAP). Daily training load (TL) and strain (TS) as well as weekly total score of fatigue (TSF) were quantified respectively by the session-rating of perceived exertion (RPE) method and an 8-item questionnaire. Also, testing was performed and 24 h urinary cortisol (C), cortisone (Cn), adrenaline (A) and noradrenalin (NA) excretion was measured before (T0) and after the IT (T1) and after the TAP (T2). The TL, TS and TSF increased during the IT and decreased during the TAP, in conjunction with a significant drop and improvement, respectively, of performance standards during the two periods. At T1, C and Cn levels increased while A and NA levels decreased, resulting in a higher C/Cn ratio and lower A/NA ratio, respectively. At T2, both C/Cn and A/NA returned to baseline values. The changes in C/Cn ratio, after the 6-week IT, were more closely related to mean TL, TS and TSF (r=0.75-0.76 vs. r=0.48-0.58, p<0.01) and to changes in the majority of performance measures than to A/NA ratio. Only the changes in C/Cn ratio after the 2-week TAP were related to mean TL, TS and TSF (r=0.61-0.68, p<0.01). The changes in hormone levels, training strain and performance standards reflected the physical and mental stressors of training, with complete recovery, as indicated by physiological homeostasis, achieved after an appropriate tapering period.

Six-minute walking test predicts maximal fat oxidation in obese children.

BACKGROUND: Obesity is associated with reduced exercise maximal fat oxidation rate (FATmax), which is generally assessed by cardiopulmonary cycling test. The six-minute walking test (6MWT) presents an alternative method in patients. OBJECTIVE: The aim of this study was to establish a practical reference equation facilitating the prediction of FATmax from the 6 MWT in obese children of both genders. DESIGN: This study is a cross-sectional study using mixed linear and multiple regression models. RESEARCH METHODS AND PROCEDURES: Anthropometric measurements were recorded and submaximal cycling test and 6 MWT conducted for 131 school-aged obese children, 68 boys and 63 girls. A multiple regression analysis for FATmax, including six-minute walking distance (6 MWD), anthropometric and cardiac parameters as the dependent variables, was performed for the two genders separately. RESULTS: Mean 6 MWD and FATmax were 564.9 ± 53.7 m and 126.5 ± 12.1 mg min(-1) for boys and 506.7 ± 55.0 m and 120.7 ± 10.0 mg min(-1) for girls, respectively. The 6MWD, body mass index, Z-score, fat-free mass, waist and hip circumferences (WC and HC), rest heart rate, and systolic and diastolic blood pressures were highly correlated with FATmax for both genders. There was a significant correlation between 6 MWD and FATmax in both boys and girls (r = 0.88 and r = 0.81, P<0.001, respectively). Stepwise regression analyses revealed that the combinations of 6 MWD with HC for boys and 6MWD with WC for girls improved the predictability of the model (R(2) = 0.81 for boys and R(2) = 0.72 for girls; P<0.001). CONCLUSION: In obese children, the 6MWT can be used to predict FATmax when formal test of exercise capacity and gas exchange analysis are unavailable or impractical. It is therefore possible to prescript targeted exercises at FATmax, without performing indirect calorimetry, just from a field test.

Exercise improves the ApoB/ApoA-I ratio, a marker of the metabolic syndrome in obese children.

AIM: This study was designed to examine the effect of training on components of the metabolic syndrome and ApoB/ApoA-I ratio in obese children. METHODS: We studied thirty-two obese children (13.3 ± 0.4 years) with 16 subjects who participated to 8-week training and 16 subjects serving as a control group. Training was individualized at the point where fat oxidation was maximal (Fat max). In each subject, pre- and postintervention anthropometric measures and biochemical tests on fasting blood were performed. RESULTS: After the programme, the training group showed an increase in VO(2peak) and fat oxidation during exercise. Body mass index (BMI), blood glucose and triglycerides were reduced, and high-density lipoprotein (HDL) was increased. ApoB/ApoA-I ratio decreased significantly (-0.43%, p < 0.01). Systolic and diastolic blood pressure also decreased (-8.4% and -10.9%, respectively). Among the training group, 10 subjects were classified as having the metabolic syndrome before the intervention and none after. No significant changes in any other variables were measured in the control group. CONCLUSIONS: Training targeted at Fat max reduces the prevalence of metabolic syndrome and its associated factors in obese children. In particular, this intervention decreases the ApoB/ApoA-I ratio, which may be considered as a marker for following this syndrome.

