Engineering implications on physiological measurements using a Monark rope braked ergometer

The Monark rope-braked ergometer is widely used by physiologists to determine the work and power output from subjects or for physiological measurements to be made at a predetermined level of effort. The power is determined by taking the product of the pedal rate (rpm) and the brake mass (kg). The brake mass is suspended in a basket attached to a pulley. A rope is connected to the pulley and is wound around the ergometer flywheel to provide resistance. MacIntosh et al. (2002) directly measured the rope tension and found that the tight and slack side tensions were 95.5% and 6.71% of the applied load. These results contradict the traditional assumption that the slack side tension is zero. There is, however, a discrepancy in these results as the moments applied to the pulley are not in equilibrium. Gordon et al. (2004) give a detailed theoretical analysis of the brake system and validated the theory with experimental results. The ratio of tension in the rope is given by, T1/T2=e μθ