title: Effect of repeated sodium phosphate loading on cycling time-trial performance and VO2peak.
abstract: Research into supplementation with sodium phosphate has not investigated the effects of a repeated supplementation phase. Therefore, this study examined the potential additive effects of repeated sodium phosphate (SP) supplementation on cycling time-trial performance and peak oxygen uptake (VO2peak). Trained male cyclists (N = 9, M ± SD VO2peak = 65.2 ± 4.8 ml · kg-1 · min-1) completed baseline 1,000-kJ time-trial and VO2peak tests separated by 48 hr, then ingested either 50 mg · kg fat-free mass-1 · d-1 of tribasic SP or a combined glucose and NaCl placebo for 6 d before performing these tests again. A 14-d washout period separated the end of one loading phase and the start of the next, with 2 SP and 1 placebo phase completed in a counterbalanced order. Although time-trial performance (55.3-56.5 min) was shorter in SP1 and SP2 (~60-70 s), effect sizes and smallest-worthwhile-change values did not differ in comparison with baseline and placebo. However, mean power output was greater than placebo during time-trial performance at the 250-kJ and 500-kJ time points (p < .05) after the second SP phase. Furthermore, mean VO2peak values (p < .01) were greater after the SP1 (3.5-4.3%), with further improvements (p < .01) found in SP2 (7.1-7.7%), compared with baseline and placebo. In summary, repeated SP supplementation, ingested either 15 or 35 d after initial loading, can have an additive effect on VO2peak and possibly time-trial performance.
authors.affiliation: School of Sport Science, Exercise and Health, University of Western Australia, Perth, WA, Australia.
authors.forename: Cameron P
authors.initials: CP
authors.lastname: Brewer
authors.forename: Brian
authors.initials: B
authors.lastname: Dawson
authors.forename: Karen E
authors.initials: KE
authors.lastname: Wallman
authors.forename: Kym J
authors.initials: KJ
authors.lastname: Guelfi
mesh_terms: D000328:Adult; D054874:Athletic Performance; D001642:Bicycling; D018592:Cross-Over Studies; D019587:Dietary Supplements; D005080:Exercise Test; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D010710:Phosphates / Q000008:administration & dosage*; D010807:Physical Endurance / Q000187:drug effects*; D011795:Surveys and Questionnaires
chemical_list: D010710:Phosphates; D019344:Lactic Acid; C018279:sodium phosphate