Cardiorespiratory fitness evaluation by the shuttle test in asthmatic subjects during aerobic training.

PURPOSE: The purpose of this study was to assess the validity of the 20-m shuttle test with 1-min stages (20-MST) to estimate maximal oxygen uptake (VO2 max) and its ability to register cardiorespiratory modifications over the course of an individualized aerobic training program for mild to moderately asthmatic children acclimatized to moderate altitude. METHODS: Forty-eight asthmatic subjects aged 12 to 17 years performed both a maximal incremental exercise test on a cycle ergometer and the 20-MST. Ten of the subjects were then randomly chosen and trained three times per week at their ventilatory threshold (Vth) intensity level for three months. Another group of ten asthmatic subjects served as control subjects. Training intensity was adjusted monthly; heart rate values at Vth were increased by the same proportion as the increase in Vo2 max as measured by the 20-MST. At the end of training, both groups were again evaluated with the two tests. The Vo2 max values by direct measurement and by the 20-MST were not significantly different for the entire population (46.5 +/- 1.6 vs 47.2 +/- 2.1 ml.min-1.kg-1). In addition, the two test results were in close agreement (r = 0.84; p < 0.01). After training, a sharp improvement in the direct Vo2 max (44.1 +/- 2.4 to 51.2 +/- 1.9 ml.min-1.kg-1) was noted in the training group as well as an increase in the Vth (25.6 +/- 1.9 to 32.1 +/- 3.4 ml.min-1.kg-1), the maximal power (152 +/- 7.1 to 185 +/- 3.8 W), and the maximal oxygen pulse (0.24 +/- 0.007 to 0.27 +/- 0.008 ml.beat-1.kg-1). CONCLUSION: The indirect measure confirmed these results: a simultaneous increase in VO2 max (43.7 +/- 2.5 to 53.8 +/- 2.1 ml.min-1.kg-1), maximal oxygen pulse (0.22 +/- 0.004 to 0.27 +/- 0.006 ml.beat-1.kg-1), and the number of stages completed (7 +/- 1.4 to 10.1 +/- 1.3) was observed. It was concluded that the 20-MST has sufficient validity to assess VO2 max and to register cardiorespiratory modifications over the course of individualized aerobic training programs in mild and moderately asthmatic children. It thus may be used to adjust training intensities during these programs.

Individualized aerobic and high intensity training for asthmatic children in an exercise readaptation program. Is training always helpful for better adaptation to exercise?

In order to define the role of individualized training intensity in a conditioning program for asthmatic children, we have trained seven asthmatics (age = 11.4 +/- 1.8 years) at their ventilatory threshold (VTh) intensity level for a three-month period (aerobic training) and at maximal intensity also for three months (high intensity training). VTh is the point at which a nonlinear increase of VE occurs. Another group of seven asthmatics (age = 11.4 +/- 1.5) served as control subjects. Cardiopulmonary fitness was determined on a cycle ergometer before and after each training session. This study demonstrated that aerobic training, correctly adapted to the child's physical ability, induces the following: (1) a rapid and marked cardiovascular fitness increase; and (2) a decrease in VE over a given work range so that VTh is increased. This is of great importance because hyperventilation is a major determinant of exercise-induced bronchospasm. In contrast, even if high intensity training is well tolerated in an indoor swimming pool, the long-term effects are unsuitable for asthmatic children because the decrease of VTh will involve an increase of hyperventilation, even when exercise is performed at submaximal intensity.