Sex Differences in Heart Rate Variability Responses to Eight Weeks of Circuit Training

October 3, 2026 updated by: Marilyn Li Yin Ong, Universiti Sains Malaysia

Circuit Training and Autonomic Recovery: Sex Differences in Heart Rate Variability Among Inactive Young Adults

The main goal of this study is to find out how an 8-week circuit training exercise program affects heart health and how the body recovers in young adults who do not regularly exercise. The researchers also want to see if these responses are different between men and women.

The body's nervous system controls automatic functions like heart rate. Measuring changes in heart rate patterns-known as heart rate variability (HRV)-helps show how well the body switches between "fight-or-flight" (stress/exercise mode) and "rest-and-digest" (recovery mode). While men and women naturally have different heart rate patterns at rest, less is known about whether they recover differently after a structured exercise program.

The main questions this study aims to answer are:

  1. Does 8 weeks of circuit training improve heart rate recovery and nervous system balance in inactive young adults?
  2. Do men and women show different heart rate responses or recovery patterns after taking part in circuit training?

To answer these questions, inactive university students took part in an 8-week supervised circuit training program. Participants were considered inactive if they did less than 150 minutes of moderate exercise or less than 75 minutes of vigorous exercise per week.

Participants completed 20 exercise sessions (2 times per week) led by the study team:

  • Exercise Sessions: Each session started with a 5-minute warm-up, followed by 10 exercise stations using light weights, resistance bands, and bodyweight movements. Exercises targeted both upper and lower body muscles.
  • Workouts and Rest: Participants did each exercise for 30 seconds, rested for 1 minute between stations, and rested for 5 minutes between full sets.
  • Progression: During Weeks 1 to 4, participants did 2 sets per session. During Weeks 5 to 8, they increased to 3 sets per session.

To measure heart rate recovery, participants wore a heart rate chest monitor while resting quietly lying down:

  1. Before starting the 8-week program (Baseline)
  2. At 10 minutes after a workout at Week 8 (Short-term recovery)
  3. At 24 hours after a workout at Week 8 (Full recovery)

The researchers compared the heart rate data between men and women across these time points to see how quickly their nervous systems returned to a resting state after exercise.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

This study evaluates the effects of an 8-week supervised circuit training program on heart rate variability (HRV) and autonomic recovery patterns among physically inactive young adults, with a specific focus on sex-related differences.

Participants undergo an 8-week exercise intervention consisting of 20 total sessions scheduled twice per week. The intervention follows a progressive volume design:

  • Weeks 1 to 4: Participants perform 2 complete sets per session (8 sessions total).
  • Weeks 5 to 8: Participants perform 3 complete sets per session (12 sessions total).

Each exercise session begins with a 5-minute dynamic warm-up. The circuit consists of 10 sequential exercise stations targeting major upper-body and lower-body muscle groups using body weight, resistance bands, and dumbbells: 1. Heel raises with dumbbells 2. Lateral raises with resistance bands 3. Leg abductions with resistance bands 4. Shoulder extensions and flexions with resistance bands 5. Jump rope 6. Triceps extensions with dumbbells 7. Half squats with resistance bands 8. Standing chest fly with dumbbells 9. Leg curls with resistance bands 10. Bicep curls with dumbbells

Participants perform each exercise station for 30 seconds, followed by a 1-minute rest interval between stations. A 5-minute rest period is provided between complete circuits. All sessions take place under direct supervision.

Autonomic function is evaluated via continuous beat-to-beat R-R interval recordings using a validated heart rate monitor while participants rest quietly in a supine position in a climate-controlled room (21 °C). Heart rate variability is assessed across three specific time points:

  1. Baseline: Pre-intervention assessment prior to beginning the 8-week training protocol.
  2. Post-10 Minutes: Immediate post-exercise recovery assessment within 10 minutes following the final training session at Week 8.
  3. Post-24 Hours: Delayed recovery assessment 24 hours following the final training session at Week 8.

Extracted frequency-domain HRV parameters include Low Frequency (LF: 0.04-0.15 Hz), High Frequency (HF: 0.15-0.40 Hz), and the LF/HF ratio, analyzed in both absolute power values (ms2) and normalized units (n.u.). Comparisons are conducted between male and female participants across time points to analyze sex-specific autonomic adaptations and recovery trajectories following circuit training.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
17

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Malaysia
    • Kelantan
      • Kubang Kerian, Kelantan, Malaysia, 16150
        • Exercise and Sports Science Laboratory, Universiti Sains Malaysia

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years to 25 years (Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Physically inactive, defined as engaging in less than 150 minutes of moderate-intensity aerobic activity or less than 75 minutes of vigorous-intensity activity per week.
  • Enrolled university student.
  • Willing and able to provide informed consent and attend supervised training sessions twice per week for 8 weeks.

