Local Anesthesia of the Sole of the Foot Alters Lower Limb Kinematics and Kinetics During Running

Abstract

1649 PURPOSE: The purpose of this study was to investigate whether local anesthesia of the sole of the foot would alter lower limb kinematics, kinetics and perceptions of comfort during running. METHODS: The study was conducted as a randomised double blind placebo controlled crossover clinical trial (n = 10). Either a topical anaesthetic cream (EMLA™, lignocaine and prilocaine 25 mg/g) or placebo (CON) was applied after which subjects rested in sitting for 60 minutes and then performed 10 running trials in the Motion Analysis Laboratory to determine their kinetics and lower limb kinematics during running. Thereafter, they were required to run 840 metres on an indoor tartan track and rate their perceived comfort (Scale 0–10) during the run. RESULTS: The step length (m) (EMLA: 0.68 ± 0.065, CON: 0.718 ± 0.081: p = 0.0036) and stride length (m) (EMLA: 1.375 ± 0.146, CON: 1.43 ± 0.18: p = 0.026) in the laboratory and mean velocity (m/sec) (EMLA: 3.87 ± 0.358, CON: 4.07 ± 0.317: p = 0.0036) on the indoor track decreased significantly following EMLA™. Peak horizontal propulsive force (BW) was significantly reduced during the EMLA trial compared with the CON trial (EMLA: 0.162 ± 0.044 BW, CON: 0.177 ± 0.049 BW: p = 0.043). There was a significant increase (p = 0.0053) in dorsiflexion of the ankle at heelstrike (Ahs) during the EMLA trial (degrees) (EMLA: −3.23 ± 4.19, CON: 0.233 ± 4.9) compared with CON. There was also a significant increase of dorsiflexion of the ankle at the time of peak knee extension (Asw) (degrees) (EMLA: −4.113 ± 4.55, CON: −1.59 ± 4.55: p = 0.0078) and at the time of peak knee flexion in the stance phase (Ast) (degrees) (EMLA: −9.69 ± 5.43, CON: −7.2 ± 6.3: p = 0.028) during the EMLA trial compared with CON. CONCLUSION: The application of a topical local anesthetic cream to the sole of the foot reduced self-selected running speed and altered selected kinetic and kinematic variables during running. Sensory input from cutaneous afferents in the foot alters gait mainly by changing running speed.