Longitudinal changes of maximal short-term peak power in girls and boys during growth

PURPOSE: The aims of this study are twofold: first, to analyze the influence of age, body mass, and lean leg volume (LLV) on short-term leg peak power (Pmax) of young females and males during growth using multilevel regression analysis and, second, to compare the regression results of boys and girls. METHODS: The individuals were 100 girls and 109 boys aged 7.5-17.5 yr old. Pmax, LLV, and mass were determined on two occasions using the cycling force-velocity test. The optimal force (Fopt) and pedaling frequency (Vopt) corresponded to the force and pedaling frequency at Pmax. RESULTS: It was observed that the increase of Pmax doesn't depend on gender until the age of 14. From that age, Pmax values are significantly lower in girls than in boys. In girls, LLV is the main predictor of Pmax variance (68%; P < 0.001), whereas in boys it is age (57%; P < 0.001). Results of ANCOVA were that for the same leg length (LL), Vopt is significantly (P < 0.001) higher in boys than in girls. It also indicated that for the same LLV, there are no significant (P > 0.05) gender differences of Fopt. CONCLUSION: These results illustrated that during the growth period, the increase of Pmax is significantly higher in boys than in girls. Qualitative muscular factors (Type II fiber, glycolytic ability, motor coordination, and motor unit activation) may account for the significantly higher Pmax production in boys than in girls. Precisely, the gender differences might be explained by neuromuscular determinants of contraction velocity. In conclusion, children should develop their neuromuscular determinants of contraction velocity rather than their lean leg volume.     

Effects of plyometric training followed by a reduced training programme on physical performance in prepubescent soccer players

BACKGROUND: In adult population, stretch-shortening cycle exercise (plyometric exercise) is often used to improve leg muscle power and vertical jump performance. In children, limited information regarding this type of exercise is available. The purpose of this study was to examine the effectiveness of plyometric training and maintenance training on physical performances in prepubescent soccer players. METHODS: Twenty boys aged 12-13 years was divided in two groups (10 in each): jump group (JG) and control group (CG). JG trained 3 days/week during 10 weeks, and performed various plyometric exercises including jumping, hurdling and skipping. The subsequent reduced training period lasted 8 weeks. However, all subjects continued their soccer training. Maximal cycling power (Pmax) was calculated using a force-velocity cycling test. Jumping power was assessed by using the following tests: countermovement jump (CMJ), squat jump (SJ), drop jump (DJ), multiple 5 bounds (MB5) and repeated rebound jump for 15 seconds (RRJ15). Running velocities included: 20, 30 and 40 m (V20, V30, V40 m). Body fat percentage (BF percent) and lean leg volume were estimated by anthropometry. RESULTS: Before training, except for BF percent, all baseline anthropometric characteristics were similar between JG and CG. After the training programme, Pmax (p<0.01), CMJ (p<0.01), SJ (p<0.05), MB5 (p<0.01), RRJ15 (p<0.01) and V20 m (p<0.05), performances increased in the JG. During this period no significant performance increase was obtained in the CG. After the 8-week of reduced training, except Pmax (p<0.05) for CG, any increase was observed in both groups. CONCLUSIONS: These results demonstrate that short-term plyometric training programmes increase athletic performances in prepubescent boys. These improvements were maintained after a period of reduced training.     

The influence of training on endurance and blood lactate concentration during submaximal exercise.

