Overhead and Wheelchair Sport-related injuries in Para Athletes: Interplay between disability and sport specific factors.

ABSTRACT: With the increasing opportunities for people with disabilities to engage in competitive Para sports, it becomes imperative to understand the injury consequences that may impact both sports participation and daily life activities. This narrative review aims to examine the intrinsic and extrinsic risk factors inherent in overhead and wheelchair summer Para sports, while also exploring prospective avenues for implementing prevention strategies. By understanding the injury epidemiology in this cohort of Para athletes, this review aims to explore the intricate interplay between the athletes' underlying disability with sport-specific factors, such as how wheelchair use might amplify injury susceptibility. Specifically, we highlight the impact of impairment, daily activity, and workload or discipline-induced overuse on injury occurrence, as well as how surveillance methods can be tailored to this population. In this regard, we propose practical injury surveillance methods that encompass a sensitive injury definition, severity assessment, incidence rate calculation, and the recording of adaptive equipment (e.g., type of wheelchair) and workload monitoring. It is worth noting that studies of prospective injury surveillance systems coupled with workload monitoring within a dedicated Para sport web-based platform are scarce. To establish a comprehensive understanding of Para athlete health, the monitoring framework should incorporate regular athlete follow-ups and facilitate knowledge transfer.

Neuromuscular Adaptations in Endurance-Trained Male Adolescents Versus Untrained Peers: A 9-Month Longitudinal Study.

BACKGROUND: Neuromuscular function is considered as a determinant factor of endurance performance during adulthood. However, whether endurance training triggers further neuromuscular adaptations exceeding those of growth and maturation alone over the rapid adolescent growth period is yet to be determined. OBJECTIVE: The present study investigated the concurrent role of growth, maturation, and endurance training on neuromuscular function through a 9-month training period in adolescent triathletes. METHODS: Thirty-eight 13- to 15-year-old males (23 triathletes [~6 h/week endurance training] and 15 untrained [<2 h/week endurance activity]) were evaluated before and after a 9-month triathlon training season. Maximal oxygen uptake (V̇O2max) and power at V̇O2max were assessed during incremental cycling. Knee extensor maximal voluntary isometric contraction torque (MVCISO) was measured and the voluntary activation level (VAL) was determined using the twitch interpolation technique. Knee extensor doublet peak torque (T100Hz) and normalized vastus lateralis (VL) electromyographic activity (EMG/M-wave) were also determined. VL and rectus femoris (RF) muscle architecture was assessed using ultrasonography. RESULTS: Absolute V̇O2max increased similarly in both groups but power at V̇O2max only significantly increased in triathletes (+13.8%). MVCISO (+14.4%), VL (+4.4%), and RF (+15.8%) muscle thicknesses and RF pennation angle (+22.1%) increased over the 9-month period in both groups similarly (p < 0.01), although no changes were observed in T100Hz, VAL, or VL EMG/M-wave. No changes were detected in any neuromuscular variables, except for coactivation. CONCLUSION: Endurance training did not induce detectible, additional neuromuscular adaptations. However, the training-specific cycling power improvement in triathletes may reflect continued skill enhancement over the training period.

Can neuromuscular differences manifest by early adolescence in males between predominantly endurance and strength sports?

