A Strength-Endurance Index for Power Grip

Introduction The purpose of this study was to quantify muscle strength and endurance in power grip. Method Workers (74 M and 74 F, 18–72 years) squeezed a dynamometer for a 60 s, 18-cycle test. Initial strength (IS) and final strength (FS) were calculated as the mean peak force for cycles 1–3 and 16–18, respectively. Endurance was defined by the strength decrement index (SDI) where SDI = (IS − FS)/IS × 100. A grip strength-endurance analyzer was constructed from IS and SDI data which were depicted on two parallel, linearly scaled axes. Discrete IS and SDI scores were connected on each axis with a vector. The vector (Vmag) was measured directly from the analyzer and its direction identified from its slope. Integer scales transformed discrete IS and SDI scores into individual strength-endurance performance scores (SEPS). Results Better than 95% of the sample (n ≥ 141) scored within acceptable test ranges defined as the combined sample mean ± 2SD, for SDI, Vmag and SEPS. Vmag was the best predictor for SEPS. Linear regression for SEPS was SEPS (combined) = 0.09 (Vmag) − 0.29: (SEE = 0.829). The analyzer revealed individual scores outside acceptable ranges for injured and uninjured efforts. Conclusion The development of a power grip strength-endurance analyzer provided a simple method to graph individual power grip performances. Converting strength and endurance scores to integers and summing them (SEPS) provided a simple means to represent individual estimates of power grip strength-endurance performance.