Effect of Hot Spring Therapy on Central Fatigue Elimination During Altitude Training (HSCF-AHT)

May 22, 2026 updated by: Ziyue Ou, Macao Polytechnic University

A Randomized Controlled Trial Investigating the Effects of Hot Spring Therapy Balneotherapy on Central Activation, Cognitive Function, and Exercise Performance in Adolescent Rowers During Altitude Training

This randomized controlled trial investigates the effects of hot spring balneotherapy on central fatigue elimination in adolescent rowers undergoing altitude training at approximately 1600 meters (Tengchong, Yunnan). Thirty adolescent athletes (aged 12-16 years) will be stratified by sex and randomly allocated to three groups: Group A (natural recovery, no immersion), Group B (38°C pure water immersion), and Group C (38°C sodium bicarbonate hot spring immersion). Interventions will be administered 3 times per week for 4 weeks. The primary outcomes are central fatigue indices including voluntary activation (VA) and central activation ratio (CAR). Secondary outcomes encompass cognitive function (Stroop test, Psychomotor Vigilance Test), cerebral hemodynamics (functional near-infrared spectroscopy, transcranial Doppler ultrasound), exercise performance (maximal oxygen uptake, 1000m test, 500m test), blood lactate, and hematological parameters (white blood cells, neutrophils, platelets).

Study Overview

Status

Status

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

Conditions

Conditions

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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

Altitude training induces central fatigue characterized by decreased descending neural drive from the brain to skeletal muscle, reduced voluntary activation, and impaired cognitive function. This study employs a stratified randomized block design to evaluate whether post-exercise hot spring immersion can accelerate central fatigue recovery compared to pure warm water immersion and natural recovery. All participants will undergo standardized rowing training at approximately 1600 meters altitude. Group C will receive immersion in natural hot spring water at 38°C for 20 minutes. Group B will receive immersion in pure water at the same temperature and duration as a thermal control. Group A will undergo standard training recovery without immersion. The study incorporates partial blinding: Groups B and C are single-blinded to participants (identical appearance and protocol); Group A serves as an open-label control. Assessments will be conducted at baseline (pre-altitude), mid-intervention (Week 2), end-intervention (Week 4), and follow-up (1-2 weeks post-altitude).

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 (Estimated)

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.
27

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 Contact

Study Contact

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Study Locations

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

  • Child

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Male or female aged 12-16 years- Healthy with no serious chronic diseases or skin conditions
  • At least 1 year of systematic rowing training experience
  • Currently undergoing centralized altitude training at approximately 1600 meters- No history of systematic hot spring or spa immersion within the past month
  • No allergy history to sodium bicarbonate or hot spring minerals- Ability to provide written informed assent (participant) and written informed consent (parent/guardian)- No acute infection, fracture, or surgery within the past month
  • Not currently taking non-steroidal anti-inflammatory drugs (NSAIDs), immunosuppressants, or medications affecting autonomic or cognitive function

Exclusion Criteria:

  • History of cardiovascular, respiratory, renal, endocrine, or neurological disorders- Uncontrolled hypertension or hypotension
  • History of syncope, heat intolerance, or severe dizziness during hot water immersion- Open wounds, severe eczema, or other skin conditions contraindicating water immersion
  • Current use of beta-blockers, anticholinergics, stimulants, sedatives, or other medications affecting central nervous system function
  • Color blindness or uncorrected visual impairment affecting Stroop test performance- Pregnancy (for female participants)- Alcohol consumption or smoking
  • Shift work or trans-meridian travel within 2 weeks prior to baseline assessment
  • Any condition deemed by the investigator as unsafe for participation

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: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

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.
Active Comparator: Natural Recovery Group
Participants in Group A will undergo standardized rowing training at approximately 1600 meters altitude for 4 weeks. After each training session, participants will receive standard training recovery procedures without any water immersion intervention. Recovery includes passive rest, self-directed light stretching, and ad libitum hydration in a thermoneutral environment (room temperature 24°C) for 20 minutes. No thermal or hydrotherapy intervention will be provided.
Behavioral: Natural recovery
Standard post-exercise recovery without water immersion. Participants rest passively in a thermoneutral environment (24°C, 50-60% humidity) for 20 minutes with ad libitum water and optional self-directed stretching. No heat, cold, or hydrotherapy interventions are applied.
Other Names:
  • NR
Active Comparator: Hot water immersion group
Subjects in Group B will undergo the same standardized rowing training at an altitude of approximately 1600 meters for 4 weeks. After each training session, subjects will receive whole-body immersion (below the neck, with the head above water) in daily tap water at 38°C ± 0.5°C for 20 minutes. The water temperature is monitored by a precision thermometer with an error of ≤ ±0.5°C. The immersion is conducted in a standardized indoor facility, and the time is 16:00 on Tuesday, Thursday, and Saturday.
Behavioral: Hot water immersion
After exercise, full-body immersion in daily tap water. Temperature: 38°C ± 0.5°C. Duration: 20 minutes per session, 3 times per week (Tuesday, Thursday, Saturday at 16:00), for 4 consecutive weeks (total of 12 sessions). Protocol: Full-body immersion below the neck for 20 minutes, followed by a 10-minute rest before leaving the facility.
Other Names:
  • HWI
Experimental: Hot Spring Immersion Group
Participants in Group C will undergo the same standardized rowing training at approximately 1600 meters altitude for 4 weeks. After each training session, participants will receive full-body immersion (below neck, head above water) in natural hot spring water at 38°C ± 0.5°C for 20 minutes. The spring water has a pH of approximately 7.4, Na+ content of 1210 mg/L, and HCO3- content of approximately 3300 mg/L. Immersion will be performed in a standardized indoor facility on Tuesday, Thursday, and Saturday at 16:00, using the same protocol as Group B to maintain blinding.
Behavioral: Hot spring balneotherapy
After exercise, full-body immersion in natural hot spring water (pH approx. 7.4, Na+ 1210 mg/L, HCO3- approx. 3300 mg/L, total dissolved solids >1000 mg/L). Temperature: 38°C ± 0.5°C. Duration: 20 minutes per session, 3 times per week (Tuesday, Thursday, Saturday at 16:00), for 4 consecutive weeks (12 sessions total). Protocol: Full-body immersion below the neck for 20 minutes, followed by a 10-minute rest before leaving the facility.
Other Names:
  • HSB