The purpose of this study was to examine the effect of short-term training on maximum oxygen uptake (VO2 max) and two different measures of endurance performance. Endurance was determined for 15 female subjects (7 training, 8 control) as (1) exercise time to exhaustion at 80% VO2 max (T80%) and (2) the highest relative exercise intensity tolerable during a 30-minute test (T30 min), before and after a 6-week training period. In addition, VO2 max and the work rate equivalent to a blood lactate concentration of 4 mmol.l-1 (OBLA) were determined. Maximum oxygen uptake increased by 24% (p less than 0.01) for the training group (TG) and 7% (p less than 0.01) for the control group (CG). Cumulative average work rate (CAWR) during T30 min increased by 25% for the TG while there was no change for the CG. No significant difference was found pre- and post-training in the %VO2 max (estimated from CAWR) at which the TG and CG performed T30 min. Exercise time to exhaustion on T80% increased by 347% (p less than 0.01) and 16% (NS) for the TG and the CG respectively. Good correlations were found between VO2 max and CAWR (W) (pre-training r = 0.84; post-training r = 0.83), OBLA (W) and CAWR (W) (pre-training r = 0.89; post-training r = 0.88) and change in endurance time and the change in submaximal blood lactate concentration (r = 0.70, p less than 0.01). The results of this study suggest that the ability to sustain a high relative exercise intensity is not enhanced following short-term training.     

Short-term peak power changes in adolescents of similar anthropometric characteristics

PURPOSE: The present study was undertaken to examine changes of cycling peak power (P(max)), optimal pedaling frequency (Vopt), and optimal pedaling force (Fopt) with age in subjects with the same lean leg volume (LLV), leg length (LL), and percentage body fat (%BF). METHOD: A total of 132 males aged 9.5-16.5 volunteered for this study. The population was divided into prepubertal (G1), pubertal (G2), and postpubertal (G3) groups. Within G1, G2, and G3, although the subjects were divided into three different age subgroups, there were no significant differences for LLV, %BF, and LL. RESULTS: Results showed that within G1, G2, and G3, P(max) increased significantly with age. Optimal velocity (Vopt) increased significantly with age in G1, whereas optimal force (Fopt) increased significantly with age into the other groups (G2 and G3). CONCLUSION: This study demonstrated that when anthropometric characteristics were controlled (LLV, LL, and %BF), P(max) and its two components (Vopt and Fopt) still increased with age. This indicates that other factors of qualitative nature have to be considered when determining P(max), Vopt, and Fopt.     

Leg muscle power in 12-year-old black and white Tunisian football players

This study examined leg muscle power of young male Tunisian black and white football players and extended the analysis to determine whether there is a relationship between cycling peak power output (PPO) and some field tests. A total of 113 children (white group (WG) = n = 56; black group (BG) = n = 57) participated in this investigation. Anthropometric data included age, body mass (BM), height, leg length (LL), body mass index (BMI), and leg muscle volume (LMV). Cycling PPO was measured including a force-velocity test. Peak power output (PPO; W and W/kg), Fopt (optimal braking force), and Vopt (optimal velocity) were significantly higher in the WG compared with the BG (p < 0.05). However, jump and sprint performances of the BG were significantly higher than the WG (p < 0.05). Multiple stepwise regression with anthropometric variables and the extrapolated values of the force-velocity test as explanatory factors showed that 33% of the variance of PPO of BG was explained by qualitative factors that may be related to cycling skill, muscle composition, and socioeconomic and training status.     

耐力训练和一次性力竭运动对大鼠心肌和骨骼肌硫氧还蛋白还原酶的影响

目的:观察运动对大鼠心肌、骨骼肌硫氧还蛋白还原酶(TR)的影响.方法:SD大鼠30只,随机分成安静对照组、耐力训练组和力竭组.训练组进行6周渐增游泳训练,5次/周.最后1次训练后24小时,断头处死安静对照组和训练组大鼠,力竭组大鼠在一次性力竭运动后即刻处死.DTNB法检测心肌、骨骼肌TR活性,RT-PCR法观察TR mRNA水平变化.结果:6周耐力训练大鼠心肌TR活性显著高于安静对照组,一次性力竭组大鼠心肌TR活性显著低于安静对照组.各组大鼠心肌TR mRNA均无显著性差异.结论:6周耐力训练显著提高大鼠心肌TR活性,而在mRNA水平上无显著性差异.     

