Effect of stroke rate on the distribution of net mechanical power in rowing

The aim of this study was to assess the effect of manipulating stroke rate on the distribution of mechanical power in rowing. Two causes of inefficient mechanical energy expenditure were identified in rowing. The ratio between power not lost at the blades and generated mechanical power (P(rower)) and the ratio between power not lost to velocity fluctuations and P(rower) were used to quantify efficiency (e(propelling) and e(velocity) respectively). Subsequently, the fraction of P(rower) that contributes to the average velocity (chi(boat)) was calculated (e(net)). For nine participants, stroke rate was manipulated between 20 and 36 strokes per minute to examine the effect on the power flow. The data were analysed using a repeated-measures analysis of variance. Results indicated that at higher stroke rates, P(rower), chi(boat), e(propelling), and e(net) increase, whereas e(velocity) decreases (P < 0.0001). The decrease in e(velocity) can be explained by a larger impulse exchange between rower and boat. The increase in e(propelling) can be explained because the work at the blades decreases, which in turn can be explained by a change in blade kinematics. The increase in e(net) results because the increase in e(propelling) is higher than the decrease in e(velocity). Our results show that the power equation is an adequate conceptual model with which to analyse rowing performance.