A comparison of running biomechanics on track, asphalt, grass, and treadmill using wearable sensors.

Inertial Measurement Units (IMUs) allow assessment of running biomechanics outdoors on various surfaces. The purpose of our study was to compare peak tibial acceleration (PTA), stance time (ST), stride frequency (SF), and maximum rearfoot eversion velocity (MREV) when running on asphalt, track, grass, and on a treadmill. Twenty healthy participants ran on each surface at their self-selected speed. IMUs were placed on their right tibia and posterior aspect of their right shoe. A timing system was used to ensure consistent speed between surfaces. Thirty steps from each surface were analysed. Separate repeated measures ANOVAs or Friedman tests were performed on each dependent measure, depending on normality. Post-hoc analyses were performed when appropriate. SF, PTA, and MREV differed (p < .001) between surfaces. SF was highest on treadmill (83.4 ± 5.4 strides/sec) and slowest on grass (81.0 ± 4.2 strides/min). PTA was greater outdoors (asphalt: 11.0 ± 2.7 g, grass: 10.7 ± 3.4 g, and track: 10.6 ± 2.3 g), but less on treadmill (7.9 ± 1.6 g). MREV was lowest on grass (394.9 ± 256.5 deg/s) and greatest on track (623.5 ± 299.3 deg/s) and asphalt (620.7 ± 289.1 deg/sec). ST did not differ between surfaces (p = .231). Laboratory-based studies on running biomechanics may not reflect the running gait used on outdoor running surfaces.