Coordinating arms and legs on a hybrid rehabilitation tricycle: the metabolic benefit of asymmetrical compared to symmetrical arm movements

The most commonly used propulsion method for handcycling is moving the arms symmetrically. Previous studies indicated that during outdoor handcycling symmetrical arm movements are more efficient. During locomotor movements, however, arm movements are performed asymmetrically in combination with leg movements. We questioned which combination of arm and leg movements is more efficient during combined arm and leg cycling for stationary use. Twenty-five able-bodied adults performed eight submaximal tests of 6 min on a hybrid handcycle at three incremental gears during four different conditions ('arms only' and 'arms & legs' with arms symmetrical and asymmetrical). Oxygen uptake (VO2), heart rate (HR) and Borg score (Borg) were assessed. Increasing workload resulted in significant increases in VO2 (16 W: 13.0 +/- A 2.4 ml kg(-1) min(-1), 31 W: 14.5 +/- A 2.9, 49 W: 15.5 +/- A 2.8; p < 0.001) and Borg (16 W: 7.7 +/- A 1.7 points, 31 W: 8.6 +/- A 1.9, 49 W: 9.5 +/- A 1.9; p < 0.001). During 'arms only', no differences were found in exercise intensity between symmetrical and asymmetrical movements. Contrarily, during 'arms & legs', both VO2 (p < 0.001) and Borg (p = 0.001) were significantly lower for the asymmetrical (VO2: 13.8 +/- A 2.6 ml kg(-1) min(-1), Borg: 8.1 +/- A 1.6 points) compared to the symmetrical condition (VO2: 14.9 +/- A 2.8, Borg: 9.1 +/- A 2.0). Results indicated that asymmetrical arm movements, especially in combination with leg movements, represented the most efficient condition on a stationary hybrid handcycle. The current results suggest that neural energy costs are lower when moving in the preferred (asymmetrical) coordination when no steering is required. These findings may have implications for stationary arm & leg cycling rehabilitation and tricycle adaptations in patients with spinal cord injury.