Children have a reduced maximal voluntary activation level of the adductor pollicis muscle compared to adults.

PURPOSE: The role of nervous factors in the muscle strength difference between children and adults is debated, and the level of physical activity may confound this comparison. The purpose of this study was thus to compare, between children and adults, the maximal voluntary activation level (MVA) of the adductor pollicis (AP) muscle, which is weakly influenced by the level of physical activity. METHODS: Thirteen boys (11.6 ± 0.1 years) and eight men (25.6 ± 1.5 years) were involved in this study. Neuromuscular function assessment included the evaluation of maximal voluntary contraction (MVC) force and of the MVA from peripheral magnetic stimulations of the ulnar nerve. The cross-sectional area of the AP muscle was determined with ultrasonography and used to calculate the specific force. A theoretical value of specific force, extrapolated for a full MVA, was finally computed (specific force@100 % MVA). RESULTS: MVC force (66.8 ± 6.2 vs. 111.0 ± 4.5 N, respectively; P < 0.001) and MVA (85.0 ± 2.7 vs. 94.8 ± 1.4 %, respectively; P < 0.05) were significantly lower in children compared to adults. The specific force was lower in children compared to adults (46.8 ± 3.6 vs. 56.9 ± 2.5 N/cm(2), respectively; P < 0.05), but the specific force@100 % MVA did not differ between groups. CONCLUSION: The results suggest that on an untrained muscle such as the AP muscle, the reduced ability of children to voluntarily activate their muscle could partly account for the difference of muscle strength between children and adults.

Nutritional responses to acute training sessions in young elite rugby players.

BACKGROUND: Acute exercise has been shown to induce nutritional adaptations in obese and lean inactive youth but it remains unclear whether youth with a high level of physical activity experience such exercise-induced energy intake and appetite modifications. METHODS: 14 (15- to 16-year-old) male elite rugby players completed sessions on three separate occasions: (1) a control session (CON); (2) an exercise session (EX) and; (3) a rugby session (RUGBY). The energy induced by the rugby and exercise sessions was matched (Polar Team2 pro technology), and participants' energy intake, food preferences (ad libitum buffet meals) and appetite feelings (Visual Analogue Scales) were assessed throughout the experimental days. RESULTS: The energy intake during lunch and snack time was not different between conditions. Dinner time energy intake was significantly increased after RUBGY compared to CON with respectively 969 ± 145 kcal and 777 ± 183 kcal (p < 0.05). The energy intake at dinner time was significantly increased during EX (1185 ± 199 kcal) compared to both CON (p < 0.001) and RUGBY (p < 0.01). None of the appetite feelings investigated were modified between sessions. CONCLUSION: Adolescent elite rugby players regulate their energy intake differently depending on the nature of their training; independently of the energy expended. This demonstrates the need for energetic and nutritional education to optimize their physical fitness and performance.

Superficial shoulder muscle co-activations during lifting tasks: Influence of lifting height, weight and phase.

This study aimed to assess the level of co-activation of the superficial shoulder muscles during lifting movement. Boxes containing three different loads (6, 12, and 18 kg) were lifted by fourteen subjects from the waist to shoulder or eye level. The 3D kinematics and electromyograms of the three deltoids, latissimus dorsi and pectoralis major were recorded. A musculoskeletal model was used to determine direction of the moment arm of these muscles. Finally an index of muscle co-activation named the muscle focus was used to evaluate the effects of lifting height, weight lifted and phase (pulling, lifting and dropping phases) on superficial shoulder muscle coactivation. The muscle focus was lower (more co-contraction) during the dropping phase compared to the two other phases (-13%, p<0.001). This was explained by greater muscle activations and by a change in the direction of the muscle moment arm as a function of glenohumeral joint position. Consequently, the function of the shoulder superficial muscles varied with respect to the glenohumeral joint position. To increase the superficial muscle coactivation during the dropping phase may be a solution to increase glenohumeral joint stiffness.

Exercises using the upper limbs hyperinflate COPD patients more than exercises using the lower limbs at the same metabolic demand.

BACKGROUND: Lower and upper body exercise are mandatory constituents of a rehabilitation programme for patients with COPD. However, it is not known how much these exercises may induce pulmonary dynamic hyperinflation (DH). OBJECTIVE: To evaluate the DH in patients with COPD exercising the upper and lower parts of the body at the same metabolic demand. METHODS: Sixteen patients aged 63 +/- 13 years and with a FEV1 of 1.5 +/- 0.7 L (41 +/- 11% pred) were studied. Patients initially performed a maximal exercise test with the arms using the diagonal movement technique. The lower limbs were exercised on a treadmill at the same metabolic demand. RESULTS: Inspiratory capacity decreased 222 +/- 158 ml (9.8%) after the upper body exercise (p < 0.0001) and 148 +/- 161 ml (7%) after exercise with the lower body (p = 0.0028) and a difference between the two groups was found (p < 0.05). There was no difference between resting IC before upper and lower limbs exercises (p = 0.8); increase in minute ventilation and in pulmonary ventilation in percentage of maximum voluntary ventilation and reduction of expiratory time were larger in the upper limbs exercise (p < 0.05). Dyspnea as measured by the Borg Scale was higher in the upper body (3.9 +/- 2.2) than in the lower body (2.3 +/- 1.3) at the end of the exercise (p = 0.033). Pulmonary ventilation and inspiratory capacity were correlated (p = 0.0001; r = 0.82). CONCLUSION: Exercise with the upper part of the body causes more DH and dyspnea than exercise with the lower part of the body at the same metabolic demand.

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.

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.

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.

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.

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.

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.

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.