Acute Effects of Bilateral Versus Unilateral Isometric Conditioning Activity on Jump Performance in Volleyball Players

NCT07709104 | Enrolling By Invitation

• 1 other identifier: 2-X/2025/002
• Study Type: interventional
• Target: 14
• Locations: 1 country
• Sites: 1

Brief Summary

This randomized crossover trial investigates the acute effects of bilateral and unilateral isometric conditioning activity on bilateral and unilateral jump performance in highly trained male volleyball players. Fourteen athletes will complete three experimental conditions in randomized order: bilateral isometric squat conditioning activity (BI), unilateral isometric squat conditioning activity (UNI), and a control condition consisting of low-intensity treadmill walking (CTRL). In both isometric conditions, participants will perform three sets of three maximal 3-second contractions, with 3-minute recovery intervals between sets. Jump performance will be assessed before each experimental condition and at 4, 8, and 12 minutes afterward using bilateral countermovement jumps and single-leg jumps performed separately with each lower limb. The primary aim of the study is to determine whether the mode of isometric conditioning activity, unilateral versus bilateral, influences the magnitude and time course of acute changes in jump performance. An additional objective is to assess whether the effects of the conditioning activity differ between bilateral and unilateral jumping tasks.

Conditions

Athletic Performance; Volleyball; Isometric Strength Training; Post Activation Potentiation

Keywords

Post-Activation Performance Enhancement; Maximal voluntary isometric contraction; Jump performance; Resistance training

Outcome Measures

Primary Outcomes (2)

• Changes in Bilateral Countermovement Jump Height

  Bilateral countermovement jump height will be assessed using dual force platforms operating at a sampling frequency of 1000 Hz. Jump height will be calculated from center-of-mass take-off velocity using the impulse-momentum method and expressed in centimeters. Participants will perform two valid trials at each time point, and the mean value will be used for analysis. Changes from the condition-specific baseline will be compared between the bilateral isometric, unilateral isometric, and control conditions.

  Baseline and 4, 8, and 12 minutes after each experimental condition

• Changes in Single-Leg Jump Height

  Single-leg jump height will be assessed separately for the right and left lower limbs using force platforms. Each jump will be performed with take-off from one limb and landing on both limbs. Jump height will be calculated from center-of-mass take-off velocity using the impulse-momentum method and expressed in centimeters. Two valid trials will be performed with each limb at each time point, and the mean value for each limb will be used for analysis.

  Baseline and 4, 8, and 12 minutes after each experimental condition

Secondary Outcomes (3)

• Changes in Bilateral Countermovement Jump Modified Reactive Strength Index

  Baseline and 4, 8, and 12 minutes after each experimental condition

• Changes in Inter-Limb Concentric Impulse Asymmetry During the Bilateral Countermovement Jump

  Baseline and 4, 8, and 12 minutes after each experimental condition

• Changes in Inter-Limb Single-Leg Jump Height Asymmetry

  Baseline and 4, 8, and 12 minutes after each experimental condition

Study Arms (3)

Bilateral Isometric Conditioning Activity

EXPERIMENTAL

Participants will perform a bilateral isometric conditioning activity consisting of three sets of three maximal 3-second isometric squat contractions against an immovable resistance. Each set will be separated by 3 minutes of recovery.

Behavioral: Bilateral Isometric Conditioning Activity

Unilateral Isometric Conditioning Activity

EXPERIMENTAL

Participants will perform a unilateral isometric conditioning activity consisting of three sets of three maximal 3-second isometric squat contractions with each lower limb against an immovable resistance. The lower limbs will be alternated, and each set will be separated by 3 minutes of recovery.

Behavioral: Unilateral Isometric Conditioning Activity

Control Condition

EXPERIMENTAL

Participants will complete 9 minutes of low-intensity treadmill walking at a speed of 6 km/h. This condition will serve as the control condition for comparison with the bilateral and unilateral isometric conditioning activities.

