Ability of Isokinetic Dynamometer to Predict Isotonic Knee Extension 1-Repetition Maximum

Joseph B. Lesnak, Dillon T. Anderson, Brooke E. Farmer, Dimitrios Katsavelis, Terry L. Grindstaff

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Context: Resistance training exercise prescription is often based on exercises performed at a percentage of a 1-repetition maximum (1RM). Following knee injury, there is no consensus when a patient can safely perform 1RM testing. Resistance training programs require the use of higher loads, and loads used in knee injury rehabilitation may be too low to elicit gains in strength and power. A maximum isometric contraction can safely be performed during early stages of knee rehabilitation and has potential to predict an isotonic knee extension 1RM. Objective: To determine whether a 1RM on an isotonic knee extension machine can be predicted from isometric peak torque measurements. Design: Descriptive laboratory study. Setting: University research laboratory. Participants: A total of 20 (12 males and 8 females) healthy, physically active adults. Main Outcome Measures: An isokinetic dynamometer was used to determine isometric peak torque (in N·m). 1RM testing was performed on a knee extension machine. Linear regression was used to develop a prediction equation, and Bland–Altman plots with limits of agreement calculations were used to validate the equation. Results: There was a significant correlation (P < .001, r = .926) between peak torque (283.0 [22.6] N·m) and the knee extension 1RM (69.1 [22.6] kg). The prediction equation overestimated the loads (2.3 [9.1] kg; 95% confidence interval, −15.6 to 20.1 kg). Conclusions: The results show that isometric peak torque values obtained on an isokinetic dynamometer can be used to estimate 1RM values for isotonic knee extension. Although the prediction equation tends to overestimate loads, the relatively wide confidence intervals indicate that results should be viewed with caution.

Original languageEnglish (US)
Pages (from-to)616-620
Number of pages5
JournalJournal of Sport Rehabilitation
Issue number5
StatePublished - Jul 2020

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation
  • Rehabilitation


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