Upper limb joint kinetic analysis during tennis serve: Assessment of competitive level on efficiency and injury risks.

The aim of this work was to compare the joint kinetics and stroke production efficiency for the shoulder, elbow, and wrist during the serve between professionals and advanced tennis players and to discuss their potential relationship with given overuse injuries. Eleven professional and seven advanced tennis players were studied with an optoelectronic motion analysis system while performing serves. Normalized peak kinetic values of the shoulder, elbow, and wrist joints were calculated using inverse dynamics. To measure serve efficiency, all normalized peak kinetic values were divided by ball velocity. t-tests were used to determine significant differences between the resultant joint kinetics and efficiency values in both groups (advanced vs professional). Shoulder inferior force, shoulder anterior force, shoulder horizontal abduction torque, and elbow medial force were significantly higher in advanced players. Professional players were more efficient than advanced players, as they maximize ball velocity with lower joint kinetics. Since advanced players are subjected to higher joint kinetics, the results suggest that they appeared more susceptible to high risk of shoulder and elbow injuries than professionals, especially during the cocking and deceleration phases of the serve.

Androgen responses to sprint exercise in young men.

The purpose of this study was to investigate the effects of a 6-month sprint training program on plasma androgens and catecholamine (CA) concentrations in response to a 6 s sprint in adolescent boys [training group (TG), n=6; control group (CG), n=6]. A 6 s-sprint test was performed on a cycle ergometer before and after training (Pre-T and Post-T, respectively). Plasma total testosterone (TT), bioavailable testosterone (BT), and CA concentrations were measured at rest, after a warm-up, immediately after a 6 s-sprint, and during the recovery (i. e. 5 and 20 min). After training period, plasma TT concentrations increased significantly at the end of the sprint and during the recovery in the TG. No effects for sampling times and period were observed in BT levels. Plasma TT concentrations after 5 min of recovery were positively correlated with the corresponding values of plasma lactate (La) concentrations and with post-6 s-sprint plasma adrenaline (A) concentrations (r=0.52; p<0.01 and r=0.61; p<0.01, respectively). These results suggest that sprint training increases plasma TT concentrations in response to sprint exercise in adolescent boys. Plasma A and plasma La concentrations increases in response to sprint exercise could be involved in this elevation of plasma TT concentrations.

Exercise-induced oxidative stress in overweight adolescent girls: roles of basal insulin resistance and inflammation and oxygen overconsumption.

HYPOTHESIS: Basal insulin resistance (IR) and inflammation exacerbate post-exercise oxidative stress (OS) in overweight adolescent girls. DESIGN: Cross-sectional study, effect of incremental ergocycle exercise until exhaustion on OS markers. PARTICIPANTS: Normal-weight (control) (n=17, body mass index (BMI): 20-24.2 kg/m(2)) and overweight adolescent girls (n=29, BMI: 24.1-36.6 kg/m(2)). MEASUREMENTS: Dietary measurement, physical activity assessment (validated questionnaires), fat distribution parameters (by dual-energy X-ray absorptiometry and anthropometry) and maximal oxygen consumption (VO2peak). Blood assays include the following: (1) at fasting state: blood cell count, lipid profile, and IR parameters (leptin/adiponectin ratio (L/A), homeostasis model assessment of IR, insulin/glucose ratio; (2) before exercise: inflammation and OS markers (interleukin-6 (IL-6), C-reactive protein (CRP), myeloperoxidase (MPO), reduced glutathione/oxidized glutathione ratio (GSH/GSSG), 15 F(2)alpha-isoprostanes (F(2)-Isop), lipid hydroperoxides (ROOH), oxidized low-density lipoprotein (ox-LDL)) and antioxidant status (superoxide dismutase (SOD), glutathione peroxidase (GPX), vitamin C, alpha-tocopherol and beta-carotene); and (3) after exercise: inflammation and OS markers. RESULTS: At rest, overweight girls had a deteriorated lipid profile and significantly higher values of IR parameters and inflammation markers, compared with the control girls. These alterations were associated with a moderate rest OS state (lower GSH/GSSG ratio, alpha-tocopherol/total cholesterol (TC) ratio and GPX activity). In absolute values, overweight girls exhibited higher peak power output and oxygen consumption (VO2peak), compared with the control girls. Exercise exacerbated OS only in the overweight group (significant increase in F(2)-Isop, ROOH and MPO). As hypothesized, basal IR and inflammation state were correlated with the post-exercise OS. However, the adjustment of F(2)-Isop, ROOH and MPO variation per exercise VO(2) variation canceled the intergroup differences. CONCLUSION: In overweight adolescent girls, the main factors of OS, after incremental exhaustive exercise, are not the basal IR and inflammation states, but oxygen overconsumption.

