The Effects of the XG4 Performance Insole on Athletic Performance in Collegiate Athletes

Abstract

Over the past 20 to 30 years, sport equipment manufacturers have investigated ways of improving athletic performance through enhanced storage and return of energy in sport shoes. The maximal returned energy from a conventional shoe sole is typically smaller than 1% of the energy needed for the task at hand (Nigg, 2010). One possible solution to increase energy return in athletic footwear is to utilize a carbon fiber shoe insole tuned for optimal energy return of the human body-footwear system. PURPOSE: To determine if a carbon fiber shoe insole (XG4 Performance Insole; ROAR Performance; Milford, CT) can improve speed, agility, and power in collegiate athletes. METHODS: Twenty-two NCAA Division II collegiate athletes (12 M, 10 F) performed the following tests with a carbon fiber shoe insole (XG4) and a sham insole (control): 1) vertical jump, 2) pro agility test, and 3) 10-yard sprint. The two conditions (XG4 or control insole) were presented in random order. Each round of testing (three vertical jumps, two pro agility tests, and two 10-yard sprints) was separated by a period of 10 minutes to minimize the effects of fatigue. A 2 × 2 repeated-measures MANOVA was used to determine the effects of shoe insole and gender on vertical jump height, pro agility test time, and 10-yard sprint time. RESULTS: There was an increase in vertical jump height (56.9 ± 12.3 cm [XG4] vs. 56.5 ± 12.3 cm [control]), a decrease in time to perform the pro agility test (4.667 ± 0.272 s [XG4] vs. 4.682 ± 0.287 s [control]), and a decrease in 10-yard sprint time (1.922 ± 0.179 s [XG4] vs. 1.941 ± 0.179 s [control]) when using a carbon fiber shoe insole as compared to a sham insole. However, none of the performance improvements were significantly different between the two shoe insole conditions. In addition, there were no significant interaction effects between shoe insole and gender. CONCLUSION: Collegiate athletes demonstrated improvements in speed, agility, and power (assessed using the 10-yard sprint, pro agility, and vertical jump tests, respectively) when using the XG4 Performance Insole as compared to a control insole. While these improvements did not reach statistical significance due to low experimental power, the practical significance may be substantial for sports in which hundredths of a second mean the difference between success and failure.