A Mechanistic Perspective on Post-Activation Performance Enhancement Responsiveness: A Randomized Controlled Study of Acute Changes in Muscle Architecture, Contractile Property Kinetics, and Muscle Excitability

Not Applicable

• Conditions: Ultrasonography; Tensiomyography; Contraction; MHC-I; Neuromuscular Function; Muscle Activation; Postactivation Potentiation

• Registration Number: NCT06982937
• Lead Sponsor: The Jerzy Kukuczka Academy of Physical Education in Katowice

Brief Summary

The goal of this study is to find out if one short set of heavy half-squats can help football players jump higher right away-and to understand what happens inside their muscles and nerves to make that boost happen.

Key questions

* Will performing 2-3 half-squats at 90% of one-rep max give a bigger jump boost than jogging on a treadmill for five minutes?

* After each warm-up, how do muscle speed and stiffness, muscle size and fiber angle, and nerve signals change over the next 12 minutes?

* Does each player's contribution of fast and slow muscle fibers affect how much and how long their jump improves?

Study Plan Researches will invite 44 healthy football players, ages 18-21, who train regularly and meet our health rules. No one will know which warm-up each player does until the end.

Participants will:

* Get baseline tests of jump height, muscle speed and stiffness (using a harmless electrical sensor), muscle size and fiber angle (using ultrasound), and nerve signals (using sticky pads on the skin).

* Be randomly assigned to either:

1. Heavy-squat group: 2-3 half-squats at 90% of their one-rep max

2. Jogging group: easy jog or walk on a treadmill for five minutes

* Repeat all tests right after the warm-up and again at 4, 6, 8, 10, and 12 minutes to see how jump height and all muscle and nerve measures change over time.

* Have their muscle fiber mix estimated from the first muscle-speed test to see if fiber type explains who gets the biggest jump boost.

All tests are safe, painless, and approved by an ethics board. Players can stop at any time without giving a reason. This study will help athletes and coaches choose the best warm-up to get stronger, faster jumps right before a game or practice.

Detailed Description

Not available

Study Timeline

• Study Start: 2025-02-02
• Status Verified: 2025-04
• Study First Submitted: 2025-05-05
• Study First Submitted QC: 2025-05-13
• Study First Posted: 2025-05-21
• Primary Completion: 2025-06-25
• Study Completion: 2025-07-01
• Last Update Submitted: 2025-07-21
• Last Update Posted: 2025-07-24

Recruitment & Eligibility

• Status: ENROLLING_BY_INVITATION
• Sex: Male
• Target Recruitment: 44

Inclusion Criteria

• Male football players aged 18-23 years
• Minimum of 3 structured training sessions per week for the past 6 months
• No history of lower-limb musculoskeletal injuries (e.g., ligament sprain, muscle tear) within the past 2 months
• No diagnosed dermatological conditions affecting electrode placement (e.g., psoriasis, eczema)
• No cardiovascular disease (e.g., hypertension, arrhythmia)
• No neuromuscular disorders (e.g., neuropathy, myopathy) on clinical examination
• Able to complete a 1RM half-squat protocol and countermovement jump without pain

Exclusion Criteria

• Use of performance-enhancing supplements/medications within 2 weeks prior to enrollment
• Missed more than 4 scheduled training sessions per month over the past 2 months
• Blood pressure >140/90 mmHg at rest or resting heart rate >90 bpm
• Any contraindication to electrical stimulation (e.g., pacemaker, implanted metal device)
• Failure to provide written informed consent or withdrawal of consent at any time

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Change from Baseline in Mean Countermovement Jump Height from 4 to 12 Minutes Post-Intervention	Baseline and 4, 6, 8, 10, and 12 minutes post-intervention (single session)	Absolute and relative change in vertical jump height (cm) measured by the OptoJump™ system at baseline and 4', 6', 8', 10', and 12' after either the 90% 1RM half-squat conditioning activity or the 5-minute treadmill warm-up.

