Abstract
An examination was made of methods of achieving and measuring minimum and maximum heart rates in sportsmen and women of various standards. These two measures were combined to form a fitness index for each individual, and called the Cardiac Assessment Factor (CAF): CAF = Maximum Heart Rate / Minimum Heart Rate x 10 The degree of reliability, validity and objectivity of CAF were established, both for operators and subjects. The correlations between maximum and minimum heart rates and CAF, and other measures of fitness were calculated. Descriptive statistics were computed for the CAF's of various sports groups, and inferential analyses performed between these. Minimum heart rate measured during sleep was found to be significantly lower and less variable than resting heart rate measured in the laboratory. Maximum exercise heart rates were calculated from post exercise recovery rates within a standard error of 2.839 beats per minute. Reliability coefficients of R= 0. 98 were obtained in measuring CAF. A group of adult sportsmen experienced an increment in their maximum heart rate after a period of special training. It was found that the Cardiac Assessment Factor in its present form was a useful method of measuring that specific element of fitness in adult sportsmen which can be developed by extensive exposure to extreme exhaustion stress. Further development of CAF is necessary before it can be more generally applied as a test of sports fitness.