NCT07431879

Acute Muscle Damage After Eccentric Quasi-Isometric Exercise of the Elbow Flexors

Acute Muscle Damage Responses in Elbow Flexors Following Eccentric Quasi-isometric Exercise

• Status: Completed
• Phase: N/A
• Study type: Interventional
• Enrollment: 30 (actual)
• Sponsor: Chinese Culture University · Academic / Other
• Sex: Male
• Age: 20 Years – 30 Years
• Healthy volunteers: Accepted

Summary

This study compared the acute muscle damage responses of the elbow flexor muscles following two types of resistance exercise: eccentric quasi-isometric (EQI) exercise and traditional eccentric (ECC) exercise. Thirty healthy young men were randomly assigned to perform either EQI or ECC using a dumbbell elbow flexion exercise. Both groups exercised with the same relative external load and performed the exercise to voluntary fatigue. Muscle function, muscle soreness, and blood markers related to muscle damage were assessed before exercise, immediately after exercise, and over a 7-day recovery period. The purpose of this study was to examine whether EQI exercise, which involves a prolonged isometric phase followed by a very slow eccentric action, induces different levels of acute muscle damage and recovery compared with traditional eccentric exercise.

Detailed description

Eccentric resistance exercise is widely used in strength training but is often associated with substantial exercise-induced muscle damage, resulting in strength loss, muscle soreness, swelling, and prolonged recovery. Eccentric quasi-isometric (EQI) exercise is a recently proposed contraction mode that combines a sustained isometric hold with a subsequent extremely slow eccentric lengthening under continuous voluntary resistance. This contraction pattern results in prolonged time under tension while avoiding rapid lengthening or abrupt force spikes. In this randomized interventional study, thirty healthy young men with no recent resistance training experience were randomly assigned to perform either EQI or traditional eccentric (ECC) exercise of the elbow flexors. Participants performed unilateral dumbbell elbow flexion exercise at 70% of their one-repetition maximum. The EQI group completed five sets of single repetitions consisting of an initial isometric hold at 90 degrees of elbow flexion until task failure, followed by very slow eccentric lengthening to full elbow extension. The ECC group performed five sets of repeated eccentric-only elbow flexion exercises at a controlled tempo until failure. Rest intervals were standardized between sets. Muscle damage and recovery were evaluated using multiple functional and biochemical indicators, including maximal voluntary isometric contraction torque, elbow joint range of motion, upper arm circumference, pressure pain threshold, and circulating concentrations of creatine kinase and myoglobin. Measurements were obtained before exercise, immediately after exercise, and at 1, 2, 3, and 7 days following the exercise bout. The primary objective of this study was to compare the acute muscle damage responses and recovery profiles of the elbow flexors following EQI and ECC exercise when performed to voluntary fatigue at the same relative external load.

Conditions

• Acute Muscle Damage Following Resistance Exercise

Interventions

Type	Name	Description
BEHAVIORAL	Eccentric Quasi-Isometric Exercise	Eccentric quasi-isometric (EQI) exercise of the elbow flexors was performed using a unilateral dumbbell preacher curl. The external load was set at 70% of each participant's one-repetition maximum. Each repetition began with a sustained isometric contraction at 90 degrees of elbow flexion until task failure, followed immediately by a very slow eccentric lengthening to full elbow extension while participants continued to resist the load. One repetition was defined as the continuous task from the onset of the isometric hold to full elbow extension. Participants completed five sets of one repetition with 90 seconds of rest between sets. All repetitions were performed to voluntary fatigue under supervision.
BEHAVIORAL	Traditional Eccentric Exercise	Traditional eccentric-only exercise of the elbow flexors was performed using a unilateral dumbbell preacher curl. The external load was set at 70% of each participant's one-repetition maximum. From a starting position of 90 degrees of elbow flexion, participants repeatedly lowered the dumbbell through the full range of motion using controlled eccentric contractions at a cadence of approximately 2.5 seconds per repetition, guided by a metronome. Each set was performed to voluntary failure, and a total of five sets were completed with 90 seconds of rest between sets.

Timeline

• Start date: 2020-08-01
• Primary completion: 2021-08-01
• Completion: 2021-08-01
• First posted: 2026-02-25
• Last updated: 2026-02-25

Locations

1 site across 1 country: Taiwan