Recovery after training or competition is a cornerstone of performance for any endurance athlete. When the goal is to return to peak performance as quickly as possible (whether during a second training session on the same day or in the next stage or competition), the speed at which we restore expended energy and repair the body can make all the difference.
During exercise, glycogen stores are progressively depleted, leading to the onset of fatigue. As a result, performance in subsequent sessions may be compromised if we do not follow an appropriate nutritional strategy. This strategy should not focus solely on what we consume after exercise, as adequate carbohydrate intake during the activity can also influence and accelerate subsequent recovery.
Carbohydrate Intake During Exercise and Subsequent Recovery
Traditionally, carbohydrate intake during exercise has been recommended to provide immediate energy, maintain blood glucose levels and mitigate the loss of performance (or durability, as we have seen in previous articles) (you can read more here and here). However, recent scientific evidence shows that what we consume during exercise also directly influences how we perform the following day.
This is what was shown in a study that evaluated the effects of consuming carbohydrates (1 g/kg/h) during a cycling exercise bout (1). The researchers simulated a cycling stage by having participants perform 2.5 hours of submaximal exercise, followed by 1-minute intervals above threshold until exhaustion. During the first phase of the session, participants consumed either carbohydrates (1 gram per kg of body weight per hour, i.e. 70 grams/hour for a 70 kg cyclist) or water.
Interestingly, the following day, participants performed a 20-km time trial, and when they had consumed carbohydrates the previous day, they were able to complete it 1 minute faster (1). In addition, blood analyses showed markers pointing to lower protein breakdown, which could indicate better muscle recovery (1).
In fact, high carbohydrate intake during extreme events may not only provide energy but also protect muscle structure. In a study led by Aitor Viribay and conducted with elite runners during a mountain marathon, the impact of consuming very high amounts of carbohydrates (120 grams per hour) was evaluated against the usual recommendations of 60 or 90 g/h (2). The results showed that the group consuming 120 g/h during the race had lower levels of markers of muscle damage (such as creatine kinase) after the race compared with the lower doses (2). This suggests that consuming carbohydrates during exercise could reduce exercise-induced stress and limit muscle damage, facilitating much faster recovery.
Optimising the Post-Exercise Window: Glycogen Resynthesis
Once exercise ends, the body enters a key phase for restoring energy availability. Although we now know that there is a longer window for protein intake after exercise (and there is no need to rush to have a protein shake immediately after finishing training), during the hours following exercise there is a metabolic “window” in which the rate of glycogen resynthesis is at its highest, thanks to increased insulin sensitivity and activation of glycogen synthase (3).
To optimally replenish glycogen stores, current guidelines recommend providing between 1.0 and 1.2 grams of carbohydrates per kilogram of body weight per hour during the first 4 hours after exercise (3). Thus, a 70 kg person should consume 70–84 grams of carbohydrates per hour during the following 4 hours after exercise if their goal is to fully replenish their glycogen stores.
In addition, the timing of carbohydrate intake is vital when the recovery time between sessions is limited. A recent study investigated the consequences of delaying carbohydrate intake after high-intensity interval training (10 × 2-minute intervals) (4). Participants repeated the protocol on two days. On one of the days, they consumed carbohydrates immediately after finishing (2.4 g/kg) during the first 3 hours, while on the other day they only drank water during those first 3 hours.
Interestingly, although total muscle glycogen restoration after 24 hours ended up being similar because both groups consumed the same total amount of carbohydrates, the athletes who began consuming carbohydrates immediately after exercise attenuated the decline in physical performance the following day when they repeated the same exercise (completing more intervals and perceiving a lower level of effort) (4). This reinforces the importance of prioritising immediate carbohydrate intake after exercise when the goal is to maximise performance during short recovery periods (≤ 24 h) (4) (Figure 1).
Figure 1. Number of intervals completed by those who consumed carbohydrates immediately after the previous day's session (white), and those who delayed carbohydrate intake for more than 3 hours (red). Obtained from Díaz-Lara et al. (4).
Conclusions
Recovery does not begin when the session ends, but while you are training or competing. Adequate carbohydrate intake during exercise reduces metabolic stress and could limit muscle damage. In addition, starting carbohydrate replenishment immediately after exercise (ideally more than 1 g/kg per hour during the following 2–3 hours) is essential to accelerate glycogen resynthesis and ensure that performance capacity remains intact for the next training session or competition.
Author: Pedro Valenzuela
References
- Clauss et al. Carbohydrate Ingestion during Prolonged Cycling Improves Next-Day Time Trial Performance and Alters Amino Acid Concentrations. Med Sci Sports Exerc. 2023; 55(12):2228–2240. Doi: 10.1249/MSS.0000000000003264.
- Viribay et al. Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon on Exercise-Induced Muscle Damage in Elite Runners. Nutrients. 2020; 12(5):1367. Doi: 10.3390/nu12051367.
- Alghannam AF, Gonzalez JT, Betts JA. Restoration of Muscle Glycogen and Functional Capacity: Role of Ingested Carbohydrate and Protein. Nutrients. 2018; 10(1):253. Doi: 10.3390/nu10020253
- Díaz-Lara FJ, Reisman G, Deldicque L, et al. Delaying post-exercise carbohydrate intake impairs next-day exercise capacity but not muscle glycogen or molecular responses. Acta Physiol (Oxf). 2024; 240(10):e14215. Doi: 10.1111/apha.14215.
