The effect of gender and load type on lower extremity biomechanics during jump landings
Introduction: Both gender and additional load have been shown to affect landing mechanics. Females are at an increased risk of sustaining an anterior cruciate ligament injury and patellofemoral pain syndrome, whereas males are at a greater risk of developing patellar tendinopathy. There is a paucity of literature examining the effects of load position or the comparison between genders during jump landings with additional load. Purpose: To examine the effects of different positions of loading on lower extremity biomechanics during a jump-landing task. An additional purpose was to compare lower extremity biomechanics between genders during loaded and unloaded jump landings. Method: Twenty-four resistance trained males (n = 12, age 21.1 ± 1.4 years, body mass 76.2 ± 10.3 kg, height 1.77 ± 0.08 m) and females (n = 12, age 20.3 ± 1.4 years, body mass 64.4 ± 7.2 kg, height 1.70 ± 0.03 m) were recruited. Three-dimensional lower-limb-joint kinematics and kinetics were measured during 5 bilateral maximal jumps were performed in a randomised order in each of four conditions: unloaded (UL), holding dumbbells (DB), wearing a weighted vest (WV), and with a barbell placed across the shoulders (BB). All loaded conditions were performed with 10% of body weight. A two-way analysis of variance (type of load * gender) was performed on kinetic and kinematic variables. Cohen’s d effect sizes were calculated for differences between load types. Results: Significant differences were shown between genders with the male group exhibiting increased jump height, lower time to peak knee flexion, smaller sagittal plane excursion (ROM), and smaller hip adduction angles at ground contact (IC) and smaller peak hip adduction angles when compared to females. Males were also shown to have significantly greater peak vertical ground reaction force (vGRF), significantly smaller time to peak vGRF, and significantly greater peak knee and hip extension moments. There was no significant interaction between load and gender in all variables measured. All loaded jumps resulted in a significant increase in the time to reach peak knee flexion. Significant decreases were observed in peak hip adduction moment and peak knee valgus moment in the male BB condition and female BB condition respectively when compared to UL jump landings. There was a significant decrease exhibited in vGRF in both genders in the BB condition when compared to the UL condition. Conclusion: Both gender and additional loading alter landing biomechanics in maximal vertical jump landings. Males and females responded similarly to each of the loaded conditions. Findings suggest use of the BB may decrease the risk of injury relative to DB and WV during maximal countermovement jumps in both genders.