Drop Jump Test

## **What is the Drop Jump Test?** The Drop Jump Test assesses drop jumps to measure explosive power, reactive strength, and the ability to execute fast stretch-shortening movements. It is widely used in sports medicine to help identify the risk of knee injuries and to track recovery progress after conditions such as ACL tears. The test also measures peak forces during the propulsive phase and evaluates how effectively an athlete uses the stretch-shortening cycle function, where muscles rapidly switch from an eccentric (lengthening) to a concentric (shortening) contraction to produce more force. Because the test uses the athlete’s own body weight as resistance, it provides a practical, sport-specific measure of lower-limb performance and resilience. For ACL recovery, the Drop Jump Test is crucial because it helps: - **Assess knee stability**: It evaluates how well the knee can handle landing impacts, which is crucial for determining if the knee is stable enough to withstand sports-related activities. - **Identify biomechanical deficits**: The test can reveal improper landing techniques or asymmetries between legs that could predispose the athlete to further injuries. - **Monitor rehabilitation progress**: It provides measurable outcomes to gauge improvement in leg strength and coordination over time during the rehabilitation process. ### **How is this test conducted?** The Drop Jump Test typically involves the following steps, including vertical jump testing: - **Setup**: The participant stands on a platform about 30-60 cm high (the height can vary based on the test protocol and the athlete's condition). - **Execution**: The client or athlete steps off the platform (not jumps off) to land on the ground and then immediately jumps vertically as high as possible upon landing. - **Observation**: The movement is often recorded on video from the side to analyze the height and the knee's movements during the landing and subsequent jump. ### **How are the results interpreted?** Results from the Drop Jump Test are interpreted by analyzing the video to assess: - **Knee alignment**: Watching for any inward collapse of the knee, known as valgus, which can indicate weakness or instability. - **Landing mechanics**: Assessing the symmetry of the landing and the ability to maintain balance and control during the jump. You can also observe the braking phase to assess the athlete's ability to stabilize quickly upon landing. - **Jump height and reaction time**: Evaluating the height and quickness of the subsequent jump, which reflect power and neuromuscular control. You calculate the Reactive Strength Index (RSI) by using the formula RSI = jump height/ground contact time. Each athlete's RSI is usually compared to normative data, but since there is limited public data available, we recommend that you create your own baseline specific to your athletes based on their age, gender, and sport. You may also use this simplified grading system as per E. Flanagan in 2016: - Fair is < 1.5 - Good is 1.5 - 2.0 - Very good is 2.0 - 2.5 - Excellent is > 2.5 Please note that this test doesn't calculate for peak braking force and rapid force production.

## **How to use our Drop Jump Test template** Our template is designed to streamline the process of conducting and recording a Drop Jump Test, a method used to assess an athlete's explosive power and reactive strength. Here's how to effectively use this template: ### **Step 1: Prepare the test environment** Before beginning the test, fill out the athlete's name, the test date, and the evaluator's name at the top of the template. This ensures that all data collected is accurately attributed and easy to track. Set up the equipment, including a box of an appropriate height (usually between 20-100 cm) and a measurement device such as force plates or a jump mat. ### **Step 2: Conduct the test** Have the athletes stand on the box with their hands on their hips to ensure that only the lower body is used for the jump. This effectively eliminates the influence of arm swing on the results and provides a more accurate assessment of leg power. 1. With feet shoulder-width apart, the athlete steps off the box and lands on the measurement device. **Note**: This is a double-leg drop jump, not a single-leg drop jump. 2. Immediately after landing and bending their knees (knee flexion), the athlete performs a maximal vertical jump, allowing for peak force and ground reaction forces. 3. The athlete lands back on the measurement device, recording the rebound jump height. This completes one trial. 4. To ensure consistency and reliability in the measurements, this process, similar to performing depth jumps, is repeated for the predetermined number of trials (typically 3-5). ### **Step 3: Record the results** After each trial, record the jump height and ground contact time directly into the template under the corresponding trial number. Once all trials are complete, calculate each trial's Reactive Strength Index (RSI) using the formula RSI = jump height/ground contact time. Enter these figures into the template. Compute the average for each metric across all trials and note it in the 'Average' row. ### **Step 4: Analyze the data** Review the metrics to assess the athlete's performance. A higher RSI typically indicates better explosive strength and reactive abilities. Record the client or athlete's jump (vertical) height directly into the template after each maximal vertical jump. Usually, this is compared to normative data. ### **Step 5: Provide feedback and recommendations** Based on the data and performance during the test, write any relevant evaluator's comments and recommendations for the athlete. This might include areas for improvement, such as techniques to reduce ground contact time, exercises to increase vertical jump height further, and any other personalized (athletic) training suggestions to lower the risk of future injuries, to improve maximum force development, enrich resistance training, and hopefully boost sports performance for athletes.

## **Reference** Flanagan, E. (2016).The Reactive Strength Index Revisited - Part 2. https://www.fitstoronto.com/wp-content/uploads/2017/12/The-Reactive-Strength-Revisited-Part-2.pdf