Effect of sodium phosphate loading on exercise performance in well-trained cyclists

Cameron Brewer

    Research output: ThesisDoctoral Thesis

    662 Downloads (Pure)


    Sodium phosphate (SP) supplementation may have an ergogenic effect on exercise performance. In particular, loading with ~4 g/d of SP for 3–6 days may improve endurance exercise performance (events > 20-min in duration). The mechanisms involved in potential performance improvements are varied, and include a greater oxidative capacity (facilitated by an increased concentration of 2, 3 diphosphoglycerate), more availability of intracellular and extracellular phosphate, which may allow for greater energy production, a faster resynthesis of ATP and PCr, plus enhanced cardiac muscle contractility and muscle buffering capacity. However, literature relating to SP supplementation is limited in regard to whether SP supplementation can enhance shorter duration (< 15-min) maximal exercise efforts and/or repeated high intensity efforts (separated by lower intensity “recovery” periods) that closely mimic the physiological requirements of actual sporting events, such as cycling road races. Further, little is known about the time frame (days/weeks) of any ergogenic benefits after loading.

    The purpose of this thesis was to investigate the effects of 6 days of SP supplementation (50 mg·kg·FFM-1·day-1) on various types of maximal exercise performances and associated oxygen consumption (VO2) responses in well-trained male cyclists. Specifically, study one investigated the effect of repeated SP loading (two phases of SP supplementation and 1 placebo phase, in randomised order) on 1000 kJ cycling time-trial performance and VO2peak. Study two examined the effect of SP supplementation on 100 kJ and 250 kJ cycling time-trial performances and VO2 1 and 8 days post-loading. Finally, study three evaluated whether SP supplementation could improve performance in a cycling race simulation involving repeated sprint and time-trial efforts 1 and 4 days post-loading.

    Overall, results indicated significantly improved cycling race simulation (repeated sprints and short time-trials) performance and VO2peak. Additionally, results indicated that supplementing with SP for 6 days showed trends towards improved performance (~2 %) for 250 and 1000 kJ cycling time-trials (repeatable for the 1000 kJ), with no benefit for a shorter duration 100 kJ effort. Further, after loading with SP for 6 days, some physiological and performance benefits were still noted at 4 and 8 days post-loading.

    Original languageEnglish
    QualificationDoctor of Philosophy
    • Guelfi, Kym, Supervisor
    • Wallman, Karen, Supervisor
    • Dawson, Brian, Supervisor
    Publication statusUnpublished - 2015


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