Graded Exercise Test (GXT) and Maximal Oxygen Uptake (V˙O2max) Determination

The GXT was designed to last ∼8–12 min, according to guidelines to assess the V˙O_2max and iV˙O_2max (Howley et al., 1995). The GXT started at 8 km⋅h^-1, with 1.5 km⋅h^-1 increments every 2 min until exhaustion (Brisola et al., 2015; de Poli et al., 2016; Zagatto et al., 2016). Exhaustion was defined as the incapacity to maintain exercise intensity. After GXT, the participants remained for 5 min in passive recovery, and then returned to the treadmill to run until exhaustion at a workload corresponding to 105% of the maximal intensity reached in the GXT, which was used as verification testing to confirm V˙O_2max (Rossiter et al., 2006).

The V˙O₂ average of the final 30 s in each GXT stage and 15 s in the rectangular test was calculated. V˙O_2max was assumed when the V˙O₂ plateau was observed (difference of ≤2.1 mL⋅kg⋅min^-1 between the last two complete stages of GXT). When no plateau could be observed, the highest average of V˙O₂ obtained during the GXT was compared with V˙O₂ reached in the rectangular test; V˙O_2max being assumed as the highest average of V˙O₂ when not different from the V˙O₂ reached in the rectangular test (Rossiter et al., 2006). The minimal exercise intensity at which the subject reached V˙O_2max was considered as iV˙O_2max.