Effects of Toe Flexor Strength on Forefoot Loading During Unanticipated Side-step Cutting in Football Players

Abstract

Lateral foot loading has been purported to relate to increased risk of fifth metatarsal fractures in cleated sports. Intrinsic foot strength can mediate the distribution of foot loading during athletic maneuvers. Increases in toe flexor strength (TSF) correlate to increases in the cross sectional area of numerous intrinsic foot muscles and have also been found to correlate to increased physical performance in a variety of tasks. Whether increases in TFS directly influences foot loading during athletic tasks is unknown. Understanding this relationship will help exemplify the risk of fifth metatarsal fracture from TFS of the hallux. PURPOSE: To examine the effects of TFS on plantar loading during an unanticipated side-step task in football players. METHODS: Sixteen subjects were allocated into tertiles of TFS. The low TFS group (n=5, height 175.0cm, mass 80.4kg, age 17.8yrs), moderate TFS group (n=6, height 175.8cm, mass 77.6kg, age 17.7yrs), and high TFS group (n=5, height 174.2cm, mass 80.3kg, age 17.6yrs) did not differ in height (p=0.9), mass (p=0.8) and age (p=0.99). TFS was measured standing on a pressure distribution platform. In-cleat plantar pressure distribution was measured during an unanticipated side-step cutting task on a synthetic turf field while wearing standard football cleats. Force time integral was calculated for 9 specific regions and normalized to total foot force time integral. This relative load for each foot region was used to determine group differences with ANOVA (p<0.05) in relative loading within each foot region. Only the forefoot and toe regions were analyzed, as those regions had approximately 90% of the total foot loading. A post-hoc pairwise comparison was performed if a significant main effect of group was found. RESULTS: A main effect of strength group was found in relative loading within the lateral forefoot (p=0.002). The lower TFS group (20.0±4.2%) had significantly greater loading in the lateral forefoot compared to the moderate (9.7±4.2%, p<0.001) and high (11.5±3.0%, p=0.004) strength groups. CONCLUSIONS: The results indicate that increases in intrinsic TFS may decrease the amount of lateral foot loading, potentially reducing the risk of fifth metatarsal fractures. The authors would like to acknowledge funding support from adidas International, Inc.