Positive versus negative foot inclination for maximum height two-leg vertical jumps

Objective. To test the hypothesis that a negative foot inclination can increase vertical jump height; to determine if an optimal degree of foot inclination exists; to design an athletic shoe based on our findings and determine the effect of the design on jump height. Background. A number of inventors claim that athletic shoes that incorporate a negative foot inclination (the heel being lower than the fore-foot) can enhance athletic performance. Methods. This study was conducted in three phases. Using an adjustable wooden platform to vary the foot inclination, phase one tested standing two-leg jumps at +4, 0, −2, −3, −4 degrees of inclination. Using the same procedures, phase two tested running two-leg jumps comparing +4 degree inclination (standard shoe) with −3.5 degrees (‘optimalʹ angle from phase one). In phase three, actual −3.5 degree prototype shoes were fabricated and compared to +4 degree standard athletic shoes. Design. Since each subject was tested at all angles, the appropriate statistical design was repeated measures. In phase one, since there were five angles, F-testing was used in the analysis, while in phases two and three, since only two angles were used, paired t-tests were used. Results. The results of phase three showed that all ten jumpers improved their jump height when using the −3.5 degree prototype shoe. The average increase was 4.8 cm, a 10% increase on average, with the minimum increase being 2.4 cm. Similar results were found for both phase one and for phase two testing. Conclusion. In conclusion, we have found convincing evidence that negative foot inclination increases jump height in two-leg vertical jumps.