Effect of individualized weight-loss programmes on adiponectin, leptin and resistin levels in obese adolescent boys.

AIM: We investigate the effects of a 2-month weight-loss programme on plasma levels of adiponectin, leptin and resistin in obese adolescent boys. METHODS: Twenty-one obese adolescent boys (BMI = 30.8 +/- 3.2 kg/m(2)) completed the weight-loss programme including: 1/ either energy restriction (R), 2/ or individualized exercise training at the point of maximum lipid oxidation (Lipox(max)) (E), 3/ or energy restriction and training (RE). Body composition, lipid oxidation and plasma levels of adiponectin, leptin and resistin were measured before and after intervention. RESULTS: Following the weight-loss programme, adolescents of the RE group showed an improvement of their body composition (p < 0.01), an increase in plasma adiponectin (+73.7%, p < 0.01) and a decrease in plasma leptin (-38.8%, p < 0.01) leading to an increase in adiponectine/leptin ratio (ALR, +144.4%, p < 0.01) higher than the R or E groups. E and RE groups only showed a similar significant increase in plasma resistin (p < 0.05) and a significant improvement of lipid oxidation rate at Lipox(max) (p < 0.01 and p < 0.001). In addition, in RE group, ALR is correlated with waist/hip and waist/height ratios, resistin level, homoeostasis mode assessment (HOMA-IR) index and Lipox(max). CONCLUSION: In obese adolescents boys, moderate exercise training completed at Lipox(max) and combined with energy restriction improves their ability to oxidize lipids, which is associated with a normalization of their adiponectin, leptin and resistin levels resulting in an improved insulin sensitivity, as attested by a higher ALR and a lower HOMA-IR.

Two-month effects of individualized exercise training with or without caloric restriction on plasma adipocytokine levels in obese female adolescents.

OBJECTIVES: To examine if, in young obese patients, an individualized training programme in association with a caloric restriction programme which had an effect on whole-body lipid oxidation, was able to induce changes on plasma adipocytokine concentrations. MATERIALS AND METHODS: Twenty-seven obese female adolescents participated in the study. Whole-body lipid oxidation during exercise was assessed by indirect calorimetry during a graded cycle ergometer test. Body mass (BM), body mass index (BMI), percentage of body fat (%BF), insulin homeostasis model assessment (HOMA-IR) and fasting levels of circulating adipocytokines were assessed prior and after a two-month diet programme, individualized training programme targeted at Lipox(max) corresponded to the power at which the highest rate of lipids was oxidized and combined diet/training programme. RESULTS: The diet/training programme induced both a shift to a higher-power intensity of Lipox(max) (+27.8 + or - 5.1 W; p<0.01) and an increase of lipid oxidation at Lipox(max) (+96.8 + or - 16.2mg/min; p<0.01). The enhancement in lipid oxidation was significantly (p<0.01) correlated with the diet/training-induced improvement in %BF (r = -0.47), HOMA-IR (r = -0.66), leptin (r = -0.41), TNF-alpha (r = -0.48), IL-6 (r = -0.38), adiponectin (r = 0.43) and resistin (r = 0.51). CONCLUSION: This study showed that in obese female adolescents a moderate training protocol targeted at Lipox(max) and combined with a diet programme improved their ability to oxidize lipids during exercise, and that this improvement was associated with changes in plasma adipocytokine concentrations.

Effects of two-month physical-endurance and diet-restriction programmes on lipid profiles and insulin resistance in obese adolescent boys.

AIM: The aim of this study was to assess the impact of a two-month programme of physical endurance and dietary restriction, alone and combined, on plasma lipids and insulin resistance in obese adolescents. METHODS: A total of 24 obese adolescent boys participated in programmes of either dietary restriction (R), physical endurance at the point of maximum lipid oxidation (LIPOX(max)) (E) or diet combined with training (R+E). Anthropometric characteristics, metabolic measures and biochemical analyses were performed in all subjects before and after the interventions. An estimated insulin resistance was calculated using the homoeostasis model assessment (HOMA-IR) index. RESULTS: At the end of the two-month programmes, adolescents in the R+E group showed greater reductions in body mass index (-3.9+/-0.7 kg/m(2)) and waist circumference (-12.3+/-4.8 cm) (P<0.001) than either the R or E group. A significant decrease (P<0.01) in HOMA-IR index (-2.13+/-0.11), plasma triglycerides, LDL and total cholesterol was also seen in the R+E group. Moreover, at the end of the programme, the ratio of HDL cholesterol to triglycerides was significantly increased from baseline in the R+E group (0.93+/-0.09 vs. 0.68+/-0.11; P<0.01). CONCLUSION: Compared with either moderate physical endurance or dietary restriction, a combination of both resulted in a significant decrease in cardiovascular risk factors and HOMA-IR index in obese adolescent boys.

