Detecting submaximal efforts in grip strength testing with the coefficient of variation

Area of Science:

• Biomechanics
• Rehabilitation Science
• Exercise Physiology

Background:

• Grip strength testing is crucial in clinical and research settings.
• The coefficient of variation (CV) is commonly used to assess effort consistency.
• The reliability of CV for distinguishing maximal from submaximal effort is not well-established.

Purpose of the Study:

• To empirically evaluate the effectiveness of the coefficient of variation (CV) in differentiating maximal (100%) from submaximal (50%) effort during grip strength testing.
• To assess the stability and accuracy of CV-based effort classification.

Main Methods:

• Twenty-nine asymptomatic subjects performed grip strength tests under 100% and 50% effort conditions.
• Each subject completed two testing sessions to assess method stability.
• Three trials per condition were conducted, totaling 12 grasps per subject.

Main Results:

• Submaximal effort conditions exhibited significantly higher variability than maximal effort conditions (p<.01).
• Intra-class correlation coefficients were very low for both maximal (.036) and submaximal (.025) efforts, indicating poor stability.
• High misclassification rates were observed: 69% of submaximal efforts were incorrectly classified as maximal using a 15% CV cutoff, and 55% with an 11% cutoff.

Conclusions:

• The current practice of using a low number of trials to calculate CV for grip strength effort is unstable and unreliable.
• The high rate of false negatives makes this method unsuitable for practical clinical or research applications.
• Revisions to grip strength testing protocols are necessary to ensure accurate effort assessment.