INTRODUCTION: Although neuromuscular function varies significantly between strength and endurance-trained adult athletes, it has yet to be ascertained whether such differences manifest by early adolescence. The aim of the present study was to compare knee extensor neuromuscular characteristics between adolescent athletes who are representative of strength (wrestling) or endurance (triathlon) sports. METHODS: Twenty-three triathletes (TRI), 12 wrestlers (WRE) and 12 untrained (CON) male adolescents aged 13 to 15 years participated in the present study. Maximal voluntary isometric contraction (MVIC) knee extensor (KE) torque was measured, and 100-Hz magnetic doublets were delivered to the femoral nerve during and after KE MVIC to quantify the voluntary activation level (%VA). The doublet peak torque (T100Hz) and normalized vastus lateralis (VL) and rectus femoris (RF) EMG (EMG/M-wave) activities were quantified. VL and RF muscle architecture was also assessed at rest using ultrasound. RESULTS: Absolute and relative (to body mass) KE MVIC torques were significantly higher in WRE than TRI and CON (p < 0.05), but comparable between TRI and CON. No significant differences were observed between groups for %VA, T100Hz or either VL or RF muscle thickness. However, VL EMG/M-wave was higher, RF fascicle length longer, and pennation angle smaller in WRE than TRI and CON (all p < 0.05). CONCLUSION: The wrestlers were stronger than triathletes and controls, potentially as a result of muscle architectural differences and a greater neural activation. Neuromuscular differences can already be detected by early adolescence in males between predominantly endurance and strength sports, which may result from selection bias and/or physical training.

Effects of a Cycling versus Running HIIT Program on Fat Mass Loss and Gut Microbiota Composition in Men with Overweight/Obesity.

PURPOSE: High-intensity interval training (HIIT) can efficiently decrease total and (intra-)abdominal fat mass (FM); however, the effects of running versus cycling HIIT programs on FM reduction have not been compared yet. In addition, the link between HIIT-induced FM reduction and gut microbiota must be better investigated. The aim of this study was to compare the effects of two 12-wk HIIT isoenergetic programs (cycling vs running) on body composition and fecal microbiota composition in nondieting men with overweight or obesity. METHODS: Sixteen men (age, 54.2 ± 9.6 yr; body mass index, 29.9 ± 2.3 kg·m -2 ) were randomly assigned to the HIIT-BIKE (10 × 45 s at 80%-85% of maximal heart rate, 90-s active recovery) or HIIT-RUN (9 × 45 s at 80%-85% of maximal heart rate, 90-s active recovery) group (3 times per week). Dual-energy x-ray absorptiometry was used to determine body composition. Preintervention and postintervention fecal microbiota composition was analyzed by 16S rRNA gene sequencing, and diet was controlled. RESULTS: Overall, body weight, and abdominal and visceral FM decreased over time ( P < 0.05). No difference was observed for weight, total body FM, and visceral FM between groups (% change). Conversely, abdominal FM loss was greater in the HIIT-RUN group (-16.1% vs -8.3%; P = 0.050). The α-diversity of gut microbiota did not vary between baseline and intervention end and between groups, but was associated with abdominal FM change ( r = -0.6; P = 0.02). The baseline microbiota profile and composition changes were correlated with total and abdominal/visceral FM losses. CONCLUSIONS: Both cycling and running isoenergetic HIIT programs improved body composition in men with overweight/obesity. Baseline intestinal microbiota composition and its postintervention variations were correlated with FM reduction, strengthening the possible link between these parameters. The mechanisms underlying the greater abdominal FM loss in the HIIT-RUN group require additional investigations.

A long-duration race induces a decrease of left ventricular strains, twisting mechanics and myocardial work in trained adolescents.

