Fig. 1

Means of heart rate [beats/min] in the NW group and the XCO group before (T1) and after (T2) the 12-week endurance training during the 5 walking speed stages (stage 1: 1.0 m/s; stage 2: 1.2 m/s; stage 3: 1.4 m/s; stage 4: 1.6 m/s; stage 5: 1.6 m/s); * = significant difference (p < 0.05) between T1 and T2 in the NW group; # = significant difference (p < 0.05) between T1 and T2 in the XCO group