Secondary Outcome Measures

Name	Time	Method
Change from Baseline in Contractile Properties of the Vastus Lateralis at 6, and 12 Minutes Post-Intervention	Baseline and 6 and 12 minutes post-intervention (single session)	Absolute changes in delay time (Td), contraction time (Tc), half-relaxation time (Tr), sustain time (Ts), and maximal displacement (Dm) of the vastus lateralis measured by tensiomyography (TMG) at baseline and again at 4, 6, 8, 10, and 12 minutes after either the 90% 1RM half-squat conditioning activity or the 5-minute light treadmill warm-up.
Change from Baseline in Muscle Architecture of the Vastus Lateralis at 6 and 12 Minutes Post-Intervention	Baseline and 6 and 12 minutes post-intervention (single session)	Absolute changes in vastus lateralis muscle thickness (millimeters) and pennation angle (degrees) measured by B-mode ultrasonography at baseline and again at 6 and 12 minutes after either the 90% 1RM half-squat conditioning activity or the 5-minute light treadmill warm-up.
Change from Baseline in Mean Vastus Lateralis EMG %MVC During CMJ at 4, 6, 8, 10, and 12 Minutes Post-Intervention	Baseline and 4, 6, 8, 10, and 12 minutes post-intervention (single session)	Absolute changes in %MVC of surface electromyography (EMG) from the vastus lateralis during each countermovement jump trial, normalized to maximal voluntary isometric contraction, measured during countermovement jumps after either the 90% 1RM half-squat conditioning activity or the 5-minute light treadmill warm-up.
Predicted Percentage of Type I Myosin Heavy Chain Fibers from Baseline Tensiomyography	Calculation after final data collection	Estimated percentage of type I myosin heavy chain fibers (%MHC-I) in the vastus lateralis calculated from baseline tensiomyography parameters (delay time, contraction time, half-relaxation time) using validated regression models.
Pearson's correlation coefficient (r) quantifying the relationship between each participant's estimated percentage of MHC-I fibers (from baseline tensiomyography regression models) and their change in countermovement jump height (ΔCMJ, in cm).	4 minutes, 6 minutes, 8 minutes, 10 minutes, and 12 minutes post-intervention	For each participant, ΔCMJ at 4, 6, 8, 10, and 12 minutes after the assigned warm-up will be calculated relative to baseline; these ΔCMJ values will then be correlated with their predicted %MHC-I to obtain r values at each time point.
Pearson's r between baseline mechanistic variables (TMG Td/Tc/Tr/Ts/Dm; USG thickness/pennation; EMG %MVC) and ΔCMJ (cm)	4, 6, 8, 10, and 12 minutes post-intervention	For each mechanistic variable, compute Pearson's r with ΔCMJ at each specified time point.
Indirect effect (a×b) estimating how much acute change in each mechanistic variable mediates the effect of the conditioning activity on ΔCMJ (cm)	4, 6, 8, 10, and 12 minutes post-intervention	For each mechanistic parameter (e.g., change in contraction time, pennation angle, EMG %MVC), compute its change from baseline at each time point. Then perform a mediation analysis-estimating path a (activity → mechanistic change) and path b (mechanistic change → ΔCMJ)-and calculate the product a×b with bootstrap 95% confidence intervals to quantify the indirect (mediated) effect.
Mean difference in ΔCMJ (cm) between participants in the upper versus lower tertile of each baseline mechanistic variable (TMG Td/Tc/Tr/Ts/Dm; USG muscle thickness/pennation angle; EMG %MVC)	4, 6, 8, 10, and 12 minutes post-intervention	For each mechanistic parameter, participants will be ranked at baseline and divided into upper and lower tertiles. At each specified post-intervention time point, the mean ΔCMJ will be calculated separately for the upper and lower tertile groups. The difference between these two means, with its 95% confidence interval, will quantify the extent to which the baseline mechanistic variable moderates the countermovement-jump response.

Trial Locations

Locations (1)

The Jerzy Kukuczka Academy of Physical Education in Katowice; 🇵🇱 Katowice, Silesia, Poland