We investigated the acute cardiac consequences of a long-duration (>5 h) adventure race in adolescent athletes from evaluations of left ventricular (LV) strains and myocardial work. Twenty trained male adolescents (i.e. 8 ± 4 h·week-1 of endurance sports) aged 14-17 years participated in a competitive long-duration adventure race. Blood samples were collected before, immediately and 24 h after the race to determine the time course of troponin I (cTnI) considered a myocardial damage biomarker. Resting echocardiography was conducted before and after the race to assess myocardial regional strains, LV twisting mechanics and myocardial work using speckle tracking echocardiography. The mean completion time of the race was 05:38 ± 00:20 h, with a mean heart rate (HR) of 83 ± 5% of maximal HR. cTnI concentration significantly increased in 16/20 participants after the race (pre: 0.001 ± 0.002 vs. post: 0.244 ± 0.203 ng·dL-1, p < .001) and returned to baseline within 24 h. Stroke volume, ejection fraction and global longitudinal strains remained unchanged after the race, while LV twist and global myocardial work significantly decreased (8.6 ± 3.3 vs. 6.3 ± 3.3 deg and 2080 ± 250 vs. 1781 ± 334 mmHg%, p < .05). Diastolic function, indexes of myocardial relaxation and LV untwisting rate (-91.0 ± 19.0 vs. -56.4 ± 29.1 deg·s-1, p < .001) were affected after the race. We demonstrated that in trained adolescents, a high-intensity endurance exercise of several hours induced an increase of the cTnI concentration associated with an alteration of myocardial function.HighlightsThis is the first study to explore the acute cardiac consequences of a very-long duration and high-intensity race in trained adolescentsThe cardiac evaluations before and immediately after the race were conducted using up-to-date advances in echocardiography, including not only regional left ventricular strains, rotations and twists, but also global myocardial work to consider changes in loading conditions that occur after such exercises.We observed exercise-induced cardiac fatigue in the adolescents, characterized by a drop in myocardial work, associated with an increase of cardiac troponin I in 16/20 participants.The cardiac alterations were principally observed at the apical level of the heart: the apical strains and rotations were decreased and delayed. Consequently, left ventricular twist and twisting rates were also delayed, which probably affected the diastolic function after the race.

Impact of long-duration adventure racing on hydration status, blood electrolytes and biomarkers of kidney function in trained adolescent athletes.

BACKGROUND: Little is known about the biochemical consequences of endurance activities in adolescents. The present study aimed to examine the impact of a long-duration adventure race (>5 h) on hydration status, blood electrolytes and biomarkers of kidney function in adolescent athletes. METHODS: Twenty male adolescents aged 14 to 17 y (mean±SD; body mass: 59.7±9.1 kg and maximal O2 uptake: 56.2±4.6 mL∙kg-1∙min-1) volunteered to participate in a competitive adventure race of 68.5 km. Volunteers could drink ad libitum and fluid intake was monitored throughout the race. Blood samples were collected before, within 15 minutes after, and 24 hours after the race to monitor blood electrolytes (sodium, potassium, chloride), creatinine and blood urea nitrogen (BUN). Body mass and urine specific gravity (USG) were also measured across the same time points. RESULTS: The race was completed on average in 05:38±00:20 h:min under cold and rainy conditions (10-15 °C and 83-93% of relative humidity). Fluid intake was 1.45±0.66 L and body mass decreased by 1.2% compared to before the race (P<0.001). Blood sodium concentrations remained stable after the race (140.4±2.1 mmol∙L-1) despite an expansion in the plasma volume of 8.9±15.6%. No significant variations in BUN or BUN-to-creatinine ratio occurred. A significant increase in creatinine (+13.5%, P=0.003) was observed immediately after the race but remained within the reference range. CONCLUSIONS: The long-duration race completed under cold and humid conditions seems not to have exposed adolescents to hypohydration, hyponatremia or clinically significant alterations in kidney function.

Effect of Concurrent Training on Body Composition and Gut Microbiota in Postmenopausal Women with Overweight or Obesity.

PURPOSE: Menopause tends to be associated with an increased risk of obesity and abdominal fat mass (FM) and is associated with lower intestinal species diversity. The aim of this study was to determine the effects of a high-intensity interval training and resistance training (HIIT + RT) program on body composition and intestinal microbiota composition in overweight or obese postmenopausal women. METHODS: Participants (n = 17) were randomized in two groups: HIIT + RT group (3× per week, 12 wk) and control group without any training. Dual-energy x-ray absorptiometry was used to measure whole-body and abdominal/visceral FM and fat-free mass. Intestinal microbiota composition was determined by 16S rRNA gene sequencing at baseline and at the study end, and the diet was controlled. RESULTS: Compared with sedentary controls, physical fitness (maximal oxygen consumption, peak power output) increased, total abdominal and visceral FM decreased, and segmental muscle mass increased in the training group. Although the HIIT + RT protocol did not modify α-diversity and taxonomy, it significantly influenced microbiota composition. Moreover, various intestinal microbiota members were correlated with HIIT + RT-induced body composition changes, and baseline microbiota composition predicted the response to the HIIT + RT program. CONCLUSIONS: HIIT + RT is an effective modality to reduce abdominal/visceral FM and improve physical capacity in nondieting overweight or obese postmenopausal women. Training modified intestinal microbiota composition, and the response to training seems to depend on the initial microbiota profile. More studies are needed to determine whether microbiota composition could predict the individual training response.