Athletic performance and weight changes during the "Marathon of Sands" in athletes well-trained in endurance.

The purpose of this study is to examine the effects of the "Marathon of Sands" (MS), a 7-day, self-sufficient-diet, multi-stage running race across a section of the Moroccan desert, on body weight and plasma volume variation (PVV) and the relationship of these factors to performance in athletes who are well-trained in endurance. Sixteen MS runners agreed to participate in this study. Weight and body composition were measured and venous blood samples were taken before the first stage (D0), after the third stage (D3) and at the end of the MS (after the sixth stage: D6). Haematocrit and haemoglobin were used to calculate PVV at (D0, D3, and D6). No significant plasma volume decrease was observed throughout the race. Significant decreases in total body weight (BW), fat-free mass (FFM) and fat mass (FM) were observed in D3 and D6 (-4.3%, -3.5%, -0.8%; and -6.1%, -5%, -1.1%, respectively, for BW, FFM and FM at D3 and D6). This study clearly shows that, despite extreme conditions, the MS did not lead to a significant PV decrease in athletes well-trained in endurance. This study also supports the hypothesis that significant body weight loss may not systematically affect performances during long duration multiple-stage races.

Alteration in sympathoadrenergic activity at rest and during intense exercise despite normal aerobic fitness in late pubertal adolescent girls with type 1 diabetes.

BACKGROUND: An impaired sympathoadrenergic response to hypoglycaemic episodes has been described in young Type 1 diabetic subjects. It is unknown if this altered response occurs with exercise, and if it could influence aerobic power. METHODS: Body composition (skinfold thickness), physical activity (questionnaire) and aerobic power (PWC170 and VO2max) were assessed in 19 post-menarcheal Type 1 diabetic (T1D) girls (13.3-18.2 years) and 19 healthy siblings. At rest and at each stage of the graded exhaustive exercise, plasma glucose, insulin, epinephrine and norepinephrine, were monitored via an intravenous catheter. RESULTS: Only when expressed per kilograms of body weight, was aerobic power impaired in T1D girls compared to controls, probably because they were overweight. Throughout exercise, plasma glucose remained stable while plasma insulin decreased in the healthy girls, whereas glucose diminished significantly with no change in plasma insulin in T1D girls. During exercise catecholamines increased in the same way in both groups. However, at rest and throughout all stages of exercise, norepinephrine levels were significantly lower by a mean difference of 1.2 nmol/L, while epinephrine levels were significantly higher by a mean difference of 0.14 nmol/L, in T1D girls compared to healthy girls. Heart rates of T1D girls were not affected by the sympathoadrenergic alteration. CONCLUSION: T1D adolescent girls display an altered sympathoadrenergic activity at rest and during intense exercise. Their reduced sympathetic activity, albeit probably compensated for by higher adrenomedullary responsiveness or sensitivity, does not affect their heart rate adaptations to exercise.

Accuracy of physical working capacity 170 to estimate aerobic fitness in prepubertal diabetic boys and in 2 insulin dose conditions.

