Evidence-Based Practice – Issue 5-2015
Unstable Surface Improves Quadriceps: Hamstrings Co-Contraction for Anterior Cruciate Ligament Injury Prevention Strategies
Article. Shultz R., et al. Unstable Surface Improves Quadriceps: Hamstrings Co-Contraction for Anterior Cruciate Ligament Injury Prevention Strategies. Sports Health 2015; 7(2): 166-171.
Purpose. The purpose of this study was to examine muscle activation in the quadriceps and hamstrings and peak kinematics of the knee, hip, and trunk when performing a single-leg drop on to a BOSU ball (unstable surface) compared with on to the floor (stable surface).
Study Design. Controlled laboratory study
Methods
- Subjects
- 39 female collegiate athletes
- Age: 19.2 years
- Height: 1.73 m
- Weight: 67.2 kg
- Data Collection
- Electromyographic activity of the vastus lateralis and lateral hamstring muscles were used to estimate peak quadriceps and hamstring activation. This established the quadriceps to hamstring activation ratio.
- Kinetmatic data of the hip, knee, and trunk were estimated.
- Procedures
- All subjects performed 3 repetitions of a single-leg drop on a BOSU ball (unstable surface)
- All subjects also performed 3 repetitions of a single-leg drop on the floor (stable surface)
- Data Analysis
- The average of kinematic and muscle activation values from the 3 respective trials were computed to compare the landing strategies on the stable versus the unstable surface using an ANOVA.
Results
- Greater hamstring activation was found when landing on the BOSU (unstable surface)
- Quad: Hamstring activation ratio was less when landing on the BOSU (unstable surface)
- Knee flexion angle was greater on the floor (stable surface).
- See Table below
Clinical Relevance
- Higher quad: hamstring activation ratios are associated with ACL tears
- Unstable surface training may lower quadriceps to hamstring activation ratios that may ultimately reduce the risk of and ACL injury.
- Using unstable surfaces when landing may better prepare athletes for challenges during sports.