Post-exercise heart rate recovery and parasympathetic reactivation are comparable between prepubertal boys and well-trained adult male endurance athletes.

PURPOSE: This study tested the hypothesis that prepubertal boys, but not untrained men, would exhibit a similar post-exercise parasympathetic reactivation as well-trained adult male endurance athletes. METHODS: Twelve prepubertal boys (12.3 ± 1.6 years), 14 untrained men (21.8 ± 2.2 years) and 16 well-trained adult male endurance athletes (24.5 ± 4.8 years) completed an incremental maximal run field test on a track. Immediately after exercise completion, heart rate recovery (HRR) was assessed in the supine position for 5 min. Heart rate variability was analyzed in the time domain, and log-transformed values of the root mean square of successive differences in heart beats (Ln RMSSD30) were calculated over consecutive 30 s windows. RESULTS: Prepubertal children and well-trained adult endurance athletes showed significantly faster HRR than untrained adults from 30 s post-exercise until the end of recovery (p < 0.05). Ln RMSSD30 was significantly higher in prepubertal children and athletes than untrained adults over the post-exercise time interval 60-150 s (p < 0.05). No significant differences were observed for HRR and Ln RMSSD30 between prepubertal children and athletes. CONCLUSION: Prepubertal children and well-trained adult endurance athletes exhibited comparable and faster HRR and parasympathetic reactivation than untrained adults following maximal exercise. This indirectly suggests that oxidative profile may be preserved by exercise training during growth and maturation to offset the decline in post-exercise HRR, parasympathetic reactivation and aspects of metabolic health.

Changes in Pulmonary Function After Long-duration Adventure Racing in Adolescent Athletes.

The present study investigated the acute effects of a mixed-modality, long-duration adventure race on pulmonary function in adolescent athletes. Twenty male adolescents aged 14 to 17 years volunteered to participate in a wilderness adventure race of 68.5-km. Expiratory function was evaluated before, immediately after, and 24 h after race completion. Measurements included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and peak expiratory flow (PEF). Maximal inspiratory and expiratory mouth static pressures (MIP and MEP, respectively) were also measured using a portable hand-held mouth pressure meter across the same time points. The mean completion time of the race was 05:38±00:20 hours. A significant post-race decrease in FVC was observed immediately after the race (-5.2%, p=0.01). However, no significant changes were observed for FEV1, PEF and the FEV1/FVC and FEV1/PEF ratios. In addition, estimates of respiratory muscle strength (MIP and MEP) were unaffected by the race. The long-duration adventure race induced no marked reduction in expiratory pulmonary function and this response was associated with no apparent respiratory muscle fatigue. Therefore, the pulmonary system of trained adolescent athletes was sufficiently robust to sustain the mixed-modality, long-duration adventure race of ~ 5-6 h.

Effect of morning versus evening exercise training on sleep, physical activity, fitness, fatigue and quality of life in overweight and obese adults.

