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This study examined the effect of a 20-week training program of two groups: six middle-aged men (37 +/- 4 yrs) (GIT) and six young male subjects (20 +/- 1 yrs) (GIIT). The training program consisted of bicycle ergometer exercise, 1 h/day, 3.5 days/week at a work load corresponding to 80%-85% of HR max. Before (S0) and at the end of the training program (S20), measurements of VO2 max, maximal work load (MWL), net efficiency, onset of blood lactate accumulation, absolute (OBLAW), and relative to MWL (OBLA %) were made on GIT and GIIT groups and on a third group (21 +/- 2 yrs) (GIIC), used as a control. Muscle fiber composition of m. vastus lateralis was studied after training for GIT and before and after the training period for GIIT and GIIC. VO2 max (ml X kg-1 X min-1), which was initially similar in GIT and GIIT (49 ml X kg-1 X min-1), increased significantly by 8% in GIT and by 19% in GIIT. OBLAW increased significantly to the same level in the two groups (38% and 42%, respectively). OBLA % increased significantly (20%) in GIT only. In the groups studied (GIIT), no change was observed for muscle fiber composition. % ST fiber type did not correlate to OBLAW or OBLA % S0 values nor to OBLAW and OBLA % changes during training. This leads to the conclusion that age and the initial physical fitness were the two major factors affecting the outcome of this endurance training program upon the two groups. Further research is needed to establish which of these two factors is the most influential.
Denis et al. (Wed,) studied this question.