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Effect of Induced Alkalosis on the Power-Duration Relationship of "All-out" Exercise


Medicine & Science in Sports & Exercise: March 2010 - Volume 42 - Issue 3 - p 563-570
doi: 10.1249/MSS.0b013e3181b71a4a

Purpose: We tested the hypotheses that sodium bicarbonate (NaHCO3) ingestion would result in no alteration in critical power (CP) but would improve performance in a 3-min all-out cycling test by increasing the total amount of work done above CP (W′).

Methods: Eight habitually active subjects completed 3-min all-out sprints against fixed resistance in a blind randomized design after a dose of 0.3 g·kg−1 body mass of NaHCO3 and 0.045 g·kg−1 body mass of sodium chloride (placebo; PL trial). Blood acid-base status was assessed from arterialized fingertip blood samples before and after exercise. The CP was calculated as the mean power output during the final 30 s of the test, and the W′ was estimated as the power-time integral >CP.

Results: The NaHCO3 dose was effective in inducing preexercise alkalosis as indicated by changes in blood pH (PL = 7.40 ± 0.02 vs NaHCO3 = 7.46 ± 0.01, P < 0.001), [bicarbonate] (PL = 21.9 ± 3.0 vs NaHCO3 = 29.0 ± 3.8 mM, P < 0.05), and base excess (PL = −1.9 ± 2.5 vs NaHCO3 = 5.0 ± 3.0 mM, P < 0.05). There were no significant differences in the total work done (PL = 62.8 ± 10.1 vs NaHCO3 = 62.7 ± 10.1 kJ), the CP (PL = 248 ± 50 vs NaHCO3 = 251 ± 51 W), or the W′ (PL = 18.2 ± 6.4 vs NaHCO3 = 17.5 ± 6.0 kJ) estimates between treatments.

Conclusions: Despite notably enhanced blood-buffering capacity, NaHCO3 ingestion had no effect on the W′, the CP, or the overall performance during 3 min of all-out cycling. It is concluded that preexercise blood alkalosis had no influence on the power-duration relationship for all-out exercise.

1School of Sport and Health Sciences, St. Luke's Campus, University of Exeter, Exeter, UNITED KINGDOM; and 2Department of Sport, Health and Exercise Science, University of Hull, Kingston-upon-Hull, UNITED KINGDOM

Address for correspondence: Anni Vanhatalo, Ph.D., School of Sport and Health Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, EX1 2LU, United Kingdom; E-mail:

Submitted for publication April 2009.

Accepted for publication July 2009.

©2010The American College of Sports Medicine