The Effect of Recovery Training on Lower Extremity Explosive Strength in Tennis Players

Primary outcomes

1. Countermovement Jump Height

   Time frame: 4 weeks

   The countermovement jump (CMJ) test was used to assess lower extremity explosive performance. Participants started from an upright standing position with hands placed on the hips. Following a rapid downward movement involving hip and knee flexion, participants immediately performed a maximal vertical jump. Jump height (cm) was recorded using [measurement device - e.g., force plate / jump mat / Optojump system]. The CMJ reflects the efficiency of the stretch-shortening cycle and is considered a reliable indicator of explosive lower limb performance.

2. Squat Jump Height

   Time frame: 4 weeks

   The squat jump (SJ) test was used to assess concentric lower extremity explosive performance. Participants started from a semi-squat position with approximately 90° of hip and knee flexion, with hands placed on the hips. After holding this position briefly to eliminate the contribution of elastic energy, participants performed a maximal vertical jump without a preparatory countermovement. Jump height (cm) was recorded using [measurement device - e.g., force plate / jump mat / Optojump system]. The SJ test allows direct evaluation of concentric muscle power of the lower limbs.

3. Reactive Strength Index

   Time frame: 4weeks

   RSI is a performance measure that reflects reactive strength and neuromuscular efficiency. It is typically assessed through a drop jump in which the participant steps off a platform, lands, and performs a quick rebound jump with minimal ground contact time. RSI is sensitive to the athlete's ability to rapidly switch from eccentric to concentric action, a capacity highly relevant to sports requiring explosive changes in direction, such as tennis .

4. Standing Long Jump

   Time frame: 4 weeks

   SLJ, also known as the broad jump, is a field-based test for assessing horizontal explosive strength of the lower extremities. The participant stands with feet shoulder-width apart, swings the arms, and jumps forward as far as possible. The landing distance, measured from the starting line to the heel mark, reflects the ability of the lower-limb muscles to generate forward propulsion .

5. Single-Leg Hop for Distance

   Time frame: 4 weeks

   SLH test evaluates unilateral lower-limb performance and limb symmetry. The participant stands on one leg, performs a maximal forward hop, and lands on the same leg while maintaining balance for at least two seconds. Distances are recorded for both legs, and comparisons provide valuable insights into side-to-side asymmetries, rehabilitation status, and injury risk.

6. Single-Leg Vertical Jump Height

   Time frame: 4 weeks

   The single-leg vertical jump (SLVJ) test was used to assess unilateral lower extremity explosive performance. Participants stood on one leg with hands placed on the hips, while the non-supporting leg was flexed and held stationary. From a stable standing position, participants performed a maximal vertical jump using the supporting leg only. Jump height (cm) was recorded separately for each limb using [measurement device - e.g., force plate / jump mat / Optojump system]. This test allows evaluation of unilateral vertical force production and identification of inter-limb asymmetries.is .