AIM: Exercise tests evaluate the effects of physical activity, which is one of the four recommendations for diabetes treatment. An adjusted and accurate measure of aerobic capacity in diabetic patients is thus needed. This study compared two estimates of aerobic fitness (maximal oxygen uptake vs physical working activity PWC170, i.e., the workload at a pulse of 170) and the usual versus a reduced insulin dose in preadolescent boys with type 1 diabetes mellitus. METHODS: Sixteen prepubertal type 1 diabetic boys performed a submaximal test, the PWC(170). Gas exchange values and capillary blood glucose levels were monitored and, when possible, the test was extended to exhaustion. In 7 boys, the test was performed twice on separate days. On one day they received their usual insulin dose and on the other, their short-acting insulin was reduced by 1/3; the two tests were held in random order. The 9 other children were tested only once after receiving their usual insulin dose. RESULTS: For the 16 boys who performed the test with the usual insulin dose, PWC(170) (W) and peak oxygen uptake (peak VO(2)) (L.min(-1)) correlated closely (r=0.81, P=0.002). Aerobic fitness did not change with insulin dose, but some hypoglycemic episodes occurred when insulin dose was not reduced. CONCLUSIONS: Since maximal effort does not add more information, routine use of the submaximal peak VO(2)-correlated test, the PWC(170), seems sufficient, possibly in association with a planned insulin dose reduction. This dose change does not interfere with performance, but could reduce the risk of hypoglycemia.

Metabolic and hormonal responses to exercise in children and adolescents.

UNLABELLED: Ethical and methodological factors limit the availability of data on metabolic and hormonal responses to exercise in children and adolescents. Despite this, it has been reported that young individuals show age-dependent responses to short and long term exercise when compared with adults. Adenosine triphosphate (ATP) and phosphocreatine stores are not age-dependent in children and adolescents. However, phosphorus-31 nuclear magnetic resonance spectroscopy (31PNMR) studies showed smaller reductions in intramuscular pH in children and adolescents during high intensity exercise than adults. Muscle glycogen levels at rest are less important in children, but during adolescence these reach levels observed in adults. Immaturity of anaerobic metabolism in children is a major consideration, and there are several possible reasons for this reduced glycolytic activity. There appear to be higher proportions of slow twitch (type I) fibres in the vastus lateralis part of the quadriceps in children than in untrained adults, and anaerobic glycolytic ATP rephosphorylation may be reduced in young individuals during high intensity exercise. Reduced activity of phosphofructokinase-1 and lactate dehydrogenase enzymes in prepubertal children could also explain the lower glycolytic capacity and the limited production of muscle lactate relative to adults. These observations may be related to reduced sympathetic responses to exhaustive resistance exercise in young people. In contrast, children and adolescents are well adapted to prolonged exercise of moderate intensity. Growth and maturation induce increases in muscle mass, with proliferation of mitochondria and contractile proteins. However, substrate utilisation during exercise differs between children and adults, with metabolic and hormonal adaptations being suggested. Lower respiratory exchange ratio values are often observed in young individuals during prolonged moderate exercise. Data indicate that children rely more on fat oxidation than do adults, and increased free fatty acid mobilisation. glycerol release and growth hormone increases in preadolescent children support this hypothesis. Plasma glucose responses during prolonged exercise are generally comparable in children and adults. When glucose is ingested at the beginning of moderate exercise, plasma glucose levels are higher in children than in adults, but this may be caused by decreased insulin sensitivity during the peripubertal period (as shown by glucose: insulin ratios). CONCLUSIONS: Children are better adapted to aerobic exercise because their energy expenditure appears to rely more on oxidative metabolism than is the case in adults. Glycolytic activity is age-dependent, and the relative proportion of fat utilisation during prolonged exercise appears higher in children than in adults.

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.

A test to approach maximal lactate steady-state in 12-year old boys and girls.

