Tyler Robbins Fitness

B.Sc. Biochemistry, Certified Strength and Conditioning Specialist (CSCS), Certified CrossFit Trainer (CCFT/CF-L3), USA Weightlifting Level 1

Filtering by Tag: anabolism

Post Exercise Nutrient Timing

Time and time again, I see individuals giving advice as to what you should consume pre and post workout. I, myself, have given such advice in the past. Fortunately (or unfortunately for some), research is always changing and finding new and important information surrounding topics just like this one. 

I came across this fantastic article over at JISSN (Journal of the International Society of Sports Nutrition). I will highlight some key points, with my own anecdotes below, but I highly recommend going and reading the full article for yourself.

It is all too common for many individuals to just assume that post-workout nutrition is not only key, but must be the same regardless of training. 

However, the importance – and even the existence – of a post-exercise ‘window’ can vary according to a number of factors. Not only is nutrient timing research open to question in terms of applicability, but recent evidence has directly challenged the classical view of the relevance of post-exercise nutritional intake on anabolism.

Various studies have shown that post-exercise consumption of carbohydrates (with or without protein, mind you) improves recovery.

Similarly, Ivy et al. [27] found that consumption of a combination of protein and carbohydrate after a 2+ hour bout of cycling and sprinting increased muscle glycogen content significantly more than either a carbohydrate-only supplement of equal carbohydrate or caloric equivalency. The synergistic effects of protein-carbohydrate have been attributed to a more pronounced insulin response [28], although it should be noted that not all studies support these findings [29]. Jentjens et al. [30] found that given ample carbohydrate dosing (1.2 g/kg/hr), the addition of a protein and amino acid mixture (0.4 g/kg/hr) did not increase glycogen synthesis during a 3-hour post-depletion recovery period.

Interesting. So some studies have shown that post-exercise consumption of protein improves muscle recovery, but others have found no difference between carb/protein combination or a carb-only concoction.  So why are so many people focused on getting that protein shake in after their workouts? Probably because that is what many of us are lead to believe.

This "window of opportunity," appears to be not as important as once thought, unless of course you are pulling doubles.

Despite a sound theoretical basis, the practical significance of expeditiously repleting glycogen stores remains dubious. Without question, expediting glycogen resynthesis is important for a narrow subset of endurance sports where the duration between glycogen-depleting events is limited to less than approximately 8 hours [31]. Similar benefits could potentially be obtained by those who perform two-a-day split resistance training bouts (i.e. morning and evening) provided the same muscles will be worked during the respective sessions. However, for goals that are not specifically focused on the performance of multiple exercise bouts in the same day, the urgency of glycogen resynthesis is greatly diminished.

Highly intense training, pushing your muscles to absolute failure seems to only deplete glycogen stores by 40% at most.

High-intensity resistance training with moderate volume (6-9 sets per muscle group) has only been shown to reduce glycogen stores by 36-39%[8,32].
So, worst-case scenario, which is highly unlikely or ill-advised, would be to work the same muscle group within a 24-hour period, but even in that event, your muscles would still be capable of producing energy as they have plenty of backup glycogen.

In most cases, individuals appear to have a much longer "window of opportunity" to replenish spent glycogen stores than previously thought. 

For example, Parkin et al [33] compared the immediate post-exercise ingestion of 5 high-glycemic carbohydrate meals with a 2-hour wait before beginning the recovery feedings. No significant between-group differences were seen in glycogen levels at 8 hours and 24 hours post-exercise. In further support of this point, Fox et al. [34] saw no significant reduction in glycogen content 24 hours after depletion despite adding 165 g fat collectively to the post-exercise recovery meals and thus removing any potential advantage of high-glycemic conditions.

So what about protein? You need protein following a strenuous workout, along with an insulin spike to promote protein synthesis, correct? Well, maybe not. You see, studies have shown that even whey proteins, which digest rather quickly, take longer to actually reach the bloodstream.

In another example, Power et al. [48] showed that a 45g dose of whey protein isolate takes approximately 50 minutes to cause blood amino acid levels to peak. Insulin concentrations peaked 40 minutes after ingestion, and remained at elevations seen to maximize net muscle protein balance (15-30 mU/L, or 104-208 pmol/L) for approximately 2 hours.
So, although it may be nice to have a post-workout meal (especially if working out in a fasted state), it is not entirely vital in the timing.

Therefore, the recommendation for lifters to spike insulin post-exercise is somewhat trivial. The classical post-exercise objective to quickly reverse catabolic processes to promote recovery and growth may only be applicable in the absence of a properly constructed pre-exercise meal.

So to summarize (you really should to and read the discussion section for the full benefit):

For those who train in the morning (fasted), such as myself, and wish to build muscle/strength: 

In practice, it is common for those with the primary goal of increasing muscular size and/or strength to make a concerted effort to consume a pre-exercise meal within 1-2 hours prior to the bout in attempt to maximize training performance. Depending on its size and composition, this meal can conceivably function as both a pre- and an immediate post-exercise meal, since the time course of its digestion/absorption can persist well into the recovery period. Tipton et al. [63] observed that a relatively small dose of EAA (6 g) taken immediately pre-exercise was able to elevate blood and muscle amino acid levels by roughly 130%, and these levels remained elevated for 2 hours after the exercise bout. Although this finding was subsequently challenged by Fujita et al. [64], other research by Tipton et al. [65] showed that the ingestion of 20 g whey taken immediately pre-exercise elevated muscular uptake of amino acids to 4.4 times pre-exercise resting levels during exercise, and did not return to baseline levels until 3 hours post-exercise.
For those who train later in the day (i.e. a few hours after your last meal):

On the other hand, there are others who might train before lunch or after work, where the previous meal was finished 4–6 hours prior to commencing exercise. This lag in nutrient consumption can be considered significant enough to warrant post-exercise intervention if muscle retention or growth is the primary goal. Layman [77] estimated that the anabolic effect of a meal lasts 5-6 hours based on the rate of postprandial amino acid metabolism. However, infusion-based studies in rats [78,79] and humans [80,81] indicate that the postprandial rise in MPS from ingesting amino acids or a protein-rich meal is more transient, returning to baseline within 3 hours despite sustained elevations in amino acid availability. It thus has been hypothesized that a “muscle full” status can be reached where MPS becomes refractory, and circulating amino acids are shunted toward oxidation or fates other than MPS. In light of these findings, when training is initiated more than ~3–4 hours after the preceding meal, the classical recommendation to consume protein (at least 25 g) as soon as possible seems warranted in order to reverse the catabolic state, which in turn could expedite muscular recovery and growth.
It is important to note that individuals who consume some sort of pre-workout meal/drink should do so with muscle protein synthesis in mind, and not necessarily for a prevention of glycogen 'bonking'.

If you workout in a fasted state, then post-exercise consumption of protein with carbohydrates is a good way to reverse the catabolic state of your muscles. However, if you consume a pre-workout meal/shake with sufficient essential amino acids, then this may remove the need for that post-workout meal. 

At the end of the day, however, it should be noted that this area of study has several limitations, and the complexity of the human body should not be discounted. Our bodies are very good at finding and utilizing resources as needed, especially in times of need, so a regimented schedule on nutrient timing is not always needed.