The effect of caffeine on post-exercise muscle glycogen resynthesis
Research type
Research Study
Full title
Muscle glycogen resynthesis during a 4 hour recovery after exhaustive running exercise with carbohydrate and caffeine ingestion versus carbohydrate ingestion alone.
IRAS ID
311234
Contact name
James A. Betts
Contact email
Duration of Study in the UK
1 years, 8 months, 1 days
Research summary
Summary of Research
Caffeine is a potent performance-enhancing supplement in sport and has been thoroughly studied. However, most of the literature focuses on its use pre-exercise. Little consideration has been given to any post-exercise effects (i.e. improved recovery).
Muscle glycogen is the stored form of carbohydrate in muscle and is critical to exercise performance. Unfortunately this store is depleted over prolonged bouts of strenuous exercise so recovery often involves replenishment of these stores. A small handful of studies have observed that caffeine co-ingestion with carbohydrate after exercise can improve the rate of muscle glycogen resynthesis versus carbohydrate alone. However, no studies have investigated this in running, which may use carbohydrate differently versus other modalities, and we are still unclear as to the mechanisms by which caffeine may enhance muscle glycogen resynthesis. Therefore, the proposed research seeks to investigate (1) the effect of caffeine co-ingestion with carbohydrate on muscle glycogen resynthesis after running-based exercise versus carbohydrate alone and (2) the mechanisms by which caffeine may exert an effect.
The study will aim to recruit 10 recreationally active adults. Once enrolled they will be taken through preliminary fitness testing and anthropometric assessments. They will then perform a separate exercise familiarisation session before performing two bouts of running exercise followed by a 4 hour recovery period in a random order with a 7 day intervening period between trials. The two sessions will consist of either: carbohydrate ingestion alone during the recovery period or carbohydrate AND caffeine ingestion during the recovery period. Muscle, blood and breath samples will be collected to investigate the effects of caffeine co-ingestion on muscle glycogen and explore potential metabolic indicators of caffeine's mechanism of action.
Summary of Results
Glycogen is the storage form of carbohydrate in the body and the majority is stored within our muscles. Glycogen is used up during exercise and this contributes to fatigue and impaired muscle function. Replacing glycogen in muscle after exercise can restore function and ingesting carbohydrate helps that recovery happen more quickly. This experiment examined whether adding caffeine into a carbohydrate drink after exercise would accelerate that storage of muscle glycogen.Eleven young active adults ran on a treadmill for 90 minutes at moderate to high intensity on two occasions, separated by at least one week. On one occaison they ingested carbohydrate during teh 4 hours of recovery after exercise and on the other they consumed that carbohydrate with added caffeine - with the order of the drinks randomly allocated and with participants unaware which they consumed each week. Muscle samples from the thigh and blood samples were obtained at key points during exercise and recovery to measure the amount of glycogen in the muscle and the availability of key fuels and hormones in the blood (eg glucose and insulin).
A similar amount of glycogen was stored during recovery whether or not caffeine was ingested. Blood responses were also similar between participants and none of these responses depended on whether participants had a genotype that would be expect dot make them a fast or slow caffeine metaboliser.
All testing for this research project will be carried out at the University of Bath with the aim to complete initial data collection by April 2023.
REC name
West of Scotland REC 4
REC reference
22/WS/0123
Date of REC Opinion
30 Sep 2022
REC opinion
Further Information Favourable Opinion