Leg Impact Accelerations And Ground Reaction Forces During Running On A Treadmill And Overground.

Abstract

PURPOSE: The purpose of the study is to determine the relationship between impact forces and leg accelerations while running on a treadmill and overground. METHODS: Subjects (n=12: 8 males, 4 females; age: 23.9 ± 6.02 y; height: 1.71 m ± 0.11 m; mass: 69.8 ± 14.5 kg) participated in a 1-day test during which ground reaction forces (GRF) and leg accelerations were recorded during overground and treadmill running. All GRF data were collected using an instrumented force treadmill (Bertec, USA) with handrails removed and treadmill surface even with floor surface. To complete overground trials, subjects ran over the treadmill (belt not moving) with speed measured suing timing gates placed before and after the treadmill surface. A wired uniaxial accelerometer was securely placed on the distal medial aspect of the right tibia to measure leg impact acceleration (legpeak). All subjects completed 10 trials for each of 3 speed conditions (preferred speed (PS) ± 0.25 m/s) for each condition (treadmill, overground). Impact force (F1), legpeak, and ratio of F1: legpeak were determined and compared between speeds and modes using repeated measures ANOVAs. RESULTS: None of the variables were influenced by the interaction of speed and mode (Ratio, p=0.701; F1, p=0.778; legpeak , p=0.736). Ratio was not influenced by speed (p=0.281) or mode (p=0.126). F1 was not different between overground and treadmill (p=0.077) but was influenced by speed (p=0.024) increasing on average 8.4% from slow to fast speed. Legpeak was 36.5% greater during overground vs. treadmill (p=0.048) but did not change over speeds (p=0.206). CONCLUSIONS: The consistent ratio between F1 and legpeak during treadmill and overground running seems to indicate the relationship between these parameters is not influenced by mode of running. However, the greater legpeak during overground running and the trend for a greater F1 overground is an indication that subjects may have used different strategies to achieve the same speeds while running overground vs. treadmill.