Background During gameplay, athletes frequently change their trunk and hand placement positions (e.g. ball handling). Changing trunk positions alters lower extremity (LE) biomechanics and subsequent injury risk during sport. However, whether changing hand positions also alters LE biomechanics during landing (a high LE injury-risk activity) is unclear.
Objective To examine if changing hand positions during landing affects LE biomechanics.
Design Repeated measures.
Participants 30 healthy participants (23.4±4.3 years, 170.7±7.7 cm, 70.2±18.9 kg).
Interventions Participants performed 5 landings from a 45cm box in 4 different hand placement (HP) conditions: 1) Holding a basketball at chest level (CH), 2) Holding a basketball at chest with arms straight in front (FR), 3) Holding a basketball straight up over head (UP), and 4) Placing hands on hips (HIP).
Main outcome measurements Sagittal hip, knee, ankle angles (°) from initial touchdown to lowest point of the vertical Center of Mass (COM min) displacement were assessed using 3-D motion analyses. Repeated measures ANOVAs and Bonferroni pairwise comparisons examined differences across HP conditions.
Results At touchdown, participants had differing hip (P<.001), but not knee (P=.09), or ankle (P=.22) flexion angles across conditions. At COMmin, participants had differing hip (P=.01), knee (P=<.001), and ankle (P<.001)angles across conditions, resulting in differing hip (P=.01)and knee (P<.001) but similar ankle (P=.06) flexion excursions across conditions. Specifically, participants had lower hip excursions in UP than in FR (P=.03) and HIP (P=.009), and lower knee excursions in CH than in FR (P=.02), UP (P=.003), and UP (P<.001).
Conclusions Overall, when landing with hands up or across the chest, participants landed in an extended posture and with decreased range of motion. Conversely, when landing with hands in front, participants had increased joint flexion angles associated with an increased range of motion. Changing hand placements during landing may alter LE biomechanics, and influence subsequent injury risk during landing. Clinicians should incorporate exercises that include hand position changes when designing injury prevention programs to decrease LE injury risk.
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