During this early period, a rough decline of citrate synthase and succinate dehydrogenase is found, both essential for ATP production. This decrease of activity still continued up to the 56 th day. VO 2 max was merely affected by the increased heart rate and 10-14% drop in stroke volume (Coyle et al, 1984). In all performance parameters including endurance, exceptional attention is given to the physiological development of adolescents. A study on adolescents still exhibit related training improvements with other age-groups, exhibiting a 5 to 6% improvement in VO 2 peak when subjected to endurance and aerobic training (Baquet et al, 2003).