GSTM1 and cancer: During exercise at the VT, TOI was similar between groups, but [Hb]total and [HHb] were significantly decreased in cancer survivors compared to controls (P < 0.01) The rate of change for TOI (ΔTOIΔ/V ̇O2) and [HHb] (Δ[HHb]/ΔV ̇O2) relative to ΔV ̇O2 were decreased in cancer survivors compared to controls (P = 0.02 and P = 0.03 respectively).