Effect of a lipid-enriched diet on body composition and some regulatory hormones of food intake in growing rats.

OBJECTIVE: The aim of the present study was to investigate the effects of a lipid-enriched diet on body composition and on main regulatory hormones of food intake (insulin, adiponectin, leptin, ghrelin). METHOD: Two groups of 16 rats, 35 days old, weighing 80+/-6 g, were constituted. One group (S) was given a standard diet during 10 weeks and served as control. The second group (L) was given a lipidic-enriched diet (containing: G: 41.5, L: 38.5, P: 20% calorie). Food and water were given "ad libitum". RESULTS: Total food intake, body weight, skeletal area and lean body mass of rats eating lipid-enriched diet were lowered (6694+/-178 vs. 8160+/-184 kcal, P=0.01; 431+/-38 vs. 468+/-25 g, P=0.003; 72.19+/-0.96 vs. 76.07+/-1.31 cm2, P=0.03; 369+/-18 vs. 409+/-23 g, P=0.0006), fat mass difference was not statistically significant (82.5+/-17 vs. 80+/-17 g, P=0.7). Blood ghrelin, adiponectin levels were lowered (1517+/-224 vs. 1915+/-579 pg/ml, P=0.03; 10+/-3 vs. 19+/-3 microg/ml, P=0.003) whereas insulin and leptin were unchanged (1.8+/-1.5 vs. 2.6+/-1.4 ng/ml, P=0.1; 16+/-11 vs. 13+/-10 ng/ml, P=0.4). CONCLUSION: A period of high fat diet in growing rats leads to a hypophagia, resulting in a lower lean body mass development. Some regulatory hormones of food intake did not change, while others significantly decreased, notably ghrelin being possible causal factor of the observed hypophagia linked to high fat diet.

[Do circannual rhythm of cortisol and testosterone interfere with variations induced by other events?]. / Les rythmes circannuels du cortisol et de la testostérone interfèrent-t-ils avec les variations de ces hormones liées à d'autres évènements?

OBJECTIVE: Cortisol and testosterone are two hormones whose levels may vary in response to sports or occupational events. We wondered if the circannual rhythm of these hormones could have an influence on such responses or whether changes can always be ascribed to a single cause. METHOD: For cortisol, we conducted a cross-sectional study among 102 adult men (mean age 42 years) using saliva samples taken one half hour after awakening. The values were combined over three-month periods corresponding to the four seasons. For testosterone, conclusions were drawn from data reported in the literature. RESULTS: The mean annual cortisol level was 14.36+/-0.44 nmol/l. There was no significant difference between average and peak values nor between maximal and minimal values. For testosterone, there have been a limited number of studies and it is unclear whether there is a seasonal change. In any case, the amplitude of variations is weak (9.7% between peak and annual average), which is partly ascribable to individual and interindividual variability. CONCLUSION: We conclude that there is no seasonal (or circannual) rhythm in cortisol levels to a degree which could interfere with effects resulting from other events. For testosterone, the circannual rhythm may account for 10% of the variation.

IGFBP-3, a sensitive marker of physical training and overtraining.

OBJECTIVE: To investigate the response of the somatotrope axis (insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3)) to intense exercise in relation to tiredness. METHODS: The study involved 11 rugby players who completed a questionnaire intended to evaluate fitness or, conversely, overtraining and who agreed to plasma samples being taken before and after an international rugby match. RESULTS: The main finding of our study is that we observed strong negative correlations between IGF-1 (r = 0.652) and IGFBP-3 (r = 0.824) levels and the overtraining state estimated using the French Society of Sport Medicine questionnaire. In particular, there was a fall (of up to 25%) in IGFBP-3 levels after the match in the more fatigued subjects compared to an increase (of up to 40%) in fit subjects. CONCLUSIONS: A fall in IGFBP-3 in response to an intense bout of exercise may represent an index of tiredness in highly trained sportsmen, as indicated by the scores obtained from the overtraining questionnaire.

