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]: 57.9 ± 5.5 mL·kg·min) completed two supplementation trials separated by a 14-day washout period. The trials consisted of 10 minutes of cycling at 65% V̇O followed by a 20 km time trial. Expired air was monitored throughout each trial for the evaluation of V̇O, minute ventilation (V̇), 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·day of either SP or placebo. There were no effects (p ≥ .05) of supplementation on physiological responses during cycling at 65% V̇O. 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 (mean difference: 3.81 L·min; 95% confidence interval: [0.16, 7.46 L·min]), 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; 95% confidence interval: [0.31, 1.80 mmol·L]). In conclusion, SP supplementation has no significant effects on submaximal physiological responses or 20 km time-trial performance.

The Effects of Sodium Phosphate Supplementation on the Cardiorespiratory System and Gross Efficiency during Exercise under Hypoxia in Male Cyclists: A Randomized, Placebo-Controlled, Cross-Over Study

“…In our study, we did not observe any significant changes in VO 2 and RER during exercise at a given workload. Similarly, no significant decrease in submaximal RER or VO 2 after phosphate loading was reported in studies conducted under normoxic conditions [10,38,44,69]. Our findings suggest that phosphate salts did not shift the use of metabolic substrates towards fat utilization and did not reduce the energy cost of exercise at an intensity > 60% of VO 2max in hypoxic conditions.…”

Phosphate Loading Does not Improve 30-km Cycling Time-Trial Performance in Trained Cyclists

“…These findings are not isolated, with several other studies reporting no ergogenic effect of sodium phosphate on time-trial performance or average power (e.g. Buck et al 2014;Brown and Glastier, 2019;Brewer et al 2014). In fact, at doses of 25 mg/kg/day, Buck et al (2014) suggested the effects may even be deleterious.…”

Effects of Short-Term Phosphate Loading on Aerobic Capacity under Acute Hypoxia in Cyclists: A Randomized, Placebo-Controlled, Crossover Study

“…Studies conducted under normoxic conditions have found that phosphate salt supplementation leads to a 3-12% increase in VO 2max and an improvement in aerobic exercise performance [20][21][22][23][24][25]. However, not all research supports these beneficial phosphate loading effects [26][27][28][29] and recommendations for the use of phosphates by athletes remain ambiguous [19,30,31]. Research into the effects of phosphate salts under hypoxic conditions is scarce.…”