Caffeine is a widely used efficacious supplement by both the general public, and athletes, with the goal of improving performance. The effects of caffeine alone are well known, but it is not clear whether a multi-ingredient supplement (containing both caffeine and polyphenols) can affect exercise performance.

This study aims to determine if a low dose of caffeine, in the form of a whole-fruit coffee extract also containing polyphenols, can improve exercise performance compared to a placebo condition, with a secondary objective of identifying if this supplement can improve post exercise refuelling (glycogen resynthesis).

Participants will consume either the supplement or a placebo before engaging in an exercise protocol. Muscle biopsies will then be obtained so as to measure subsequent glycogen resynthesis, with multiple blood samples being taken through the day. The following morning another biopsy will be taken before the exercise protocol will be repeated.

This research will inform us of the efficacy of caffeine and polyphenols on improving exercise performance.

Exclusion criteria:

• Allergy to Lidocaine
• Exclusion critera
• Any diagnosed metabolic health condition
• Pregnant
• Non-habitual caffeine intake
• Smoker
• No endurance training
• Diagnosed Cardiovascular disease
• Beta-Blockers
• Recent history of musculoskeletal injury

Inclusion criteria:

• Age 18-40
• Heathy
• Highly trained endurance athletes (V̇O2max: males >55 and females >50 mL⋅kg bm-1⋅min-1)
• Both males and females are allowed to participate. If females are on the oral contraceptive pill they are to be tested on consecutive weeks. If they are not on the oral contraceptive pill, then female subjects are to be tested every 4 weeks, at the same point of their menstrual cycle.