Evaluating raw versus body-weight-normalized McGill core endurance composite scores in recreational weightlifters: implications for strength and functional performance.

Abstract

Background: The effectiveness of using McGill trunk endurance scores as raw values or body-weight-normalized metrics remains uncertain for evaluating weight classes, especially given the increasing number of recreational weightlifters. The study compared the raw McGill composite score with the body-weight-normalized score to examine their relationships with absolute strength, relative strength, and functional performance.

Methods: The study included 70 participants aged 18 to 30 years, both genders, divided into two groups based on body mass index: lower (less than 28.2 kg/m², n = 35) and higher (greater than 28.2 kg/m², n = 35). Participants completed the McGill battery tests (trunk flexion, extension, and bilateral side planks) until exhaustion. Two composite scores from the McGill battery tests were calculated: the raw composite, which used the mean of four hold times, and the normalized composite, which divided this mean by body weight. Absolute strength was measured through back squat and bench press 1RM tests, while relative strength was calculated by dividing 1RM by body weight. Functional performance was evaluated using seated medicine ball throws and countermovement jumps.

Results: The raw composite scores from both groups showed no significant difference (lower vs. higher: 130.46 ± 18.50 s vs. 124.94 ± 16.58 s; p = 0.27). The lower-weight group scored better on the normalized composite test compared to the higher-weight group (1.78 ± 0.24 s/kg vs. 1.36 ± 0.20 s/kg; p < 0.001). The raw composite scores had larger correlations with absolute strength measures (r = 0.71 for back squat and r = 0.64 for bench press) and smaller correlations with relative strength (r = 0.42 and 0.37), whereas the normalized scores showed stronger correlations with relative strength (r = 0.70 and 0.66). Moreover, the normalized scores had stronger correlations with functional performance measures, including the medicine ball throw (r = 0.69) and the countermovement jump (r = 0.63). Individual McGill test results did not differ significantly. The body mass normalization process for McGill core endurance composites helps identify size-related differences between weightlifting groups.

Conclusion: Body-mass-normalized McGill composite scores reveal clear differences between lower- and higher-body-mass lifters, whereas raw scores do not. Raw composites are more strongly related to absolute 1RM strength, while normalized composites have better associations with relative strength and functional performance.