This study compared the acute effects of a session of isometric strength training (ISO) with heavy resistance training (HRT) training on 20-m sprint, countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) performance.

Ten resistance-trained athletes (age: 26.7 ± 6.2 years, body mass: 71.5 ± 16.2 kg, height: 1.68 ± 0.10 m) performed baseline measures for 20-m sprint, CMJ and IMTP prior to either an ISO or HRT session. During both training sessions, participants performed back squats, Romanian deadlift and split squat. Post-test performances were measured 5 min and 24 h after each training session. Participants returned a week later to perform the other training session.

A significant time × condition effect was found for 20-m sprint time (P = 0.007) and IMTP peak force (P = 0.003). Main time effect was observed for 20-m sprint (P < 0.001), CMJ height (P < 0.001) and IMTP peak force (P < 0.001). HRT resulted in a greater increase in sprint time at 5 min (0.17 ± 0.12 vs. 0.06 ± 0.05 s, P = 0.013, g = 1.15) and 24 h (0.01 ± 0.09 vs. 0.00 ± 0.05 s, P = 0.004, g = 1.32) post-training as compared to ISO. Similarly, HRT resulted in a significantly larger reduction in IMTP peak force than ISO at both 5 min (− 363.3 ± 248.8 vs. − 98.9 ± 230.3 N, P = 0.024, g = 1.06) and 24 h (− 289.2 ± 256.2 vs. 37.9 ± 177.8 N, P = 0.004, g = 1.42) post-training. Total impulses generated during each exercise were greater during ISO than HRT (P < 0.001–0.006). Rating of perceived recovery post 24 h was higher in ISO than HRT (P = 0.002).

The above results indicated that acute HRT led to a greater reduction in sprinting strength performance and lower perceived recovery post-24 h than ISO.

Isometric strength training (IST) with rapid non-sustained contraction (RIST) is effective in improving the ability to generate force rapidly. However, the neuromuscular adaptation of IST with sustained contraction (SIST) and RIST is not known. Therefore, the aim of the study was to compare the neuromuscular adaptations of RIST with SIST.

Thirty-three national floorball players (23.9 ± 3.1 years old; 1.69 ± 0.08 m; 64.6 ± 11.1 kg) were recruited for this study. Pre- and post-test included countermovement jump (CMJ), 30-m sprint (TT30), isometric squat at 90° (ISqT90) and 120° (ISqT120) knee angles. They were randomly assigned to either control (Con) (n = 9), RIST (n = 12) or SIST (n = 12) group and performed 12 sessions of intervention training. All groups performed the same sets of exercises, but RIST and SIST had to perform ISqT with and without sustained contraction, respectively.

Time × group effect for CMJ height (P = 0.01, ƞ_p² = 0.25), peak force (PF) (P = 0.03, ƞ_p²= 0.22) and rate of force development (RFD) (P = 0.02, ƞ_p²= 0.22) obtained from ISqT120 were noted. A main effect for time was observed in CMJ height, PF obtained from ISqT90 and ISqT120, and RFD obtained from ISqT90 (P < 0.01, 0.27 < ƞ_p² < 0.57). There was greater improvement in TT30 (P = 0.043, d = 3.00), ISqT90 PF (P = 0.034, d = 3.12), ISqT120 PF (P = 0.003, d = 4.54) and ISqT120 RFD (P = 0.033, d = 1.36) in the SIST than the Con group.

SIST was more effective in improving strength and dynamic performance as compared to RIST, making it a viable training method to enhance dynamic performances.

The aim of the study was to establish the optimum variable resistance (VR) intensity for loaded countermovement jump (LCMJ) to induce post-activation potentiation (PAP).

Eleven male athletes (age 23 ± 2.3 years, height 1.77 ± 0.05 m, body mass 73.7 ± 9.0 kg) attended one familiarization and four testing sessions. Subjects performed their own pre-competition warm up before performing two countermovement jumps (CMJ) for baseline measure. Subsequently, they performed 2 × 3 unloaded (UCMJ) or loaded CMJ (LCMJ) with one of the three VR intensities, Orange (6.7 ± 0.6 kg), Red (14.0 ± 0.9 kg) and Blue (24.0 ± 1.4 kg), in random order, before performing two more CMJ for post-test measure. Each testing session was separated by at least 48 h.

There was significant increase in jump height in all conditions (P < 0.05), but no significant difference in change in jump height between conditions (P > 0.05). There were small to moderate effect when comparing Orange and the other conditions. Peak force and velocity increased in Red (P < 0.05) and Orange (P < 0.05), respectively. Change in jump height was significantly correlated to change in peak velocity (r = 0.46, P = 0.002) and peak power (r = 0.46, P = 0.002).

The findings of the study showed that UCMJ and LCMJ were effective in improving jump height acutely, and an intensity level of about 10% body weight contributed by VR seems to be the optimum resistance level.