Dexamethasone in resting and exercising men. II. Effects on adrenocortical hormones.

This study presents the reactions of adrenocorticosteroids (cortisol and aldosterone) and sex steroids [testosterone, androstenedione, and dehydroepiandrosterone and its sulfate (DHAS)] 1) to a dexamethasone (Dex) treatment, which is expected to lower steroid levels via the ACTH blockade, and 2) to an exercise bout at maximal O(2) consumption, which is expected to increase steroid production via ACTH stimulation. Consistent with the decrease in ACTH, all steroids except testosterone reacted negatively to Dex, independently of the dose (0.5 and 1.5 mg administered twice daily for 4.5 days). After exercise, plasma ACTH rose to 600% of basal value, resulting in a significant increase in aldosterone and adrenal androgens, but cortisol and DHAS were unaffected. This apparently surprising result can be explained by differences in peripheral metabolism: a theoretical calculation predicted that after 15 min the increase in hormone concentration may only reach 12% for cortisol and 2% for DHAS. For cortisol and adrenal androgens, assays were carried out using plasma and saliva. The consistent results obtained from the two matrices allow us to consider salivary assays as a useful tool for steroid abuse detection.

Dexamethasone in resting and exercising men. I. Effects on bioenergetics, minerals, and related hormones.

A placebo and a low and a high dose of dexamethasone (Dex) were administered for 4.5 days, at 3-wk intervals, to 24 healthy men, following a double-blind, random-order, crossover procedure. After the last dose the subjects performed a maximal cycling exercise, during which respiratory exchanges, electrocardiogram, and blood pressures were monitored. Blood was sampled just before and after each exercise bout. Dex showed no significant effect on fitness, sleep, exhaustion during exercise, maximal O(2) consumption, ventilatory threshold, maximal blood lactate, or rest and exercise blood pressures. On the contrary, both doses of Dex significantly decreased heart rate at rest and during maximal exercise. Blood glucose at rest was higher after both doses of Dex than after placebo; the opposite was found during exercise. Blood levels of ACTH, beta-endorphin, cortisol, and cortisol-binding globulin were lowered by Dex at rest and after exercise. Dex stimulated the increase in atrial natriuretic factor during exercise and lowered rest and postexercise aldosterone. Finally, no difference between "fit or trained" and "less fit or untrained" subjects could be found with respect to Dex effects.

Influence of clenbuterol on bone metabolism in exercised or sedentary rats.

This paper reports that the selective beta(2)-adrenergic receptor agonist clenbuterol affects bone metabolism in growing 3-mo-old male Wistar rats treated over 8 wk. Thirty-two 3-mo-old growing Wistar rats weighing 234 +/- 2 g were assigned to a progressive isometric force, strength-training exercise program plus oral clenbuterol (2 mg x kg body wt(-1) x day(-1)) for 5 days each week, exercise program without clenbuterol 5 days each week, no exercise program plus oral clenbuterol (2 mg x kg(-1) x day(-1)) for 5 days each week, or no exercise without clenbuterol 5 days each week. At the end of 8 wk, lean mass, fat mass, and right total femoral, distal metaphyseal femoral, and diaphyseal femoral bone mineral density were measured by Hologic QDR 4,500 dual X-ray absorptiometry (DEXA) technique. Left femoral bones were harvested after death on day 58, and femoral resistance was determined by three-point bending testing. We found that fat mass was decreased in rats given strength training exercise and decreased further in rats treated with clenbuterol. Lean mass was increased in clenbuterol-treated animals. Strength-training exercise appeared to have no effect on bone mineral density, serum osteocalcin, or urinary deoxypyridinoline. However, clenbuterol treatment decreased femoral length, diameter, bone mineral density, and mechanical resistance. Clenbuterol had no effect on osteocalcin but increased urinary deoxypyridinoline. We concluded that clenbuterol treatment decreased bone mineral density and increased bone resorption independent of the level of exercise rats were given.

Progressive isometric force training and bone mass in rats.

