CARDIORESPIRATORY AND MUSCLE OXYGENATION COMPARISONS DURING ARM CRANKING AND TASK-SPECIFIC PUSHING-PULLING IN HEALTHY WOMEN

Abstract

Fitness assessment is an important part of employee screening programs and for determination of return to work following rehabilitation. The validity of standardized upper or lower body test protocols for the assessment of occupational fitness has been questioned. PURPOSE: To compare the cardiorespiratory and localized muscle oxygenation responses between arm cranking (AC) and task-specific pushing-pulling (PP). METHODS: Eleven healthy women (mean ± SD for age: 24.5 ± 3.5 y; height: 163 ± 7 cm; mass: 57.6 ± 9.4 kg) consented to perform stepwise incremental AC (Cybex, MET300, CA) and PP (BTE Work Simulator, MD) tests until voluntary fatigue in random order in two sessions. Specific load increments were: AC - 25 watts every 2 minutes; and PP - 30 lb-in torque every 2 minutes. Cardiorespiratory responses were monitored using an automated metabolic cart and wireless heart rate monitor. Muscle deoxygenation (Mdeox) was recorded noninvasively from the right biceps using near infrared spectroscopy (MicroRunman, NIM Inc., PA). Mechanical efficiency (peak power/peak oxygen uptake[pVO2]) and deoxygenation ratio (peak power/Mdeox) were calculated at peak exercise. RESULTS: The respective values of peak power output (114 vs 25 Watts), pVO2 (1.56 vs 1.23 L/min) and oxygen pulse (8.9 vs 7.1 ml/beat) were significantly (p < 0.5) higher during AC compared to PP, while peak heart rate (176 vs 171) was not significantly different (P > .05). Muscle deoxygenation was significantly (P < .05) higher (greater deoxygenation) during PP compared to AC (−0.212 vs −0.121 optical density units). As a result, mechanical efficiency was significantly lower (P < .01) and deoxygenation ratio was significantly higher (P < .01) during PP compared to AC. CONCLUSIONS: These findings: (1) suggest greater peripheral limitation during PP compared to AC, and (2) highlight the importance of using task-specific tests for employee fitness screening. SUPPORT: Small Faculties Council, Univ. of Alberta.