Effects of Bicarbonate Spring Water Immersion on Cognitive Reliability and Post-Maximal Exercise Recovery in Adolescent Rowers During Altitude Training: A Sex-Stratified Three-Arm Randomized Controlled Trial

Macao Polytechnic University27 enrolled

Overview

This randomized controlled trial aims to investigate the effects of hot spring bath therapy on cognitive function recovery, cerebral hemodynamics, and athletic performance in athletes undergoing altitude training. Participants will be randomly assigned to either a hot spring intervention group, a hot water control group, or a blank control group. The hot spring intervention group receives hot spring baths (38°C, 20 minutes) combined with altitude training; the hot water control group receives hot water baths (38°C, 20 minutes) combined with altitude training; and the blank control group receives standard recovery procedures combined with altitude training. Primary outcome measures include cognitive performance assessments (Stroop test, psychomotor vigilance test) and cerebral hemodynamic indicators (functional near-infrared spectroscopy, transcranial Doppler ultrasound). Secondary outcomes included exercise capacity (maximal oxygen uptake, triathlon performance, 500-meter test), blood lactate, and hematological parameters (white blood cells, neutrophils, platelets). These findings may provide evidence for non-pharmacological interventions to enhance cognitive recovery and brain adaptation during altitude training.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

OTHER

Masking

DOUBLE

Enrollment

Conditions

Altitude Training Adaptation Cognitive Function

Interventions

Control Group：Natural RecoveryBEHAVIORAL

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.

Hot water immersion groupBEHAVIORAL

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 includes whole-body immersion up to the neck for 20 minutes, followed by a 10-minute rest before leaving the facility. Three times per week.

hot spring immersion groupBEHAVIORAL

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 includes whole-body immersion to the neck for 20 minutes, followed by a 10-minute rest before leaving the facility. Three times per week.

Eligibility

Sex: ALLMin age: 11 YearsMax age: 17 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Male or female aged 11-17 years- 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 * No color blindness or uncorrected visual impairment that would affect Stroop test performance Exclusion Criteria: * History of cardiovascular, respiratory, renal, or endocrine disorders * Current use of medications affecting autonomic function or cognition (e.g., beta-blockers, anticholinergics, stimulants, sedatives) * History of syncope, heat intolerance, or neurological disorders * 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 * History of traumatic brain injury, stroke, or psychiatric disorders

Outcomes

Primary Outcomes

Psychomotor Vigilance Test (PVT)

5-minute PVT measuring sustained attention and psychomotor vigilance. Outcome variables: mean reciprocal response time (1/RT). Administered via standardized software on a tablet/computer. Unit: second.

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.

Stroop Test Performance

Computerized Stroop Color-Word Test measuring executive function and cognitive inhibition. Outcome variables: reaction time (ms). Administered in a quiet, temperature-controlled room (22-24°C). Unit: milliseconds (ms).

Cerebral Oxygenation (fNIRS)

Changes in oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) in the prefrontal cortex during cognitive tasks, measured by functional near-infrared spectroscopy (fNIRS) with a multichannel system. Outcome: relative changes in HbO and HbR concentrations. Unit: micromolar (μM).

Time frame: Baseline, Week 2, Week 5

Cerebral Blood Flow Velocity (TCD)

Mean blood flow velocity in the middle cerebral artery (MCA) and anterior cerebral artery (ACA) measured by transcranial Doppler ultrasound (TCD) with 2MHz probe. Measurements taken in supine position after 10 minutes of rest. Outcome: mean velocity (cm/s). Unit: centimeters/second (cm/s).

Time frame: Baseline, Week 2, Week 4

Secondary Outcomes

Maximal Oxygen Uptake (VO2max)

Maximal oxygen uptake measured using a portable metabolic analyzer during a graded exercise test on a rowing ergometer. Test protocol: incremental ramp test to exhaustion. Unit: mL/kg/min.

Time frame: Baseline, Week 5

1000-Meter Running Test

1000-meter maximal effort running test on a standard 400m track or treadmill. Total completion time recorded. Unit: seconds (s).

Time frame: Baseline, Week 3, Week4

Peripheral Oxygen Saturation (SpO2)

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

Time frame: one month.