This study compares the effectiveness of a 12-week moderate exercise training program (METP), performed in the morning versus the evening, on sleep, physical activity, physical fitness, sleepiness, fatigue and health-related quality of life (HRQoL) in overweight and obese patients. Sedentary and inactive overweight/obese adults (n = 36) were included in METP and randomized into two groups: morning group (GM) and evening group (GE). Twenty-eight participants successfully completed METP (3 × 90 min exercise session per week for 12 weeks, completion rates >80%). Sleep, physical activity, and bedtime temperature were measured using accelerometry and infrared tympanic temperature during 3 separate weeks of the study (Week1, Week6, and Week12). Participants also took part in baseline and endpoint assessments including physical fitness as well as subjective physical activity, chronotype, sleep quality, sleepiness, fatigue and HRQoL. METP did not impact objective sleep quality differently between the two groups (morning vs evening). Bedtime and mid-sleep were advanced when METP was done in the morning whereas they were delayed when METP was practiced in the early evening (p = .003). Beside this finding, no valuable differences between the two groups were noted in all the remaining measures. METP resulted in improvements of body composition, cardiorespiratory and muscular endurance, as well as a favorable impact on subjective sleep quality, diurnal sleepiness, fatigue and HRQoL in both groups (all p < .05). Evening METP could be an effective alternative for overweight/obese adults when morning METP is not possible.

Neuromuscular Fatigue After Long-Duration Adventure Racing in Adolescent Athletes.

PURPOSE: To characterize the acute effects of a long-duration adventure race on knee extensor (KE) fatigue and the knee functional ratio in adolescent athletes. METHODS: Twenty trained male adolescents (aged 14-17 y) performed an adventure race of 68.5 km. Maximal voluntary isometric contraction (MVIC) KE and knee flexor torques were measured before and immediately after the race. Central and peripheral components of neuromuscular fatigue were quantified from the maximal voluntary activation level and the doublet peak torque (Tw100), respectively. The peak eccentric knee flexor torque to concentric KE torque ratio was also measured to determine functional ratio. RESULTS: The race completion time was 05:38 (00:20) hours. Significant reductions in MVICKE (-14.7%, P < .001) and MVICKF (-17.0%, P < .01) were observed after the race. Voluntary activation level decreased by 8.3% (P < .001) while Tw100 remained unchanged. Peak eccentric knee flexor torque decreased 16.0% (P < .001) while peak concentric KE torque did not change. This resulted in a significant reduction in functional ratio (-12.0%, P < .01). CONCLUSION: The adventure race induced a moderate fatigue, which was mainly explained by central factors without significant peripheral fatigue. However, particular attention should be paid to the knee muscular imbalance incurred by the race, which could increase the risk of ligament injury in adolescent athletes.

Acute metabolic responses after continuous or interval exercise in post-menopausal women with overweight or obesity.

This pilot study compared the effects of acute high-intensity intermittent exercise (HIIE) and moderate-intensity continuous exercise (MICE) on post-exercise VO2 , fat utilization, and 24-hours energy balance to understand the mechanism of higher fat mass reduction observed after high-intensity interval training in post-menopausal women with overweight/obesity. 12 fasted women (59.5 ± 5.8 years; BMI: 28.9 ± 3.9 kg·m-2 ) completed three isoenergetic cycling exercise sessions in a counterbalanced, randomized order: (a) MICE [35 minutes at 60%-65% of peak heart rate, HRmax ], (b) HIIE 1 [60 × (8-s cycling-12-s recovery) at 80%-90% of HRmax ], and (c) HIIE 2 [10 × 1min at 80%-90% of HRmax  - 1-min recovery]. Then, VO2 and fat utilization measured at rest and during the 2 hours post-exercise, enjoyment, perceived exertion, and appetite recorded during the session and energy intake (EI) and energy expenditure (EE) assessed over the next 24 hours were compared for the three modalities. Overall, fat utilization increased after exercise. No modality effect or time-modality interaction was observed concerning VO2 and fat oxidation rate during the 2 hours post-exercise. The two exercise modalities did not induce specific EI and EE adaptations, but perceived appetite scores at 1 hour post-exercise were lower after HIIE 1 and HIIE 2 than MICE. Perceived exertion was higher during HIIE 1 and HIIE 2 than MICE, but enjoyment did not differ among modalities. The acute HIIE responses did not allow explaining the greater fat mass loss observed after regular high-intensity interval training in post-menopausal women with overweight/obesity. More studies are needed to understand the mechanisms involved in such adaptations.

