What you need to know about the “window of opportunity”: what it is, when it matters most, and when purposefully ignoring it may be advantageous.
Whether you are a strength athlete or an endurance athlete, you have probably been told how important it is to eat or ritualistically consume some form of recovery drink right after your workout. Over the last few years, this practice has become more commonplace than ever and, in most scenarios, it is to the athlete’s benefit. After all, consuming a recovery drink (a mixture of carbohydrate and protein, usually in a 4:1 or 3:1 ratio) after hard training has been shown to bolster muscle protein synthesis, expedite glycogen replenishment, and prepare you for the next training session as quickly as possible. However, making slight sacrifices to the quality of a workout or temporarily delaying recovery can significantly enhance the training stimulus when done intelligently, which can often be a trade-off worth making. For example, fasted long runs are common practice for many marathon and ultra marathon runners, as is pre-fatiguing certain muscle groups through strength training prior to an endurance workout. In both of these cases, a sacrifice is made to one aspect of the workout in order to amplify the training effect in a very specific way. That is, a fasting runner may run slower while enjoying greater fat burning adaptations. A pre-fatigued runner may need to reduce training duration or intensity, but they will have greater muscle fiber recruitment, tapping into otherwise untouched and untrained fibers.
Recovery is typically used as a catch-all term to describe all the regenerative processes that occur between training sessions, but recovery itself can be manipulated to dampen or amplify the prior or subsequent training stimuli. If the goal of a workout is to stress the central nervous system and improve ground reaction force through hill sprints, then beginning the workout in a fatigued or glycogen-deprived state would dampen the training stimulus by reducing training quality in a counterproductive way. On the other hand, if the goal of a training session is to stress the aerobic system and improve fat utilization then starting the workout in a pre-depleted state can make the session even more productive. While the ideas of pre-fatigue and pre-depletion are fairly common, intentionally choosing to remain in a depleted state after training is not. However, it can be just as potent a stimulus and, depending on the conditions, you may benefit from eschewing the post workout window.
If you are training multiple times per day or have a high intensity workout planned within the next 48 hours of a given training session, taking advantage of the post workout window would be a good idea, as it is virtually impossible to replenish glycogen stores in a short time period without doing so. On the flip side, if your next workout or two are going to be recovery oriented or you have a rest day planned, then is it actually important that you replenish your glycogen right away? Perhaps it would be more beneficial to spend a few hours of your “recovery” still in a depleted state before refueling. The insulin response to carbohydrate consumption down-regulates the AMPK signaling pathway responsible for many aerobic adaptations, thus postponing glycogen replenishment can allow for a larger training effect. However, there are negative consequences, such as reduced muscle protein synthesism that should not be ignored. Instead of trying to make your recovery as fast and efficient as possible, start viewing it as simply another variable that you can manipulate. By evaluating what adaptations will be inhibited and which ones will be enhanced by utilizing the post workout window or not, you have just added another powerful tool to your training arsenal.
Like any other tool, timing is essential. I recommend trying things like fasted long runs and extended post-exercise depletion during your off-season or early pre-season when you can afford to make the trade-off between training quality and energetic adaptations. When you are close to a big event, it would usually not be a good idea, as training quality and recovery become of paramount importance. For example, when you are close to a race or big climb, it would be better to get your gut used to handling fuel and to practice race pace for extended durations than it would be to try to squeeze out an extra 1% of raw aerobic fitness on a fasted long run.
The post workout window is not a myth. It is a very real phenomenon, but expedited recovery should not necessarily take precedence over training stimulus. After all, it is the very disruption from homeostasis that pushes your body to adapt!
References:
1. Best Recovery Practices for Endurance Athletes
2. Train Your Gut To Fuel and Hydrate Better On Race Day
3. Should You Fast Before A Run?
4. The Science of Running: How to find your limit and train to maximize your performance. Steve Magness.
