Sodium phosphate and cycling performance in trained male cyclists
What it found
Taking sodium phosphate for four days did not change how fast 20 trained male cyclists rode a 20 km time trial.
It did make them breathe more heavily, feel the effort was harder, and have higher blood lactate after the ride.
What they found
Studies in people
Cycling time trial speed
The riders finished the 20 km course in about 32.8 minutes whether they took sodium phosphate or the dummy pill. Power output and pedalling speed were also about the same in both cases.
Breathing during hard riding
During the time trial, the men breathed out about 3.81 litres more air per minute when they had taken sodium phosphate compared to the dummy pill.
Feeling of effort
The cyclists rated the ride as slightly harder after taking sodium phosphate than after the dummy pill. The difference on the effort scale was 0.39 points.
Blood lactate after riding
Right after the time trial, blood lactate was 1.06 mmol per litre higher when the men had taken sodium phosphate instead of the dummy pill. Before the ride, levels were the same.
Resting blood phosphate
Taking sodium phosphate for four days did not raise the amount of phosphate resting in the blood. Levels stayed at about 0.76 to 0.77 mmol per litre in both cases.
Steady moderate cycling
During ten minutes of easier cycling before the time trial, sodium phosphate made no difference to heart rate, breathing, oxygen use, or blood lactate.
What the authors conclude
- They conclude that taking sodium phosphate for four days does not improve 20 km cycling time trial performance in trained men.
- They note that the supplement actually made the riders feel like they were working harder to achieve the same result.
- They suggest that because oxygen use and heart rate did not change, sodium phosphate does not offer the aerobic benefits some athletes expect.
How it was done
Some athletes take sodium phosphate hoping it helps the body use oxygen better and improves endurance. Earlier studies gave mixed results, often using very small groups of people, so the authors wanted to test this with a larger group.
Twenty trained male cyclists took either sodium phosphate or a dummy pill every day for four days before riding a bike hard for 20 km. Each man did this twice, once with each pill, with a 14 day break between rides. The men were around 31 years old and weighed about 76.3 kg on average.
What it can’t tell you
- This trial only tested trained male cyclists, so the results may not apply to women, beginners, or people who do not cycle.
- The study measured what happened over just four days of taking the supplement, so longer term effects are unknown.
- These findings relate to intense exercise and do not show what happens when sodium phosphate is eaten in normal food amounts.
Who paid
- Authors work at
- St. Mary's University, UK
The paper
- Title
- The Effects of Sodium Phosphate Supplementation on Physiological Responses to Submaximal Exercise and 20 km Cycling Time-Trial Performance
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Brown JA, Glaister M (2019). The Effects of Sodium Phosphate Supplementation on Physiological Responses to Submaximal Exercise and 20 km Cycling Time-Trial Performance. Journal of dietary supplements. doi:10.1080/19390211.2018.1472708Free full textPubMed 29985679DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error