RESUMEN
ACL injuries are common among athletes playing team sports. The impact of divided attention during team sports on landing mechanics is unclear. Twenty-one healthy females jumped at a 60° angle to their right and performed a second jump to their right or left at a 60° angle. The direction of the second jump was shown before movement (baseline) or mid-flight of the first jump (dual task). The signal for the dual-task conditions showed five arrows and the middle one indicated the jump direction (Flanker paradigm). The other arrows pointed in the same (congruent) or the opposite (incongruent) direction as the middle arrow. Results indicated larger initial and peak knee flexion angles, smaller peak knee valgus moments, and smaller vertical and posterior GRFs during baseline right jumps compared to other conditions. Peak posterior GRF was increased in the incongruent condition compared to the congruent condition during left jumps. Performance was decreased with longer stance times for the dual task compared to the baseline in both jump directions. Further, the incongruent condition had a longer stance time than the congruent condition during left jumps. More research focusing on decision-making with more challenging visual stimuli mimicking dynamic team sports is merited.
RESUMEN
ACL injuries are common among athletes. The injury usually occurs during sport movements involving sudden direction changes when landing and cutting. Twenty-one healthy females performed a series of jump-land-jump movements. They jumped from a 28 cm box onto two in-ground force platforms, followed by a maximal vertical jump. The direction of the first jump was tested with seven entry angles, jumping to the right (90 R, 60 R and 30 R), straight forward (0), and jumping to the left (90 L, 60 L and 30 L). Kinematic and kinetic data were recorded for data analysis. During the first 100 ms of landing, participants had significantly smaller peak knee flexion angles, larger initial knee valgus angles and larger peak knee joint external valgus moments when jumping to the right (90 R, 60 R and 30 R) compared to straight forward (0), and jumping to the left (90 L, 60 L and 30 L). Thus, entry angles to the right may increase the risk of ACL injury in the right knee. We suggest that these types of jumps should be used with caution during ACL rehabilitation, but may be useful for testing ACL risk factors in healthy individuals.
RESUMEN
The purpose of this study was to assess an upper body exoskeleton during automotive assembly processes that involve elevated arm postures. Sixteen team members at Toyota Motor Manufacturing Canada were fitted with a Levitate Airframe, and each team member performed between one and three processes with and without the exoskeleton. A total of 16 assembly processes were studied. Electromyography (EMG) data were collected on the anterior deltoid, biceps brachii, upper trapezius, and erector spinae. Team members also completed a usability survey. The exoskeleton significantly reduced anterior deltoid mean active EMG amplitude (p = .01, Δ = -3.2 %MVC, d = 0.56 medium effect) and fatigue risk value (p < .01, Δ = -5.1 %MVC, d = 0.62 medium effect) across the assembly processes, with no significant changes for the other muscles tested. A subset of nine assembly processes with a greater amount of time spent in arm elevations at or above 90° (30 vs. 24%) and at or above 135° (18 vs. 9%) appeared to benefit more from exoskeleton usage. For these processes, the exoskeleton significantly reduced anterior deltoid mean active EMG amplitude (p < .01, Δ = -5.1 %MVC, d = 0.95 large effect) and fatigue risk value (p < .01, Δ = -7.4 %MVC, d = 0.96 large effect). Team members responded positively about comfort and fatigue benefits, although there were concerns about the exoskeleton hindering certain job duties. The results support quantitative testing to match exoskeleton usage with specific job tasks and surveying team members for perceived benefits/drawbacks.