Effect of high intensity intermittent training on heart rate variability in prepubescent children.

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.

Evidence of ventilatory constraints in healthy exercising prepubescent children.

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.

Exercise flow-volume loops in prepubescent aerobically trained children.

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.

Exercise testing in children: comparison in ventilatory thresholds changes with interval-training.

The aim of this investigation was, first, to examine comparatively the changes in first and second ventilatory thresholds (VT1 and VT2 ) and, secondly, to compare with peak oxygen uptake (${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $) changes following high-intensity interval training (HIT) in prepubescent children. Eighteen prepubescent children (aged 10.1 ± 0.7 years) performed an incremental exhaustive exercise on a cycle ergometer with pulmonary gas exchange measurements before and after an 8-week period. During this period, nine children (five girls and four boys; initial ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $: 39.6 ± 6.0 ml O2 · min(-1) · kg(-1) ) took part in a HIT and nine other children (three girls and six boys; initial ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $: 39.8 ± 7.8 ml O2 · min(-1) · kg(-1) ), considered as controls, were not trained. After the training period, VT1 , VT2 , and ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $ were significantly (P < 0.01) improved (21%, 24%, and 14%, respectively) without significant changes in the control group. However, the changes in VT1 (ΔVT1 = +4.35 ± 4.36 ml O2 · min(-1) · kg(-1) ), VT2 (ΔVT1 = +7.17 ± 5.17 ml O2 · min(-1) · kg(-1) ), ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $ ($\Delta {\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $ = +5.51 ± 4.17 ml O2 · min(-1) · kg(-1) ) induced by HIT in trained children were not related. In conclusion, for prepubescent children, in addition to VT1 and ${\dot {\rm {V}}}_{{\rm O}_{{\rm 2}} {\rm peak}} $, VT2 can also be significantly improved by training. Therefore, HIT represents a good way to obtain great improvement in these parameters in only 8 weeks. However, the time courses of these aerobic fitness parameters are dissociated, which implies the need to differentiate among them during aerobic fitness exercise testing.

Breathing strategy in master athletes and untrained elderly subjects according to the incremental protocol.

To analyze the influence of step-duration protocol (1 vs. 3 min) on breathing strategy according to the physical fitness of healthy elderly subjects, this study compared the ventilatory responses and exercise tidal flow-volume loops (ETFVL) at the first and second ventilatory thresholds (VT(1) and VT(2)). Nineteen master athletes (mean age (+/- SD), 63.1 +/- 3.2 y; (.)VO(2)(max), 41.5 mL x (min x kg)(-1)) and 8 untrained elderly subjects (age, 65.5 +/- 2.3 y; (.)VO(2)(max), 25.8 mL x (min x kg)(-1)) performed 2 exhaustive exercise tests on a cycle ergometer. In untrained subjects, at VT(1) and VT(2), no significant difference was measured in ventilatory responses and ETFVL between protocols. Master athletes, at VT(2), presented a significantly higher (.)VCO(2) (P < 0.01), ventilation ((.)VE; P < 0.01), breathing frequency (f(b); P < 0.05), tidal volume relative to inspiratory capatcity (V(t)/IC) (P < 0.01),V(t) relative to forced vital capacity (V(t)/FVC; P < 0.05), and lower inspiratory reserve volume relative to FVC (IRV/FVC; P < 0.01) during the 1 min protocol than during the 3 min protocol. Master athletes, at maximal exercise, expressed significantly higher (.)VCO(2) (P < 0.01) and dyspnea (P < 0.05) with the shorter protocol. We concluded that, in untrained subjects, neither incremental exercise test had an impact on respiratory responses during exercise. Nevertheless, in master athletes, breathing strategy seems to be protocol dependent. The short test induced higher mechanical ventilatory constraints and dyspneic feeling than the long protocol, which could be explained by a higher (.)VE itself linked to a greater (.)VCO(2) and a higher blood lactate concentration.

Incremental exercise tests in master athletes and untrained older adults.

This study aimed to analyze the impact of step-duration protocols, 1-min vs. 3-min, on cardiorespiratory responses to exercise, whatever the aerobic-fitness level of sedentary (65.5 +/- 2.3 years, n = 8) or highly fit (63.1 +/- 3.2 years, n = 19) participants. Heart rate and VO2 at the first and second ventilatory thresholds (VT1 ,VT2) and maximal exercise were not significantly different between the two protocols. In master athletes, the 3-min protocol elicited significantly lower ventilation at VT2 and maximal exercise (p < .01). In the latter, breathlessness was also lower at maximal exercise (p < .05) than in sedentary participants. In trained or sedentary older adults, VT1, VT2, and were not influenced by stage duration. According to the lower breathlessness and ventilation, however, the 3-min step protocol could be more appropriate in master athletes. In untrained participants, because the cardiorespiratory responses were similar with the two incremental exercise tests, either of them could be used.

High-intensity intermittent running training improves pulmonary function and alters exercise breathing pattern 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.

Effects of a short-term interval training program on physical fitness in prepubertal 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.

Evidence of exercise-induced arterial hypoxemia in prepubescent trained children.

Exercise-induced arterial hypoxemia (EIAH) is a recognized phenomenon in highly trained adults. Like adult athletes, prepubescent trained children may develop high-level metabolic demand but with a limited lung capacity in comparison with adults. The purpose of this investigation was to search for evidence of EIAH in prepubescent trained children. Twenty-four prepubescent (age: 10.3 +/- 0.2 y) trained children (10.0 +/- 0.7 h of weekly physical activity) performed pulmonary function tests and a graded maximal exercise test on a cycle ergometer. EIAH was defined as a drop of at least 4% from resting level arterial oxygen saturation (Sao(2)) measured by pulse oximetry. EIAH was observed in seven children. Forced vital capacity (FVC), ventilatory response to exercise (Delta(E)/Deltaco(2)), and breathing reserve at maximal exercise were significantly lower, whereas tidal volume relative to FVC was higher in hypoxemic children than in nonhypoxemic children; weekly physical activity and maximal oxygen uptake were similar. Moreover, positive relationships were found between Sao(2) at maximal exercise and breathing reserve (r = 0.56; p < 0.05) or volume relative to FVC (r = 0.70; p < 0.01). EIAH may occur in prepubescent trained children with a relatively low maximal oxygen uptake (42 mL. min(-1). kg(-1)); however, the mechanisms remain unclear and need to be investigated more accurately.