Effect of sand on landing knee valgus during single leg land and drop jump tasks: Possible implications for ACL injury prevention and rehabilitation.

Context: Despite significant emphasis on Anterior Cruciate Ligament (ACL) injury prevention, injury rates continue to rise and re-injury is common. Interventions to reduce injury have included resistance, balance and jump training elements. The use of sand-based jump training has been postulated as an effective treatment. However, evidence on landing mechanics is limited. Objective: To determine potential differences in landing strategies and subsequent landing knee valgus when performing single leg landing (SLL) and drop jump (DJ) tasks onto sand and land, and compare between both male and female populations. Design: A randomised repeated measures crossover design. Setting: University Laboratory. Participants: 31 participants (20 males, 11 females) from a university population. Interventions: All participants completed DJ and SLL tasks on both sand and land surfaces. Main Outcome Measures: 2-dimensional Frontal Plane Projection Angle (FPPA) of knee valgus was measured in both the DJ and SLL tasks (right and left) for both sand and land conditions. Results: FPPA was lower (moderate to large effect) for SLL in sand compared to land in both legs (Left: 4.3⁰ ±2.8⁰; Right: 4.1⁰ ±3.8⁰) for females. However, effects were unclear (Left: -0.7⁰ ±2.2⁰) and trivial for males (Right: -1.1⁰ ±1.9⁰). FPPA differences for males and females performing DJ were unclear, thus more data is required. Differences in FPPA (land vs sand) with respect to grouping (sex) for both SLL (Left: 4.9⁰ ±3.0⁰) and (Right: 5.1⁰ ±4.0⁰) were both very likely higher small/ possibly moderate for females compared to males