In ten growing male Wistar rats, isometric strength training for 69 days (3-6 times vertical gripping position on a wire-netting during 2 x 30 s, with progressive loading of the tail through a 50-200 g indwelling clip), fat mass and plasma leptin concentrations were lower on day 70 than in ten sedentary controls. Muscle mass and femoral trabecular and cortical bone mineral density were simultaneously higher in exercised animals than in controls. Such an effect might result from decreased bone resorption. At the end of the training period no difference concerning plasma osteocalcin concentration was observed between exercised and resting rats while urinary deoxypyridinoline excretion was lower in the former than in the latter.

Effects of 16 weeks of training prior to a major competition on hormonal and biochemical parameters in young elite gymnasts.

The aim of this study was to investigate the response to 16 weeks of training on selected hormonal and biological parameters in seven international competition level female artistic gymnasts (14.5 +/- 1.2 years). Data were collected at the beginning of the first training week (W1) and in the 16th week (W16). Assessments also included anthropometric measurements, dietary intake for 7 days and Tanner staging. No gymnast had reached menarche and the puberty stages corresponded to Tanner's pubertal stage 2. The gymnasts were smaller than average for their age group, with a height:weight ratio above the 50th percentile. Energy intake was about 31% lower than recommendations. Significant decreases in IGF-I, IGFBP3, IGF-I:C ratio and triglyceride values and increases in uric acid and creatinine levels were noted. Cortisol values were high regardless of the period. This training provided evidence for alterations in resting somatotropic and adrenocorticotropic parameters.

High-impact loading training induces bone hyperresorption activity in young elite female gymnasts.

The aim of this study was to investigate the effect of intensive exercise on bone turnover (as reflected by bone resorption) in young elite female gymnasts. Forty-five healthy girls including 24 gymnasts (11.9+/-2 yr) and 21 controls (12.3+/-1.4 yr) were studied. Body weight, height, bone age and body composition were measured. Bone mineral density (BMD) was assessed at the whole body, lumbar vertebrae, hip and radius by means of DXA. Volumetric density (BMAD) was calculated. Bone velocity (SOS) and attenuation (BUA) were measured by QUS at the calcaneus. Urinary androstenedione (delta4), dehydroepiandrosterone sulfate (DHEA-S), and CrossLaps (CTx) were measured. BMD and BMAD were significantly greater in the gymnasts at all sites except whole body. SOS was found significantly higher. Delta4 values were significantly lower in the gymnasts. The distribution of the subjects according to Tanner stages was not different between groups. CTx levels were significantly higher in the gymnasts (989.08+/-154.63 microg/mmol Cr.) vs controls (580.25+/-123.99 microg/mmol Cr., p=0.02). CTx values decreased from Tanner stage 1 to stage 4 in each group, the gymnasts' levels always being higher than those of the controls. In conclusion, gymnastics seems to stimulate bone resorption activity in highly-trained young females. The coexistence of bone hyperresorption and higher BMD in gymnasts suggests increased bone turnover resulting in increased bone density in these subjects.

Salivary testosterone and cortisol in rugby players: correlation with psychological overtraining items.

BACKGROUND: A psychocomportemental questionnaire has been devised by the consensus group of the Société Française de Médecine du Sport to characterise and quantify, using a list of functional and psychocomportemental signs, a state of "staleness", for which no biological indicator is unanimously recognised. OBJECTIVES: To determine the relation between this diagnostic method and two hormones (cortisol and testosterone) often used as indicators of a state of fitness or staleness. METHODS: The subjects were young rugby players. They were asked to complete the overtraining questionnaire and gave three saliva samples (at 8 am, 11 am, and 5 pm) during a rest day. Concentrations of cortisol and testosterone in the saliva were determined by radioimmunoassay. RESULTS: A preferential relation was found between the questionnaire score and testosterone concentration but not between the questionnaire score and cortisol concentration. CONCLUSIONS: The questionnaire may be a useful tool for screening subjects at risk of overtraining. Testosterone concentration is influenced by tiredness, and is therefore a valid marker of tiredness.

A rat model of progressive isometric strength training.

This study presents an isometric model of strength resistance training in rats. Seven rats were trained for five weeks with increasing load, once a day for six days per week while seven rats served as control group. Mechanical strength of the hindlimb muscle group was measured on anaesthetised rats with a force transducer linked to the Achilles tendon after electrical stimulation of the sciatic nerve. Training resulted in a 74 +/- 2% strength gain in experimental (E) vs control (C) rats and in a reduction of fatigability with no change in gastrocnemius, soleus and extensor digitorum longus weights. The fibres composition of the gastrocnemius showed a 50% increase of IIA fibres and a 17% fall of IIB fibres. Consequently, this new model of isometric training is suitable for physiological studies.