Exclusion Criteria:

  • Regular engagement in structured exercise or training programs.
  • Current consumption of dietary supplements.
  • Inability or unwillingness to refrain from caffeine, alcohol, and vigorous physical activity for 24 hours prior to heart rate variability (HRV) testing sessions.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Male Group

Male participants undergoing an 8-week supervised circuit training intervention (2 sessions per week; 2 sets per session for weeks 1-4, 3 sets per session for weeks 5-8).
Behavioral: Circuit Training Program

Participants complete an 8-week supervised circuit training intervention consisting of 20 total sessions (2 sessions per week). Each session begins with a 5-minute warm-up, followed by 10 exercise stations targeting both upper-body and lower-body muscle groups using body weight, resistance bands, and dumbbells.

The 10 stations include: heel raises with dumbbells, lateral raises with resistance bands, leg abductions with resistance bands, shoulder extensions and flexions with resistance bands, jump rope, triceps extensions with dumbbells, half squats with resistance bands, standing chest fly with dumbbells, leg curls with resistance bands, and bicep curls with dumbbells.

Each exercise station is performed for 30 seconds with a 1-minute rest interval between stations, and a 5-minute rest interval between complete sets. Training volume progresses from 2 sets per session in Weeks 1-4 (8 sessions) to 3 sets per session in Weeks 5-8 (12 sessions)

Other Names:
  • Progressive Circuit Training Protocol
Experimental: Female Group

Female participants undergoing the identical 8-week supervised circuit training intervention (2 sessions per week; 2 sets per session for weeks 1-4, 3 sets per session for weeks 5-8).
Behavioral: Circuit Training Program

Participants complete an 8-week supervised circuit training intervention consisting of 20 total sessions (2 sessions per week). Each session begins with a 5-minute warm-up, followed by 10 exercise stations targeting both upper-body and lower-body muscle groups using body weight, resistance bands, and dumbbells.

The 10 stations include: heel raises with dumbbells, lateral raises with resistance bands, leg abductions with resistance bands, shoulder extensions and flexions with resistance bands, jump rope, triceps extensions with dumbbells, half squats with resistance bands, standing chest fly with dumbbells, leg curls with resistance bands, and bicep curls with dumbbells.

Each exercise station is performed for 30 seconds with a 1-minute rest interval between stations, and a 5-minute rest interval between complete sets. Training volume progresses from 2 sets per session in Weeks 1-4 (8 sessions) to 3 sets per session in Weeks 5-8 (12 sessions)

Other Names:
  • Progressive Circuit Training Protocol

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in Low-Frequency (LF) Power in Normalized Units (LF n.u.)
Time Frame: Measured at Baseline (Week 0), Post-10 minutes (Week 8), and Post-24 hours (Week 8).

Frequency-domain heart rate variability metric reflecting combined sympathetic and parasympathetic autonomic modulation (measured in normalized units, n.u.).
Measured at Baseline (Week 0), Post-10 minutes (Week 8), and Post-24 hours (Week 8).
Change in High-Frequency (HF) Power in Normalized Units (HF n.u.)
Time Frame: Measured at Baseline (Week 0), Post-10 minutes (Week 8), and Post-24 hours (Week 8).

Frequency-domain heart rate variability metric reflecting parasympathetic (vagal) autonomic modulation (measured in normalized units, n.u.)
Measured at Baseline (Week 0), Post-10 minutes (Week 8), and Post-24 hours (Week 8).
Change in Low-Frequency to High-Frequency Ratio (LF/HF Ratio)
Time Frame: Measured at Baseline (Week 0), Post-10 minutes (Week 8), and Post-24 hours (Week 8).

Ratio of LF power to HF power, used as an index of sympathovagal balance during recovery.
Measured at Baseline (Week 0), Post-10 minutes (Week 8), and Post-24 hours (Week 8).

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Universiti Sains Malaysia

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Marilyn Li Yin Ong, PhD, Universiti Sains Malaysia

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
March 6, 2025

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
March 5, 2026

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
March 5, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 28, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 28, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 2, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
October 7, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • USM/JEPeM/KK/25010089

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared to maintain participant privacy and confidentiality. All relevant aggregated datasets generated and analyzed during the current study are provided within the results section of the published article.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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