Sodium Bicarbonate and Time-to-Exhaustion Cycling Performance: A Retrospective Analysis Exploring the Mediating Role of Expectation

William H Gurton; Guilherme G Matta; Lewis Anthony Gough; Mayur Krachna Ranchordas; David G King; Philip Hurst

doi:10.1186/s40798-023-00612-5

Sodium Bicarbonate and Time-to-Exhaustion Cycling Performance: A Retrospective Analysis Exploring the Mediating Role of Expectation

Sports Med Open. 2023 Jul 31;9(1):65. doi: 10.1186/s40798-023-00612-5.

Authors

William H Gurton^{1

2}, Guilherme G Matta¹, Lewis Anthony Gough³, Mayur Krachna Ranchordas⁴, David G King⁵, Philip Hurst¹

Affiliations

¹ School of Psychology and Life Sciences, Canterbury Christ Church University, Canterbury, UK.
² Sport and Physical Activity Research Centre, College of Health, Wellbeing and Life Sciences, Sheffield Hallam University, Sheffield, UK.
³ Human Performance and Health Research Group, Centre for Life and Sport Sciences, Birmingham City University, Birmingham, UK.
⁴ Sport and Physical Activity Research Centre, College of Health, Wellbeing and Life Sciences, Sheffield Hallam University, Sheffield, UK. m.ranchordas@shu.ac.uk.
⁵ School of Biosciences and Medicine, University of Surrey, Guildford, UK.

Abstract

Background: Research has shown that ingesting 0.3 g·kg^-1 body mass sodium bicarbonate (NaHCO₃) can improve time-to-exhaustion (TTE) cycling performance, but the influence of psychophysiological mechanisms on ergogenic effects is not yet understood.

Objective: This study retrospectively examined whether changes in TTE cycling performance are mediated by positive expectations of receiving NaHCO₃ and/or the decline in blood bicarbonate during exercise.

Methods: In a randomised, crossover, counterbalanced, double-blind, placebo-controlled design, 12 recreationally trained cyclists (maximal oxygen consumption, 54.4 ± 5.7 mL·kg·min^-1) performed four TTE cycling tests 90 min after consuming: (1) 0.3 g·kg^-1 body mass NaHCO₃ in 5 mL·kg^-1 body mass solution, (2) 0.03 g·kg^-1 body mass sodium chloride in solution (placebo), (3) 0.3 g·kg^-1 body mass NaHCO₃ in capsules and (4) cornflour in capsules (placebo). Prior to exercise, participants rated on 1-5 Likert type scales how much they expected the treatment they believe had been given would improve performance. Capillary blood samples were measured for acid-base balance at baseline, pre-exercise and post-exercise.

Results: Administering NaHCO₃ in solution and capsules improved TTE compared with their respective placebos (solution: 27.0 ± 21.9 s, p = 0.001; capsules: 23.0 ± 28.1 s, p = 0.016). Compared to capsules, NaHCO₃ administered via solution resulted in a higher expectancy about the benefits on TTE cycling performance (Median: 3.5 vs. 2.5, Z = 2.135, p = 0.033). Decline in blood bicarbonate during exercise was higher for NaHCO₃ given in solution compared to capsules (2.7 ± 2.1 mmol·L^-1, p = 0.001). Mediation analyses showed that improvements in TTE cycling were indirectly related to expectancy and decline in blood bicarbonate when NaHCO₃ was administered in solution but not capsules.

Conclusions: Participants' higher expectations when NaHCO₃ is administered in solution could result in them exerting themselves harder during TTE cycling, which subsequently leads to a greater decline in blood bicarbonate and larger improvements in performance.

Key points: Ingesting 0.3 g·kg^-1 body mass sodium bicarbonate in solution and capsules improved time-to-exhaustion cycling performance Positive expectancy about the benefits of sodium bicarbonate and decline in blood bicarbonate were higher when sodium bicarbonate was administered in solution compared with capsules Improvements in time-to-exhaustion cycling performance for sodium bicarbonate administered in solution were related to expectancy and the enhanced extracellular buffering response.

Keywords: Beliefs; Ergogenic aids; Extracellular buffering; High-intensity exercise; Placebo effect.