This study examined whether a short, high-intensity isometric exercise can influence physical performance and muscle characteristics several hours after it is performed. Specifically, the study compared the effects of a maximal isometric conditioning activity with a typical volleyball-specific warm-up routine.

Highly trained male volleyball players participated in the study. Each participant completed two experimental conditions in a randomized crossover design: (1) a maximal isometric conditioning activity and (2) a volleyball-specific warm-up used as a control condition. The researchers evaluated changes in countermovement jump performance, muscle viscoelastic properties of the rectus femoris, and skin surface temperature over the quadriceps muscle.

Measurements were taken before the intervention and again 6 hours and 30 hours later to determine whether the conditioning activity produced delayed improvements in neuromuscular performance. Understanding these delayed effects may help coaches and athletes optimize training and competition preparation strategies.

The results of this study may provide insights into whether specific conditioning exercises can enhance or maintain explosive performance in volleyball players several hours after they are performed.

This study investigated the delayed effects of a maximal isometric conditioning activity on neuromuscular performance and muscle mechanical properties in highly trained male volleyball players. Conditioning activities are often used in sport to induce post-activation performance enhancement (PAPE), which may improve explosive performance such as jumping. While most studies have examined the acute effects occurring within minutes after the conditioning activity, less is known about possible delayed responses occurring several hours later.

The aim of this study was to determine whether a maximal isometric conditioning protocol could influence countermovement jump performance, muscle viscoelastic properties, and skin surface temperature several hours after its application. The study also compared these effects with those produced by a volleyball-specific warm-up routine commonly used in training and competition settings.

A randomized crossover design was used. Participants completed two experimental conditions on separate occasions: (1) a maximal isometric conditioning activity and (2) a volleyball-specific warm-up serving as a control condition. All participants were highly trained male volleyball players with experience in resistance and plyometric training.

Neuromuscular performance was assessed using countermovement jump tests. In addition, muscle mechanical properties of the rectus femoris were evaluated using a myotonometric device to determine muscle stiffness and other viscoelastic characteristics. Skin surface temperature over the quadriceps muscle group was also measured to monitor potential physiological responses to the conditioning activity.

Measurements were collected at baseline before the intervention and repeated 6 hours and 30 hours after the conditioning protocol or the control warm-up. This design allowed the researchers to examine whether a single high-intensity isometric stimulus could induce delayed changes in neuromuscular performance or muscle properties.

Understanding delayed performance responses to conditioning activities may help coaches and athletes better plan training sessions and competition preparation. If such activities can produce beneficial effects several hours later, they could be strategically implemented earlier in the day to optimize performance during later training sessions or competitions.

Inclusion Criteria:

• minimum of 7 years of systematic volleyball training,
• at least 3 resistance training sessions per week during the preceding 5 years,
• no musculoskeletal injury requiring training cessation longer than 4 weeks within 6 months prior to enrollment,
• absence of tattoos over the rectus femoris muscle that could interfere with thermographic assessment.

Exclusion Criteria:

• less than 7 years of systematic volleyball training,
• less than 3 resistance training sessions per week during the previous 5 years,
• any musculoskeletal injury within the 6 months prior to enrollment that required cessation of training for longer than 4 weeks,
• current musculoskeletal pain or injury that could affect jumping performance or participation in maximal isometric exercise,
• tattoos, scars, or skin conditions over the rectus femoris muscle that could interfere with thermographic measurements,
• use of medications or substances that may affect neuromuscular performance or muscle function,
• failure to comply with study procedures or testing requirements.

De-identified individual participant data will be shared upon reasonable request after publication of the study results. Requests should be directed to the corresponding author.

Individual participant data and supporting documents will be available beginning 3 months after publication of the study results and ending 5 years following publication.

Researchers may request access to de-identified individual participant data by contacting the corresponding author. Data will be shared upon reasonable request for scientific research purposes.

Complete blinding of participants and intervention providers was not feasible due to the visibly distinct nature of the isometric conditioning activity (ICA) and control activation (CON) protocols. However, investigators responsible for outcome assessments (spike-specific test, spike velocity, and countermovement jump performance) were blinded to the intervention allocation. In addition, researchers performing the statistical analyses remained blinded to the intervention condition to minimize potential assessment and analytical bias. Participants were not informed about the sequence of experimental conditions until completion of the study.