A method for monitoring reactive strength index

Ubiquitous motion sensors in shoes and clothing are becoming more prevalent. This new data stream opens a large opportunity to gain a deeper understanding of human movement. This paper describes the development and validation of an algorithm to calculate reactive strength index (RSI) from an accelerometer mounted at the ankle. Compared to the gold standard force-plate, the accelerometer and algorithm RSI had r = 0.98, mean difference = 0.001 m/sec and a confidence interval ranging from 0.12 to -0.11 m/sec. Difficulty in accurately identifying take-off using the accelerometer was the main source of measurement error.