A SIMPLE ISOKINETIC CYCLE FOR MEASUREMENT OF LEG MUSCLE FUNCTION

The measurement of net pedaling torque during isokinetic cycling allow s for the evaluation of leg muscle strength and work capacity over fix ed time intervals. However, the expense and difficulty of constructing an isokinetic cycle have limited the widespread application of this u seful research tool. We have modified a simple commercially available isokinetic cycle that uses hydraulics to maintain pedaling velocity. A strain gauge on the flywheel axle strut measures the torsion on the s trut caused by pedaling. To evaluate this device, seven healthy subjec ts (3 males and 4 females) were each tested twice at 60, 90, and 120 r pm for peak power during a 10-s sprint and at 100 rpm for total work p erformed during a 30-s sprint. These results were compared with predic ted values for age, height, and sex developed on a more complicated is okinetic cycle. Subjects also performed a progressive cycle ergometry test. For the group, peak power was 97.30 +/- 12.64% of predicted (mal es 883.70 +/- 202.76 W; females 657.00 +/- 66.42 W) and work output wa s 107.70 +/- 15.75% of predicted (males 15.50 +/- 2.85 kJ; females 11. 70 +/- 2.17 kJ), whereas maximal progres sive exercise capacity was 12 6.40 +/- 25.84% (males 245.30 +/- 56.58 W; females 212.30 +/- 35.49 W) . The relatively lower work values generated on this cycle (compared w ith the maximal progressive exercise capacity) can be attributed to th e location of the strain gauge, resulting in measurement of effective work output on the flywheel. Peak power related significantly to lean body mass (r = 0.914, P < 0.001), whereas 30-s work output related str ongly to both lean body mass (r = 0.950, P < 0.001) and maximal exerci se capacity (r = 0.783, P < 0.05). We conclude that this simple isokin etic cycle can be used to make the same physiological measurements as the more complex device but that normative values should be establishe d for this cycle.