Figure 3: Yo-Yo Intermittent Endurance level 1 performance (a) as well as heart rate after controlled intermittent submaximal exercise (% , (b)) before and after 15 wks with thrice-weekly training sessions of high-intensity swimming (HIT) and moderate-intensity swimming (MOD) in comparison to an inactive control group (CON). Data are presented as means ± SEM. denotes significant difference between the training groups and CON.