Effect of Hot Spring Therapy on Central Fatigue Elimination During Altitude Training

NCT07615478 | Recruiting

• 1 other identifier: 202502AS100005-2
• Study Type: interventional
• Target: 27
• Locations: 1 country
• Sites: 1

Brief Summary

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).

Conditions

Central Fatigue; Altitude Training; Cognitive Impairment; Hydrotherapy; Balneotherapy; Sports Performance

Keywords

Altitude Sickness; Cognition; Hydrotherapy; Hot Springs; Athletic Performance

Outcome Measures

Primary Outcomes (2)

• Voluntary Activation

  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

  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 Outcomes (6)

• Stroop Test Performance

  Baseline, Week 2,Week 4, Follow-up (Week 1-2 post-altitude)

• Cerebral Oxygenation

  Baseline, Week 2, fellow up

• Psychomotor Vigilance Test

  Baseline, Week 2, Week 3, Week 4, Follow-up (Week 1-2 post-altitude)

• Maximal Oxygen Uptake (VO2max)

  Baseline (Week 0), Follow-up (Week 5-6 post-altitude)

• White Blood Cell Count (WBC)

  Baseline, Week 2, Follow up (Week 5-6 post-altitude)

Study Arms (3)

Natural Recovery Group

ACTIVE COMPARATOR

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

Hot water immersion group

ACTIVE COMPARATOR

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

Hot Spring Immersion Group

EXPERIMENTAL

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

Interventions

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.

Also known as: NR

Natural Recovery Group

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.

Also known as: HSB

Hot Spring Immersion Group

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.

Also known as: HWI

Hot water immersion group

Eligibility Criteria

• Age: 12 Years - 16 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17)

You may qualify if:

• 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

You may not qualify if:

• 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

Sponsors & Collaborators

• Macao Polytechnic University: lead

Study Sites (1)

Macao Polytechnic University

Macao, Macao, China

RECRUITING

Related Publications (7)

• Roerink ME, van der Schaaf ME, Dinarello CA, Knoop H, van der Meer JW. Interleukin-1 as a mediator of fatigue in disease: a narrative review. J Neuroinflammation. 2017 Jan 21;14(1):16. doi: 10.1186/s12974-017-0796-7.

  PMID: 28109186 BACKGROUND

• Goodall S, Gonzalez-Alonso J, Ali L, Ross EZ, Romer LM. Supraspinal fatigue after normoxic and hypoxic exercise in humans. J Physiol. 2012 Jun 1;590(11):2767-82. doi: 10.1113/jphysiol.2012.228890. Epub 2012 Apr 2.

  PMID: 22473785 BACKGROUND

• Ando S, Tsukamoto H, Stacey BS, Washio T, Owens TS, Calverley TA, Fall L, Marley CJ, Iannetelli A, Hashimoto T, Ogoh S, Bailey DM. Acute hypoxia impairs posterior cerebral bioenergetics and memory in man. Exp Physiol. 2023 Dec;108(12):1516-1530. doi: 10.1113/EP091245. Epub 2023 Oct 29.

  PMID: 37898979 BACKGROUND

• Koral J, Oranchuk DJ, Wrightson JG, Twomey R, Millet GY. Mechanisms of neuromuscular fatigue and recovery in unilateral versus bilateral maximal voluntary contractions. J Appl Physiol (1985). 2020 Apr 1;128(4):785-794. doi: 10.1152/japplphysiol.00651.2019. Epub 2020 Mar 12.

  PMID: 32163332 BACKGROUND

• Amann M, Sidhu SK, McNeil CJ, Gandevia SC. Critical considerations of the contribution of the corticomotoneuronal pathway to central fatigue. J Physiol. 2022 Dec;600(24):5203-5214. doi: 10.1113/JP282564. Epub 2022 Nov 23.

  PMID: 36326193 BACKGROUND

• Tamaoki S, Matsumoto S, Sasa N, Hoei T, Tojo R, Nakamura T, Aoyagi Y. Effects of sodium bicarbonate bath on the quality of sleep: An assessor-blinded, randomized, controlled, pilot clinical trial. Complement Ther Clin Pract. 2023 Feb;50:101714. doi: 10.1016/j.ctcp.2022.101714. Epub 2022 Dec 14.

  PMID: 36528983 BACKGROUND

• Grgic J, Pedisic Z, Saunders B, Artioli GG, Schoenfeld BJ, McKenna MJ, Bishop DJ, Kreider RB, Stout JR, Kalman DS, Arent SM, VanDusseldorp TA, Lopez HL, Ziegenfuss TN, Burke LM, Antonio J, Campbell BI. International Society of Sports Nutrition position stand: sodium bicarbonate and exercise performance. J Int Soc Sports Nutr. 2021 Sep 9;18(1):61. doi: 10.1186/s12970-021-00458-w.

  PMID: 34503527 BACKGROUND

MeSH Terms

Conditions

Cognitive Dysfunction; Altitude Sickness

Condition Hierarchy (Ancestors)

Cognition Disorders; Neurocognitive Disorders; Mental Disorders; Respiration Disorders; Respiratory Tract Diseases

Central Study Contacts

Ziyue Ou, PHD

CONTACT

+8615626121623; p2521734@mpu.edu.mo

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator

Study Record Dates

• First Submitted: May 19, 2026
• First Posted: May 29, 2026
• Study Start: May 25, 2026
• Primary Completion (Estimated): June 25, 2026
• Study Completion (Estimated): June 25, 2026
• Last Updated: May 29, 2026

Record last verified: 2026-05

Locations

CN (1)