Sweet success: can mixing your post-exercise carb intake boost recovery?

 

It’s impossible to understate the importance of rapid recovery after training. The faster and more fully you recover, the sooner you’ll be ready to train again, the better you’ll perform when you do train and the more benefits you’ll get from your training efforts. In broad-brush terms, there are four major nutritional requirements for rapid recovery after long and/or strenuous exercise. Of these nutrients, carbohydrate is the most researched, and over the past three decades, much has been written about the benefits of consuming carbohydrate following exercise. As a result, we now know that the highest muscle glycogen (stored muscle carbohydrate – your body’s premium fuel source) synthesis rates occur when relatively large amounts of carbohydrate (1.0 – 1.5 grams per kilo of bodyweight per hour) are consumed immediately after exercise, and then at 30–60 minute intervals thereafter, for up to five hours (depending on the duration of the prior exercise)1.

But which type of carbohydrate is most effective at promoting recovery? Most of the early research was conducted with glucose and glucose polymers such as maltodextrin, which consists of chains of glucose molecules linked together. However, some later research suggested that consuming the same number of calories of carbohydrate as a blend of fructose and glucose (rather than just glucose) had the additional benefit of boosting stores of liver glycogen, which the body can use as a reserve when muscle glycogen runs low. Until now, little research has been carried out to see if consuming this blend during recovery results in improved endurance capacity in a later bout of exercise. However, one recent study by British scientists has provided some answers this question.

The fructose edge

In the study, eight trained endurance runners and triathletes performed experimental trials in a single-blind, randomised, and counterbalanced crossover design [Med Sci Sports Exerc. 2018 May;50(5):1039-1045]. The subjects completed two trials which involved running to exhaustion at 70% of their maximum oxygen uptake (moderate intensity) followed by a 4-hour recovery during which they again ran to exhaustion at the same intensity. In both of the recovery periods in the two trials, the runners consumed 90 grams per hour of carbohydrate. However, the carbohydrate type varied; in one trial they consumed two parts of glucose to three parts of maltodextrin. In the other trial, the consumed two parts of fructose to three parts of maltodextrin. The results of the two trials were then compared.

What they found

The results showed a very big advantage for consuming the fructose-maltodextrin blend compared to the glucose-maltodextrin drink. When the fructose blend was consumed, the runners averaged 81 minutes of running in the second run. This compared with just 61 minutes when they consumed the glucose blend. Further analysis showed that the performance advantage was most likely due the fact that the athletes were able to oxidise more carbohydrate when they had consumed the fructose blend drink compared to the glucose blend drink.

Implications for runners, cyclists and triathletes

A number of studies have shown that consuming a glucose-fructose blend during exercise results in improved exercise capacity, so perhaps we shouldn’t be surprised that it also helped to replenish glycogen stores more rapidly, and thus help the athletes to recover faster and run again for longer. Given these findings, athletes who need to recover as quickly as possible (for example when competing in multi-stage races or multi-event competitions) are probably better consuming recovery products containing a fructose-glucose blend.

PRACTICAL SUGGESTIONS

  • When rapid recovery is required before a repeat bout of exercise, consuming a 2:3 fructose-maltodextrin carbohydrate is recommended.
  • The dosage required will depend on how depleted your muscles are; for maximum repletion, 90 grams per hour is recommended.
  • Don’t forget about your other recovery needs. Rehydration is essential as is the replacement of electrolyte minerals such as sodium, magnesium, potassium and calcium. During a multi-day event, protein replacement (in the form of whey) is also recommend, as it has been shown to help prevent muscle and strength losses.

See also:

 

References

  1. Clin Sports Med. 1984 Jul;3(3):595-604
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