Gérard Lac

Oxidative stress : relationship with exercise and training.

Free radicals are reactive compounds that are naturally produced in the human body. They can exert positive effects (e.g. on the immune system) or negative effects (e.g. lipids, proteins or DNA oxidation). To limit these harmful effects, an organism requires complex protection — the antioxidant system. This system consists of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and non-enzymatic antioxidants (e.g. vitamin E [tocopherol], vitamin A [retinol], vitamin C [ascorbic acid], glutathione and uric acid). An imbalance between free radical production and antioxidant defence leads to an oxidative stress state, which may be involved in aging processes and even in some pathology (e.g. cancer and Parkinson’s disease). Physical exercise also increases oxidative stress and causes disruptions of the homeostasis. Training can have positive or negative effects on oxidative stress depending on training load, training specificity and the basal level of training. Moreover, oxidative stress seems to be involved in muscular fatigue and may lead to overtraining.

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.

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.

Different modalities of exercise to reduce visceral fat mass and cardiovascular risk in metabolic syndrome: the RESOLVE* randomized trial

BACKGROUND Opinions differ over the exercise modalities that best limit cardiovascular risk (CVR) resulting from visceral obesity in individuals with metabolic syndrome (MetS). As little is known about the combined effects of resistance and endurance training at high volumes under sound nutritional conditions, we aimed to analyze the impact of various intensities of physical activity on visceral fat and CVR in individuals with MetS. METHODS 100 participants, aged 50-70 years, underwent a diet restriction (protein intake 1.2g/kg/day) with a high exercise volume (15-20 h/week). They were randomized to three training groups: moderate-resistance-moderate-endurance (re), high-resistance-moderate-endurance (Re), or moderate-resistance-high-endurance (rE). A one-year at-home follow-up (M12) commenced with a three-week residential program (Day 0 to Day 21). We measured the change in visceral fat and body composition by DXA, MetS parameters, fitness, the Framingham score and carotid-intima-media-thickness. RESULTS 78 participants completed the program. At D21, visceral fat loss was highest in Re (-18%, p<.0001) and higher in rE than re (-12% vs. -7%, p<.0001). Similarly, from M3, visceral fat decreased more in high-intensity-groups to reach a visceral fat loss of -21.5% (Re) and -21.1% (rE)>-13.0% (re) at M12 (p<.001). CVR, MetS parameters and fitness improved in all groups. Visceral fat loss correlated with changes in MetS parameters. CONCLUSION Increased intensity in high volume training is efficient in improving visceral fat loss and carotid-intima-media-thickness, and is realistic in community dwelling, moderately obese individuals. High-intensity-resistance training induced a faster visceral fat loss, and thus the potential of resistance training should not be undervalued (ClinicalTrials.gov number: NCT00917917).

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.

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.

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.

Psychoendocrine and physical performance responses in male Tunisian rugby players during an international competitive season.

The aim was to investigate a follow-up study based on hormonal, physical, and psychological parameters among rugby players who trained during a whole season interspersed with competitions on an international level. Fitness or reciprocally tiredness as well as competitive anxiety were evaluated, respectively, using the French Society for Sports Medicine (SFMS) and the sport competition anxiety test (SCAT) questionnaires. In this study, SFMS and SCAT scores increased respectively over the competitive season. The SFMS score revealed a state of relative tiredness at the end of the season, highlighted by a slight decrement in physical performances. The SCAT score changes are related to the competition context and therefore increased accordingly to the importance of the competition stake. We analyzed the corticotrope and the gonadotrope axis before (T(1)), and at the end of the national and international rugby season (T(2)). Training did not affect the resting salivary cortisol (Csal) levels, but induced a decrease in resting testosterone (Tsal) values, resulting in a dropped T/C ratio. Competition, in both periods (T(1)-T(2)), provoked a significant increase in Csal levels, but the Tsal responses depended on the match stake. Their concentrations increased when the competition generated an important stress and decreased when the psychological conditions remained relatively stable. SFMS is preferentially correlated with resting Csal levels and T/C values measured at 08:00 hr but not with Tsal. SCAT is highly correlated with competitive Csal and Tsal concentrations measured before and after the matches.

Effect of Individualized Exercise Training combined with Diet Restriction on Inflammatory Markers and IGF-1/IGFBP-3 in Obese Children

Aims: The present study was designed to examine the possible changes in body composition, insulin-like growth factor 1 (IGF-1), insulin-like growth factor-binding protein-3 (IGFBP-3) and inflammatory markers of obese children in response to a 2-month program of exercise training combined with dietary restriction. Methods: Twenty-eight obese children (age 13.2 ± 0.7 years, body mass index 30.9 ± 1.3) were randomly assigned to a diet/training group or a control group and were tested two times: once before and once at the end of the experimental period. They performed a progressive cycle ergometer test at each visit. Substrate oxidation was evaluated by indirect calorimetry. Training was individualized at the point when fat oxidation was maximal (Lipoxmax). Results: Diet/training induced a significant decrease in body weight and body fat (after vs. before, p < 0.01). Plasma concentrations of IGF-1, IGFBP-3 and inflammatory markers were significantly decreased after the completion of the program. The diet/training program resulted in an increase in VO2maxACSM (24.6 ± 2.5 to 33.1 ± 3.1 ml/min/kg, p < 0.001) at the end of the intervention period. Conclu- sion: These data suggest that in the presence of weight loss, exercise training improves inflammatory markers and IGF-1 and IGFBP-3 levels in obese children.

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.