Reliability and validity of a low-cost portable force platform

BACKGROUND: A small, portable, inexpensive FP is a helpful test instrument in many strength and conditioning settings. OBJECTIVE: To assess the reliability and validity of a portable FP. METHODS: The FP was assessed statically for linearity and regionality using known weights and known weight placements across nine regions. Dynamic assessment was conducted by placing the FP on a laboratory-grade one-dimensional FP and performing static jumps, countermovement, and drop jumps with synchronized data acquisition. Frequency response of the FP was assessed by striking the top surface with a hammer. RESULTS: Excellent static linearity (r> 0.99), trivial differences in regional forces, excellent correlation between FPs in the static, countermovement, and anchored FP for the drop jump (all r> 0.98) were observed. Frequency response from an impact was poor when the FP was not anchored. However, once anchored the FP showed a dominant frequency of more than 10 times the typical jump frequencies and excellent synchrony with the laboratory FP (r> 0.98). CONCLUSION: The FP showed good to excellent characteristics in the static and countermovement jumps and the drop jumps when anchored. The primary limitation of the FP is its small size and light weight.