The Vmaxshuttle were used to individualize the HIIT sessions. The HIIT sessions consisted
of two 6-min sets interspersed with 5-min passive recovery. The first set was composed of a series
of 10 s bouts at 110% of Vmaxshuttle and 20 s of passive recovery. The second set was composed
of 15 s bouts at 105% of Vmaxshuttle and 20 s of passive recovery. The nonplaying HIIT
session was conducted on the tennis court instrumented with four markers on the ground (see
S1 Fig. for Tennis court instrumentation for HIIT sessions). The players began each set at the
center of the baseline, running to each mark and touching it with one foot, and returning back
to the baseline center before running to the next mark. The distances between the baseline