Biomedical subjects

G Lac

Publications and source records attributed to G Lac.

At least 37 records · Page 2Linked to original sources

PubMed2001

Food restriction, performance, psychological state and lipid values in judo athletes.

Dietary intake, plasma lipids, lipoprotein and apolipoprotein levels, anthropometric measurements and anaerobic performance were studied in eleven judo athletes during a period of weight maintenance (T1) and after a 7d food restriction (T2). Dietary data were collected using a 7-day diet record. Nutrient analysis indicated that these athletes followed a low carbohydrate diet whatever the period of the investigation. Moreover, mean micronutrient intakes were below the French recommendations. Food restriction resulted in significant decreases in body weight. In addition, it had significant influence on triglyceride and free fatty acid, although glycerol, total cholesterol, LDL-C, HDL-C, apolipoprotein A-1 and B did not alter. Left arm strength and 30 s jumping test decreased significantly. The 7 s jumping test was not affected by the food restriction. Regardless of psychological parameters, tension, anger, fatigue and confusion were significantly elevated from T1 to T2; vigor was significantly lower. The data indicated that a 7-day food restriction adversely affects the physiology and psychology of judo athletes and impairs physical performance, possibly due to inadequate carbohydrate and micronutrients.

Adult↗

PubMed2001

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.

Absorptiometry, Photon↗

PubMed2001

Psychophysiological stress in judo athletes during competitions.

BACKGROUND: The relationships between psychophysiological variables were investigated by comparing physiological responses (salivary cortisol and testosterone concentrations) and psychological responses (measured by the Competitive State Anxiety Inventory-2 -CSAI-2-and by the State-Trait Anxiety Inventory -STAY-) prior to judo competitions at two levels (regional versus interregional). METHODS: Twelve male judo competitors at interregional level (mean age 22.2+/-1.6 years) entered the experimentation after informed consent. Judo athletes completed the CSAI-2 prior to both competitions and collected saliva for cortisol and testosterone analysis on three occasions: during a resting day (baseline values) and prior to and after both competitions. Trait scales of the STAI (Y-2) were used during a resting baseline period with no stressful situations in order to measure participant's self reported anxiety. RESULTS: Cognitive and somatic anxiety were higher in interregional championships compared to regional championships whereas self-confidence was significantly lower. Cortisol levels increased sharply (about 2.5 fold resting levels) throughout both competitions with no changes in testosterone levels. Positive relationships between anxiety components (somatic and cognitive anxiety) and cortisol were noted in both competitions. CONCLUSIONS: Salivary cortisol, together with anxiety components, may provide a better sensitive index of physiological stress than testosterone concentrations.

Adult↗

PubMed2000

Dehydroepiandrosterone (DHEA) rather than testosterone shows saliva androgen responses to exercise in elite female handball players.

The aim of the investigation was to evaluate in fourteen elite female handball players the resting values of saliva levels of testosterone -- T -- and dehydroepiandrosterone -- DHEA -- in comparison with ten sedentary women and the response to exercise of the same hormones in handball players. Saliva samples were taken from the handball players upon wakening (resting values) (8 a. m.), 5 minutes before and after a simulated handball match (6 p. m.; 8 p. m.) and upon wakening the following morning (8 a. m. + 24 h). The samples of saliva from the sedentary controls were taken at the same time of day but the controls did not perform any exercise. Resting hormonal levels were lower in handball players than in controls (P < 0.01). The exercise did not induce significant changes in T and DHEA salivary concentrations in handball players. Positive correlations between testosterone concentrations and DHEA were observed at all the time points studied. These findings showed that the T and DHEA concentrations followed a remarkably similar pattern. Considering the very low concentrations of testosterone in women, in particular in saliva, and its biosynthetic pathway, we suggest that measurements of DHEA could serve as a substitute for testosterone measurements to study training responses in elite sportswomen.

Adult↗

PubMed2000

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).

Adult↗

PubMed1999

Saliva cortisol, testosterone and T/C ratio variations during a wrestling competition and during the post-competitive recovery period.

UNLABELLED: This study presents saliva cortisol (C) and testosterone (T) levels in a group of 15 young wrestlers (national and international) during a two-days competition. Values are compared to references established on a resting day (3 weeks before the competition). Post-competition recovery was studied by recording evening hormonal levels (5.30 pm) for 8 days. RESULTS: C levels increased sharply (about 2.5 fold resting levels) throughout the competition with no further changes in T levels. The rise in C appeared before entering the competition, traducing a striking phenomenon of anticipation. At the end of the competition, C levels fell very quickly (within 1.5 h) to basal value when T rose significantly, resulting in a very high T/C ratio. During the recovery period, C levels corresponded to basal ones and T remained high, resulting in a high T/C ratio (>30% than basal one) till the 5th day. CONCLUSION: Competition resulted in a low T/C ratio, considered as a catabolic phase. The recovery which is associated with a feeling of tiredness and an incapacity to train strenuously recognized by the trainers, paradoxically corresponded to a high T/C ratio (so-called anabolic phase).

