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6 min readrunning / endurance

2.9 seconds over 1500 m: when sodium bicarbonate works

I run about 5,000 km a year and race up to 100 km. Sodium bicarbonate does nothing for me on those days. For a 3 km on the track, or for the climb that decides a mountain race, dozens of pooled trials put the gain near 1.7% 1. Effort duration separates the two cases, and the dose and the timing trip up most people who try it.

What the research shows.

Carr, Hopkins and Gore pooled 59 usable studies and 188 performance observations in 2011 1. The sodium bicarbonate subset, 38 studies and 137 estimates, gave a 1.7% performance gain (90% confidence limits ±2.0%) at a typical dose of 3.5 mmol per kilo of body mass, about 0.3 g/kg, measured on a single one-minute sprint in blinded male athletes.

Grgic and colleagues then read the eight bicarbonate meta-analyses of moderate or high methodological quality 2. Bicarbonate raised peak anaerobic power, anaerobic capacity, muscle endurance, 2,000 m rowing performance, high-intensity intermittent running, and performance in endurance events lasting around 45 seconds to 8 minutes. It did nothing for muscle strength or repeated-sprint ability. The same review graded several of those outcomes as low-quality evidence, with publication bias strongly suspected, and noted that the participants were overwhelmingly men.

The trial closest to a real race comes from Bird, Wiles and Robbins 3. Twelve middle and long distance runners ran six simulated 1500 m races, two after 300 mg/kg of sodium bicarbonate, two after placebo, two after nothing. Mean times: 253.9 s on bicarbonate, 256.8 s on placebo, 258.0 s in the control trial. Call it 2.9 seconds off a 4:14 baseline.

Hadzic, Eckstein and Schugardt sorted 35 randomised trials by effort duration 4. At or below 4 minutes, 11 of 20 trials found a gain. Above 4 minutes, 6 of 15 did. The International Society of Sports Nutrition position stand puts the established window at 30 seconds to 12 minutes 5.

Past 12 minutes the effect disappears.

Freis, Hecksteden, Such and Meyer gave 18 trained runners (VO2peak 61.2 ml/min/kg) either 0.3 g/kg of sodium bicarbonate or 4 g of salt, both diluted in 700 ml of water 6. The test: 30 minutes at 95% of individual anaerobic threshold, then 110% until exhaustion. Time to exhaustion was 39.6 minutes on bicarbonate and 39.3 on placebo, p = 0.78. Blood pH held inside the normal range on bicarbonate and fell to 7.34 on placebo two minutes after exercise. The dose held blood pH steady and left the finishing time where it was.

Extracellular buffering helps when an effort produces hydrogen ions faster than the body clears them. A pace you can hold for 40 minutes does not reach that point. So a marathon, a 100 km and a long tempo have nothing to gain here. An 800 m, a 3 km, a hard interval set, or the short repeated climbs of a trail race do.

The dose that works and the dose that wrecks your warm-up.

Gut distress is why most people try bicarbonate once and never again. Two findings make it manageable.

Jones and colleagues gave 16 men single doses of 0.1, 0.2 or 0.3 g/kg and tracked blood chemistry for three hours 7. Time to peak bicarbonate concentration ranged from 30 to 150 minutes at the low dose, 40 to 165 at the middle dose, and 75 to 180 minutes at 0.3 g/kg. The size of the rise varied as much: between 6.0 and 12.3 mmol/L on the top dose. A blanket instruction to take it 90 minutes out will miss most people by half an hour or more in either direction.

Carr and colleagues ran 13 active subjects through eight different ingestion protocols for the same 0.3 g/kg dose, plus a placebo 8. Taking the dose with food produced the highest blood bicarbonate and pH (7.49) and the lowest incidence of gut symptoms. Their recommendation: swallow it with a high-carbohydrate meal, 120 to 150 minutes before the effort.

Hilton and colleagues compared a delayed-release capsule against the same dose in solution in trained males 9. Symptom incidence dropped 45.1% and severity 47.5%, with the trade-off that peak buffering arrived later.

