Periodically manipulating dietary carbohydrates and subsequently muscle glycogen availability during exercise improves cycling performance for some.
Sleep Low, Train Low!
No, it isn’t April Fool’s day! No, this isn’t an article debunking the science behind altitude training. Are you relieved? Sleep low – train low is something entirely different. It involves Carbohydrates. Are you no longer relieved? I don’t blame you.
Carbohydrates! The Hero Nutrient We Love to Hate
Out of a relatively unfounded fear that all dietary carbohydrates lead to fat mass gains, there has been an unrelenting attempt to modify carbohydrates needs amongst athletes. If we cut the carbs, we will lose the weight – the saying goes.
To avoid derailing the topic at hand, I will leave it at not all carbs contribute equally to one’s weight gain (more on this in a future blog). However, the physiological performance benefits of a low carbohydrate diet revolve around the idea that while on such a diet, your body is better able to tap into body fat stores for fuel.
Why Low Carb?
Typically, we think of carbohydrates as our primary energy provider, and it is for most people under most conditions! We break down dietary carbohydrates into glucose which is either immediately utilized for fuel or stored away in the liver and muscle tissue, as glycogen, for future use.
Unfortunately, we only have a limited supply of stored glycogen, and without regular consumption of carbohydrates, these stores will become depleted. When consuming a low-carb diet, the fuel availability shifts towards lipid oxidation (fat burning) as glycogen becomes less readily available.
The decrease in glycogen, or we can even say that this increased reliance on fat for fuel, triggers a cascade of enzymatic reactions, leading to increased concentration of mitochondria – the aerobic powerhouse of your cellular machinery – and increased fat metabolism. These alterations to mitochondria have a significant impact on endurance performance.
Although there is theoretical merit to this form of dietary restriction, the thought of removing the majority of carbohydrates from one’s diet is atomic. My mother’s side of the family, for example, is of Italian descent. The words ‘low carb’ would send shockwaves across the dinner table with chants of “Ma, che sei grullo” ringing from my grandmother’s mouth.
The Theory Behind Sleep Low - Train Low
Perhaps not as catastrophic for most people. Nevertheless, limiting carbohydrates is quite undesirable by many. To achieve the physiological benefits of low carbohydrate dieting without the complete obliteration of the macronutrient from our meals, researchers and coaches have begun using the sleep low, train low technique.
Not to be confused with altitude training (historically in the exercise world, ‘train high’ refers to training at altitude for other physiological benefits), but rather, the idea we lower our muscle’s glycogen concentration soon before bedtime and spend our sleeping hours (sleep low) in a state of low muscle glycogen availability.
The following morning while remaining fasted, we perform a moderate duration and moderate-intensity exercise session with low muscle glycogen (train low). The result is a more robust state of fat burning during the train low session resulting in similar aerobic (mitochondrial) benefits noted above.
The method was most recently tested in a study using trained at-home cyclists. Yes, just like you!
Researcher Bennett et al. (2021) recruited 55 cyclists to complete a 3-week virtual training intervention. Half the participants were placed in a sleep low group, while the other half served as a control group and completed similar training sessions. The intervention consisted of performing 6 x 5min efforts at 105% FTP with 5min recovery soon before bedtime.
After this effort, the sleep low group received no carbohydrates, while the control consumed 2g/kg on average. The following morning, all participants performed a one-hour lower intensity effort at 75% FTP. After nine sessions, the sleep low group had improved their 20min FTP (PRE: 271 W to POST: 282 W) to a significantly greater extent than their control counterparts.
The reason, as noted earlier, is that training at a lower threshold for a moderate duration in a glycogen lowered state increases mitochondrial efficiency (i.e., aerobic efficiency) and mitochondrial (aerobic power plants) concentration (officially coined mitochondrial biogenesis).
Tips For Implementing Sleep Low - Train Low
Incorporating this nutrition intervention into your training program may be helpful to achieve your goals, but it does require some discipline.
Of first concern, it is not easy to exercise while in a glycogen lowered state. In the study above, participants in the sleep low group reported feeling more stressed from the workouts than their controls.
Secondly, removing carbohydrates from late-night snacking is not a simple feat. It means no booze, chips, pop, sweets, fruits – nothing. Killjoy, I know!
Thirdly, when athletes begin restricting one nutrient from their diet without proper education and guidance, it often leads to a significant deficit in total calories. This is hugely problematic, not just for your performance but also for your overall health.
Editors Note: Check out Dr. Upshaw’s articles on “A Healthy Relationship with Food” and “RED-S, Are we Cycling our Way to Illness?” for more insight into this important topic.
Guidelines For Incorporating Sleep Low - Train Low
For simplicity, here are some guidelines:
- Hydrate normally the day you are going to “sleep low.”
- Perform your HIIT session 2-3 hours before bedtime.
- Have dinner after your session limited to 0g/kg of Carbohydrates.
- Wake up at a similar time that you would typically (changing this can alter her hunger cues).
- Complete a 60-90min lower intensity exercise session and hydrate normally.
- Return to your regular eating habits (I assume they are already very nutritious, Right?) immediately after your exercise.
- Limit this strategy to 2 times a week.
- Ensure daily dietary protein intake is optimal (~1.2-1.4 g/kg). This will aid recovery and optimize muscle protein turnover.
What Can You Expect?
As I have noted in other articles, there is likely not one nutrition strategy that will optimize a physiological performance marker for everyone in the same way.
For those who attempt to incorporate this periodized nutrition strategy into their weekly workouts, you may find FTP increases of 1-2% or more or none at all, especially if you are at the top end of the training and performance (elite or near-elite status) ladder.
Do note that when one goes from daily carbohydrate consumption to very low carbohydrate consumption, acute physiological and psychological changes occur, such as increased anxiety, depression, and irritability. So maybe stay away from others in the morning!
Conclusion
As with most exercise and sport nutrition strategies, the more trained you are, the better you can handle a new intervention. If you are new to cycling, working on other facets of your training will be more beneficial. Conversely, if you are a seasoned veteran, a little change to your exercise ‘diet’ might be helpful!
Your Thoughts?
Do you think Sleep Low – Train Low is the little change your exercise diet needs? Comment below. Your fellow virtual cyclists want to know.
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Adam Upshaw has a PhD in Exercise Metabolism and a MSc. in Exercise Physiology. He is a licensed Kinesiologist and certified Clinical Exercise Physiologist with the Canadian Society for Exercise Physiology. A proud member of the DIRT Zwift family, Adam enjoys triathlons, cooking, and exploring life’s adventures with his wife and four children.