Behavioral: Low-Intensity Treadmill Walking

Interventions

Bilateral Isometric Conditioning Activity BEHAVIORAL

Three sets of three maximal 3-second bilateral isometric squat contractions performed against an immovable resistance, with 3-minute recovery intervals between sets. Participants will be instructed to push as hard and as fast as possible during each contraction.

Also known as: BI

Bilateral Isometric Conditioning Activity

Unilateral Isometric Conditioning Activity BEHAVIORAL

Three sets of three maximal 3-second unilateral isometric squat contractions performed with each lower limb against an immovable resistance. The lower limbs will be alternated, and 3-minute recovery intervals will be provided between sets. Participants will be instructed to push as hard and as fast as possible during each contraction.

Also known as: UNI

Unilateral Isometric Conditioning Activity

Low-Intensity Treadmill Walking BEHAVIORAL

All participants will complete all three experimental conditions in a randomized and counterbalanced order, with a standardized recovery interval between sessions. Each participant will therefore serve as his own control.

Control Condition

Eligibility Criteria

• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• The Jerzy Kukuczka Academy of Physical Education in Katowice: lead

Study Sites (1)

Academy of Physical Education in Katowice

Katowice, Silesian Voivodeship, 40-065, Poland

Location

Related Publications (5)

• Krzysztofik M, Wilk M, Pisz A, Kolinger D, Tsoukos A, Aschenbrenner P, Stastny P, Bogdanis GC. Effects of Unilateral Conditioning Activity on Acute Performance Enhancement: A Systematic Review. J Sports Sci Med. 2022 Dec 1;21(4):625-639. doi: 10.52082/jssm.2022.625. eCollection 2022 Dec.

  PMID: 36523899 BACKGROUND

• Jarosz J, Szwarc A. Isometric Conditioning Activity and Jump Performance: Impact of Training Status in Male Participants. J Clin Med. 2025 Sep 3;14(17):6214. doi: 10.3390/jcm14176214.

  PMID: 40943974 BACKGROUND

• Lum D, Barbosa TM. Brief Review: Effects of Isometric Strength Training on Strength and Dynamic Performance. Int J Sports Med. 2019 May;40(6):363-375. doi: 10.1055/a-0863-4539. Epub 2019 Apr 3.

  PMID: 30943568 BACKGROUND

• Helbin J, Gawel D, Terbalyan A, Wilk M, Krzysztofik M, Lum D, Jarosz J. Acute Effects of Isometric Contraction Distribution on Jump Performance in Volleyball Players. J Funct Morphol Kinesiol. 2025 Sep 9;10(3):343. doi: 10.3390/jfmk10030343.

  PMID: 40981042 BACKGROUND

• Jarosz J, Drozd M, Gawel D, Wilk M, Helbin J, Krzysztofik M. Acute effects of isometric conditioning activity with different distribution contraction on countermovement jump performance in resistance trained participants. Sci Rep. 2025 May 15;15(1):16960. doi: 10.1038/s41598-025-02126-4.

  PMID: 40374844 BACKGROUND

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: Participants will complete all three experimental conditions in a randomized and counterbalanced order. The conditions will include bilateral isometric conditioning activity, unilateral isometric conditioning activity, and a control condition. Experimental sessions will be separated by a standardized washout period to minimize carryover effects.

Study Record Dates

• First Submitted: July 13, 2026
• First Posted: July 16, 2026
• Study Start: July 23, 2026
• Primary Completion (Estimated): August 3, 2026
• Study Completion (Estimated): August 3, 2026
• Last Updated: July 16, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP
• Time Frame: De-identified individual participant data and supporting documents will be available beginning 3 months after publication of the primary study results and will remain available for 5 years.
• Access Criteria: De-identified individual participant data and supporting documents will be made available to qualified researchers who submit a methodologically sound research proposal. Requests should be directed to the corresponding author and will be reviewed by the study investigators. Access will be granted for analyses consistent with the approved proposal and may require a data-use agreement.

Locations

PL (1)