Effect of whole‐body vibration on neuromuscular performance and body composition for females 65 years and older: a randomized‐controlled trial

We examined whether the effect of multipurpose exercise can be enhanced by whole‐body vibration (WBV). One hundred and fifty‐one post‐menopausal women (68.5±3.1 years) were randomly assigned to three groups: (1) a training group (TG); (2) training including vibration (VTG); and (3) a wellness control group (CG). TG and VTG performed the same training program twice weekly (60 min), consisting of aerobic and strength exercises, with the only difference that leg strength exercises (15 min) were performed with (VTG) or without (TG) vibration. CG performed a low‐intensity “wellness” program. At baseline and after 18 months, body composition was determined using dual‐X‐ray‐absorptiometry. Maximum isometric strength was determined for the legs and the trunk region. Leg power was measured by countermovement jumps using a force‐measuring plate. In the TG lean body mass, total body fat, and abdominal fat were favorably affected, but no additive effects were generated by the vibration stimulus. However, concerning muscle strength and power, there was a tendency in favor of the VTG. Only vibration training resulted in a significant increase of leg and trunk flexion strength compared with CG. In summary, WBV embedded in a multipurpose exercise program showed minor additive effects on body composition and neuromuscular performance.     

A reduction in training volume and intensity for 21 days does not impair performance in cyclists

OBJECTIVES: (a) To investigate the effects of reduced training on physical condition and performance in well trained cyclists; (b) to study whether an intermittent exercise programme would maintain physiological training adaptations more effectively than a continuous exercise programme during a period of reduced training. METHODS: Twelve male cyclists participated in a 21 day training programme and were divided into two training groups. One group (age 25.3 (7) years; weight 73.3 (5.7) kg; VO(2)MAX 58.6 (4.5) ml/kg/min; means (SD)) underwent a continuous endurance exercise training programme (CT) whereas the second group (age 22.8 (3.5) years; weight 74.1 (7.0) kg; VO(2)MAX 59.7 (6.7) ml/kg/min) followed an intermittent endurance exercise training programme (IT). During this reduced training period, both groups trained for two hours a day, three days a week. RESULTS: Neither group showed changes in maximal workload (WMAX) (4.6 (0.5) v 4.8 (0.5) W/kg and 4.6 (0.5) v 4.7 (0.6) W/kg for the CT and IT group respectively) and VO(2)MAX (58.6 (4.5) v 60.1 (5.8) ml/kg/min and 59.7 (6.7) v 58.8 (7.5) ml/kg/min for the CT and IT group respectively). During the submaximal steady state exercise test, substrate use and heart rate remained unchanged after reduced training. CONCLUSIONS: These results indicate that well trained cyclists who reduce training intensity and volume for 21 days can maintain physiological adaptations, as measured during submaximal and maximal exercise. An intermittent training regimen has no advantage over a continuous training regimen during a detraining period.     

Aerobic capacity of older adults: a training study

The effects of a four month aerobic conditioning program on heart rate, blood pressure, maximal oxygen consumption (VO2max), and physical work capacity of 55-70 year old sedentary individuals were evaluated. Twenty-eight men and women participated in either 4 months of supervised fast walking or jogging at a prescribed target heart rate or stretching exercises for one hour, three days per week. Gains in VO2max (ml/kg/min) obtained during a Balke maximal treadmill test in aerobic and exercise control subjects were 27% and 9%, respectively. At posttesting subjects in both groups demonstrated improved maximal work rate, increased treadmill time, and experienced lower resting and recovery heart rates, lower resting systolic blood pressure, and fewer premature ventricular depolarizations during exercise testing. In 67 physician-supervised maximal exercise tests, only one subject did not achieve VO2max due to exercise induced arrhythmias. No events of morbidity or mortality occurred as a result of the exercise testing and training. Subjects were contacted 4 years after study participation to determine if they were adhering to an exercise program. Sixty-four percent reported exercising at least 3 days per week in large muscle activities. We conclude that four months of supervised aerobic and nonaerobic exercise training is sufficient to improve aerobic capacity and other indicators of fitness in older, sedentary men and women, and that these previously sedentary people are likely to continue exercising on an individual basis once they have experienced improved physical capacity.     