Nutritional status and body composition of juvenile elite female gymnasts.

BACKGROUND: The purpose of this study was to examine body composition, dietary intake and energy expenditure in 12 young female elite gymnasts aged 10.1 +/- 0.3 years, doing a physical exercise of 15 hrs x week-1. The results were compared with a control group consisting of nine volunteer school girls age matched doing less than 4 hrs x wk-1 of physical exercise. METHODS: Assessments included dietary intake for 7 days, anthropometric measurements (body weight, height, arm circumference, triceps and subscapular skinfolds, body mass index). Body fat percentage was estimated using the Slaughter equation. Anthropometric measurements and nutritional intake were recorded in autumn. RESULTS: The gymnasts were shorter and had lower body weight compared with controls (p<0.05). Percentage of body fat was significantly lower in gymnasts versus controls (p<0.01). Gymnasts had higher percentage of fat free mass (p<0.01) than the reference group. Daily energy intake met daily energy requirement in both groups. Distribution of energy for both groups was almost identical, with approximately 14% from protein, 48% from carbohydrate, and 37% from fat. The average intakes of polyunsaturated fat were low in the two groups. The main daily intake of most nutrients in both groups were in accordance with recommendations; exceptions were dietary fibre, E and B6 vitamins. CONCLUSIONS: The primary finding of this investigation is that in both groups, the mean daily energy intake met the energy requirement. Thus, the gymnasts did not restrict total energy. The overall nutrient intake of the two groups may appear adequate. Prepubertal gymnasts have higher percentage of fat free mass and daily energy expenditure and dietary intakes, but lower percent body fat than age matched controls.

Changes in cortisol and testosterone levels and T/C ratio during an endurance competition and recovery.

BACKGROUND: To describe the evolution of cortisol and testosterone levels and testosterone/cortisol (T/C) ratio in long-distance runners during a relay competition and during the three days following the competition. METHODS: Two teams of four relayers (one male, one female) took part into this six-hour relay race. Hormonal control during the race was made possible thanks to saliva sampling during rest periods at each relay. The runners were subelite runners, (VO2max = 67.0 ml x min(-1) x kg(-1) in males and 56.8 ml x min(-1) x kg(-1) in females). RESULTS: During the race, cortisol levels reached approximately 1.5-fold basal levels. These levels remained high till late evening, (higher than morning values, when normal resting levels are 4 to 6-folds lower). Surprisingly, wakening levels during the following days were lower than resting levels. Testosterone did not vary in females; then, male values only are reported. During the race they decreased gradually and remained low till night. During the following three days, testosterone levels were higher than resting day levels. The T/C ratio amplifies these variations: low during the race till retiring, (currently associated with a catabolic tendency) and reversely high during the following three days (associated with a high anabolic tendency). CONCLUSIONS: As expected, a catabolic tendency occurs during a long distance run (increase in cortisol level followed by a drop in testosterone level). More surprising is the high anabolic tendency noted during the recovery period (low cortisol and high testosterone levels).

Salivary cortisol response to a 30 mn submaximal test adjusted to a constant heart rate.

BACKGROUND: The aim of this study was to analyse the salivary cortisol variations during a 30 min sub-maximal exercise, the load being fitted so that the heart rate remains constant at 170 +/- 4 bpm. METHODS: Tests were conducted at 10 a.m. precisely (in order to avoid circadian variations), and cortisol values were recorded every 5 mn by means of a sampling collector over 40 mn), (30 mn bout + 10 mn post-exercise) and then at 30 mn, 1 h 30 mn and 5 h following the end of the exercise. Test values were compared to reference values, (average cortisol resting levels obtained at comparable hours on a previous day). Nine sport-students, (5 boys, 4 girls) entered the study. RESULTS: The cortisol level presented a significant increase from the first step of the exercise and then, as opposed to an exercise where a constant load is applied, it did not keep increasing but remained steady until the end of the test. After stopping, a new significant increase surprisingly appeared; the values then dropped to reference levels, but they were still higher 1h 30 mn after exercise had stopped. CONCLUSIONS: It appears that when the perceived stress of the body reaches an equilibrium, as controlled by monitoring the heart rate, cortisol levels quickly rise to a steady state, about two folds higher than resting values in our experimental conditions.