BACKGROUND: The study aimed to assess the acute effects of overcoming isometric split squats on subsequent single-leg drop jump (DJ) performance and the contralateral effect in volleyball players, considering training status differences. METHODS: Ten male elite (ELI) and ten amateur (AMA) volleyball players took part in two experimental sessions in which they performed conditioning activity (CA) consisted of 3 sets of overcoming isometric 3-second split squats, differing in the limb used: dominant (DL) or non-dominant (ND-L). Single-leg DJ was performed before and at the 4th and 8th minute post-CA for both limbs. The best post-CA attempt in terms of jump height (JH) was analyzed. RESULTS: Results revealed a significant increase in jump height (JH) in the non-dominant limb (ND-L) from 13.7 ± 2.6 cm to 15.5 ± 2.7 cm after CA performed by the ND-L (p = 0.001; Hedge's g = 0.65). Similarly, the reactive strength index (RSI) of the ND-L improved from 0.40 ± 0.06 to 0.45 ± 0.08 (p = 0.008; g = 0.58). Additionally, contact time in the ND-L increased significantly from 342 ± 36 ms to 375 ± 42 ms after CA performed by the dominant limb (p = 0.001; g = 0.66). In the elite (ELI) group, JH significantly increased from 16.4 ± 2.4 cm to 18.3 ± 3.3 cm (p < 0.001; g = 0.79), while RSI in the dominant limb (DL) improved from 0.47 ± 0.06 to 0.53 ± 0.07 (p = 0.011; g = 0.68). CONCLUSIONS: Results suggest that the examined CA effectively induces the post-activation performance enhancement in DJ among elite volleyball players, with a predominantly local impact on the limb executing the CA. TRIAL REGISTRATION: NCT06459050 (Retrospectively registered).

• Keywords
• Explosive strength, Isometric exercise, Neuromuscular performance, Plyometric training, Post-activation potentiation, Unilateral movement,
• Publication type
• Journal Article MeSH

The phenomenon of post-activation performance enhancement plays an unidentified role in movement eccentric speed and individual muscle group responses. Therefore, this study aimed to determine whether the loaded front squat (FSq) speed of the eccentric phase would influence the post-activation performance enhancement effect and whether the FSq would elicit similar performance enhancement of knee flexion, knee extension, hip flexion, and hip extension muscles. Twenty resistance-trained handball players performed the FSq under maximum eccentric-concentric speed and 2-s eccentric speed (only the eccentric phase performed), while pre- and post-front squat countermovement jump, knee, and hip isokinetic flexion/extension performance were tested. The FSq conditioning activity was performed in a single set of three repetitions with either 90% (maximum eccentric-concentric speed) or 120% (2-s eccentric speed) of one repetition maximum, and post-performance was measured 4-12 min after the FSq. Athletes randomly changed the FSq eccentric speed and tested the hip or knee isokinetic flexion/extension strength at 180°/s. ANOVA showed that the rate of force development during the jump increased (Cohen d = 0.59-0.77) with no differences between 2-s eccentric and maximum speed eccentric protocols. Isokinetic strength increased after the 2-s eccentric FSq in hip extension (d = 0.76-0.86), knee flexion (d = 0.74-0.88), and hip flexion (d = 0.82), with no differences in knee extension strength. After maximum eccentric-concentric speed, isokinetic strength increased in hip extension (d = 1.25). In conclusion, the FSq conditioning activity enhances hip extensors' performance more than knee extensors' performance. Different eccentric types of muscle action during a conditioning activity alter the level of local muscle enhancement.

• Keywords
• complex training, handball, isokinetic, post-activation potentiation, power training,
• Publication type
• Journal Article MeSH