Specific inspiratory muscle training in well-trained endurance athletes

PURPOSE: It has been reported that arterial O2 desaturation occurs during maximal aerobic exercise in elite endurance athletes and that it might be associated with respiratory muscle fatigue and relative hypoventilation. We hypothesized that specific inspiratory muscle training (SIMT) will result in improvement in respiratory muscle function and thereupon in aerobic capacity in well-trained endurance athletes. METHODS: Twenty well-trained endurance athletes volunteered to the study and were randomized into two groups: 10 athletes comprised the training group and received SIMT, and 10 athletes were assigned to a control group and received sham training. Inspiratory training was performed using a threshold inspiratory muscle trainer, for 0.5 h x d(-1) six times a week for 10 wk. Subjects in the control group received sham training with the same device, but with no resistance. RESULTS: Inspiratory muscle strength (PImax) increased significantly from 142.2 +/- 24.8 to 177.2 +/- 32.9 cm H2O (P < 0.005) in the training but remained unchanged in the control group. Inspiratory muscle endurance (PmPeak) also increased significantly, from 121.6 +/- 13.7 to 154.4 +/- 22.1 cm H2O (P < 0.005), in the training group, but not in the control group. The improvement in the inspiratory muscle performance in the training group was not associated with improvement in peak VEmax, VO2max breathing reserve (BR). or arterial O2 saturation (%SaO2), measured during or at the peak of the exercise test. CONCLUSIONS: It may be concluded that 10 wk of SIMT can increase the inspiratory muscle performance in well-trained athletes. However, this increase was not associated with improvement in aerobic capacity, as determined by VO2max, or in arterial O2 desaturation during maximal graded exercise challenge. The significance of such results is uncertain and further studies are needed to elucidate the role of respiratory muscle training in the improvement of aerobic-type exercise capacity.     

Training-induced hypervolemia: lack of an effect on oxygen utilization during exercise

To investigate the effect of training-induced increases in plasma volume on maximal aerobic power, 8 male subjects (age 19 to 24 yr) underwent a 4-d training program (2 h X d-1) at an estimated 71% maximal aerobic power. Following training, plasma volume measured using 131I-human serum albumin increased by 20.3% (P less than 0.01) whereas red cell volume remained unchanged and total blood volume increased by 12.3% (P less than 0.01). During progressive sub-maximal cycle exercise, oxygen consumption, carbon dioxide production, ventilation, and blood lactate concentration remained unchanged following the training whereas heart rate was significantly elevated (P less than 0.05). Significant post-training elevations were also noted in carbon dioxide production (P less than 0.05), blood lactate (P less than 0.01), and peak power output (P less than 0.05) during maximal exercise. Maximal aerobic power and ventilation were not altered. It is concluded that hypervolemia induced by short-term exercise training does not affect oxygen consumption either during sub-maximal or maximal exercise.     

Metabolic effects of heavy physical training on female ''age-group'' swimmers.

Twelve female age-group swimmers and twelve female controls, aged ten to sixteen, performed a pre-training discontinuous maximal cycle ergometer test to determine the capacities of their anaerobic (alactacid and lactacid) and aerobic energy systems. Heart rate and oxygen uptake were determined during rest, exercise, and recovery. Blood samples were collected before and after exercise for determination of blood lactic acid concentrations. Tests were readministered to both groups immediately following the swimmers' competitive season. It was concluded that female swimmers possess significantly superior oxygen transport systems as compared to the untrained controls and that the high level of aerobic fitness is maintained throughout their training programme.     

The effect of detraining and reduced training on the physiological adaptations to aerobic exercise training

