Reliability and validity of a low-cost, wireless sensor and smartphone app for measuring force during isometric and dynamic resistance exercises

The aim of this study was to investigate the reliability and validity of an affordable wireless force sensor in measuring mean and peak forces during resistance training.A Suiff Pro wireless force sensor (Suiff, Spain) and a MuscleLab force platform (Ergotest, Norway) were used concurrently to assess tensile load and the ground reaction force resulting from an upright row exercise. Thirteen participants (28.2 +/- 5.7 years, 76.2 +/- 9.6 kg, 178.2 +/- 9.2 cm) performed the exercise under three velocity conditions and isometrically. Each condition involved three sets of exercise. Mean (F-mean) and peak (F-peak) force values from both sensors were collected and compared.Suiff Pro exhibited excellent reliability for F-mean and F-peak (ICCs = 0.99). When compared to the criterion measures, Suiff Pro showed trivial standardized bias for F-mean (Mean = 0.00 [CI 95% = 0.00 to 0.01]) and F-peak (-0.02 [-0.04 to 0.00]). The standardized typical error was also trivial for F-mean (0.03 [0.02 to 0.03]) and F-peak (0.07 [0.05 to 0.09]). Correlations with the MuscleLab force platform were nearly perfect: F-mean (0.97 [0.94 to 0.98]; p<0.001); F-peak (0.96 [0.92 to 0.97]; p<0.001).The findings demonstrate that the Suiff Pro sensor is reliable and valid device for measuring force during isometric and dynamic resistance training exercises. Therefore, practitioners can confidently use this device to monitor kinematic variables of resistance training exercises and to obtain real-time augmented feedback during a training session.