Purpose: The purpose of this study was to standardize an isokinetic testing protocol for quadriceps and hamstrings in children who are typically developing and are six through 13 years of age, to establish percentile charts of isokinetic peak torque strength for quadriceps and hamstrings by gender and age, and to determine the best predictors of strength for each of three testing speeds.
Methods: A total of 3587 children were tested for isokinetic knee strength according to our protocol on Biodex System II and III isokinetic dynamometers. Therapists participating in the study were trained on the protocol and inter-rater reliability was established. Both dominant and nondominant legs were tested at three speeds. Data were collected on peak torque, time to peak torque, and agonist/antagonist ratio. Data were also gathered on maturation level, gender, height, weight, leg length, laterality, and activity level to allow for investigation of correlations with peak torque. All data were entered in an Excel spreadsheet.
Results: Percentile charts of normal isokinetic muscle strength were generated using SPSS 12.0 for each age and gender at three speeds (60, 120, and 180 degrees per second). Stepwise regression analysis determined height to be the best predictor of peak torque for both quadriceps and hamstrings at all speeds.
Conclusions: This study is the first to report normative peak torque values for quadriceps and hamstrings in children. By using a standardized testing protocol and normative data, clinicians will be able to assess the degree of muscle weakness as well as the effectiveness of intervention strategies.