In previously sedentary individuals, regularly performed aerobic exercise results in significant improvements in exercise capacity. The development of peak exercise performance, as typified by competitive endurance athletes, is dependent upon several months to years of aerobic training. The physiological adaptations associated with these improvements in both maximal exercise performance, as reflected by increases in maximal oxygen uptake (VO2max), and submaximal exercise endurance include increases in both cardiovascular function and skeletal muscle oxidative capacity. Despite prolonged periods of aerobic training, reductions in maximal and submaximal exercise performance occur within weeks after the cessation of training. These losses in exercise performance coincide with declines in cardiovascular function and muscle metabolic potential. Significant reductions in VO2max have been reported to occur within 2 to 4 weeks of detraining. This initial rapid decline in VO2max is likely related to a corresponding fall in maximal cardiac output which, in turn, appears to be mediated by a reduced stroke volume with little or no change in maximal heart rate. A loss in blood volume appears to, at least partially, account for the decline in stroke volume and VO2max during the initial weeks of detraining, although changes in cardiac hypertrophy, total haemoglobin content, skeletal muscle capillarisation and temperature regulation have been suggested as possible mediating factors. When detraining continues beyond 2 to 4 weeks, further declines in VO2max appear to be a function of corresponding reductions in maximal arterial-venous (mixed) oxygen difference. Whether reductions in oxygen delivery to and/or extraction by working muscle regulates this progressive decline is not readily apparent. Changes in maximal oxygen delivery may result from decreases in total haemoglobin content and/or maximal muscle blood flow and vascular conductance. The declines in skeletal muscle oxidative enzyme activity observed with detraining are not causally linked to changes in VO2max but appear to be functionally related to the accelerated carbohydrate oxidation and lactate production observed during exercise at a given intensity. Alternatively, reductions in submaximal exercise performance may be related to changes in the mean transit time of blood flow through the active muscle and/or the thermoregulatory response (i.e. degree of thermal strain) to exercise. In contrast to the responses observed with detraining, currently available research indicates that the adaptations to aerobic training may be retained for at least several months when training is maintained at a reduced level. Reductions of one- to two-thirds in training frequency and/or duration do not significantly alter VO2max or submaximal endurance time provided the intensity of each exercise session is maintained.(ABSTRACT TRUNCATED AT 400 WORDS)     

Is ventilatory anaerobic threshold a good index of endurance capacity?

This study was undertaken to assess whether ventilatory anaerobic threshold (T vent) reflected endurance capacity (EC) in sports medical control. Fifteen subjects performed two cycle ergometer tests. The first was a maximal exercise test, which consisted of increasing the load 20 W/min until exhaustion. During this test, the gas exchange anaerobic threshold was determined and VO2 max was measured. The second was an endurance exercise test, which consisted of asking the subject to work, as long as possible, a load representing 80% of his maximal aerobic power. During this test, we measured endurance time (ET). The statistical analysis showed the lack of relationship between VO2 max and ET and the linear correlations between VO2 T vent ml/min/kg and ET min (r = 0.521, P less than 0.05), VO2 T vent l/min and ET min (r = 0.524, P less than 0.05), and T vent % VO2 max and ET (r = 0.738, P less than 0.01). These results establish that ventilatory anaerobic threshold actually reflects endurance capacity. This relation can be explained referring to the muscle energetic metabolism during exercise. Therefore, T vent should be determined systematically in addition to VO2 max during maximal exercise tests to better evaluate physical fitness.     

Effect of a short-term graded exhaustive exercise on the susceptibility of serum lipids to oxidation

