Guy R. Brisson

Aerobic fitness level and reactivity to psychosocial stress: physiological, biochemical, and subjective measures.

&NA; Aerobic fitness is associated with numerous physiological adaptations which permit physical stress to be coped with more efficiently. The present experiment examined whether aerobic fitness influences emotional response. Heart rate, biochemical measures (catecholamines, cortisol, prolactin, lactic acid), and self‐reported arousal and anxiety were monitored in 15 highly trained and 15 untrained subjects at various points before, during and following exposure to a series of psychosocial stressors. Heart rate and subjective arousal level increased markedly during the stressors in both groups. Trained subjects showed higher levels of norepinephrine and prolactin early in the stress period, more rapid heart rate recovery following the stressors, and lower levels of anxiety at the conclusion of the session. This more rapid heart rate and subjective recovery from psychosocial stress, suggests that aerobically trained individuals may be capable of faster recovery in both physiological and subjective dimensions of emotionality. The differences in reactivity profiles between the aerobically trained and untrained were discussed in light of models that have dealt with the adaptiveness of emotional response.

A simple and disposable sweat collector

SummaryApart from in cystic fibrosis, where sweat analysis provides valuable diagnostic information, sweat yields remain an overlooked biological fluid. Technical problems (dilution, condensation, contamination, evaporation, etc.) linked to currently available collection procedures are of concern and thwart their use. To overcome some of these technical difficulties, an original sweat-collection technique is described. A collection capsule is created inside a flexible, adhesive and disposable anchoring membrane pasted onto the skin. A fluid-tight window is positioned in the upper part of the pocket and gives access to its content. Through the collection window, complete emptying of the sweat collector can be achieved repeatedly by suction using a vacutainer tube inserted in a tube holder equipped with a long dull needle. With prior addition of a suitable marker, fractional samplings can also be performed using a precision micropipette. This collecting method allows for kinetic studies on sweat rate and sweat content. The limited bias-inducing manipulations linked to the described technique, coupled with the ease of performing kinetic studies on sweat volume and content, make this original tool a reliable and accurate sweat-collection technique.

Trait anxiety, submaximal physical exercise and blood androgens

SummaryThis study evaluates the relationship between trait anxiety and both androgen and gonadotrophic hormone levels at rest and during severe physical exercise. Twelve volunteers were selected among 160 untrained male collegial students and classified as anxious (N=6) or non-anxious (N=6) subjects according to their scores on three trait-anxiety tests (STAI, IPAT, 16 PF). Serum Δ4-androgen (testosterone and Δ4-androstenedione), Δ4-androgen (DHEA and DHEA-SO4) and gonadotrophin (LH and FSH) concentrations were measured by radioimmunoassay before, during and after 20 minutes of intensive bicycle exercise (80% of maximal heart rate). Results indicate significantly lower serum Δ4-androgens in anxious subjects before exercise. However, for each subject and irrespective of his anxiety level, all measured serum androgen concentrations increased significantly during exercise, although Δ4-androstene-dione remained lower in anxious subjects than in non-anxious ones. Serum LH concentrations (but not FSH) were signicantly higher in anxious subjects throughout the observation periods. However, exercise induced in each subject a significant decrease in the serum level of both gonadotrophic hormones. The results suggest that trait anxiety level may constitute an important factor that affects both pre-exercise and exercise serum androgen concentrations in untrained subjects.

Plasma catecholamines at rest and exercise in subjects with high- and low-trait anxiety.

&NA; The purpose of this study was to compare the plasma catecholamine concentration at rest and in response to exercise in subjects with low and high trait anxiety (TA). Six subjects with low TA and six subjects with high TA were selected among 149 males college students on the basis of their results on three TA tests (STAI, IPAT, 16 PF). Plasma norepinephrine (NE) and epinephrine (E) concentrations (pg/ml) were measured at rest in supine position and during mild and moderate exercises of 5 min duration (about 40% and 60% of the individual VO2max) on bicycle ergometer. Plasma E concentrations at rest and exercise were not significantly different in subjects with low (33 +/‐ 6, 82 +/‐ 11, and 197 +/‐ 49) or high TA (41 +/‐ 7, 62 +/‐ 13, and 229 +/‐ 52). Plasma NE concentration was not significantly different at rest and in response to mild exercise in low (235 +/‐ 52; 666 +/‐ 64) and high‐TA subjects (223 +/‐ 36; 610 +/‐ 88) but was significantly higher in high‐TA than in low‐TA subjects in response to moderate exercise (2510 +/‐ 618 vs. 1243 +/‐ 234). These results show 1) that plasma NE and E concentrations at rest and in response to light exercise are similar in low‐ and high‐TA subjects, and 2) that subjects with high TA have a greater plasma NE response to the psychologic stress and/or to the homeostatic challenge of moderate exercise.

