A False Sense of Urgency: Glycogen Repletion and Resistance Training

Nutrient timing is a nutritional strategy that involves consuming particular nutrients (likely a combination of protein and carbs) around our training session. The post-workout period, especially, has been consistently claimed to be the most critical part of nutrient timing.

There’s a lot of hype around nutrient timing (for good reason), but a lot of focus is placed primarily around post-workout carbohydrates and the concept of replenishing glycogen stores. While I agree, pre- and post-workout nutrition is an essential part of maximizing our progress, there still seems to be some misunderstanding around glycogen replenishment and resistance training. That is, the sense of urgency some may have around nutrient timing and what the literature actually says about the relationship between glycogen depletion/repletion and your standard resistance training programming.

Glycogen Repletion

The rationale behind post-workout carbohydrates is traditionally for the purpose of replenishing your muscle glycogen stores after your training bout. This undoubtedly holds true for a subset of individuals (for example, high intensity endurance sports or individuals who need to train more than once per day). The question is if this urgency is needed for resistance training populations.

Studies show that a single set to failure at 80% 1 RM decreased muscle glycogen stores by about 12%, while three sets at the same intensity resulted in a 24% decrease in glycogen (MacDougall, 1999). This would leave many with the idea that traditional bodybuilding-style training can be a mode of exercise that depletes a majority of your glycogen stores (thus making post-workout carbohydrates a pressing concern), but based on the literature, this isn’t the case. Studies have shown that even at a high intensity, resistance training with moderate volume is only able to reduce glycogen stores by about 36-39%. Not what we would consider a glycogen-depleting training bout.

Not only that, but complete resynthesis to pre-training levels of glycogen has been shown to occur well within 24 hours of that completed exercise bout regardless of whether or not you delay that post-training carb consumption. This is, unless, for some odd reason you decide to train the same muscle group exhaustivelywith less than 24 hours between bouts – which is not happening for the majority of serious trainees who know how to manage recovery properly. Hard pass.

So, where does this leave us?

Evidence for this “anabolic window” is far from convincing, and with that, traditional rationales just doesn’t hold up when we actually take into context the athlete and their type of training. Understanding the “why” behind these methods is important for the athlete so that they can structure and prioritize their regimen based on their specific goals, not just because “it’s always been done this way.”

 Who needs to worry about it then?

None of this is saying nutrient timing doesn’t hold importance. Bodybuilders and those with physique- and strength-related training just simply do not have performance goals that align with this rationale.

Regardless of these findings and the shortcomings of this method (regarding resistance training), there is stillvalid reasoning for post-workout carbohydrates and prioritizing the meals surrounding our training period. Alongside this, there is also a subset of individuals where glycogen replenishment is a real concern and priority.

Endurance athletes are the primary group of individuals, as they train for long periods of time at high intensities, compounded with the fact that they likely don’t have a long duration of time between these glycogen-depleting training bouts (i.e. less than 8 hours).

Another place where post-workout glycogen replenishment may be well suited is for those who train in a fasted state, skip the pre-workout meal, and/or decide to train more than once per day (granted that the same muscle groups are being trained in these two sessions).

Post-workout recommendations for the resistance-trained
The most important variable of nutrient timing concerns protein and its stimulation of muscle protein synthesis. Studies have identified that maximizing muscle hypertrophy more so comes down to making sure that we have a sufficient amount of daily protein each day to facilitate those muscular adaptations, rather than specifically timing those feedings to the exact minute you step out of the gym.

Now this doesn’t mean you can go and have 1 giant protein meal a day and be good to go – we still want to space protein through the day to some extent in order to maximize muscle protein synthesis throughout the day. We always recommend spreading your protein out evenly throughout the day, aiming for about 3-5 protein feedings per day based on your individual needs and preferences.

Carbohydrate amount/timing is still considered a “gray area” within the literature. There are plenty of studies that have investigated carbohydrate + protein ingestion, which have produced conflicting results. Overall, getting high quality protein in your pre- and post-training meal is a great guideline to follow, however, the urgency of glycogen resynthesis is almost an exclusive concern for endurance athletes with multiple glycogen-depleting events, and not for those with physique- and/or strength-related goals.

References:

MacDougall, J.D., Ray, S., Sale, D.G., McCartney, N., Lee, P., Garner, S. Muscle substrate utilization and lactate production. Can J Appl Physiol. 1999, 24(3); 209-15.

Aragon, A.A., Schoenfeld, B.J. Nutrient timing revisited: is there a post-exercise anabolic window? Journal of the International Society of Sports Nutrition 2013, 10:5.

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