Design and analysis of research on sport performance enhancement

Purpose The purpose of this study was to assess research aimed at measuring performance enhancements that affect success of individual elite athletes in competitive events. Analysis: Simulations show that the smallest worthwh ile enhancement of performance for an athlete in an international event is 0.7-0.4 of the typical within-athlete random variation in performance betwe en events. Using change in performance in events as the outcome measure in a crossover study, researchers could delimit such enhancements with a sampl e of 16-65 athletes, or with 65-260 in a fully controlled study. Sample siz e for a study using a valid laboratory or field test is proportional to the square of the within-athlete variation in performance in the test relative to the event; estimates of these variations are therefore crucial and shou ld be determined by repeated-measures analysis of data from reliability stu dies for the test and event. Enhancements in test and event may differ when factors that affect performance differ between test and event; overall eff ects of these factors can be determined with a validity study that combines reliability data for test and event. A test should be used only if it is v alid, more reliable than the event, allows estimation of performance enhanc ement in the event, and if the subjects replicate their usual training and dietary practices for the study; otherwise the event itself provides the on ly dependable estimate of performance enhancement. Publication of enhanceme nt as a percent change with confidence limits along with an analysis for in dividual differences will make the study more applicable to athletes. Outco mes can be generalized only to athletes with abilities and practices repres ented in the study. Conclusion: Estimates of enhancement of performance in laboratory or field tests in most previous studies may not apply to elite a thletes in competitive events.