New practical treadmill protocol for clinical use.

A new continuous treadmill protocol (USAFSAM) has been designed using a constant treadmill speed (3.3 miles/hour) and regular equal increments in treadmill grade (5%/3min). The constant treadmill speed requires only initial adaptation in patient stride, reduces technician adjustments and produces less electrocardiographic motion artifact than do protocols using multiple or higher treadmill speeds, or both. The regular equal increments in treadmill grade are easy to implement and provide a larger number of work loads than do protocols that are discontinuous or require larger changes in work load. The USAFSAM protocol was compared with the older Balke-Ware protocol in 26 healthy men (aged 30 to 59 years). Each fasting subject completed two maximal treadmill tests from each protocol. Measurements included minute heart rate from the electrocardiogram, auscultatory blood pressures and oxygen consumption obtained with standard techniques. Similarities in between-protocol measurements for submaximal and maximal treadmill efforts were impressive; differences were small and unimportant. Further, both protocols showed equal reproducibility for the measurements noted. Importantly, time to maximal effort was reduced by 24% with the USAFSAM protocol. The USAFSAM treadmill protocol has since been used in more than 500 clinical and screening examinations, thus confirming its advantages and practicality for routine clinical stress testing. Normal reference values previously established for the Balke-Ware protocol are shown to apply to the new USAFSAM protocol as well.