Effects of internal vs external focus of attention on ankle and knee joint kinematics in the sagittal plane and center of mass displacement during deep squat performance

Introduction: Verbal instructions provided during training and rehabilitation can shift focus of attention (FOA) toward internal (body-related) or external (effect-related) cues, which may alter movement execution. Aim: This study examined whether internal vs external FOA affected ankle and knee flexion, squat depth, and center of mass (COM) displacement in the final phase of a deep squat. Materials and methods: A total of 40 adults performed 6 deep squat trials: 3 with an internal focus of attention (IFA) instruction followed by 3 with an external focus of attention (EFA) instruction. Photographs in the bottom position were used to estimate sagittal-plane ankle and knee flexion angles, squat depth (greater trochanter–floor distance), and COM displacement (indirect method). IFA and EFA were compared using t tests (α = 0.05). Sex differences, correlations with age, height, and body mass, as well as differences by prior lower-limb injury were also examined. Results: In comparison with EFA, IFA produced greater mean (SD) ankle flexion (29.13 [6.74] vs 21.18 [6.43] °; P <0.001; d = 2.14) and greater knee flexion (141.23 [5.08] vs 139.48 [5.46] °; P = 0.003; d = 0.5). IFA was associated with a lesser mean squat depth (29 [6.15] vs 24.05 [6.06] cm; P <0.001; d = 1.57) and more anterior COM displacement (0.37 [0.24] vs –0.07 [0.21] arbitrary units; P <0.001; d = 2.17). No significant effects were found for sex, age, height, body mass, or history of lower-limb injury. Conclusions: FOA modulated deep-squat kinematics and COM behavior. IFA cues increased ankle and knee flexion but were accompanied by a shallower squat and anterior COM shift, whereas EFA cues favored a deeper squat and more posterior COM position. Clinicians and coaches may tailor instructions to the desired movement outcome.