Submaximal alternatives to the Harvard pack index as guides to maximal oxygen uptake (physical fitness)

Four exercise tests have been examined as guides to maximal oxygen uptake measured directly using as subjects 101 volunteer mine rescue brigadesmen. The following indices were compared: (1) maximal O2 uptake per kg body mass during running on treadmill ([ndot]O2maxkg-1), (2) Harvard pack index (HPI), (3) cardiac frequency in the sixth minute of treadmill walking (speed 5 kph, incline 7.5°), (4) cardiac frequency in the sixth minute of stepping exercise (box height 32cm, frequency 20 per minute), (5) workload per kg body mass associated with cardiac frequency of 150 per minute during progressive cycle test (2 min each at 100,125 and 150 W). The scores for tests 3,4 and 5 were intercorrelated (r in the range 0.72-0.80) and each could be used to predict HPI (coefficient of variations ≃ 10%). None of the tests were reliable predictors of [ndot]O2maxkg-1. Thus there is a need for an alternative approach.