The Effect of Cushioned Insoles on Tibial Acceleration During Running

Abstract

Background: Running through fatigue has been found to place an excessive amount of stress to lower extrimities that may increase the risk of overuse injuries. Cushioned insoles are suggested to help attenuate shock and reduce impact forces caused by running. PURPOSE: To investigate the effect of implementing cushioned insoles on subjects before and after a fatigue protocol run to determine whether the insoles significantly lessened impacts. METHODS: Four male college students (age = 22.8± 4yr; weight = 80.2± 5kg; height = 187.3± 3cm) participated in the study. The participants were tested three times over a period of three weeks. During the first visit, lactate threshold speed (LTS) was assessed via blood samples (7.8±.5mph). During the second and third visits participants were randomly assigned to undergo incremental treadmill tests with and without insoles. The incremental runs included two rounds of seven 30-second bouts at stages -20% below to +40% above the LTS, with a 20 minute run at LTS in between the two trials. A triaxial accelerometer that was placed at each subject’s dominant tibial plateau recorded acceleration before and after the 20m run. Tibial acceleration (TA), stride length and frequency were calculated through Matlab. RESULTS: A two way repeated ANOVA (2 fatigue states by 2 insoles conditions) showed that there was a main effect of state (p=0.003) and a main effect of insole condition (p<0.001), as well as an interaction (p=0.044). Post hoc analysis revealed that TA was significantly lower during the non-fatigue control run with insoles when compared to the other conditions. Over the course of both pre- and post-fatigue incremental tests, stride length and frequency did not change. CONCLUSION: The findings indicate that insoles are an effective way to reduce tibial acceleration during running, but to a greater extent in the absence of fatigue (22% vs. 13%).