Effects of Inter-Set Rest Intervals on Muscle Damage After Flywheel Exercise in Untrained Men (RCT)

NCT07679971 | Not Yet Recruiting

• 2 other identifiers: 7.151.52581740024.5.0000.5153
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

This randomized parallel-group clinical trial will compare the acute effects of three different inter-set rest intervals during a single lower-limb flywheel resistance exercise session in untrained men. Participants will be randomly allocated to one of three groups: 1-minute, 2-minute, or 3-minute inter-set rest interval. The primary outcome will be the change in maximal voluntary isometric contraction of the knee extensors 48 hours after exercise. Secondary outcomes will include mechanical variables during the exercise session, countermovement jump performance, knee flexor maximal voluntary isometric contraction, muscle soreness, pressure pain threshold, range of motion, ultrasound-derived muscle thickness and echo intensity, perceived exertion, perceived discomfort, perceived recovery status, creatine kinase, and lactate dehydrogenase.

Conditions

Exercise-induced Muscle Damage

Keywords

Flywheel exercise; Resistance training; Muscle damage; Maximal voluntary isometric contraction; Untrained men

Outcome Measures

Primary Outcomes (2)

• Change in maximal voluntary isometric contraction of the knee extensors

  Maximal voluntary isometric contraction of the knee extensors will be assessed using a load cell with the knee positioned at 90 degrees of flexion. The primary outcome will be the change in force between baseline and immediately, 48 hours, and 96 hours after the experimental exercise session using a flywheel.

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

• Change in maximal voluntary isometric contraction of the knee flexors

  The maximum voluntary isometric contraction of the knee flexors will be assessed using a load cell with the knee positioned at 45 degrees of flexion. The primary outcome will be the change in force between baseline and immediately, 48 hours, and 96 hours after the experimental exercise session using a flywheel.

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

Secondary Outcomes (11)

• Change in vastus lateralis and biceps femoris long head muscle thickness

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

• Change in vastus lateralis and biceps femoris long head echo intensity

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

• Change in countermovement jump performance

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

• Change in active and passive knee flexion and extension range of motion

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

• Change in lower-limb muscle soreness score assessed by the Visual Analogue Scale

  Baseline, 10 minutes after the experimental exercise session, 48 hours after the experimental exercise session, and 96 hours after the experimental exercise session

Study Arms (3)

1-Minute Inter-set Rest Interval

EXPERIMENTAL

Participants allocated to this group will perform a single lower-limb flywheel resistance exercise session using a 1-minute inter-set rest interval. The session will include squat, Romanian deadlift, knee extension, and knee flexion exercises.

Behavioral: Flywheel resistance exercise with 1-minute inter-set rest

2-Minute Inter-set Rest Interval

EXPERIMENTAL

Participants allocated to this group will perform a single lower-limb flywheel resistance exercise session using a 1-minute inter-set rest interval. The session will include squat, Romanian deadlift, knee extension, and knee flexion exercises.

Behavioral: Flywheel resistance exercise with 2-minute inter-set rest

3-Minute Inter-set Rest Interval

EXPERIMENTAL

Participants allocated to this group will perform a single lower-limb flywheel resistance exercise session using a 1-minute inter-set rest interval. The session will include squat, Romanian deadlift, knee extension, and knee flexion exercises.

Behavioral: Flywheel resistance exercise with 3-minute inter-set rest

Interventions

Flywheel resistance exercise with 1-minute inter-set rest BEHAVIORAL

Participants will perform a single lower-limb flywheel resistance exercise session using a 1-minute inter-set rest interval. The session will include squat, Romanian deadlift, knee extension, and knee flexion exercises. Each exercise will be performed for 4 sets of 2 preparatory repetitions followed by 8 valid repetitions, using the same flywheel inertia, exercise order, and execution instructions across all groups. Participants will be instructed to perform the concentric phase as fast as possible and to brake the eccentric phase during the final portion of the movement. The interval between exercises will be standardized at 3 minutes.

1-Minute Inter-set Rest Interval

Flywheel resistance exercise with 2-minute inter-set rest BEHAVIORAL

Participants will perform a single lower-limb flywheel resistance exercise session using a 2-minute inter-set rest interval. The session will include squat, Romanian deadlift, knee extension, and knee flexion exercises. Each exercise will be performed for 4 sets of 2 preparatory repetitions followed by 8 valid repetitions, using the same flywheel inertia, exercise order, and execution instructions across all groups. Participants will be instructed to perform the concentric phase as fast as possible and to brake the eccentric phase during the final portion of the movement. The interval between exercises will be standardized at 3 minutes.

2-Minute Inter-set Rest Interval

Flywheel resistance exercise with 3-minute inter-set rest BEHAVIORAL

Participants will perform a single lower-limb flywheel resistance exercise session using a 3-minute inter-set rest interval. The session will include squat, Romanian deadlift, knee extension, and knee flexion exercises. Each exercise will be performed for 4 sets of 2 preparatory repetitions followed by 8 valid repetitions, using the same flywheel inertia, exercise order, and execution instructions across all groups. Participants will be instructed to perform the concentric phase as fast as possible and to brake the eccentric phase during the final portion of the movement. The interval between exercises will be standardized at 3 minutes.

3-Minute Inter-set Rest Interval

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Age between 18 and 40 years;
• Apparently healthy and clinically able to perform physical exercise;
• No participation in structured resistance training during the previous 6 months;
• Agreement to comply with all study visits and procedures;
• Signed informed consent form.

You may not qualify if:

• History of lower-limb musculoskeletal injury or surgery that may impair performance or safety during the proposed exercise protocol;
• Current pain, injury, or functional limitation in the lower limbs;
• Use of ergogenic aids that may affect physical performance or muscle recovery;
• Use of analgesic or anti-inflammatory medication during the study period;
• Failure to attend the scheduled visits required for the primary outcome assessment.

Sponsors & Collaborators

• Federal University of Vicosa: lead

Study Sites (1)

Federal University of Viçosa

Viçosa, Minas Gerais, 36570-900, Brazil

Location

Study Design

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

Model Details: Participants will be randomly allocated to one of three parallel groups differing only in the inter-set rest interval used during a single flywheel resistance exercise session.

Study Record Dates

• First Submitted: May 29, 2026
• First Posted: July 1, 2026
• Study Start: June 1, 2026
• Primary Completion: July 1, 2026
• Study Completion: July 1, 2026
• Last Updated: July 1, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share

Locations

BR (1)