The purpose of this study was to observe the effect of high intermittent exercise training on children's heart rate variability (HRV). Thirty-eight children (age 9.6 +/- 1.2 years) were divided into an intermittent (IT, n = 22) and a control group (CON, n = 16). At baseline and after a 7-week training period, HRV parameters, peak oxygen consumption (VO(2peak)) and maximal aerobic velocity (MAV) were assessed. Training consisted of three 30-min sessions composed by short maximal and supramaximal runs at velocities ranging from 100 up to 190% of MAV. HRV was computed in time and frequency domains. Training resulted in a significant increase in MAV and VO(2peak) in IT (P < 0.05) only without any significant change in HRV parameters for the two groups. Thus, 7 weeks of high intermittent exercise training allows to improve aerobic fitness. However, this modality of training was not sufficient enough to underline a possible effect on the heart rate autonomic regulation in children.

We investigated the effects of short duration running training on resting and exercise lung function in healthy prepubescent children. One trained group (TrG) (n = 9; three girls and six boys; age = 9.7 +/- 0.9 year) participated in 8 weeks of high-intensity intermittent running training and was compared to a control group (ContG) (n = 9; four girls and five boys; age = 10.3 +/- 0.7 year). Before and after the 8-week period, the children performed pulmonary function tests and an incremental exercise test on a cycle ergometer. After the 8-week period, no change was found in pulmonary function in ContG. Conversely, an increase in forced vital capacity (FVC) (+7 +/- 4% ; P = 0.026), forced expiratory volume in one second (+11 +/- 6% ; P = 0.025), peak expiratory flows (+17 +/- 4% ; P = 0.005), maximal expiratory flows at 50% (+16 +/- 10% ; P = 0.019) and 75% (+15 +/- 8% ; P = 0.006) of FVC were reported in TrG. At peak exercise, TrG displayed higher values of peak oxygen consumption (+15 +/- 4% ; P < 0.001), minute ventilation (+16 +/- 5% ; P = 0.033) and tidal volume (+15 +/- 5% ; P = 0.019) after training. At sub-maximal exercise, ventilatory response to exercise DeltaV(E)/DeltaV(CO(2)) was lower (P = 0.017) in TrG after training, associated with reduced end-tidal partial oxygen pressure (P < 0.05) and higher end-tidal partial carbon dioxide pressure (P = 0.026). Lower deadspace volume relative to tidal volume was found at each stage of exercise in TrG after training (P < 0.05). Eight weeks of high-intensity intermittent running training enhanced resting pulmonary function and led to deeper exercise ventilation reflecting a better effectiveness in prepubescent children.

The aim of this study was to analyze the effects of a 7-week interval-training program on different aspects of physical fitness in children who were 8-11 years old. Forty-six boys and 54 girls (9.7 +/- 0.8 years) were divided into an experimental group and a control group. The 2 groups performed selected tests from the European physical fitness test battery before and after training. Training consisted of 2 specific 30-minute sessions per week of short high-intensity, intermittent-running aerobic exercises at velocities ranging from 100-130% of maximal aerobic speed. After training, the experimental group demonstrated a significant improvement in the standing broad jump (9.6%, p < 0.001, F = 12.9) and 20-meter shuttle run (5.4%, p < 0.001, F = 14.4), whereas for the control group, no significant changes were observed. It was concluded that a high-intensity, intermittent-running program improved children's aerobic performance and explosive strength.

We assessed expiratory airflow limitation (exp FL) in 18 healthy prepubescent children (6 girls and 12 boys, 10.1 +/- 0.3 years old), and examined how it might modulate regulation of tidal volume (V(T)) during exercise. The children performed a maximal incremental exercise on a cycle ergometer, preceded and followed by pulmonary function tests. Throughout exercise, breathing flow-volume loops were plotted into the maximal flow-volume loop (MFVL) measured at rest. End-expiratory and end-inspiratory lung volumes were estimated by measuring expiratory reserve volume relative to forced vital capacity (ERV/FVC), and inspiratory reserve volume relative to forced vital capacity (IRV/FVC), respectively. The exp FL, expressed as a percentage of V(T), was defined as the part of the tidal breath meeting the boundary of the MFVL. Ten children (FL) presented an exp FL at peak exercise (range, 16-78% of V(T)), and the remaining 8 constituted a non-flow-limited group (NFL). At peak exercise, FL presented a higher IRV/FVC and lower ERV/FVC (P < 0.01) than NFL children, demonstrating two different exercise breathing patterns. These results suggest that the NFL regulated V(T) at high lung volume, avoiding exp FL, while the FL breathed at low lung volume, leading to exp FL. At peak exercise, FL presented lower values of minute ventilation (P<0.05) and oxygen uptake (P<0.05) than NFL. Nevertheless, oxygen arterial saturation and dyspnea were similar in the two groups. In conclusion, ventilatory constraints may occur in healthy prepubescent children and result in relative dynamic hyperinflation or expiratory flow limitation.

We studied mechanical ventilatory constraints in 13 aerobically trained (Tr) and 11 untrained (UT) prepubescent children by plotting the exercise flow-volume (F-V) loops within the maximal F-V loop (MFVL) measured at rest. The MFVL allowed to determine forced vital capacity (FVC) and maximal expiratory flows. Expiratory and inspiratory reserve volumes relative to FVC (ERV/FVC and IRV/FVC, respectively) were measured during a progressive exercise test until exhaustion. Breathing reserve (BR) and expiratory flow limitation (expFL), expressed in percentage of tidal volume (V(T)) and defined as the part of the tidal breath meeting the boundary of the MFVL, were measured. Higher FVC and maximal expiratory flows were found in Tr than UT (P < 0.05) at rest. Our results have shown that during exercise, excepting one subject, all Tr regulated their V(T) within FVC similarly during exercise, by breathing at low lung volume at the beginning of exercise followed breathing at high lung volume at strenuous exercise. In UT, ERV/FVC and IRV/FVC were regulated during exercise in many ways. The proportion of children who presented an expFL was nearly the same in both groups (approximately 70% with a range of 14 to 65% of V(T)), and no significant difference was found during exercise concerning expFL. However, higher ventilation (V(E)), ERV/FVC, and dyspnea associated with lower BR, IRV/FVC, and SaO2 were reported at peak power in Tr than UT (P < 0.05). These results suggest that, because of their higher Ve level, trained children presented higher ventilatory constraints than untrained. These may influence negatively the SaO2 level and dyspnea during strenuous exercise.