The aim of this study was to investigate the effect of differences in stroke rate (SR) on energy expenditure during rowing. Oxygen uptake (VO₂) was measured under different SR conditions with the same power output. Eight male collegiate rowers (age: 21.6±1.4 yr, height: 171.1±1.8 cm, weight: 68.7±1.9 kg) participated in the study. First, they performed an incremental test on a rowing ergometer to determine power output at the blood lactate threshold (P_LT). On other days, they performed 6 different SR trials maintaining their power output at 80% P_LT (80% LT test) and 90% P_LT (90% LT test), respectively. During the 80% and 90% LT tests, each subject used a triaxial accelerometer sensor placed on the back, and integrals of the absolute value of the accelerometer output from three directions (IAA) were calculated as an index of physical activity level. The most economical SR, at which VO₂ was lowest, was found at 80% and 90% LT. In both tests, a higher IAA was observed with increasing SR. Under SR conditions higher than the economical point, there was a significant correlation between the increasing amount of IAA (ΔIAA) and VO₂ (ΔVO₂) from the economical SR during the 90% LT test ( r =0.673, P <0.001). There were strong correlations ( r >0.9) between IAA and VO₂ in many subjects at a SR higher than the economical point. These results suggest that there is an economical SR point with the same power output during rowing. Additionally, an increasing amount of VO₂ associated with IAA at a higher SR than the economical point. This suggests that IAA is useful for estimation of energy expended by the moving body during rowing.