Biomedical subjects

G Lac

Publications and source records attributed to G Lac.

At least 19 recordsLinked to original sources

PubMed2006

[Do circannual rhythm of cortisol and testosterone interfere with variations induced by other events?].

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.

Adult↗

PubMed2006

Antioxidant status and oxidative stress in professional rugby players: evolution throughout a season.

Physical training is known to increase the antioxidant defence system and reduce exercise-induced oxidative stress. However, intense physical aerobic and anaerobic training and competition such as those imposed on professional rugby players, can induce an increase of oxidative stress which can be implicated with the arrival of overtraining. The aim of this study was to test the effect of training and competition load on oxidative stress, antioxidant status, haematological, and cell damage markers in high-level rugby players during a competitive season. Blood samples were collected four times in one year. Oxidative stress (Rmax), antioxidant (vitamin E, uric acid, TAC, and lag phase), haematological (neutrophils and monocytes) and biochemical (CK and myoglobin) parameters, as well as training and competition load, and competition results were measured. Intense periods of training and competition (T1 and T4) induced a significant higher maximum rate of conjugated dienes oxidation (+67.2% in T1 and +40.6% in T4) compared to those observed at the reference time (T3). Those periods also induced an increase in uric acid (+6.9% and 3.2%), and inflammatory markers such as monocytes (+13.3% and 10.7%). On the other hand, vitamin E (-8.7% in T1) and lag phase (-23.0% and -14.7%) were lower during these periods showing a possible training-induced antioxidant down-regulation. The less intense period of training (T2) was accompanied by lower neutrophils (-8.5%), CK (-53.7%), and myoglobin (-16.2%) values. The results suggest that oxidative stress and antioxidant measurement are significant in the biological follow-up of athletes.

Adult↗

PubMed2006

Food restriction, performance, biochemical, psychological, and endocrine changes in judo athletes.

In order to test the hypothesis that dietary restriction may have a negative influence on physiological and psychological adaptation to a judo competition, we examined the effects of weight loss induced by restricting energy and fluid intake on the physiology, psychology, and physical performance of judo athletes. Twenty male judoka were randomly assigned to one of two groups (Group A: called diet, n = 10; height 174.8 +/- 1.9 cm, body weight 75.9 +/- 3.1 kg; they were asked to lose approximately 5 % of their body weight through self-determined means during the week before the competition; Group B: called control, n = 10; height 176.4 +/- 1.1 cm, body weight 73.3 +/- 6.3 kg maintained their body weight during the week before the competition). A battery of tests was performed during a baseline period (T1), on the morning of a simulated competition (T2) and 10 min after the end of the competition (T3). The test battery included assessment for body composition, performance tests, evaluation of mood, determination of metabolic and hormonal responses. Dietary data were collected using a 7-day diet record. The nutrient analysis indicated that all the athletes followed a low carbohydrate diet whatever the period of the investigation. For the Group A, the food restriction (- 4 MJ per day) resulted in significant decreases of the body weight and altered the mood by increasing Fatigue, Tension and decreasing Vigour. Dietary restriction had also a significant influence on metabolic and endocrine parameters and was associated with poor performance. After the competition, significant decreases of the levels in testosterone, T/C ratio, alkali reserve, and free fatty acid were observed in both groups, whereas the plasma concentrations in insulin, ammonia, urea, and uric acid were increased. In conclusion, our results suggest that the combination of energy restriction and intense exercise training, which causes weight reduction before a competition, adversely affects the physiology and psychology of judo athletes and impairs physical performance before the competition. Our data are the first to demonstrate that a competition including five 5-min bouts induced the same changes of physiological and psychological variables and performance whatever the dietary intake (dietary restriction or not) during the seven days before the competition.

Adult↗

PubMed2006

Bone mineral content and density of Tunisian male rugby players: differences between forwards and backs.

The purpose of this study was to examine the effects of long-term rugby participation on bone mineral content (BMC) and density (BMD) of male rugby players and to determine if the diverse stimuli elicited by the actions of forwards and backs affect their skeleton differently. Dual energy X-ray absorptiometry (DXA) scans were obtained from 20 male rugby players (10 Forwards and 10 Backs) who actively participated in rugby for the past 13 yr, and from 29 age matched non active subjects of the same ethnic origin. Both groups (rugby players and controls) had comparable age (23.6 +/- 3.7 yr vs. 25.6 +/- 3.4 yr), height (178.1 +/- 4.0 cm vs. 178.3 +/- 6.0 cm), and body fat percentage (14.2 +/- 4.4 vs. 16.5 +/- 5.1). Rugby players showed greater total body mass, and greater total lean and fat body masses than control subjects (p < 0.01). Whole spine BMC and BMD were 52 % and 15 % higher, respectively, in the rugby players than in the control subjects (p < 0.001). Furthermore, rugby players displayed higher skeletal BMC (40 %, 37 % and 58 % for legs, arms and pelvis, respectively) and BMD (16 %, 21 % and 17 %, respectively) than controls. Within the rugby group, forwards were taller, heavier and had greater body fat percentage, and greater total lean and fat body masses than backs (p < 0.05 to p < 0.001). Likewise, BMC, BMD and bone area for the whole body and at specific sites such as arms, spine and legs were also greater in the forwards (p < 0.05 to p < 0.001). Long-term rugby participation, starting at pubertal age, is associated with markedly increased BMC, BMD and bone size at all skeletal sites, except at the head. The musculo-skeletal adaptations, greater in forwards than in backs, could mimic training responses and therefore explain the bone features, localized in specific stressed regions.