The objective of our study was to evaluate the effect of short-term intensive exercise on the susceptibility of serum lipids to ex-vivo peroxidation. We assessed the association between aerobic capacity, serum composition, and serum lipid oxidizability as well as the association between aerobic capacity and the effect of short-term maximal exercise on the kinetics of ex-vivo copper-induced peroxidation of serum lipids. The study involved 30 healthy male volunteers (age 22-39 years, BMI 19.4-29.8). Following 12-hr fasting, blood was withdrawn for determination of blood lipids, LDL, HDL, and TG, and Vitamin E, and for oxidizability assay of the serum lipids. Subsequently, each volunteer underwent an incremental all-out cardiopulmonary exercise stress test (CPET), performed on a motor-driven treadmill (Quinton Q65, USA). The test protocol was a modified Balke protocol. The results of this test were expressed in terms of mass-dependent maximal oxygen uptake (VO2max, ml.kg(-1).min (-1)) and of ventilatory anaerobic threshold (VAT, ml.kg(-1).min(-1)). Immediately after exercise, blood was re-drawn for the determination of serum Vitamin E and for ex-vivo oxidizibility assay, expressed in terms of maximal absorption of oxidation products (OD(max), absorbance units), maximal rate of their production (V(max), OD min(-1)) and the time at which the rate was maximal (t(max), min). Maximal graded exercise had no significant effect on the susceptibility of serum lipids to peroxidation as measured by OD(max) (p = 0.38 at 245 nm, and 0.27 at 268 nm),V(max) (p = 0.34 at 245 nm, and 0.49 at 268 nm) and t(max) (p = 0.17 at 245 nm, and 0.07 at 268 nm). Also no effect was found on the concentration of serum Vitamin E (p = 0.39). Aerobic capacity was not associated either with the susceptibility of serum lipids to ex-vivo peroxidation or with serum Vitamin E concentration. The present findings indicate that a short graded maximal exercise, lasting 8-12 min, is not sufficient to increase the susceptibility of the serum lipids to peroxidation. Thus it may be assumed that the antioxidant capacity of most healthy subjects provides proper protection from a short exhaustive exercise challenge. Also, aerobic capacity in the range represented by our subjects does not seem to influence the susceptibility of serum lipids to peroxidation.     

Evaluation of maximal exercise performance, fatigue, and depression in athletes with acquired chronic training intolerance.

OBJECTIVE: This study compared differences in maximal strength and aerobic capacity and symptoms of fatigue and depression in athletes with acquired training intolerance (ATI) and control athletes (CON) matched for age and current training volume who did not have symptoms of excessive or chronic fatigue associated with their sporting activity. SETTING: University of Cape Town, Sports Science Institute of South Africa. PARTICIPANTS: Twenty ATI and 10 CON athletes participated in the trial. Although the ATI athletes reported symptoms of excessive fatigue during exercise, or symptoms of fatigue that occurred at rest and during activities of daily living, they did not fulfill the criteria for a diagnosis of chronic fatigue syndrome. MAIN OUTCOME MEASURES: A training and comprehensive medical history was recorded from all subjects. The Beck Depression Inventory Short Form (BDI-SF) was used to assess levels of depression in both ATI and control subjects. Maximal force output during a 5-second isometric voluntary knee extensor muscle contraction, and maximal aerobic capacity (VO2max), maximal heart rate (HRmax), and maximal blood lactate concentrations during a treadmill running test were measured in all subjects. RESULTS: There were no differences in maximal isometric force output, peak treadmill running speed, VO2max, HRmax, or blood lactate concentration at rest or after maximal exercise testing between the ATI and CON athletes. However, the BDI-SF scores were higher in the ATI (7.7 +/- 6.6 arbitrary units) than in the CON athletes (1.7 +/- 1.5 arbitrary units; (P = 0.0052). CONCLUSIONS: These findings suggest that the symptoms of excessive fatigue and acquired training intolerance described by these ATI athletes do not affect their maximal isometric and maximal aerobic capacity, and may be associated with psychologic depression in these athletes.     

Normalization of the blood lactate profile in athletes

The power output-blood lactate or velocity-blood lactate relationship, the lactate "profile", is a widely used method for the evaluation of athletes. Recent observations have suggested a shift in the blood lactate profile when athletes are fatigued, as at training camps. This study was designed to determine whether the blood lactate profile could be corrected for progressive muscle glycogen depletion by normalizing for the peak exercise blood lactate concentration. Ten well-trained subjects performed incremental cycle ergometer exercise followed by supramaximal exercise (Wingate test) following 3 days of usual and 3 days of heavier than usual training. Following heavier than usual training, blood lactate accumulation was reduced during submaximal exercise such that the power output associated with a lactate concentration of 4 mM was significantly increased (3.08 vs 3.51 W/kg). The maximal blood lactate concentration was also reduced (14.8 vs 12.7 mM) although average supramaximal power output was unchanged (9.03 vs 8.92 W/kg). When the submaximal blood lactate concentrations were normalized for the maximal blood lactate concentration, there were no significant differences in the power output associated with 20% (2.6 vs 2.7 W/kg), 25% (3.1 vs 3.2 W/kg), or 30% (3.3 vs 3.5 W/kg) of maximal lactate. The results suggest that normalization based on peak exercise blood lactate may be a useful strategy for circumventing one of the primary practical barriers to the use of the blood lactate profile in athletes.     

