Effects of electrolyzed hydrogen water ingestion during endurance exercise in a heated environment on body fluid balance and exercise performance
Ito H, Kabayama S, Goto K. · Temperature. 2020;7(3):290–299.
What kind of evidence is this?
Human
Randomized crossover exercise trial
Exercise and recovery
H₂-rich water
Not reported in this record.
Not reported in this record.
Methods at a glance
Twelve trained triathletes, mean age 20.0 years, exercising in heat.
12 participants; all performed both water conditions.
Two exercise trials at least three days apart; 60 minutes fixed-load cycling plus a post-rest incremental test.
During 60 minutes of cycling at 65% of VO₂max in 32°C and 50% relative humidity, participants drank 2.0 mL/kg electrolyzed hydrogen water every 15 minutes, followed by an incremental test to exhaustion.
H₂ in alkaline electrolyzed drinking water — H₂ only, not Brown's gas.
The article reports pH 9.7±0.2 for intervention water but does not report a measured numerical dissolved-H₂ concentration; the average consumed volume was 926±13 mL.
Not applicable — drinking water, not gas inhalation.
No O₂ was co-delivered as part of the intervention.
Purified water made with the same generator, pH 7.4±0.1.
Outcomes and reported result
Body mass, plasma volume, serum osmolality, electrolytes, acid-base and lactate measures, skin and muscle temperature, energy expenditure and time to exhaustion.
Body mass fell by about 1.1 kg in both conditions. Plasma volume, osmolality, sodium, potassium, pH, lactate, bicarbonate, temperature changes and time to exhaustion did not differ between waters. Energy expenditure during fixed-load cycling was slightly lower with electrolyzed water (13.2 versus 13.7 kcal/min, p=0.04), without improved exercise performance.
The complete PubMed Central article, randomization, water preparation, volumes, environmental protocol, primary null findings, funding and conflict disclosure were checked.
A reported association, difference or mechanism is not automatically a clinical benefit. Null findings, outcome type, study design and precision all matter.
Cautions and applicability
Only 12 young trained athletes, acute crossover exposure, multiple physiological endpoints and no measured dissolved-H₂ concentration. The significant energy-expenditure difference was small and did not translate to time-to-exhaustion benefit. The work was funded by Nihon Trim Co., maker of the generator, and one author was a company employee involved in generator preparation and pH checking.
Acute hydration during endurance exercise in heat among trained young triathletes; no demonstrated performance or hydration benefit.
Not reported in this record.
Not reported in this record.
Not reported in this record.
No single-study GRADE certainty rating is assigned. Certainty is assessed by important outcome across a complete eligible evidence set, not by attaching a final grade to one source.
Sources and record status
PMID: 33117861 · DOI: 10.1080/23328940.2020.1742056
Free full article on PubMed Central.
PubMed metadata and complete PubMed Central article; full-text extraction checked 8 August 2026.
2026-08-10