Abstract
BackgroundThe aim of this study was to examine the influence of caffeine supplementation on knee flexor and knee extensor strength before, during and after intermittent running exercise in female team-sport players taking oral contraceptive steroids (OCS).MethodTen healthy females (24 ± 4 years; 59.7 ± 3.5 kg; undertaking 2–6 training sessions per week) taking low-dose monophasic oral contraceptives of the same hormonal composition took part in a randomised, double-blind, placebo-controlled crossover-design trial. Sixty minutes following the ingestion of a capsule containing 6 mg∙kg−1 body mass anhydrous caffeine or artificial sweetener (placebo), participants completed a 90-min intermittent treadmill-running protocol. Isometric strength performance and eccentric and concentric strength and power of the knee flexors and knee extensors (using isokinetic dynamometer), as well as countermovement jump (CMJ), was measured before, during and after the exercise protocol, as well as ~12 h post-exercise. Blood samples were taken before, during and post-exercise to measure glucose, insulin and free fatty acids (FFA).ResultsCaffeine supplementation significantly increased eccentric strength of the knee flexors (P < 0.05) and eccentric power of both the knee flexors (P < 0.05) and extensors (P < 0.05). However, there was no effect on isometric or concentric parameters, or CMJ performance. FFA was elevated with caffeine supplementation over time (P < 0.05) while levels of glucose and insulin were not affected by caffeine intake.ConclusionCaffeine supplementation increased eccentric strength and power in female team-sport players taking OCS both during an intermittent running protocol and the following morning.
Highlights
The aim of this study was to examine the influence of caffeine supplementation on knee flexor and knee extensor strength before, during and after intermittent running exercise in female team-sport players taking oral contraceptive steroids (OCS)
free fatty acids (FFA) was elevated with caffeine supplementation over time (P < 0.05) while levels of glucose and insulin were not affected by caffeine intake
Approximately 12 h post-caffeine ingestion. These results suggest that evening caffeine supplementation has the potential to promote eccentric knee flexor performance during intermittent exercise both immediately after and the day following ingestion in female team-games players taking OCS
Summary
The aim of this study was to examine the influence of caffeine supplementation on knee flexor and knee extensor strength before, during and after intermittent running exercise in female team-sport players taking oral contraceptive steroids (OCS). The effects are less clear, supplementation appears to increase peak strength of the knee extensors [3] and time to fatigue in submaximal isometric contractions [4, 5]. No effect on performance was seen in male team-sport athletes during 20 m sprints following ingestion of 6 mg · kg−1 caffeine [16]. Research determining the effects of caffeine supplementation on leg strength variables in team-sport athletes has often been conducted in the absence of ‘background’ running [18, 19] seen in the prolonged intermittent exercise characteristic of team-sports, limiting its application to performance in competition
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