Improvement in maximal isokinetic cycle ergometry with cardiac rehabilitation

It is unclear whether improvements in short-term (30 s) exercise capacity are associated with the increased aerobic exercise tolerance frequently observed in cardiac patients following training. Carefully selected patients with documented coronary artery disease were randomly allocated either to a control group (N = 10) or to 12 wk of endurance exercise training (N = 12); both progressive incremental cycle ergometer testing (maximal power output and peak VO2) and 30 s maximal isokinetic cycle ergometry (peak power, total work, and fatigue index) were measured on entry into the study and 12 wk later. Initial maximum performance measures in progressive incremental exercise and in maximal short-term isokinetic cycling were similar in both groups. Following the training program, maximum power output measured during progressive incremental exercise increased by 21% (P less than 0.005) and peak VO2 increased by 18% (P less than 0.005) in the exercise group, but they were unchanged in the control group. Isokinetic peak power and total work improved by 14% (P less than 0.001) and 11%, respectively, in the exercise group, whereas there were corresponding reductions of 6 and 8% in the control subjects, with little change in fatigue index in either group. The similar relative increases in isokinetic peak power and peak VO2 suggest that improvement in short-term exercise capacity may be an important contributor to the improvement in aerobic exercise tolerance frequently observed in cardiac patients undergoing an endurance exercise program.     

High-intensity intermittent activities at school: controversies and facts

In comparison to continuous aerobic type activity, little is known about high-intensity intermittent physical activity in children. Repeated short-term high-intensity activities (> maximal aerobic speed and <10 s) are more characteristic of the spontaneous physical activity of children. Recent studies have shown during repetitive bouts of sprints separated by short recovery intervals, that prepubescent children compared with adults are more able to maintain their performance without substantial fatigue. Moreover, repetitive runs at high velocities (near and higher than the maximal aerobic speed) separated by short recovery periods may elicit a high oxygen consumption in children. Several studies using interval training programmes for 7 weeks, twice a week for 30 min in physical education lessons showed that children's aerobic performance (maximal O2 uptake, maximal aerobic speed) could be enhanced. Training based on these repeated short-term high-intensity exercises could also improve children's anaerobic performance (short-term muscle power, strength and speed). Current evidence suggests that recovery from high-intensity exercises is faster in children than in adults and that repeated runs at high velocities separated by short recovery intervals can improve both aerobic and anaerobic performance. Although continuous aerobic type activity is more scientifically established as a training mode, repeated short-term high-intensity exercises in physical education programmes should be considered to enhance aerobic, as well as, anaerobic fitness in children.     

Effects of high intensity intermittent training on peak VO(2) in prepubertal children

This study was designed to examine peak VO(2) responses of prepubescent children following a 7-week aerobic training. Twenty-three boys and thirty girls (9.7 +/- 0.8 years) were divided into a high intensity experimental group (HIEG: 20 girls and 13 boys) and a control group (CG: 10 girls and 10 boys). A graded 20-m shuttle run with measurement of gas exchange values was performed prior to and after the 7-week training program. The test consisted of a 3-min run at 7 km x h(-1) to determine energy cost of running, immediately followed by a 20-meter shuttle run test. HIEG had two 30 min-sessions of short intermittent aerobic training per week at velocities ranging from 100 up to 130 % of the maximal aerobic speed. For HIEG, absolute peak VO(2)(9.1 %) and relative to body mass peak VO(2)(8.2 %) increased significantly (p < 0.001); it was unchanged in the CG. Similarly, maximal shuttle run improved significantly in HIEG (5.1 %, p < 0.001). In contrast, there was no significant change for CG. For both groups energy cost of running remained unchanged. These findings show that prepubescent children could significantly increase their peak VO(2) and maximal shuttle velocity with high intensity short intermittent aerobic exercises.