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Completed

NCT Number: NCT07608887

Effect of Hot Spring Therapy on Autonomic Nervous System and Exercise Performance During Altitude Training

This randomized controlled trial aims to investigate the effects of balneotherapy (hot spring bathing) on cardiac autonomic nervous system function and exercise performance in healthy athletes undergoing high-altitude training. Participants will be randomly assigned to the intervention group (receiving hot spring baths three times per week (38°C, 20 minutes) combined with high-altitude training), the control group (receiving routine recovery protocols combined with high-altitude training), or the hot water immersion group (receiving hot water baths three times per week (38°C, 20 minutes) combined with high-altitude training). Primary outcome measures include heart rate variability (HRV) indices and exercise performance indicators. Secondary outcomes include blood lactate, peripheral oxygen saturation (SpO2), and subjective fatigue. These findings may provide evidence for non-pharmacological interventions to enhance high-altitude training adaptation and exercise recovery.

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Key information

Conditions

Altitude Training Adaptation Altitude Sickness Autonomic Nervous System Exercise Performance Hydrotherapy Respiration Disorders Respiratory Tract Diseases

Age range

11 year–17 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Macao Polytechnic University

Macao, China

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • Male or female aged 11-17years
  • Regular endurance training (≥3 sessions/week) for ≥2 years
  • No history of altitude exposure >2000m in the past 3 months
  • No contraindications to hot water immersion (e.g., uncontrolled hypertension, severe cardiovascular disease, open wounds, pregnancy)
  • Ability to provide written informed consent- Willingness to abstain from other recovery modalities (e.g., massage, cryotherapy, compression garments) during the study period

Exclusion criteria

  • History of cardiovascular, respiratory, renal, or endocrine disorders
  • Current use of medications affecting autonomic function (e.g., beta-blockers, anticholinergics)- History of syncope or heat intolerance
  • Acute musculoskeletal injury within the past 6 months- Regular use of sauna, hot tub, or spa within the past month
  • Pregnancy or breastfeeding (for female participants)- Shift work or trans-meridian travel within 2 weeks prior to baseline assessment
  • Alcohol consumption >14 units/week or smoking

Treatment and study plan

Control Group：Natural Recovery

Behavioral

Control group participants will undergo the same altitude training protocol (altitude 1600 meters) for 4 weeks. After each training session, participants will receive standard recovery procedures, including 20 minutes of passive rest in a thermoneutral environment (room temperature 24°C), supplemented with mild hydration and self-selected stretching. No hydrothermal intervention will be provided.

Other names: NR

Hot water immersion group

Behavioral

The hot water immersion group will undergo a 4-week altitude training at 1600 meters above sea level. Subjects will receive a 20-minute hot water immersion (daily tap water, 38°C±1°C) in a standardized indoor hot spring facility. The immersion protocol involves soaking the body below the chest for 20 minutes, followed by a 10-minute rest before leaving the facility. Three times per week.

Other names: HWI

hot spring immersion group

Behavioral

The hot spring immersion group will undergo a 4-week high-altitude training at an altitude of 1600 meters. Subjects will receive a 20-minute hot spring therapy (natural hot spring water, 38°C ± 1°C) in a standardized indoor hot spring facility. The immersion protocol involves soaking the body below the chest for 20 minutes, followed by a 10-minute rest before leaving the facility. Three times per week.

Other names: HSI

Primary outcomes

  1. Heart Rate Variability (HRV) - RMSSD

    Time frame: Baselines were measured at the formal start of the experiment, at night during the 2nd, 3rd, and 4th weeks (post-intervention) after ascending the plateau, and post-tests were conducted one week after descending the plateau.

    Root mean square of successive differences (RMSSD) between normal heartbeats, measured from a 5-minute seated ECG recording in a quiet, temperature-controlled (22-24°C) room after 15 minutes of rest. A higher RMSSD value indicates stronger parasympathetic activity. Unit: milliseconds (ms). Baseline, Week 2, Week 3 (post-intervention).

Secondary outcomes

  1. HRV - SDNN

    Time frame: Baselines were measured at the formal start of the experiment, at night during the 2nd, 3rd, and 4th weeks (post-intervention) after ascending the plateau, and post-tests were conducted one week after descending the plateau.

    Standard deviation of NN intervals (normal-to-normal R-R intervals), reflecting overall autonomic modulation. Unit: milliseconds (ms). Baseline, Week 2, Week 3, Week4, post-tests

  2. Peripheral Oxygen Saturation (SpO2)

    Time frame: one month.

    Resting peripheral oxygen saturation measured via fingertip pulse oximeter after 10 minutes of seated rest. Unit: percentage (%)

  3. Rating of Perceived Exertion (RPE)

    Time frame: one month.

    Borg 6-20 scale rating of perceived exertion recorded immediately after each training session. Higher scores indicate greater subjective effort. Unit: score (6-20). Daily during intervention

  4. Maximum oxygen uptake

    Time frame: The baseline measurement was taken before the official start of the experiment, and the post-test was conducted one week after descending from the plateau.

    Testing maximum oxygen uptake on a rowing ergometer combined with a cardiopulmonary function tester. Protocol: Using a graded incremental protocol to test maximal oxygen uptake (VO2max). Units: mL·kg-1 ·min-1. Baseline, Week 5.

  5. 30-second anaerobic power.

    Time frame: The tests are scheduled before entering the plateau (baseline), during the 4th week of plateau training, and 1 week after leaving the plateau.

    Perform a 30-s all-out test on a rowing ergometer. Protocol: sprint at maximum effort to measure the 30-second average power. Record power. Units: watt. Baseline, Week 4，1 week after altitude training.

Sponsors and collaborators

Lead sponsor

Macao Polytechnic University

Other

Registry information

Official study title

A Randomized Controlled Trial to Investigate the Effects of Balneotherapy on Cardiac Autonomic Regulation and Exercise Performance in Healthy Adolescents Undergoing Real 1600-meter Altitude Training and Athlete Training.

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
May 27, 2026
Registry last updated
Jun 26, 2026

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

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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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