Immediate Responses to Trunk Muscle Coordination Cueing on Maximal Isometric Lifting Force, Low Back Postural Displacement, Lumbar Spine Rotational Stiffness, and Trunk Muscle Co-Contraction

Pinto, BL, Beach, TAC, Howarth, SJ, and Callaghan, JP. Immediate responses to trunk muscle coordination cueing on maximal isometric lifting force, low back postural displacement, lumbar spine rotational stiffness, and trunk muscle co-contraction. J Strength Cond Res XX(X): 000–000, 2026—Cueing trunk muscle bracing has the potential to reduce the risk of injury by stiffening the spine to prevent motion. However, the effects on force production in high-demand tasks such as deadlifting are unpredictable. In addition, various approaches have been used in research and practice settings to cue trunk muscle coordination, ranging from simple verbal directives to detailed coaching. However, the efficacy of these approaches to immediately modify spine stiffness has not been compared. The objective of this investigation was to compare the immediate effects of a simple verbal directive to “activate your core” and detailed trunk muscle bracing coaching on maximal isometric lifting force production, low back postural displacement, muscular contributions to spine rotational stiffness, and trunk muscle agonist-antagonist co-contraction. Forty subjects (50% women) performed maximal isometric lifting exertions across 3 conditions (baseline, directive, and coached). Data were assessed with linear mixed-effects models ( α = 0.05). Postural displacement decreased and rotational stiffness increased in the coached, but not the directive condition. However, both cueing approaches decreased maximal lifting force to a similar extent, which was not solely explained by agonist-antagonist co-contraction, as co-contraction only increased in the coached condition. Decreases in lifting force may instead be attributable to the cognitive effort and attentional focus imposed by the cues. Thus, cueing trunk muscle coordination for the first time can decrease force production, and simple verbal directives are insufficient at modifying trunk muscle coordination. Instead, detailed coaching with practice may ensure the acquisition and implementation of new muscle coordination patterns.