Moderate-Intensity Continuous Training or High-Intensity Interval Training with or without Resistance Training for Altering Body Composition in Postmenopausal Women.

PURPOSE: This study aimed to compare body composition changes induced by moderate-intensity continuous training (MICT), high-intensity interval training (HIIT), or HIIT + resistance training (RT) programs (3 d·wk, 12 wk) in overweight/obese postmenopausal women, and to determine whether fat mass reduction is related to greater fat oxidation (FatOx). METHODS: Participants (n = 27) were randomized in three groups: MICT (40 min at 55%-60% of peak power output), HIIT (60 × 8 s at 80%-90% of peak HR, 12 s active recovery), and HIIT + RT (HIIT + 8 whole-body exercises: 1 set of 8-12 repetitions). Dual-energy x-ray absorptiometry was used to measure whole-body and abdominal/visceral fat mass (FM) and fat-free mass. FatOx was determined at rest, during a moderate-intensity exercise (40 min at 50% of peak power output), and for 20 min postexercise, before and after training. RESULTS: Overall, energy intake and physical activity levels did not vary from the beginning to the end of the intervention. Body weight and total FM decreased in all groups over time, but significant abdominal/visceral FM losses were observed only in HIIT and HIIT + RT groups. When expressed in percentage, total FM, fat-free mass, and muscle mass were significantly modified only by HIIT + RT training. FatOx did not change at rest but increased similarly in the three groups during and after exercise. Therefore, the HIIT-induced greater FM loss was not related to higher FatOx during or after exercise. CONCLUSIONS: MICT or HIIT ± RT could be proposed to nondieting postmenopausal women who are overweight/obese to decrease weight and whole-body FM. The HIIT programs were more effective than MICT in reducing abdominal/visceral FM. RT addition did not potentiate this effect but increased the percentage of muscle mass.

Four-month course of soluble milk proteins interacts with exercise to improve muscle strength and delay fatigue in elderly participants.

BACKGROUND: The benefit of protein supplementation on the adaptive response of muscle to exercise training in older people is controversial. OBJECTIVE: To investigate the independent and combined effects of a multicomponent exercise program with and without a milk-based nutritional supplement on muscle strength and mass, lower-extremity fatigue, and metabolic markers. DESIGN: A sample of 48 healthy sedentary men aged 60.8 ± 0.4 years were randomly assigned to a 16-week multicomponent exercise training program with a milk-based supplement containing, besides proteins [total milk proteins 4 or 10 g/day or soluble milk proteins rich in leucine (PRO) 10 g/day], carbohydrates and fat. Body composition, muscle mass and strength, and time to task failure, an index of muscle fatigue, were measured. Blood lipid, fibrinogen, creatine phosphokinase, glucose, insulin, C-reactive protein, interleukin-6, tumor necrosis factor-α soluble receptors, and endothelial markers were assessed. RESULTS: Body fat mass was reduced after the 4-month training program in groups receiving 10 g/day of protein supplementation (P < .01). The training program sustained with the daily 10 g/day PRO was associated with a significant increase in dominant fat free mass (+5.4%, P < .01) and in appendicular muscle mass (+4.5%, P < .01). Blood cholesterol was decreased in the trained group receiving 10 g/day PRO. The index of insulin resistance (homeostasis model assessment-insulin resistance) and blood creatine phosphokinase were reduced in the groups receiving 10 g/day PRO, irrespective of exercise. The inflammatory and endothelial markers were not different between the groups. Training caused a significant improvement (+10.6% to 19.4%, P < .01) in the maximal oxygen uptake. Increased maximum voluntary contraction force was seen in the trained groups receiving 10 g/day of proteins (about 3%, P < .05). Time to task failure was improved in the trained participants receiving a 10 g/day supplementation with PRO (P < .01). CONCLUSIONS: Soluble milk proteins rich in leucine improved time to muscle failure and increase in skeletal muscle mass and strength after prolonged multicomponent exercise training in healthy older men.

