Developing normalized strength scores for neuromuscular research

Introduction: The Accurate Test of Limb Isometric Strength (ATLIS) device can reliably measure the strength of 12 muscle groups using a fixed load cell. The purpose of this study was to analyze ATLIS data from healthy adults to calculate an individual's predicted strength scores. Methods: ATLIS data were collected from 432 healthy adults. Linear regression models were developed to predict each muscle group's strength. The R-squared statistic assessed variability accounted for by the models. Results: Simple main effects models stratified by gender were used to establish regression equations for each muscle using factors of age, weight, and height. Conclusions: Normalizing raw strength scores controls for biometric factors, thus enabling meaningful comparisons between subjects and allowing each muscle to contribute equally to a summary score. Normalized scores are easily interpreted for broad clinical uses, and derived summary scores establish individuals' disease progression rates using a common scale, allowing for more efficient clinical trials.