Drop jumps (DJ) can be used as a performance and screening test.
Particularly, kinetic measures such as jump height and RSI can inform performance potential, while kinematic variables can inform movement mechanics.
Assessment of motor skills with cognitive factors (attention and decision making) are important as they may affect the movement strategy.
Previous research has shown that adding coordinative or cognitive demands to a drop jump protocol can have a significant impact on lower extremity mechanics.
However, those studies have not utilized sport-specific tasks during the drop jump.
What are the effects of adding a ball to drop jumps?
What did the researchers do?
Researchers compared drop jump performance and strategy with and without the inclusion of catching a basketball.
What they did
- Participants perform a drop jump from a 30 cm box with hands on hips.
- Bilateral and unilateral drop jumps were done bilaterally and unilaterally and performed with and without catching a basketball.
- 12 amateur basketball players (male: n = 5, female: n = 7) that played for at least 5 years of competitive experience.
- All participants were right handed.
What they mesured
The participants jumped onto a force plate and had an accelerometer attached to their lower back. The following metrics were tracked:
- Force plate metrics of Jump Height, Reactive Strength Index (RSI), and Contact Time were measured.
- Accelerometer metric of Movement Variability (MV) was calculated by using Sample Entropy.
What happened?
For jump height, contact time, and reactive strength index there were no significant differences between catching and not catching a ball.
Movement variability was significantly different for:
- Catching a basketball increased the movement variability in the bilateral condition and in the right leg, but not in the unilateral condition with the left leg.
- In the no ball condition, left leg drop jump had higher movement variability than right leg drop jump.
- The asymmetry in movement value was higher in the no ball conditions (~15%) than the ball conditions (~5%)
What does this mean?
- Since all players were right handed, and thus left leg dominant, they may feel more comfortable with their left leg leading to a similar performance even when the ball was passed at them, and more uncomfortable with their right leg leading to a difference in performance when the ball was passed at them.
- The use of the ball as a constraint during drop jumps demands higher levels of coordination patterns and require more adaptability of the participant to the constraint.
- There is no prior research on asymmetry in movement variability measures by sample entropy, so the interpretation of the results are limited.
Coach's Takeaway
Screening
- Physical and cognitive constraints can change a player’s movement pattern.
- Thus how an athlete moves in one context may change in another, even if the movement or task is the same (e.g. drop jumps performed with and without a ball).
Programming
- Coaches can integrate dual tasks into exercises to align with their specific sport, such as adding a ball during drop jumps.
- To progress the difficulty, coaches can combine the sport-specific coordinative constraint (inclusion of the ball) with a cognitive constraint, such as a decision-making component.
