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.

Kamila Płoszczyca,Miłosz Czuba,Robert Gajda

doi:10.3390/nu13103556

Abstract

The main aim of this study was to evaluate the effects of six days of tri-sodium phosphate (SP) supplementation on the cardiorespiratory system and gross efficiency (GE) during exercise under hypoxia in cyclists. Twenty trained male cyclists received SP (50 mg·kg−1 of fat-free mass/day) or placebo for six days in a randomized, cross-over study, with a three-week washout period between supplementation phases. Before and after each supplementation phase, the subjects performed an incremental exercise test to exhaustion under normobaric hypoxia (FiO2 = 16%, ~2500 m). It was observed that short-term SP supplementation led to a decrease in heart rate, an increase in stroke volume, and an improvement in oxygen pulse (VO2/HR) during low and moderate-intensity exercise under hypoxia. These changes were accompanied by an increase in the serum inorganic phosphate level by 8.7% (p < 0.05). No significant changes were observed in serum calcium levels. GE at a given workload did not change significantly after SP supplementation. These results indicated that SP promotes improvements in the efficiency of the cardiorespiratory system during exercise in a hypoxic environment. Thus, SP supplementation may be beneficial for endurance exercise in hypoxia.

Highlights

Over the years, it has been suggested that supplementation with phosphate salts may have a positive effect on athletic performance [1]
A number of mechanisms have been proposed to explain the ergogenic effects of phosphate loading, including increasing oxidative metabolism and adenosine triphosphate (ATP) synthesis, and more rapid restoration of ATP and phosphocreatine in the muscles, an improvement of oxygen unloading in muscles by reducing Hb-O2 affinity, increasing buffering capacity, and improving myocardial function [1]
Our study revealed that short-term sodium phosphate (SP) supplementation leads to a decrease in heart rate (HR), an increase in stroke volume (SV), and an improvement in oxygen pulse (VO2/HR) during exercise at low to moderate intensity (≤lactate threshold (LT)) under hypoxia (2500 m)

Summary

Introduction

It has been suggested that supplementation with phosphate salts may have a positive effect on athletic performance [1]. Several studies have supported the exercise performance benefits of phosphate salt supplementation in normoxic conditions. These studies showed an increase in maximal oxygen uptake [3,4,5,6,7,8] and anaerobic threshold [4,7,9], better time trial performance [10,11], and improvements of the repeated-sprint ability [11,12,13,14]. A number of mechanisms have been proposed to explain the ergogenic effects of phosphate loading, including increasing oxidative metabolism and adenosine triphosphate (ATP) synthesis, and more rapid restoration of ATP and phosphocreatine in the muscles (through greater availability of extracellular and intracellular phosphates), an improvement of oxygen unloading in muscles by reducing Hb-O2 affinity (via increasing erythrocyte 2,3-diphosphoglycerate concentrations), increasing buffering capacity (via enhancing extracellular hydrogen phosphate concentration), and improving myocardial function [1]

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