Carbohydrates are often seen as the enemy as brands and social media influencers seemingly push carb-free-everything. And, while cutting carbohydrates can be a sensible way to reduce excess energy intake, those who push their bodies hard must keep up with their carb intake, especially post workout, in order to replenish glycogen levels in a timely manner, explains a groundbreaking new study.
While experts have long known that post-exercise carb digestion is necessary for replenishing glycogen in our bodies, the amount of carbs, and the time required for recovery, has been less understood. A new study, published in the National Library of Medicine and undertaken by The Journal of Physiology has attempted to answer those questions, however.
Why Does the Body Need Glycogen?
When glucose is stored in the body, it takes the form of glycogen, and is the body’s primary source of energy, derived from carbohydrates. Both the muscle and the liver store glycogen for later use, but if your reserves are too depleted, energy levels will crash, and your performance will suffer. Taken to the extreme, glycogen depletion can lead to low blood pressure and hypogycemia, so it stands to reason that athletes and those who train hard would want to replenish their levels adequately.
How as the Study Carried Out?
12 experienced male cyclists with an average age of 25yrs were split into two groups. Both cycled for around two hours to deplete their glycogen stores. One group was then put on a carbohydrate refeeding protocol for 12 hours, while the other group were fasted and only provided with water or tea. Measurements were then taken to determine the effects on glycogen after 12 hours of recovery.
What Were the Results?
“Exercise strongly reduces glycogen contents of both muscle and liver tissue,” read the report. “Without carbohydrate ingestion muscle and liver glycogen levels remain depleted.”
Indeed, post exercise, all participants experienced an average 64% fall in the glycogen held in the muscle, and a 34% drop in the liver. Without carb replenishment, the fasted group remained depleted for the full 12 hours post training. The carbohydrate refeeding group were able to fully restore liver glycogen levels within 6 hours, however, while data showed that the muscle required up to 24 hours of carbohydrate refueling to get back to restored levels. “During post-exercise recovery, plasma glucose, lactate, and insulin concentrations increased, providing the necessary substrates and hormonal environment to support hepatic glycogen synthesis,” stated the report, on the significance of carbohydrates after getting your sweat on.
The actual number of carbs provided to the refeed group was 10 grams per kilogram of body mass, so this may act as a guide for those who want to train hard the next day. However, the researchers note that the transportation of glycogen to the muscle is slower than that of the liver, so simply increasing carb intake further than 10 grams does not necessarily mean a faster recovery time.
