An anatomical model to determine step height in step testing for estimating aerobic capacity

Physical fitness has been reported to be inversely related to coronary heart disease and other health related problems. One of the most valid means of assessing physical fitness is the test of aerobic capacity. Aerobic capacity is the greatest rate at which the body can consume oxygen and represents the most efficient integration of the various physiological processes which make up the oxygen transport system. However, direct measurement of aerobic capacity requires sophisticated laboratory equipment, and is adversive to subjects. Step tests are widely used to estimate aerobic capacity. Because the biomechanical efficiency and work rate is determined by step height, accomodation of step height to the subject's statute height should provide a better estimation of aerobic capacity. A hip angle of 73·3°, when stepping, was found to give the best relationship of recovery heart rate of a step test to direct measurement of aerobic capacity. Using 73·3°, the following equations were developed for determining the stepping height when using the step test: H f = 0·189 I h and H f = 0·192 I h for females and males respectively, where h f is the step height and I h is the statute height of the subject. A correlation coefficient ( r) of 0·93 was calculated between various hip angles and calculated foot height of 182 observations of 47 females while a correlation coefficient ( r) of 0·96 was calculated from 208 observations of 53 males. Using these equations to determine step height, measurement of 30 females showed a mean hip angle of 73·3°± 2·2 and measurement of 30 males showed a mean hip angle of 73·3° ± 2·1. These data indicate that the model can be used to accurately predict foot height, given statute height and hip angle; or hip angle, given statute height and foot height, and is useful when normalizing working efficiency of stepping in step testing for estimating aerobic capacity of individuals of various heights.