The Effects of Sodium Phosphate Supplementation on Physiological Responses to Submaximal Exercise and 20 km Cycling Time-Trial Performance

ABSTRACT

The aim of this study was to examine the effects of sodium phosphate (SP) supplementation on physiological responses to submaximal exercise and 20 km cycling time-trial performance. Using a randomized, double-blind, crossover design, 20 endurance-trained male cyclists (age: 31 ± 6 years; height: 1.82 ± 0.07 m; body mass: 76.3 ± 7.0 kg; maximal oxygen uptake [V̇O_2max]: 57.9 ± 5.5 mL·kg⁻¹·min⁻¹) completed two supplementation trials separated by a 14-day washout period. The trials consisted of 10 minutes of cycling at 65% V̇O_2max followed by a 20 km time trial. Expired air was monitored throughout each trial for the evaluation of V̇O₂, minute ventilation (V̇_E), and respiratory exchange ratio (RER). Heart rate was monitored during each trial along with ratings of perceived exertion (RPE) and blood lactate concentration. For four days before each trial, participants ingested 50 mg·kg fat-free mass⁻¹·day⁻¹ of either SP or placebo. There were no effects (p ≥ .05) of supplementation on physiological responses during cycling at 65% V̇O_2max. There were also no effects of supplementation on time-trial performance (placebo: 32.8 ± 2.2 min; SP: 32.8 ± 2.3 min). Nevertheless, relative to placebo, SP increased V̇_E (mean difference: 3.81 L·min⁻¹; 95% confidence interval: [0.16, 7.46 L·min⁻¹]), RER (mean difference: 0.020; 95% confidence interval: [0.004, 0.036]), and RPE (mean difference: 0.39; 95% confidence interval: [0.04, 0.73]) during time trials, as well as post time-trial blood lactate concentration (mean difference: 1.06 mmol·L⁻¹; 95% confidence interval: [0.31, 1.80 mmol·L⁻¹]). In conclusion, SP supplementation has no significant effects on submaximal physiological responses or 20 km time-trial performance.

KEYWORDS:

• ergogenic
• endurance
• serum phosphate
• 2,3-diphosphoglycerate

Acknowledgments

The authors express their gratitude to all the participants for their enthusiasm and commitment to the project.

Declaration of interest

The authors declare no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Additional information

Notes on contributors

Jack Alexander Brown

J. A. Brown, BSc, MSc, received his undergraduate degree from the University of Bath and his postgraduate degree from St. Mary's University. He works as an exercise physiologist for the Great Britain Rowing Team, preparing athletes for international competitions including the 2020 Summer Olympics in Tokyo.

Mark Glaister

M. Glaister, BSc, PhD, FACSM, gained his doctorate from The University of Edinburgh and is currently a reader in exercise physiology at St Mary's University. His research interests are in physiological responses to multiple sprint work as well as the effects of various ergogenic aids, particularly caffeine.