Detraining-induced alterations in metabolic and fitness markers after a multicomponent exercise-training program in older men.

The aim of the present study was to investigate the effects of a 8-week detraining period after a 16-week multicomponent training program including strength and aerobic exercises on the main determinants of aerobic fitness, muscle strength and some metabolic markers in 24 older subjects (60.2 ± 3.0 years). The oxygen uptake at the second ventilatory threshold (VO(2)V(T2)) and at the end of exercise (VO(2max)), maximum voluntary contraction force (MVC) of knee extensors and some metabolic indexes, i.e., insulin sensitivity, blood lipid profile, inflammatory cytokines, and endothelial function, were evaluated at baseline and after the training and detraining periods. The training program induced significant improvements in VO(2)V(T2) (16%, p < 0.05), VO(2max) (14%, p < 0.05), MVC (6.5%, p < 0.05), insulin sensitivity (16%, p < 0.05), and endothelial function (p < 0.05) but induced no significant change in lipid profile and inflammatory cytokines. Interestingly, VO(2)V(T2) and VO(2max) (mL·min(-1)·kg(-1)) scores remained significantly above pretraining values after the 8-week detraining period. However, the detraining period reversed MVC values, the insulin sensitivity and endothelial function to baseline levels. To conclude, the 8-week detraining partially reversed the major components of aerobic fitness but totally abolished the gains in muscle strength and some metabolic indexes after a 16-week multicomponent training program in older men. Taken as a whole, the results of this study emphasize the importance of exercise prescriptions for older subjects and the need not to interrupt exercise-training over a prolonged period.

Changes in basal and insulin and amino acid response of whole body and skeletal muscle proteins in obese men.

CONTEXT: Obesity-related insulin resistance of glucose and lipid metabolism may also affect protein kinetics, notably at the muscle level. OBJECTIVE: We hypothesized that muscle protein response to insulin and amino acid is blunted during obesity. RESEARCH DESIGN AND METHODS: Total (Tot) and mitochondrial (Mit) muscle proteins fractional synthesis rates (FSR) together with whole-body protein kinetics (WB) have been determined in postabsorptive state (PA) and during a hyperinsulinemic, hyperaminoacidemic, euglycemic clamp by using a continuous infusion of (13)C-leucine in six obese and eight nonobese subjects. RESULTS: Responses of WB glucose disposal rate and protein breakdown to insulin and amino acid infusion were significantly lower in obese than in nonobese subjects (P < 0.05). In PA, Tot and Mit FSR were significantly lower (P < 0.05) in obese (Tot, 0.044 +/- 0.005% . h(-1); Mit, 0.064 +/- 0.008% . h(-1)) in comparison with nonobese subjects (Tot, 0.082 +/- 0.010% . h(-1); Mit, 0.140 +/- 0.006% . h(-1)). Tot FSR was similarly stimulated by insulin and amino acid in both groups (0.094 +/- 0.013 vs. 0.117 +/- 0.006% . h(-1), obese vs. nonobese; P < 0.05). Mit FSR was increased in nonobese subjects (0.179 +/- 0.007% . h(-1); P < 0.05) but not in obese subjects (0.078 +/- 0.012% . h(-1); P = not significant). CONCLUSIONS: The obesity-related impairment of protein metabolism is characterized by 1) a reduced turnover rate of skeletal muscle proteins in PA; 2) a lack of stimulation of mitochondrial protein synthesis by insulin and amino acid; and 3) a lower inhibition of WB proteolysis by insulin and amino acid. Alterations of selective muscle protein kinetics may predispose obese subjects to muscle metabolic dysfunction leading to type 2 diabetes.

Determination of the maximal fat oxidation point in obese children and adolescents: validity of methods to assess maximal aerobic power.

