Gross efficiency responses to exercise conditioning in adult males of various ages

This study investigated gross efficiency changes in a group of 60 adult males (mean age 39.2 +/- 1.2 years) resulting from endurance training and age-related responses to such training in sub-groups (each n = 20) of younger (30.7 +/- 0.7 years), intermediate (38.3 +/- 0.5 years) and older (48.6 +/- 1.1 years) subjects. Gross efficiency (%) was calculated from work output, oxygen consumption and RER energy equivalents following 10 min standard cycle ergometry exercise at 100 W and 50 rev min-1. Measurements were made at pre-, mid- and post-8 months of training, which involved progressive walking/jogging activities designed to enhance endurance capacity. In the total group, VO2 decreased pre- to post-training from 2.15 +/- 0.02 to 1.93 +/- 0.01 1 min-1 (P less than 0.01). In the sub-groups, both the younger and older subjects showed a significantly reduced VO2, from 2.17 +/- 0.01 to 1.98 +/- 0.04 1 min-1 and 2.05 +/- 0.08 to 1.86 +/- 0.03 1 min-1 respectively (P less than 0.05), but no significant changes were noted at mid-training. In the intermediate age subjects, while there were trends towards a reduced VO2, none was significant. The ANOVA revealed increased mean gross efficiency in the total group from pre- (14.3 +/- 0.1%) to post- (15.5 +/- 0.2%) (P less than 0.05) but not at mid-training (14.8 +/- 0.2%). While similar trends were observed in the sub-groups, gross efficiency increases were not significant, although changes in gross efficiency were reflected in VO2. The findings suggest that during standardized exercise, oxygen cost may be reduced and gross efficiency increased in adult males following endurance training and that such changes may take place over a variety of age ranges.