Adult↗

PubMed2005

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.

Adult↗

PubMed2004

Biological and psychological responses to two rapid shiftwork schedules.

This study presents the biological responses to shiftwork in two groups of workers with different shiftwork rotas. Biological responses were studied by recording the heart rate and the changes in the circadian profile of salivary cortisol over 24 h (RIA assays). Various items were recorded through questionnaires aimed at determining self appreciation of sleep quantity, stress, health, satisfaction at work and in private lives. Thirty two male subjects aged from 23 to 56, working for the same company, having given their informed consent, took part in the study. The study was carried out under realistic conditions (at the work place) under the control of an occupational physician. Sixteen day-workers (8 am-6 pm) served as a reference group. Eight shiftworkers included in alternate schedules (morning M 4 am-12 am, evening E 12 am-8 pm, night N 8 pm-4 am) according to a system M, S, N 3/2, (3 work, 2 rest) and eight according to a system 7/5 (3M/2S/2N/5R, 2/3/2/5, 2/2/3/5) constituted the groups of shiftworkers respectively named 3/2 and 7/5. All subjects had comparable ages and BMIs. Shiftworkers expressed a higher stress level and frequency of health problems and a lower satisfaction at work than the control. Among the three groups, the 7/5 group had the best health and fitness score and was in need of less sleep. Heart rate was not affected by shift work. Conversely, consistent changes appeared in cortisol circadian profiles, the greatest changes appearing for the night shift and among the two groups of shiftworkers, more particularly for the 7/5 group. These changes correlated with self-perceived constraints of work and showed the difficulties of adaptation to shiftwork.

Adult↗

PubMed2004

Biological markers for the follow-up of athletes throughout the training season.

During the training season, a state of fatigue known as overtraining may occur, resulting from an excessive load of training, both in volume and intensity. Even now, difficult to predict the risk of overtraining, although this syndrome has been the subject of numerous studies. A lot of biological markers have been propounded. Taken alone, none of them have an absolute significance. This paper aims to review these markers, considering their biological interest, the ease with which they can be measured and the cost, from the simplest (body weight daily recording) to the most up to date markers (e.g. anti-oxidant status). They are grouped into three categories: non-invasive behavioural and biological markers, biochemical markers, and hormonal and immunological markers.

Biomarkers↗

PubMed2004

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.

Adolescent↗

PubMed2003

Behaviour of saliva cortisol [C], testosterone [T] and the T/C ratio during a rugby match and during the post-competition recovery days.

Competition is a more demanding situation than other strenuous exercise of equivalent duration; it results in stronger physiological changes. The object of this study was to get information on the duration of the recovery period by measuring changes of saliva cortisol [C], testosterone [T] and their ratio T/C in a group of international rugby players ( n=20) during the week following a rugby match (6 days). Using non-invasive saliva assays, we were able to take samples during the day of competition and the post-competitive days. Hormone levels were assayed with a routine in-house radioimmunoassay (RIA) method. Throughout the competition, C levels increased sharply (about 2.5-fold compared resting values) and returned to basal values within 4 h. Conversely, the T level decreased slightly. During the recovery period, C levels were lower and T levels were higher than basal values, resulting in a very high T/C ratio until the 5th day. This high post-competitive T/C ratio phase is probably required to restore the break-down of homeostasis induced by the very hard mental and physical strain associated with a rugby match. Thus, a period of 1 week recovery appears to be the minimal duration between two competitions.

Adaptation, Physiological↗

PubMed2003

Elevated salivary cortisol levels as a result of sleep deprivation in a shift worker.

BACKGROUND: This paper reports a case from a group of 63 shift-workers for whom adaptation to shift-work was evaluated through measurement of salivary cortisol levels. METHODS: Workers' saliva was sampled and cortisol levels measured at intervals of 2 h during morning, evening and night shifts. RESULTS: For one subject among the 63, very high values of cortisol (an approximately 6-fold increase) were observed for the morning (M) shift, but with normal values found for evening (E) and night (N) shifts. Individual mean and peak cortisol values were 48.4 and 67.8 nmol/l against group mean and peak cortisol values of 8.9 and 11.0 nmol/l. Retrospective questioning showed that this subject was healthy and there were no indicators of long-term stress. CONCLUSION: This cortisol rise was deduced to be caused by sleep deprivation as a result of rapidly rotating shift patterns.

