Comparison of Step Rate and Tibial Acceleration During Treadmill and Real-World Running

Abstract

OBJECTIVE: to compare step rate and tibial acceleration during an 8-km run performed outdoors versus on a treadmill. DESIGN: Repeated measures observational study. METHODS: Healthy adult runners (females: 9, males: 19) ran 8 km at a self-selected speed outdoors and on a treadmill. A chest mounted inertial measurement unit (IMU) was used to measure step rate while a tibial mounted IMU collected tibial acceleration. Linear mixed-effects models adjusted for speed were used to assess step rate, as well as peak vertical (PV) and peak resultant (PRES) tibial accelerations between conditions and across the 8 km, as well as their interaction. RESULTS: There was a significant interaction between distance and location (est [95% CI] = 0.71 [0.38 to 1.05], p < 0.001) for step rate, with an increase in step rate observed over distance outdoors. There was also a significant interaction between distance and location for PV (-0.13 [-0.25 to -0.00], p = 0.047) and PRES (-0.16 [-0.31 to -0.00], p = 0.047), with both increasing over distance during treadmill running. Overall, PV (3.34 [2.85 to 3.83], p < 0.001) and PRES (5.05 [4.45 to 5.65], p < 0.001) were significantly greater when running outdoors compared to treadmill running. CONCLUSION: Treadmill and overground assessment of step rate were relatively comparable. Tibial acceleration may not be interchangeable with gait analysis in the field.