Reliability of ground reaction forces in the aquatic environment

The aim of this study was to verify the reliability of the kinetic parameters of gait using an underwater force platform. A total of 49 healthy participants with a median age of 21 years were included. The kinetic gait data were collected using a 0.6 × 0.6 × 0.1 m aquatic force plate (Bertec®), set in a pool (15 × 13 × 1.30 m) with a water depth of 1.20 m and water temperature of 32.5 °C. Participants walked 10 m before reaching the platform, which was fixed to the ground. Participants were instructed to step onto the platform with their preferred limb and data from three valid attempts were used to calculate the average values. A 48-h interval between tests was used for the test-retest reliability. Data were analyzed using interclass correlation coefficients (ICC) and results demonstrated that reliability ranged from poor to excellent, with ICC scores of between 0.24 and 0.87 and mean differences between ( d ) = -0.01 and 0.002. The highest reliability values were found for the vertical (Fz) and the lowest for the mediolateral components (Fy). In conclusion, the force platform is reliable for assessing the vertical and anteroposterior components of power production rates in water, however, caution should be applied when using this instrument to evaluate the mediolateral component in this environment.