Assessing the reliability of baseline maximum voluntary contraction protocols

Background Maximum Voluntary Isometric Contractions (MVICs) are commonly used to normalize contraction intensity as a percentage of maximum; however, there is substantial variation in reported baseline MVIC protocols and no known consensus on their reliability. As such, the purpose of this study was to determine the method of baseline MVIC calculation that maximizes between-session reliability. Methods Eighteen participants performed five knee extension, elbow flexion, and hand grip MVICs during four experimental sessions. Thirty-two methods of calculating baseline MVIC were evaluated using differing numbers of contractions, using the peak or average, and the presence of a familiarisation session and/or practice contraction. The level of significance was set at p ≤ 0.05 for all results presented. Reliability statistics were assessed across the 32 calculation methods, as was the effect of contraction and session number on MVIC strength. Results Within-day Intraclass Correlation Coefficients (ICCs) estimates ranged from 0.94 to 0.98 for all contraction types and sessions, with between-day ICC estimates ranging from 0.85 to 0.99. Reliability marginally increased as more contractions were factored for both average and peak. Familiarisation and practice only improved reliability for elbow flexion. All baseline MVIC methods had acceptable between-day reliability. Multiple approaches to calculating baseline MVIC are reliable, but the most efficient method is to use the peak of one contraction. This approach balances high reliability with reduced participant fatigue and testing time, making it a practical option for both research and clinical applications.