The purpose of this study was to measure the running velocity corresponding to the individual maximal lactate steady-state of a group of 12-year old boys and girls on a treadmill. This running velocity (v MLST) was compared with the maximal aerobic running velocity (v a max) at which maximal oxygen uptake (VO2 max) occurs. Thirteen pupils of the same school whose puberal maturation corresponded to the end of stage 2 and the beginning of stage 3 of Tanner: 6 boys (12.2 years old +/- 0.5, 38.4 +/- 2 kg, 150 +/- 4.8 cm: group 1) and 7 girls (12.3 years old +/- 0.5, 37.6 +/- 6 kg, 151.4 +/- 5.6 cm: group 2) carried out two tests at one week interval. The first test was a maximal incremental test for the determination of VO2 max with Douglas's bag method and v a max. The purpose of the second test was the determination of maximal lactate steadystate velocity (v MLST) With two stages of ten minutes at 60 +/- 5% and 74 +/- 4.5% v a max separated by 40 minutes of complete rest (Billat, 1992); VO2max and v a max were significantly different, equal to 49.4 +/- 7 ml.min-1.kg-1, 40.4 +/- 4.7 ml.min-1.kg-1 and 12.6 +/- 0.2 km.h-1, 11.2 +/- 1.2 km.h-1 for group 1 and 2 respectively (P < 0.05). Moreover, maximal lactate steady state velocity (v MLST) was respectively equal to 64.8 +/- 12.5% and 64.6% +/- 12.5% VO2 max respectively, representing 67.8 +/- 6.2% and 68.8% +/- 8.3% v a max and was not significantly different for group 1 and 2. In conclusion, this study shows that maximal lactate steady-state velocity is not significantly different between young boys and girls of 12 years old, when expressed in fraction of VO2 max or v a max. However, VO2 max and v a max were significantly higher in boys: +27.2 and +11.6% higher respectively.

Physiological profile of handball players.

BACKGROUND: The purpose of this study was to determine the physiological profile of handball players compared to sprinters, endurance trained and untrained subjects. METHODS: Forty-six subjects aged between 19 and 28 years took part in this study: 10 were national handball players (NHB); 7 were international handball players (IHB), 11 were sprint trained subjects (ST); 8 were endurance trained subjects (ET); and 10 were untrained subjects (UT). They performed an incremental treadmill test to determine the maximal oxygen uptake (VO2max), and a Wingate anaerobic test (WanT) to determine maximal power (Wmax). Plasma lactate (La) concentration was measured 5 minutes after the end of the Wingate-test. RESULTS: The VO2max of NHB was similar to that of the IHB and ST athletes but higher than that of the untrained and lower than the endurance trained athletes. Values for Wmax were similar in the IHB and NHB groups and very close to the sprinters. When normalized for body mass or to lean body mass, Wmax was greater in handball players when compared to untrained or endurance trained subjects. Lactate values were in the same range in the NHB, IHB and ST groups and were statistically higher in the NHB and IHB groups than in the UT or ET groups. CONCLUSIONS: The results suggest that the anaerobic metabolism seems to be important for the handball players similarly to sprinters. Since handball is known as a sport with typically short exercise periods of high intensity alternating with rests, anaerobic metabolism appears then to be higbly relevant to performance.

Effects of submaximal intensity cycle ergometry for one hour on substrate utilisation in trained prepubertal boys versus trained adults.

AIM: Substrate utilisation during exercise might be different in trained prepubertal boys compared to trained adults, so dietary advice usually given to endurance trained adults may need to be adapted for endurance trained children. EXPERIMENTAL DESIGN: subjects pedalled for 1 hour on an ergocycle at 40% or 60% of Wmax (maximal aerobic power). PARTICIPANTS: 14 boys and 13 adults active in endurance sport (swimming). MEASURES: pulmonary respiratory gas-exchange ratio [RER = VCO(2)/VO(2)], used as the equivalent of the non protein respiratory quotient (RQ), was measured at rest, at the 15(th), 30(th), 45(thv and 60(th) min of exercise in order to calculate energy expenditure. RESULTS: Relative resting energy expenditure was significantly higher in boys than in adults. During exercise, energy expenditure (EE) was significantly lower in children than in adults (p<0.001), whereas fat-free mass relative EE was only influenced by intensity. Relative EE from carbohydrates (EE(CHO)) was lower in children compared to adults, even if the highest intensity involves a higher EE(CHO) in both groups (p<0.05). Boys oxidised more lipid at 40% of Wmax than 60% of Wmax or adults at either intensity. CHO utilisation was significantly increased at 60% vs 40% of Wmax, yet lower in boys than in men (p<0.01). Lipids' use, in g x min(-1) x kg-1)FFM, was significantly higher in boys than in men at 40% of Wmax (p<0.01). CONCLUSION: Trained children, at rest, had greater fat-free mass energy expenditure than adults, which may be linked to growth processes that remain unclear. During exercise, in boys, the main observation was the increase in CHO dependence relative with the intensity. Thus, it appears that CHO feeding is as important in endurance-trained boys as in endurance-trained adults, especially when exercise intensity approaches that of competition or training sessions.