The protocol.

  1. Reserve it for efforts of 30 seconds to 12 minutes, or an interval set made of them 5. Leave it in the cupboard for anything you can hold past 20 minutes 6.
  2. Weigh 0.3 g per kilo of body mass. At 70 kg that is 21 g, roughly four level teaspoons. Trials stop finding gains below 0.2 g/kg 5, so treat that as the floor and 0.3 as the target.
  3. Swallow it with a carbohydrate-rich meal, 120 to 150 minutes before the start 8. Split the dose into four or five portions over about 20 minutes with 500 to 700 ml of water.
  4. Run the full protocol on three separate hard training days before you use it in a race. Log the gap between ingestion and the effort, and whether your gut held. Peak buffering lands anywhere from 75 to 180 minutes out depending on the person 7, and three trials give you your own number.
  5. If your stomach rebels at 0.3 g/kg, drop to 0.2 and move ingestion back to about 180 minutes before the start 5. Still rebelling: switch to enteric-coated or delayed-release capsules and push the timing later again, since the peak shifts with them 95.
  6. Count the sodium. 21 g of sodium bicarbonate carries about 5.7 g of sodium, more than a day's intake for many people. Clear it with a doctor if you have high blood pressure or any sodium restriction, and do not stack it on top of a separate pre-race salt protocol.
  7. Size your expectations to the numbers: 1.7% on a one-minute effort 1, 2.9 seconds over 1500 m 3, and almost all of it measured in men 2. Worth four teaspoons on the morning of a 5 km personal best attempt, worth skipping on the morning of an ultra.

Sources.

  1. Carr, A. J., Hopkins, W. G., & Gore, C. J. (2011). Effects of acute alkalosis and acidosis on performance: a meta-analysis. Sports Medicine, 41(10), 801-814. record
  2. Grgic, J., Grgic, I., Del Coso, J., Schoenfeld, B. J., & Pedisic, Z. (2021). Effects of sodium bicarbonate supplementation on exercise performance: an umbrella review. Journal of the International Society of Sports Nutrition, 18(1), 71. doi
  3. Bird, S. R., Wiles, J., & Robbins, J. (1995). The effect of sodium bicarbonate ingestion on 1500-m racing time. Journal of Sports Sciences, 13(5), 399-403. doi
  4. Hadzic, M., Eckstein, M. L., & Schugardt, M. (2019). The impact of sodium bicarbonate on performance in response to exercise duration in athletes: a systematic review. Journal of Sports Science and Medicine, 18(2), 271-281. full text
  5. Grgic, J., Pedisic, Z., Saunders, B., Artioli, G. G., Schoenfeld, B. J., McKenna, M. J., et al. (2021). International Society of Sports Nutrition position stand: sodium bicarbonate and exercise performance. Journal of the International Society of Sports Nutrition, 18(1), 61. doi
  6. Freis, T., Hecksteden, A., Such, U., & Meyer, T. (2017). Effect of sodium bicarbonate on prolonged running performance: a randomized, double-blind, cross-over study. PLOS ONE, 12(8), e0182158. doi
  7. Jones, R. L., Stellingwerff, T., Artioli, G. G., Saunders, B., Cooper, S., & Sale, C. (2016). Dose-response of sodium bicarbonate ingestion highlights individuality in time course of blood analyte responses. International Journal of Sport Nutrition and Exercise Metabolism, 26(5), 445-453. doi
  8. Carr, A. J., Slater, G. J., Gore, C. J., Dawson, B., & Burke, L. M. (2011). Effect of sodium bicarbonate on [HCO3-], pH, and gastrointestinal symptoms. International Journal of Sport Nutrition and Exercise Metabolism, 21(3), 189-194. doi
  9. Hilton, N. P., Leach, N. K., Sparks, S. A., Gough, L. A., Craig, M. M., Deb, S. K., & McNaughton, L. R. (2019). A novel ingestion strategy for sodium bicarbonate supplementation in a delayed-release form: a randomised crossover study in trained males. Sports Medicine - Open, 5(1), 4. doi

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