Effect of heavy-intensity 'priming' exercise on oxygen uptake and muscle deoxygenation kinetics during moderate-intensity step-transitions initiated from an elevated work rate.

We examined the effect of heavy-intensity 'priming' exercise on the rate of adjustment of pulmonary O2 uptake (τV˙O2p ) initiated from elevated intensities. Fourteen men (separated into two groups: τV˙O2p ≤25s [Fast] or τV˙O2p >25s [Slow]) completed step-transitions from 20W to 45% lactate threshold (LT; lower-step, LS) and 45% to 90%LT (upper-step, US) performed (i) without; and (ii) with US preceded by heavy-intensity exercise (HUS). Breath-by-breath V˙O2p and near-infrared spectroscopy-derived muscle deoxygenation ([HHb+Mb]) were measured. Compared to LS, τV˙O2p was greater (p<0.05) in US in both Fast (LS, 19±4s; US, 30±4s) and Slow (LS, 25±5s; US, 40±11s) with τV˙O2p in US being lower (p<0.05) in Fast. In HUS, τV˙O2p in Slow was reduced (28±8s, p<0.05) and was not different (p>0.05) from LS or Fast group US. In Slow, τ[HHb+Mb] increased (p<0.05) in US relative to HUS; this finding coupled with a reduced τV˙O2p indicates a priming-induced improvement in matching of muscle O2 delivery-to-O2 utilization during transitions from elevated intensities in those with Slow but not Fast V˙O2p kinetics.