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

Official 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

Overview

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).

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).

Interventions

• 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.
• 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.
• 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.

Primary outcome measures

• Voluntary Activation [Time frame: 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)]

Secondary outcome measures (6)

• Stroop Test Performance [Time frame: Baseline, Week 2,Week 4, Follow-up (Week 1-2 post-altitude)]
• Cerebral Oxygenation [Time frame: Baseline, Week 2, fellow up]
• Psychomotor Vigilance Test [Time frame: 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)]
• White Blood Cell Count (WBC) [Time frame: 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)]

Eligibility criteria

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

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Single blind

Primary purpose

Treatment

Study locations

China · 1 center

• Macao Polytechnic University — Macao

Publications

• 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
• 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
• 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
• 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
• 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
• 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
• 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

Identifiers

NCT: NCT07615478 · 202502AS100005-2

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