Adolescent↗

PubMed1999

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.

Animals↗

PubMed1999

The relationship between salivary adrenocortical hormones changes and personality in elite female athletes during handball and volleyball competition.

Salivary cortisol, androstenedione delta 4, and dehydroepiandrosterone (DHEA) in 20 elite sportswomen were measured using radioimmunoassay in samples taken 5 min before and after a handball or volleyball competition. Three psychometric tests--State Trait Anxiety Inventory, Bortner, and Questionnaire de Personnalité pour Sportifs (questionnaire of personality for sports participants)--were used to evaluate the participants' personalities. Results indicated higher concentrations of cortisol and lower concentrations of delta 4 and DHEA in handball players before and after the competition. Cortisol values increased significantly during the competition in both groups. No changes were observed in androgen levels. The state of anxiety was higher in handball players, characterized by Pattern A behavior, whereas Pattern B behavior defined the volleyball players. The results suggest that adrenocortical changes during handball and volleyball competition are influenced by the different energy systems required by the two activities, individual personality characteristics, and the athlete's anxiety level relative to winning or losing.

Adult↗

PubMed1999

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.

Adrenocorticotropic Hormone↗

PubMed1999

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.

Adrenal Cortex Hormones↗

PubMed1998

Effects of training for two ball games on the saliva response of adrenocortical hormones to exercise in elite sportswomen.

In a group of 20 elite female handball or volleyball players, an evaluation was made of the response to a 4-month training period of cortisol, androstenedione and dehydroepiandrosterone in the saliva. At the beginning of the training programme (W1) and at the 7th (W7) and 16th weeks (W16), hormone concentrations were measured on awakening (8 a.m.; resting samples), and also before (t0) and at the end (t120) of a 2-h exercise session (simulated match) which took place at 6 p.m. The training programme increased the concentrations of adrenal androgens in the saliva at rest (P < 0.05) for both groups of subjects, with no change being noted in cortisol concentrations. In contrast, amongst the volleyball players, stressful stimuli produced by an increase in the amount of training did not affect adrenocortical metabolism during exercise. Indeed, a simulated volleyball match resulted in a decrease in salivary cortisol (P < 0.05) and androgen concentrations (P < 0.05) without regard for the week chosen for the test investigations. In contrast, a simulated handball match caused an increase in cortisol concentrations at W1 only (P < 0.05), with no change in the adrenal androgens concentration in any week of the training programme. The regulators of these hormones during a period of exercise and during the course of a training programme would seem to be different.

Adrenal Cortex Hormones↗

PubMed1998

Effects of amount of training on the saliva concentrations of cortisol, dehydroepiandrosterone and on the dehydroepiandrosterone: cortisol concentration ratio in women over 16 weeks of training.

This study was designed to investigate in the saliva the influence in female athletes of handball or volleyball training on concentrations of cortisol [C], dehydroepiandrosterone [DHEA], and on the [DHEA]:[C] ratio over 16 weeks of training. Data were compared to those of sedentary women. Saliva samples were collected upon waking after an overnight fast during the 1st week (W1) of the training programme and in the 16th week (W16). The training programme increased the resting concentrations of saliva [DHEA] in all the sportswomen. In contrast, a decrease of [DHEA] was noted in the sedentary group (W16 < W1; P < 0.05). In none of the women did the [C] at rest change significantly during the study. Between W1 and W16, the [DHEA]:[C] ratio increased by more than 30% in all the sportswomen. In addition, the athletes with the highest performance levels and greatest amount of training had the lowest [DHEA]:[C] ratio. Negative linear relationships between the amount of training and the [DHEA]:[C] ratio were found both at W1 (r = -0.53 P < 0.001), and W16 (r = -0.73 P < 0.001), suggesting that the latter could be used as an indicator of the training status of sportswomen.

Adult↗

PubMed1997

[Is a 11-year-old tennis player indifferent to competition stress?].

