Effect of exercise protocol on deoxy[Hb + Mb]: incremental step versus ramp exercise

Abstract

Purpose: The aim of the present study was to investigate whether the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise is specific to non-steady-state conditions.

Methods: Ten highly trained cyclists performed an incremental step (40 W x 3 min(-1)) and ramp (35 W x min(-1)) exercise. Deoxy[Hb + Mb] was measured at the distal and proximal sites of the musculus vastus lateralis throughout the exercises using near-infrared spectroscopy. Deoxy[Hb + Mb] was set out as a function of work rate (% peak power), and using curve-fitting techniques, the best-fitting model was determined.

Results: These procedures showed that the sigmoid pattern also provided the best fit for the pattern of deoxy[Hb + Mb] in the step exercise. Furthermore, it was observed that the sigmoid model was similar for the ramp (d = 6.9% +/- 1.1% and 6.9% +/- 1.4% x %(-1) peak power; c/d = 52.1% +/- 3.8% and 52.1% +/- 4.5% peak power, for the proximal and distal measurement sites, respectively) and the step exercise (d = 7.4% +/- 1.5% and 6.4% +/- 1.5% x %(-1) peak power; c/d = 52.3% +/- 6.0% and 52.5% +/- 4.2% peak power, for the proximal and distal measurement sites, respectively). The pattern of deoxy[Hb + Mb] was not influenced by measurement site.

Conclusions: From the present study, it can be concluded that the sigmoid pattern of deoxy[Hb + Mb] during incremental exercise is not specific to non-steady-state conditions. It was hypothesized that this pattern is an expression of a nonlinear Q x m/V x O2m relationship, related to changes in muscle fiber-type recruitment.