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
Voluntary Activation
Time Frame: Baseline (Week 0), Week 2, Week 3, Week 4 (post-intervention), Follow-up (Week 1-2 post-altitude)
Voluntary activation assessed by the interpolated twitch technique (ITT) during maximal voluntary contraction (MVC) of the quadriceps femoris using percutaneous electrical stimulation. A single stimulus is superimposed on MVC; VA is calculated as: VA = (1 - superimposed twitch force / potentiated resting doublet force) × 100%. Higher VA indicates greater central neural drive. Unit: percentage (%).
Baseline (Week 0), Week 2, Week 3, Week 4 (post-intervention), Follow-up (Week 1-2 post-altitude)
Central Activation Ratio
Time Frame: Baseline (Week 0), Week 2, Week 3, Week 4, Follow-up (Week 5-6 post-altitude)
Central activation ratio measured as the ratio of maximal voluntary contraction force to the force evoked by supramaximal electrical stimulation of the femoral nerve during quadriceps contraction. CAR = MVC force / (MVC force + superimposed twitch force). Values closer to 1.0 indicate less central fatigue. Unit: ratio (0-1, no units).
Baseline (Week 0), Week 2, Week 3, Week 4, Follow-up (Week 5-6 post-altitude)

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Stroop Test Performance
Time Frame: Baseline, Week 2,Week 4, Follow-up (Week 1-2 post-altitude)
Computerized Stroop Color-Word Test measuring executive function and cognitive inhibition. Outcome variables: reaction time (ms) for congruent and incongruent trials, with interference effect calculated as incongruent minus congruent reaction time. Administered in a quiet, temperature-controlled room (22-24°C). Unit: milliseconds (ms).
Baseline, Week 2,Week 4, Follow-up (Week 1-2 post-altitude)
Cerebral Oxygenation
Time Frame: Baseline, Week 2, fellow up
Changes in oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (Hb) in the prefrontal cortex during rest and cognitive tasks, measured by functional near-infrared spectroscopy (fNIRS) with a multichannel system. Outcome: relative concentration changes (ΔμM) in HbO2 and Hb from baseline. Unit: micromolar (μM).
Baseline, Week 2, fellow up
Psychomotor Vigilance Test
Time Frame: Baseline, Week 2, Week 3, Week 4, Follow-up (Week 1-2 post-altitude)
5-minute Psychomotor Vigilance Test measuring sustained attention and psychomotor vigilance. Outcome variables: mean response time, and number of lapses (reaction time >500 ms). Administered via standardized software on a tablet/computer in a quiet environment. Unit: milliseconds (ms).
Baseline, Week 2, Week 3, Week 4, Follow-up (Week 1-2 post-altitude)
Maximal Oxygen Uptake (VO2max)
Time Frame: Baseline (Week 0), Follow-up (Week 5-6 post-altitude)
Maximal oxygen uptake measured during a graded exercise test on a rowing ergometer using a portable metabolic cart. Protocol: incremental ramp test (starting at 100W, increasing 20W every 2 minutes) until volitional exhaustion. Unit: mL/kg/min.
Baseline (Week 0), Follow-up (Week 5-6 post-altitude)
White Blood Cell Count (WBC)
Time Frame: Baseline, Week 2, Follow up (Week 5-6 post-altitude)
Total white blood cell count measured from fasting venous blood sample using automated hematology analyzer. Unit: 10^9 cells per liter (10^9/L).
Baseline, Week 2, Follow up (Week 5-6 post-altitude)
Neutrophil Count (NEUT)
Time Frame: Baseline, Week 2, Follow-up (Week 5-6 post-altitude)
Absolute neutrophil count measured from fasting venous blood sample using automated hematology analyzer. Unit: 10^9/L. Baseline, Week 4 11 Platelet Count (PLT) Platelet count measured from fasting venous blood sample using automated hematology analyzer. Unit: 10^9/L.
Baseline, Week 2, Follow-up (Week 5-6 post-altitude)

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.
Macao Polytechnic University

Publications and helpful links

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General Publications

Study record dates

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Study Major Dates

Study Start (Estimated)

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.
May 25, 2026

Primary Completion (Estimated)

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.
June 25, 2026

Study Completion (Estimated)

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.
June 25, 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).
May 19, 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.
May 22, 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.
May 29, 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.
May 29, 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.
May 22, 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.
May 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.
  • 202502AS100005-2

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

IPD Plan Description

The project is still ongoing, and there are no current plans to contribute the data. Whether to share it will be considered after the data is officially published.

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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