Sodium phosphate and cycling exercise in low oxygen
What it found
In 20 trained male cyclists, six days of sodium phosphate led to a lower heart rate and a higher stroke volume during low and moderate intensity exercise in low oxygen conditions.
Gross efficiency did not change.
What they found
Studies in people
Heart rate during exercise
During low and moderate intensity exercise in low oxygen, heart rate dropped by 3.9% and 3.4% after sodium phosphate compared to placebo. At the lactate threshold, heart rate fell by 1.9%, which was not statistically significant.
Stroke volume and oxygen pulse
Stroke volume increased by 4.1% at one workload below the lactate threshold and by 2.5% at the threshold. Oxygen pulse improved by 5.2% at one workload below the threshold.
Gross efficiency
Gross efficiency at a given workload did not change significantly after sodium phosphate or placebo. Oxygen uptake and respiratory exchange ratio also did not change.
Blood phosphate and calcium
Serum inorganic phosphate rose by 8.7% after sodium phosphate. Serum calcium levels did not change significantly.
Maximal exercise values
Maximal oxygen uptake, maximal heart rate, maximal cardiac output and maximal stroke volume did not change significantly after either treatment.
What the authors conclude
“Short-term sodium phosphate supplementation promotes improvements in the efficiency of the cardiorespiratory system during low- and moderate-intensity exercise in a hypoxic environment without calcium-phosphate imbalance.”
Also in their conclusions
- They conclude that short-term sodium phosphate supplementation improves the efficiency of the cardiorespiratory system during low and moderate intensity exercise in low oxygen without causing calcium-phosphate imbalance.
- They suggest that sodium phosphate should be considered as an ergogenic aid for endurance athletes, especially for ultra-race competitors.
How it was done
The authors wanted to see if phosphate salts, which have helped athletes in normal oxygen conditions, could also improve how the heart and lungs work during exercise in low oxygen. They also wanted to check if phosphate salts change how efficiently the body turns energy into work.
Twenty trained male cyclists took either sodium phosphate (50 mg per kg of fat-free mass per day) or a placebo for six days, then switched to the other after a three-week break. Before and after each phase, they did an incremental cycling test to exhaustion in a chamber with low oxygen (16% oxygen, about 2500 m altitude).
What it can’t tell you
- The study only included trained male cyclists, so the results may not apply to women, untrained people, or other types of athletes.
- The cyclists did not all sleep or train under the same conditions, which could have influenced the results.
Who paid
- Funding
- Funded by National Science Center (from the PubMed record).
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Institute of Sport, Poland; Center for Sports Cardiology, Poland
The paper
- Title
- The Effects of Sodium Phosphate Supplementation on the Cardiorespiratory System and Gross Efficiency during Exercise under Hypoxia in Male Cyclists: A Randomized, Placebo-Controlled, Cross-Over Study
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Płoszczyca K, Gajda R, Czuba M (2021). The Effects of Sodium Phosphate Supplementation on the Cardiorespiratory System and Gross Efficiency during Exercise under Hypoxia in Male Cyclists: A Randomized, Placebo-Controlled, Cross-Over Study. Nutrients. doi:10.3390/nu13103556Free full textPubMed 34684557DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error