Glucose tolerance during moderate prolonged exercise in women with oral contraceptives as compared to non-users.

BACKGROUND: The purpose of this study was to assess gluco-se tolerance during exercise in women on oral contraceptives. METHODS: To this end, we investigated the effects of glucose ingestion on glucose and hormonal responses in 7 women on oral contraceptives (OC(+); 21.3+/-1.3 yrs) and 7 normally menstruating (OC(-); 22.6+/-1.3 yrs) during an ergocycle test (30 min, 60% VO2max). Venous blood samples were withdrawn at 0, 3, 5, 10, 15 and 30 min exercise and at the 30th min postexercise. Glucose was ingested per os (0.5 g x kg(-1) b.w) between the 2nd and the 3rd min of the exercise. RESULTS: Under resting condition, plasma glucose and catecholamine concentrations were similar in both groups whereas plasma GH and insulin levels were greater in OC(+) (p<0.05). Glucose/insulin ratio (G/I), used as an indicator of insulin resistance, suggested a reduced insulin sensitivity at rest in the OC(+) (p<0.05). No significant differences were observed between OC(+) and OC(-) in plasma glucose, insulin, and catecholamine concentrations during exercise. Plasma GH values were greater in OC(+) from the 15th min of the exercise and during the recovery period (p<0.01). CONCLUSIONS: This study indicated that oral glucose ingestion at the onset of prolonged submaximal exercise induced similar glucose tolerance in women taking or not oral contraceptives.

Effect of sprint duration (6 s or 30 s) on plasma glucose regulation in untrained male subjects.

AIM: We have explored in the following study the glucoregulatory responses (glycemia, insulinemia, catecholamines) at the end of 2 supramaximal tests of different durations. METHODS: Seven untrained male subjects (21.9+/-0.3 y) performed an isolated exercise of 6 s (T6) and a Wingate-test of 30 s. To determine the levels of lactate (La), plasma concentrations of glucose, insulin, adrenaline (A) and noradrenaline (NA), blood samples have been collected successively at rest, after a warm-up period of 15 min, immediately after T6 and T30, and after 5, 10, 20, and 30 min of recovery. RESULTS: Whether expressed as absolute or relative values, the peak power recorded during the 2 tests is statistically the same in T6 and T30. The maximal value of lactate (L(amax)) measured 5 min after the end of the 2 exercises is significantly greater after T30 (12.3+/-0.9 mmol x L(-1)) than after T6 (5.4+/-0.4 mmol x L(-1)) and T30 (4.2+/-0.2 mmol x L(-1)). No significant difference is observed between the plasma glucose concentrations recorded after the 2 tests until the first 10 min of recovery. However the plasma glucose values recorded after 20 and 30 min of recovery are significantly higher after T6 than after T30. Whatever the duration of the test, the insulinemia level remains unchanged at the end of the exercise and during the 30 min of recovery. On the other hand, the values of adrenaline and noradrenaline after T6 and T30 become considerably higher than those recorded at rest. However, the increase remains significantly higher after T30 (13.5+/-1.8 nmol x L(-1) for NA and 2.7+/-0.7 nmol x L(-1) for A) than after T6 (4.9+/-0.3 nmol x L(-1) for NA and 1.2+/-0.2 nmol x L(-1) for A). CONCLUSION: These results suggest that the mechanism responsible for increasing blood glucose surpass those which decrease it during supramaximal exercise. However, plasma glucose concentrations is affected by the duration of supramaximal exercise. The lower increase of plasma glucose concentration after T30 than after T6 might be explained by the resting of muscle glycogen stores which are more used during T30 than after T6, but in the absence of muscle glycogen content measurement we cannot conclude.

Metabolic dysfunction in late-puberty adolescent girls with type 1 diabetes: relationship to physical activity and dietary intakes.

