Discussion
Endurance training brings about many adaptive
changes in adults reflected in an increased ‡O2max and
in the anaerobic threshold [5]. A 10-week swimming
training applied to young men increase their ‡O2max
in swimming tests but not in treadmill tests [6]. Those
effects were attributed to differences in the environmental
(position, water/land environment) and cardiorespiratory
conditions and to a specific adaptation to
those conditions in the training process. Those reports
were not fully confirmed by the presented results which
showed no improvement in swimming performance of
12-year old boys subjected to 8-week training at steady
swimming speed, equivalent to the critical one (CSS), in
free and classical styles; yet, that 8-week training in
given style did not affect swimming performance in the
test in other, untrained style.
Our results are difficult to explain unequivocally.
Endurance training induces increases in ‡O2max ranging
15 – 30% in adults [9] but in children such changes are none or do not exceed 6% [1]. Such small relative
changes in children may be attributed to an inadequate
training stimulus [1] or to insufficient motivation for
regular training [8]. A random monitoring of heart rate
during training (140 – 160 bpm) and immediately after
having completed the 12-min swimming tests showed
that the postulated [1] intensity of 80% of HRmax, necessary
to increase aerobic capacity, had not been attained.
It ought to be emphasised that the boys were voluntary