Verbal Instruction Reduces Patellofemoral Joint Loading During Bodyweight Squatting.

Abstract

CONTEXT\nThe bodyweight squat exercise is a common component of treatment and prevention for patellofemoral pain; however, it can also place a high load on the patellofemoral joint. Restricting anterior motion of the knees relative to the toes during squatting appears to reduce patellofemoral loading. However, exercise professionals typically rely on verbal instructions to alter squat technique.\n\n\nOBJECTIVE\nThe purpose of this study was to evaluate the influence of verbal instructions regarding squat technique on patellofemoral joint loading.\n\n\nDESIGN\nCross-sectional study.\n\n\nSETTING\nMotion analysis laboratory.\n\n\nPARTICIPANTS\nEleven uninjured females.\n\n\nPROTOCOL\nParticipants performed bodyweight squats before (baseline) and after receiving verbal instructions to limit anterior knee motion. Two different types of verbal instruction were used; one intended to promote an internal focus of attention and the other intended to promote an external focus of attention. Three-dimensional kinematics and kinetics were recorded using a multi-camera system and force plate.\n\n\nMAIN OUTCOME MEASURES\nSagittal plane patellofemoral joint forces and stress were estimated using a musculoskeletal model.\n\n\nRESULTS\nParticipants demonstrated a reduction in patellofemoral joint forces (35.4 N/kg vs. 31.3 N/kg; p=.008) and stress (10.7 MPa vs. 9.2 MPa; p=.002) after receiving instructions promoting an internal focus of attention, compared to their baseline trials. Participants also demonstrated a reduction in patellofemoral joint forces (35.4 N/kg vs. 32.3 N/kg; p=.03) and stress (10.7 MPa vs. 9.6 MPa; p=.04) after receiving instructions promoting an external focus of attention (vs. baseline). However, there were not significant differences in patellofemoral forces (p=.84) or stress (p=.41) for trials performed with an internal vs. external attentional focus.\n\n\nCONCLUSION\nIt appears that verbal instruction regarding knee position influences patellofemoral joint loading during squatting.