For most women, maximal oxygen consumption was measured on a treadmill at 4.8 to 7.2 km (3.0 to 4.5 miles) per hour, with progressive increases in grade until the woman could no longer continue, as described elsewhere11. Three women whose main form of exercise was bicycling used a bicycle ergometer for the determination of maximal oxygen consumption, with the work rate increased by 25 W every two minutes. If the maximal heart rate was considerably lower than the predicted value (220 minus the woman's age) or if there was no plateau in oxygen consumption with increasing workload, the test was repeated on another day.