Fifteen outfield futsal players of a local team from Brazilian first division volunteered for participation in this study. Based on a previous study [6]
with male soccer players, a minimum of 12 athletes were estimated to be necessary for our purposes. Athletes performed in random order a laboratory ramp test for VO2max assessment [8] and an on court Yo-Yo IR1 test [5]. These tests were performed individually with a minimum of 48 hrs between evaluations over a 10 days period at the start of the in-season period. They were informed of all the risks and procedures and provided informed written consent.
The ramp test [8] started at 8 km·h-1 and zero incline for 4 min on a treadmill (Inbramed Millenium, Super ATL, Brazil). The speed was then increased by 0.5 kmh-1 every 30 s until volitional exhaustion. The highest velocity completed was considered as the peak treadmill speed associated to the last complete stage (Speak). Expired gases were continuously measured (Cortex Biophysik, Germany) and the VO2max (mL·kg·min-1) recorded was the mean of the values reached during the last 20 s before exhaustion. Heart rate (HR) was continuously recorded at 5 s intervals