Loaded Hex Bar Jump Landing Does Not Increase Frontal Plane Knee Angles And Torques

Abstract

PURPOSE: To determine if loaded Hexagonal Barbell (HB) jump-landings elicit hip/knee kinematics and kinetics patterns typical of ACL injury during the landing phase of this exercise. METHODS: 10 male NCAA athletes (20.4 + 2.4 y; 108.8 + 14.0 kg) performed 5 maximal HB jumps at 0% (control), 20%, 40%, and 60% of their HB deadlift 1-repetition maximum (mean: 216.6 ± 10.9 kg). A 45 marker full body model was utilized to collect the dominant limb landing phase of the maximal HB jumps using a 10 camera Vicon motion + AMTI force plate capture system (200 Hz/1000 Hz). Plug in Gait analysis yielded peak hip, knee flexion and adduction angles as well as and peak hip, knee sagittal and frontal plane torques. A RMANOVA with Fisher’s post hoc was used to evaluate differences (p < 0.05). RESULTS: Loads in peak hip adduction angle decreased (0%: -10.516° + 4.001, 20%: -5.089° + 3.600, 40%: -4.853° + 4.071, 60%: -4.846° + 4.538; p ≤ 0.0001); with post hoc noting 20, 40 and 60 were lower than the control (p = 0.0001) but not between loaded conditions. Peak knee flexion angle decreased with increased loads (0%: -69.723° + 13.231, 20%: -69.884° + 11.282, 40%: -66.103° + 9.902, 60%: -64.558° + 9.757; p = 0.03); with differences noted 60% lower than the control (p = 0.01) and 20% (p = 0.01). Peak sagittal knee torque increased (0%: 2.511 N.mm/kg + .616, 20%: 2.646 N.mm/kg + .728, 40%: 2.314 N.mm/kg + .668, 60%:2.233 N.mm/kg + .516; p = 0.43); with 20% exhibiting lower values than 40% (p = 0.03) and 60% (p = 0.01). Peak sagittal hip torque increased (0%: 3.390 N.mm/kg + 1.518, 20%: 2.946 N.mm/kg + 1.515, 40%: 2.293 N.mm/kg + 1.038, 60%: 1.727 N.mm/kg + .869; p = <0.0001) with lower values for 40% compared to 20% (p = 0.03) and control (p = 0.0009) and significantly lower hip torque values for 60% compared to 20% (p = 0.0003) and control (p < 0.0001). No significant differences were found in peak hip flexion angle, peak knee varus angle, peak frontal plane knee torque, and peak frontal plane hip torque (p > 0.251). CONCLUSIONS: Higher loads during the landing portion of a hex bar jump result in decreased hip peak hip adduction and a more erect, less flexed knee. However, increased HB loads did not appear to incite the representative ACL injury factors of higher frontal plane knee valgus angles or torques.