The Influence of Forward Trunk Lean During Single-Limb Landing on Achilles Tendon Force in Physically Active Females

It is unknown if forward trunk lean during single-limb landing influences the Achilles tendon force (ATF). This study examined the effect of forward trunk lean during single-limb landing on the ATF in physically active females. Thirty physically active females (23.7 [3.6] y) performed 5 landing trials (0.25 m) using self-selected and forward trunk lean strategies. Dependent variables included peak ATF; average ATF development rate; and sagittal trunk, hip, knee, and ankle angles and moments at the time of peak ATF. The increased forward trunk lean (mean difference (MD) = 14.1°; 95% CI, 11.0 to 17.2; P < .001) caused a decrease in peak ATF (MD = -3.5 N/kg; 95% CI, -5.8 to -1.2; P = .004) and ankle plantar flexion moment (MD = -0.2 N·m/kg; 95% CI, -0.4 to -0.1; P = .002). In contrast, forward trunk lean resulted in greater hip (MD = 15.2°; 95% CI, 11.9 to 18.4; P < .001) and knee flexion (MD = 7.7°; 95% CI , 4.7 to 10.7; P < .001) angles, and hip extension moment (MD = 0.3 N·m/kg; 95% CI, 0.1 to 0.5; P = .002). Forward trunk lean changes predicted peak ATF changes (r = .33, P = .04). Sagittal trunk posture influences the ATF in physically active females during single-limb landing and may effectively alter loading in patients recovering from Achilles tendinopathy.