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NCT Number: NCT07615478

Effect of Hot Spring Therapy on Central Fatigue Elimination 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).

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Key information

Conditions

Central Fatigue Altitude Sickness Altitude Training Balneotherapy Cognition Disorders Cognitive Dysfunction Cognitive Impairment Hydrotherapy Mental Disorders Neurocognitive Disorders Respiration Disorders Respiratory Tract Diseases Sports Performance

Age range

12 year–16 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

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).

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Natural recovery

Behavioral

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

Hot water immersion

Behavioral

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

Hot spring balneotherapy

Behavioral

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

Primary outcomes

  1. 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 (%).

  2. 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).

Secondary outcomes

  1. 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).

  2. 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).

  3. 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).

  4. 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.

  5. 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).

  6. 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.

Study contacts

Contact information is provided by the study sponsor or research team.

Ziyue Ou, PHD

CONTACT

[email protected]

+8615626121623

Sponsors and collaborators

Lead sponsor

Macao Polytechnic University

Other

Registry information

Official study title

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

Acronym: HSCF-AHT

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
May 29, 2026
Registry last updated
May 29, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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