The influence of the rotational energy of a flywheel on the load pulse sum during pedalling on a cycle ergometer

Summary

Employing seven male subjects, the influence of four different ergometer flywheels with the moments of inertia at the crankshaft (J′)=5.5, 10.5, 16.5, and 19.5 kg·m² on 6-min load pulse sum (LPS), the heart rate integrated over 6-min was investigated. TheJ/t' was demonstrated to influence LPS at each of the corresponding rotational energies of the flywheels (75, 144, 226 and 276J at 50 rev·min⁻¹) in the four work-load steps (50, 100, 150 and 200 W). Between the valuesJ′=5.5 kg·m² and 10.5 kg·m² the LPS decreases, to rise again in the rangeJ′=10.5 kg·m²–19.5 kg·m². For equal work-loads the minimum LPS was reached at aJ′ of 10.5 kg·m². For the workloads of 100, 150 and 200 W it was possible to show statistically significant differences. The moment of inertia of ergometer flywheelsJ has a smoothing effect on the fluctuations of the rotational speed which are unavoidable during work on a cycle ergometer. The flywheel stores the leg forces acting on the pedals as rotational energy and opposes any rotational acceleration. If theJ used is too small, equalization of the fluctuations of the rotational speed remains unsatisfactory. Flywheels with largerJ require larger torques at the crankshaft for acceleration. For the most effective delivery of work to a cycle ergometer, an optimal rotational energy of the flywheel was found. For equal physical work, smaller or larger rotational energies require a larger expenditure of biological energy. AJ′=11±2 kg·m² was incorporated into the draft for the German standard DIN 13405 — cycle-type ergometers.