GSTM1 and chronic obstructive pulmonary disease: Expressing the quadriceps oxygenation data taking into account cumulative work during the 1STS did not alter the results, with the exception of Δ deoxy [Hb-Mb] whose increase per unit of cumulative work during the first 30 s of recovery after 1STS was more pronounced in people with COPD compared with healthy controls (p = 0.009) (Fig. 3b).