BACKGROUND: In adults, competition generates a relatively important level of stress. This could be revealed by psychological questionnaires and adrenocortical responses. This study was aimed to evaluate the load of stress in young tennis players in situations of competition compared to that observed during a training session. POPULATION AND METHODS: The 16 best young tennis players of the Auvergne area (mean age: 10.9 +/- 1.7 years) entered the study. The degree of anxiety was measured with the aid of the Martens' SCAT questionnaire and the result of salivary cortisol testing during a training session, and after each of the three competition rounds of the Auvergne championship (three samples were collected at each time: at rest, before and after exercise. RESULTS: Regarding the degree of anxiety, no significant difference was found between the competition and the training session. Cortisol levels did not change during the training session: during the competition, same moderate increase (less than 50%, P < 0.05) was noted for the first two rounds between rest and post-competition values. No difference was found at the third round. CONCLUSION: The high levels of stress described in adults are not found in young tennis players.

Age Factors↗

PubMed1997

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.

Adult↗

PubMed1996

Saliva cortisol, physical exercise and training: influences of swimming and handball on cortisol concentrations in women.

The aim of this study was to observe the influence of physical exercise and training on saliva cortisol concentrations in women. Three groups of adult women were studied: one group of sedentary controls (n = 7) and two groups of sportswomen who competed in either handball (n = 14) or swimming (n = 10) at a national level. These sportswomen gave six saliva samples during a day that included exercise which was part of their annual training programme. We noticed a significant increase in saliva cortisol concentration after exercise in the handball players (6 p.m. vs 7.30 p.m. P < 0.05) which did not appear in the swimmers or the sedentary group. There was no difference between the sedentary group and the swimmers for each sample of the day. These results showed that the type of sport played seemed to influence the concentration of saliva cortisol, the type of stress involved, the respective haemodynamic conditions of swimming and running and thermal stress also playing a part. Moreover, it seemed that the level of performance influenced the secretion of cortisol in the saliva.

Adult↗

PubMed1995

Salivary cortisol and testosterone variations during an official and a simulated weight-lifting competition.

This study was undertaken to compare salivary levels of cortisol (C), testosterone (T) and T/C ratio during an official and a simulated weight-lifting competition. Thirteen top-level weight-lifters (French team) including 7 national level athletes (NG) and 6 international level athletes (IG) entered the study. The performance levels corrected with the IWF index (an index which relates the performance to body weight) obtained during the competition were higher than those obtained during the simulation and were higher in IG than in NG. Salivary samples were collected for each session after weighing, snatch and clean-and-jerk. The mean T-levels of these athletes were the same as those obtained in the laboratory on sedentary adults; they did not vary throughout the competition, nor between the competition and the simulation. Conversely the C-levels were statistically higher in the competition than in the simulation (p < 0.05). These C-levels are correlated with the performance levels corrected with the IWF index obtained during the competition (r = 0.67; p < 0.05; n = 13). Moreover, C-levels noted at the time of the competition were higher in the international athletes than in the national ones. Therefore, we concluded that the cortisol level may be considered as a performance factor in weight-lifting.

Adult↗

PubMed1993

Analysis of performance of prepubertal swimmers assessed from anthropometric and bio-energetic characteristics.

The relationship between anthropometric and bio-energetic data and timed performance over 50 to 400 m was studied in 25 young male swimmers [11.3 (SD 1) years]. Anthropometric measurements included height, body mass, body fat mass, body area, thoracic section area (Ats) thoracic circumferences, lengths of upper limb, bi-acromial and bi-iliac diameters. Maximal oxygen consumption (VO2max; direct method), maximal anaerobic power (W(an),max; force-velocity test) and mean power in 30 s sprint (W30 s; Wingate test) were also measured. Each of these bio-energetic variables was expressed in absolute terms, relating to body mass, body area and Ats. The stepwise regression method was used to determine contribution of the variables (anthropometric and/or bio-energetic) of the time achieved over the distance. The W30 s/Ats accounted for 46% of the time over 50 m (negative correlation). The VO2max/Ats and height were negatively correlated with the times of performances over 100 m, 200 m and 400 m, these two variables accounted for 71% to 77% of the performance. These results would indicate that even in young boys, anthropometric and bio-energetic characteristics are both important in swimming performance, particularly the bio-energetic variables expressed per Ats.

Body Composition↗

PubMed1993

[Does the time change affect school children?].

The aim of the study was to determine in young pupil the physiological effect of a 1 hour earlier awakening (summer time) by measuring: the salivary cortisol level. Results showed that the cortisol circadian rhythm synchronized with summer clock time after remaining synchronized with winter time (previous rhythm) for 15 days at least.

Child↗