Arm use and posture alter metabolic cost during non-impact cardiovascular cross training at a constant machine workload

While the popularity of non-impact cardiovascular cross trainers has led to an increase in the number of metabolic studies that use the equipment, there is a lack of scientific information regarding the effect of incorporating arm use and postural shifts on metabolic cost. The aim of this study was to determine the influence of using the arms and shifting the posture on metabolic cost during exercise on a non-elliptical cross trainer. Fifteen healthy subjects exercised at ~70% of their age-predicted heart rate maximum while heart rate (HR), oxygen consumption (V[O.sub.2]), and energy expenditure were measured. At a constant machine workload, the subjects exercised: (a) upright while unsupported; (b) upright while using the machine's handles; and (c) while leaning forward with the upper body anchored. Relative to working upright and unsupported, introducing arm use or a forward postural shift resulted in a significant increase in HR [73.4 [+ or -] 4.81% vs. 76.4 ± 4.51% (P = 0.01) and 76.9 ± 5.92% (P < 0.01)], V[O.sub.2] [23.37 ± 3.53 mL * [min.sup.-1] * [kg.sup.-1] vs. 24.69 ± 3.67 (P = 0.001) and 25.11 ± 3.74 (P < 0.001)], and derived energy expenditure [9.126 ± 2.09 kcal [min.sup.-1] vs. 9.674 ± 2.16 (P < 0.001) and 9.826 ± 2.07 (P < 0.001)]. These results suggest that changes in user-machine interaction at a constant workload can have a significant, albeit small to moderate effect (d = 0.258-0.649) on metabolic cost on this particular cross trainer. Key Words: Exercise, Oxygen Consumption, Energy Expenditure