We aimed to examine the interchangeability of techniques used to assess maximal oxygen consumption (VO2max) and maximal aerobic power (MAP) employed to express the maximal fat oxidation point in obese children and adolescents. Rate of fat oxidation were measured in 24 obese subjects (13.0 +/- 2.4 years; Body Mass Index 30.2 +/- 6.3 kg m(-2)) who performed a five 4-min stages submaximal incremental cycling exercise. A second cycling exercise was performed to measure VO2max. Results are those of the 20 children who achieved the criterion of RER (>1.02) to assess the attainment of VO2max. Although correlations between results obtained by different methods were strong, Bland-Altman plots showed little agreement between the maximal fat oxidation point expressed as a percentage of measured VO2max and as % VO2max estimated according to ACSM guidelines (underestimation : -5.9%) or using the predictive equations of Wasserman (-13.9%). Despite a mean underestimation of 1.4% several values were out of the limits of agreement when comparing measured MAP and Theoretical MAP. Estimations of VO2max lead to underestimations of the maximal fat oxidation point.

Effect of physical activity intervention on body composition in young children: influence of body mass index status and gender.

AIM: To fight overweight and obesity in childhood, this study proposes an additional physical activity (PA) in young children aged 6-10 years. The objective was to evaluate the effect of school-based PA on the body composition according to body mass index (BMI) categories (nonobese vs. obese) and gender. METHODS: This 6-month study examined the effect of this intervention on body composition in 425 children in 14 primary schools (2 weekly PA sessions of 1 h each) compared to 5 control schools. Adiposity indices were evaluated or calculated: BMI, BMI z-score, waist circumference, sum of skinfolds and fat-free mass. RESULTS: No difference in the prevalence of obesity and anthropometric characteristics was found between the intervention and control groups at baseline. In girls, PA intervention had significant effect on all anthropometric variables (p < 0.05 to p < 0.001), except on BMI. In contrast, in boys only BMI z-score (p < 0.001) and fat-free mass (p < 0.001) were affected. CONCLUSIONS: Six months of preventive PA intervention offer an effective means to improve body composition in obese children. The pattern of response related to PA was similar between girls and boys. In contrast, the pattern was different according to BMI category, with a higher response in obese than nonobese children.

Lower-limb and whole-body tissue composition assessment in healthy active older women.

AIM: The study evaluated, in active elderly women, the accuracy and bias of anthropometry and bioelectrical impedance analysis (BIA) for lower-limb and whole-body tissue composition measures using dual-energy X-ray absorptiometry (DXA) as the criterion method. METHODS: Nineteen individuals (66.1 +/- 4.2 years) participated in the study. Whole-body fat mass (FM) and fat-free mass (FFM) were measured by anthropometry, BIA and DXA. Lower-limb volume (LLV) and lower-limb FFM (LLFFM) were assessed by anthropometry and DXA. RESULTS: LLV and LLFFM were significantly overestimated by anthropometry vs. DXA (p < 0.05 and p < 0.001, respectively) but significant relationships were observed [coefficient of determination (R(2)) > 0.25, p < 0.05]. No significant difference was observed between FM(A) (where (A) stands for anthropometry) vs. FM(DXA) and FFM(A) vs. FFM(DXA) and significant relationships were observed [R(2) = 0.93, p < 0.001, coefficient of variation (CV) = 7.3%; and R(2) = 0.85, p < 0.001, CV = 4.4%, respectively]. No significant difference was observed between FM(BIA) and FM(DXA) and a significant relationship was observed (R(2) = 0.80, p < 0.001, CV = 11.6%). FFM was significantly underestimated by BIA vs. DXA (p < 0.01). CONCLUSIONS: In active elderly women, (i) compared with DXA, anthropometry overestimates LLV and LLFFM; (ii) anthropometry can be an accurate method for assessing whole-body composition; and (iii) despite a non-significant bias for the FM measurement, the BIA tends to overestimate FM and underestimate FFM.