Cardiorespiratory and hemodynamic responses during repetitive incremental lifting and lowering in healthy males and females

Abstract

The purposes of this study were twofold. First, to evaluate the cardiorespiratory and muscle oxygenation (OXY)/blood volume (BV) responses during repetitive incremental lifting and lowering (RILL) in healthy males and females. Second, to develop a predictive equation for predicting peak aerobic power ($\dot V$O_2peak) during RILL from the cardiorespiratory, OXY/BV and body composition variables. Fourteen males and 18 females [mean (SD) for age, height and body mass were: 29.6 (8.2) years; 1.75 (0.07) m; 78.9 (10.4) kg and 23.9 (2.1) years; 1.63 (0.06) m; 62.3 (6.3) kg, respectively] completed a RILL from floor to table height at 10 lifts/min to voluntary fatigue. Cardiorespiratory responses were measured using open circuit spirometry and hemodynamic trends were monitored bilaterally at the third lumbar vertebra via near infrared spectroscopy. Significant sex differences (p<0.05) were observed for the peak values of oxygen uptake ($\dot V$O_2peak), ventilation rate ($\dot V$ _E), oxygen pulse, BV-max and BV-delta. Erector spinae OXY decreased systematically until $\dot V$O_2peak was attained, while BV decreased until ~50% of $\dot V$O_2peak and then leveled off. Stepwise regression analysis indicated that ~75% of the variance in $\dot V$O_2peak was predicted from cardiorespiratory, hemodynamic and body composition variables, with the most important predictors for absolute and relative $\dot V$O_2peak being $\dot V$ _E (r=0.75) and fat mass (r=−0.63) respectively. Inclusion of left side OXY/BV responses increased the predictability of the common variance in $\dot V$O_2peak from 40% to 74%, implying that muscle hemodynamics play an important role in determining $\dot V$O_2peak during RILL.