Both caffeine and sodium phosphate are nutritional aids popular for endurance and improving exercise performance (the former currently sits under the spotlight in the UK for its alleged abuse by Premiere League footballers).
Researchers from the University of Western Australia wanted to know to what extent these two supplements can aid athletes, in what particular area of their athletic performance, and if there are any changes in effect when taken together.
The study, published in the Journal of Science and Medicine in Sport, looked specifically at repeated-sprint performance, which is the ability for athletes to recover and maintain maximal effort during subsequent sprints, which the Strength and Conditioning Journal described as “an attribute considered important to team sports.”
Eleven male athletes from various team sports—Australian football, basketball, hockey, and soccer—around the age of 20 were recruited with the condition that they had not taken any nutritional supplements for at least two months prior to the study.
The participants were then randomized to one of four experimental trials: They were either supplemented with (1) sodium phosphate and caffeine, (2) sodium phosphate and a placebo, (3) caffeine and a placebo, or (4) just a placebo.
Ingredients for the sodium phosphate supplement came from Challenge Chemicals Australia, while the caffeine was No-Doz from Key Pharmaceuticals.
Participants were told to load on their sodium phosphate supplements (or placebo) into four equal doses a day over six consecutive days for a mean participant daily dose of 3.75 g. The anhydrous caffeine (or placebo) was taken as a single dose 60 minutes prior to each clinical trial.
Exercise testing was performed in an indoor gymnasium on a sprung wooden surface. Warm ups were conducted first (light jogging and dynamic movements), then after a three minute rest, clinical trials of one set of 6 x 20 m sprints were performed. Sprints were timed using infrared timing gates.
Sodium phosphate fared better than caffeine
Observation of sprint times showed that, despite absent interaction effect for first 20-m sprint times, these sprints were faster after sodium phosphate suppplementaion for every set performed, with moderate effect sizes and “’likely’ chances of benefit found when compared with placebo for all sets,” the researchers wrote.
“While results were not significant, there is some evidence to suggest that [sodium phosphate] supplementation [may] improve [repeated sprint ability] in male team-sports athletes when fresh and/or fatigued compared with placebo,” they added.
As for caffeine, there was “minimal benefit.” Additionally, sodium phosphate and caffeine loading combined did not result in better repeated-sprint ability than sodium phosphate alone. “These results are important to coaches and athletes who wish to improve repeated-sprint ability during a team-sport game,” they wrote.
Source: Journal of Science and Medicine in Sport
Published online ahead of print, doi:10.1016/j.jsams.2015.04.001
Effects of sodium phosphate and caffeine ingestion on repeated-sprint ability in male athletes
Authors: Benjamin J. Kopec, Brian T. Dawson, Christopher Buck, Karen E. Wallman