AIMS: At puberty, type 1 diabetes (T1D) among young girls can lead to excess body weight, insulin resistance, deterioration of glycaemic control and dyslipidaemia. Although biological factors contribute largely to such metabolic dysfunction, little is known of the role of behavioural factors such as physical activity and diet. METHODS: This study investigated the association between metabolic dysfunction measured after a 12-h overnight fast and behavioural factors, including diet (4-day diary) and physical activity (validated questionnaire), in 19 postmenarchal adolescent girls with T1D compared with 19 healthy girls. RESULTS: T1D girls displayed higher levels of fat mass, insulin resistance (higher plasma glucose, serum leptin and waist-to-hip ratios) and dyslipidaemia (higher LDL-C and apolipoprotein B levels, lower HDL-C and apolipoprotein A-1 levels). Also, contrary to what is usually observed in T1D adults, serum adiponectin, an important vessel protector, was not raised in T1D adolescent girls compared with healthy controls. Quantity and quality of dietary macronutrient intakes as well as physical activity levels were comparable in both groups, although the T1D girls with the poorest metabolic profiles reported having the healthiest diets (fewer total calories, more protein and less carbohydrates). However, in T1D girls, less physical activity and more time spent watching television were associated with poorer metabolic profiles (higher waist-to-hip ratios, fat mass and leptin levels, and lower adiponectin, HDL-C and apolipoprotein A-1 levels). CONCLUSION: Collectively, these data suggest that physical inactivity is linked to metabolic dysfunction to a greater extent than unhealthy dietary habits in postmenarchal T1D adolescent girls.

Clinical assessment of external rotation for the diagnosis of anterior shoulder hyperlaxity.

The aim of this study was to evaluate two methods of clinical assessment for external rotation of the shoulder to optimise the diagnosis of hyperlaxity in patients being selected for surgery for stabilisation of chronic anterior instability. External rotation was evaluated in 70 healthy student volunteers by two examiners (intertester study) using two methods of assessment at 15-day intervals (intratester study). The first method used was the protocol described for the Instability Severity Index Score (ISIS). In this case, the subject was evaluated in the sitting position, bilaterally with passive range of motion movements. The shoulder was considered hyperlax if ER1 was greater than 85°. With the second, so-called "elbow on the table" (EOT) method, the subject was evaluated in the decubitus dorsal position, unilaterally with passive range of motion. The subject was considered to be hyperlax if ER1 was greater than 90°. Kappa values for intra- and intertester agreement with the ISIS method were average, while they were satisfactory with the intraclass coefficient (ICC). Kappa values for inter- and intratester agreement with the EOT method were average and good, respectively. This tendency was confirmed by the ICC which went from good to excellent for the two examiners in both series of measurements using the EOT method, showing better reproducibility with this method. Our study confirms that the most reproducible method for assessing external rotation is obtained by unilateral assessment of the patient in the decubitus dorsal position, with passive range of motion. An ER1 of 90° is the necessary threshold for hyperlaxity because of elbow retropulsion with this method, which provides immediate and visual evaluation and eliminates the necessity of goniometry.

Effect of training and detraining on catecholamine responses to sprint exercise in adolescent girls.

Training is well known to influence catecholamine responses to exercise. In women, this training effect is still not well characterized and has been studied mostly in adults. Hence, we investigated in this longitudinal study, the effects of a 6-month sprint training program followed by 5 months of detraining on plasma catecholamine responses to a sprint exercise in young female subjects. Twelve healthy adolescent girls [training group (TG), n=6; control group (CG), n=6] took part in our study. TG participated in 6 months of supervised sprint training program (3 days/week) and has no training past whereas, CG continued with it's normal activity. A 6s-sprint test was performed on a cycle ergometer before training (P1) and after training (P2) in both the groups. TG only realized a 6s-sprint test after 5 months of detraining (P3). Blood lactate concentrations (La) as well as plasma adrenaline (A) and noradrenaline (NA) concentrations were measured at rest, immediately after the warm-up and the 6s-sprint and during recovery. Peak power W peak), expressed both in absolute and relative values, were significantly increased in TG in P2 (P<0.01) but did not change in CG. After the sprint-training period, the warm-up and the 6s-sprint induced plasma A increase and the maximal A concentrations were significantly higher than in P1 and P3 for TG only (P<0.05). Plasma A did not change in CG after 6 months. In P3, W peak and maximal lactate concentrations ([La]max) were significantly greater compared to P1 and P2 in TG (P<0.05). In CG, [La]max were significantly increased in P2 (P<0.05). The present study demonstrates that 6 months of sprint training in adolescent girls induce both an increase in performances and in A responses to sprint exercise. This adrenergic adaptation disappears after 5 months of detraining whereas the gain in performance is maintained. These new data may lead to practical considerations.