Adaptation, Physiological↗

PubMed2003

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.

Adolescent↗

PubMed2003

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.

Journal Article↗

PubMed2002

Cortisol, DHEA, performance and training in elite swimmers.

Salivary cortisol (C) and DHEA concentrations were measured in 9 elite swimmers (4 female and 5 male) over a 37-week period, 5 to 12 times per swimmer, before 68 competitions. For female and male swimmers, no significant relationship was found between C, DHEA and performance. For the whole group, C was negatively correlated with week number of training (r = -0.31, p < 0.01). The incorporation of the cumulated distance swum as a second variable in the regression increased r to 0.56 (p < 0.01). The higher the cumulated distance swum, the higher C. No significant relationship was found between DHEA and distance swum. For individual swimmers, 3 of 4 females showed a significant negative relationship between C and cumulated dry-land training. No equivalent relationship was found for DHEA. The 2 males practicing dry-land training showed a significant and negative relationship between DHEA and cumulated dry-land training. No equivalent relationship was found for C. Thus, C and DHEA were not good predictors of swimming performance. C for individual females, and DHEA for individual males were considered useful markers for dry-land training stress.

Adolescent↗

PubMed2002

Carbohydrate dependence during hard-intensity exercise in trained cyclists in the competitive season: importance of training status.

To test the hypothesis that intensive endurance training increases CHO utilisation during hard-intensity exercise, seven competitive road cyclists (Cy) performed three 50-min steady-state exercise tests on a cycle ergometer above their ventilatory threshold (+ 15 %) over the course of a cycling season (January [ET1], May [ET2] and September [ET3]). We compared the data with the baseline values of seven sedentary controls (Sed). CHO oxidation in Cy was higher in ET2 and ET3 than in ET1 (p < 0.05), was lower in ET3 than in ET2 (p < 0.05) and was higher in Cy than in Sed only in ET2 (p < 0.05). Lactate kinematics were lower in Cy than in Sed in all conditions (p < 0.05), but in Cy they were lower in ET2 than in ET1 and higher in ET3 than in ET2 (p < 0.05). Race performance was impaired and the overtraining score was increased at ET3 in comparison with ET2 (p < 0.05). We conclude that competitive cyclists increase CHO oxidation during hard-intensity exercise over the course of a season, but show a decline by the end of the season in association with the appearance of an overtraining state. Thus, well-trained cyclists develop a CHO dependence, which is modified with training status.

Adult↗

PubMed2002

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.

Adrenergic beta-Agonists↗

PubMed2002

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.

Anthropometry↗

PubMed2001

Preliminary results on mood state, salivary testosterone:cortisol ratio and team performance in a professional soccer team.

Mood, as measured by the profile of mood states questionnaire (POMS), salivary cortisol (F) and testosterone (T) levels, and performance were examined in 17 male soccer players 4 times during a season. Soccer players provided three saliva samples when getting up (resting values, 8 a.m.), before breakfast (11.30 a.m.), and between 4.00 p.m. and 6.00 p.m. The initial measures were performed 1 day following the start of season training (T1). They were then performed before and after a high-intensity training programme (T2 and T3, respectively) and 16 weeks after T3 (T4). Iceberg profiles of POMS were observed during T1, T2 and T3, which coincided with successful performance. Subsequent decreased performance between T3 and T4 coincided with a decrease in vigor and an increase in tension and depression. Indeed, when the normal nycthemeral rhythm for F was observed (i.e. a decrease from morning until evening at all times; T1-T4), there was seemingly a non-statistical elevation of F on the morning of T3, which only became statistically significant at 11.30 a.m. on T3. In spite of a post-high-intensity training programme (T3) increase in catabolism, the soccer players presented iceberg profiles together with a high percentage of winning. Our results could suggest that in team soccer, a decreased T:F ratio does not automatically lead to a decrease in team performance or a state of team overtraining. It appears that combined psychological and physiological changes during high-intensity training are primarily of interest when monitoring training stress in relation to performance.

Adult↗

PubMed2001

Saliva assays in clinical and research biology.

This paper is an update of the current knowledges about saliva components whose assays are of biological interest and have been validated. It begins by a recall of saliva physiology: role, flow rate, main components and their mode of entry into saliva. Infectious agents and their markers are not reviewed. Peptidic molecules (catecholamines, short hormonal peptides), lipids, minerals (Na, K, Li), proteins (hormones and immunoglobulins) and steroids are examined. Assays of hormonal steroids (cortisol and sexual hormones) are described in more detail because these assays have been largely used since 1980 (many papers appeared using these methods) and are well validated. This method which allows an unstressful sampling versus venipuncture is of great interest, particularly for cortisol. Saliva assays present a lot of advantages when compared to blood assays: the sampling is very easy to do especially in a non medical environment, it does not disturb intimacy when control is needed and the risk of contamination for the laboratory technician is lower than for blood. Moreover, for molecules which are linked to blood protein carriers, the saliva concentration reflects the free blood concentration.

Animals↗