Metabolic, Respiratory, and Muscle Oxygenation Responses to Sub-maximal Eccentric and Concentric Isokinetic Exercise to Exhaustion (MUSOX-EX)

Responses to Sub-maximal Eccentric and Concentric Isokinetic Exercise to Exhaustion

This study aims to measure and compare the metabolic response during sub maximal eccentric and concentric isokinetic exercise performed to exhaustion. Fourteen healthy female participants in the early phase of the menstrual cycle will perform concentric exercise with one lower limb and eccentric exercise with the contralateral limb. The assignment of exercise mode to limb and the order of testing will be randomized. The exercise protocol will consist of repeated knee extensor contractions on an isokinetic dynamometer for 10 minutes at 40% of maximal torque, followed by exercise at 70% of maximal torque until exhaustion. Oxygen consumption and respiratory quotient and will be measured continuously throughout exercise using open-circuit spirometry. Muscle oxygenation will be measured also continuously using near infrared spectroscopy. Lactate and pH concentration will be measured at frequent time points during the exercise to exhaustion.

Study Overview

• Status: Completed
• Conditions: Eccentric Exercise; Isokinetic Test
• Intervention / Treatment: Other: Sub maximal concentric exercise; Other: Sub maximal eccentric exercise

Detailed Description

The purpose of this study is to investigate and compare the metabolic responses during sub maximal eccentric and concentric isokinetic exercise performed to exhaustion. Eccentric and concentric muscle actions differ in their physiological and metabolic demands, but their effects on respiratory parameters during fatiguing isokinetic exercise are not fully understood. This study is designed to examine whether these two contraction modes produce distinct metabolic responses under controlled exercise conditions.

Fourteen healthy female participants will be recruited and tested during the early phase of their menstrual cycle in order to reduce the possible influence of hormonal variation on physiological responses. A within-subject design will be used, with each participant completing both exercise conditions. One lower limb will perform concentric exercise and the contralateral lower limb will perform eccentric exercise. The limb allocation and the order of the two exercise conditions will be randomized.

All exercise testing will be conducted on an isokinetic dynamometer. The protocol will involve repeated contractions of the knee extensor muscles. Each trial will begin with 10 minutes of exercise at 40% of maximal torque. Following this initial stage, the intensity will be increased to 70% of maximal torque and maintained until volitional exhaustion is reached.

Oxygen consumption and respiratory quotient will be measured continuously throughout the exercise bout using open-circuit spirometry. Continuous monitoring of gas exchange during exercise will allow evaluation of substrate utilization and metabolic responses associated with each mode of contraction. Muscle oxygenation will be measured also continuously using near infrared spectroscopy. Lactate and pH concentration will be measured at frequent time points during the exercise to exhaustion.

The study is expected to provide further insight into the metabolic and respiratory differences between eccentric and concentric exercise performed under submaximal but fatiguing isokinetic conditions. The findings may have implications for exercise testing, training prescription, and rehabilitation settings in which eccentric and concentric muscle actions are used for different physiological purposes.

• Study Type: Interventional
• Enrollment (Actual): 14
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Greece
  • Attica
    • Athens, Attica, Greece, 17234
      • School of Physical Education and Sport Science

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Physically active young females
• No experience in activities involving significant resistance exercise components
• No experience in muscle-damaging activities for at least 6-months prior to the study.

Exclusion Criteria:

• Any musculoskeletal injuries in the lower limbs within the past 6 months
• Use of contraceptives
• Irregular menstrual cycles
• Smoking
• Consumption of protein and antioxidant supplements
• Potential inflammatory conditions.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Isokinetic concentric exercise; The concentric isokinetic exercise will be consisted of 10 minutes at 40% of maximal torque followed by repetitions at an intensity of 70% of maximal torque until exhaustion.	Other: Sub maximal concentric exercise; Based on their maximal performance on isokinetic concentric muscle contractions, participants performed sub-maximal concentric knee extensor exercise on an isokinetic dynamometer. The protocol consists of 10 minutes exercise at 40% of maximal torque followed by exercise at 70% of maximal torque until exhaustion. The exercise protocol was continuous, which mean that no interval was adopted at any stage of the protocol.
Experimental: Isokinetic eccentric exercise; The eccentric isokinetic exercise will be consisted of 10 minutes at 40% of maximal torque followed by repetitions at an intensity of 70% of maximal torque until exhaustion.	Other: Sub maximal eccentric exercise; Based on their maximal performance on isokinetic eccentric muscle contractions, participants performed sub-maximal concentric knee extensor exercise on an isokinetic dynamometer. The protocol consists of 10 minutes exercise at 40% of maximal torque followed by exercise at 70% of maximal torque until exhaustion. The exercise protocol was continuous, which mean that no interval was adopted at any stage of the protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Oxygen consumption	Oxygen consumption will be measured continuously using a open circuit chart during the whole duration of the isokinetic (either eccentric or concentric) exercise.	From the first intervention to the last intervention 2 weeks
Muscle oxygenation	Muscle oxygenation will be measured continuously using a open circuit chart during the whole duration of the isokinetic (either eccentric or concentric) exercise.	From the first intervention to the last intervention 2 weeks
Duration of the isokinetic exercise	The whole duration of both isokinetic concentric and eccentric exercise will be recored	From the first intervention to the last intervention 2 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Respiratory quotient	Respiratory quotient will be measured continuously using a open circuit chart during the whole duration of the isokinetic (either eccentric or concentric) exercise.	From the first intervention to the last intervention 2 weeks
Lactate concentration	Blood from fingertips will be collected periodically during the isokinetic exercise for both types of muscle contraction (concentric and eccentric)	From the first intervention to the last intervention 2 weeks
pH measurement	Blood will be collected periodically during the isokinetic exercise for both types of muscle contraction (concentric and eccentric)	From the first intervention to the last intervention 2 weeks

Collaborators and Investigators

• Sponsor: National and Kapodistrian University of Athens

Study record dates

Study Major Dates

• Study Start (Actual): September 12, 2025
• Primary Completion (Actual): January 18, 2026
• Study Completion (Actual): March 28, 2026

Study Registration Dates

• First Submitted: April 17, 2026
• First Submitted That Met QC Criteria: April 17, 2026
• First Posted (Actual): April 23, 2026

Study Record Updates

• Last Update Posted (Actual): April 30, 2026
• Last Update Submitted That Met QC Criteria: April 25, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: oxygen consumption; muscle oxygenation; Eccentric exercise; Concentric exercise
• Other Study ID Numbers: 1424/21-11-2022

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be made publicly available.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No