Early effects of short-term aerobic training. Physiological responses to graded exercise

The aim of this study was to find out how early the moderate training effects appear and to check the hypothesis that familiarization with exercise protocol may contribute to an early physiological responses to training in previously sedentary subjects.

Twelve male, sedentary volunteers (22.0+/-0.7 yrs) were submitted to 3 weeks of a bicycle ergometer training, consisting of 45 min of exercise (at 70% VO(2)max), 3-4 times a week. The subjects performed 4 incremental exercise tests until volitional exhaustion: 2 before training (C1 and C2), and then after 1 (T1) and 3 (T3) weeks of training. During exercise HR, VO(2), electrical activity (EMG) of rectus femoris, biceps femoris, soleus and trapezius muscles were recorded and blood samples were taken for blood lactate (LA) determination.

Already after 1 week of training HR decreased (p<0.05) with a further decline after 3 weeks the training (p<0.01). Maximal work load after 3 weeks of training increased to 277+/-10.4 W vs 250+/-9.5 W (p<0.05), VO(2)max achieved higher values than in C1 and C2 tests (p<0.05) and LA and EMG thresholds were elevated (p<0.05).

A decrease in the resting and submaximal heart rate is the earliest effect of increased physical activity. Familiarization to exercise protocol decreased EMG of biceps femoris and soleus muscles during exercise, but did not influence that of rectus femoris muscle the most engaged during cycling.