Stroboscopic computerized determination of humeral rotation in overarm throwing.

Analysis of the final phase of the overarm handball throw was carried out by a microcomputerized treatment of photographic images taken simultaneously in two grid layouts. Reflective stickers on the joints of the throwing arm (shoulder, elbow, wrist) allowed the coordinates of these three points to be measured against a reference on the wall. Using a mathematical treatment and Euler matrices, the movement could be studied in space. The results confirmed that humeral rotation occurs during the overarm handball throw. Initial external rotation was immediately followed with internal rotation about 40 ms before ball release.

Thermoregulation at rest and during exercise in prepubertal boys.

Thermal balance was studied in 11 boys, aged 10-12 years, with various values for maximal oxygen uptake (VO2max), during two standardized sweating tests performed in a climatic chamber in randomized order. One of the tests consisted in a 90-min passive heat exposure [dry bulb temperature (Tdb) 45 degrees C] at rest. The second test was represented by a 60-min ergocycle exercise at 60% of individual VO2max (Tdb 20 degrees C). At rest, rectal temperature increased during heat exposure similar to observations made in adults, but the combined heat transfer coefficient reached higher values, reflecting greater radiative and convective heat gains in the children. Children also exhibited a greater increase in mean skin temperature, and a greater heat dissipation through sweating. Conversely, during the exercise sweating-test, although the increase in rectal temperature did not differ from that of adults for similar levels of exercise, evaporative heat loss was much lower in children, suggesting a greater radiative and convective heat loss due to the relatively greater body surface area. Thermophysiological reactions were not related to VO2max in children, in contrast to adults.

Lactate and catecholamine responses in male and female sprinters during a Wingate test.

A total of six male and six female sprinters at the same national competition level and aged 18-20 years performed a force/velocity test and a 30-s supramaximal exercise test (Wingate test) on 2 different days, separated by a maximal interval of 15 days. The maximal anaerobic power (Wmax) was determined from the force/velocity test, and the mean anaerobic power (W) from the Wingate test. Immediately after the Wingate test, a 5-ml venous blood sample was drawn via a heparinized catheter in an antebrachial vein for subsequent catecholamine (adrenaline and noradrenaline) analysis. After 5 min recovery a few microliters of capillary blood were also taken for an immediate lactate determination. Even expressed per kilogram lean body mass, Wmax and W were significantly lower in women. The lactate and adrenaline responses induced by the Wingate test were also less pronounced in this group whereas the noradrenaline levels were not significantly different in men and women. Above all, very different relationships appeared between lactate, adrenaline, noradrenaline and W according to sex. Thus, as reported by other authors, the adrenergic response to a supramaximal exercise seemed to be lower in women than in men. Nevertheless a different training status between the two groups, even at same national competition level, could not be excluded and might contribute, at least in part, to the gender differences observed in the present study.

Extent of lactic anaerobic metabolism in handballers.

The authors investigated lactic anaerobic metabolism in handball players during practice games. Seven players aged 18-21, belonging to second division league clubs, took part in the study. In the laboratory, VO2 max and the onset of blood lactate accumulation (OBLA) were determined with progressive maximal ergocycle tests. On the field, video recordings, cardiotelemetry, and rectal temperature measurements made during the first half of the game were used to quantify exertion. An intravenous catheter worn permanently was used to draw blood for lactate measurements at the 5th, 10th, 15th, 20th, and 30th min of play and after a 10-min rest period. The results confirmed earlier observations showing the need for an excellent maximal aerobic power and capacity in handballers. However, the maximal lactate levels observed (4-9 mmol X l-1) were above those that could be expected from samples drawn only at the end of play. These findings indicate that players must be trained to tolerate high lactate levels to preserve their maximal efficiency throughout the game. Finally, lactate production increased with player exertion and with increasing OBLA.