Exercise-induced blood prolactin variations in trained adult males: a thermic stress more than an osmotic stress.

Blood prolactin (PRL) variations have been linked to temperature and osmotic changes in several species. The latter factors are here explored to better understand blood PRL responses frequently induced during physical exercise. Since body heat generated by exercise can lead to marked body fluid shifts, it was postulated that PRL changes observed during exercise could be associated with variations in body temperature and/or blood osmolality (OSM). A wide range (38.5-40.5 degrees C) of rectal temperatures (Tr; used here to appreciate core temperatures) were theoretically selected and randomly assigned as targets to male runners. Measured by thermistor probe, target Tr were obtained by a combination of factors: (a) increases heat production by treadmill running, and (b) decreases heat losses by appropriate clothing (decreases evaporation) in warmed (decreases radiation) and hypoventilated (decreases convection) laboratory conditions. For each subject, target Tr was attained not prior to 30 min after initiation of running, and had to be maintained for at least 10 min, for a mean (+/- SD) running time of 52.6 +/- 10.0 min. In a first protocol, hypohydration was provoked in 26 runners (23.9 +/- 4.7 years) by total restriction of water intake. In a second protocol (10 different runners: 22.3 +/- 3.3 years), euhydration was maintained by water intake (20 ml/kg body weight). Venous blood was sampled at rest before and immediately after the run. PRL was assayed by RIA; OSM was measured by freezing point depression; sodium was analyzed by flame photometry. At rest, before the heat-producing exercise, mean PRL values were 9.4 +/- 3.4 ng/ml for both eu/hypohydrated groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of exercise during normoxia and hypoxia on the growth hormone—insulin-like growth factor I axis

The response of plasma insulin-like growth factor I (IGF I) to exercise-induced increase of total human growth hormone concentration [hGHtot] and of its molecular species [hGH20kD] was investigated up to 48 h after an 1-h ergometer exercise at 60% of maximal capacity during normoxia (N) and hypoxia (H) (inspiratory partial pressure of oxygen = 92 mmHg (12.7 kPa);n = 8). Lactate and glucose concentrations were differently affected during both conditions showing higher levels under H. Despite similar maximal concentrations, the increase of human growth hormone (hGH) was faster during exercise during H than during N[hGHtot after 30 min: 8.6 (SD 11.4) ng · ml−1 (N); 16.2 (SD 11.6) ng · ml−1 (H);P < 0.05]. The variations in plasma [hGH20kD] were closely correlated to those of [hGHtot], but its absolute concentration did not exceed 3% of the [hGHtot]. Plasma IGF I concentration was significantly decreased 24 h after both experimental conditions [N from 319 (SD 71) ng · ml-1 to 228 (SD 72) ng · ml−1,P < 0.05; H from 253 (SD 47) to 200 (SD 47) ng · ml−1,P < 0.01], and was still lower than basal levels 48 h after exercise during H [204 (SD 44) ng · ml−1,P < 0.01]. Linear regression analysis yielded no significant correlation between increase in plasma [hGHtot] or [hGH20kD] during exercise and the plasma IGF I concentration after exercise. It was concluded that the exercise-associated elevated plasma [hGH] did not increase the hepatic IGF I production. From our study it would seem that the high energy demand during and after the long-lasting intensive exercise may have overridden an existing hGH stimulus on plasma IGH I, which was most obvious during hypoxia.

Face cooling-induced reduction of plasma prolactin response to exercise as part of an integrated response to thermal stress

SummaryThis study was designed to verify if the decrease in blood prolactin (PRL) induced by selective face cooling during exercise could be part of a response to specific body thermal stress. Five healthy trained male cyclists presenting a significant plasma PRL elevation to exercise were, on three occasions and at weekly interval, submitted to a submaximal exercise (approx. 65%

Contribution of hGH20K variant to blood hGH response in sauna and exercise

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