5 Tips to Improve Rest Day "Fueling"

We all love the high of getting a good sweat and hammering out a solid workout. It’s a feeling of accomplishment. 

Sweet satisfaction!

But the physical and mental work it took to complete that workout wasn’t easy. You really had to push through in order to not give up. That is tough to maintain day-after-day, week-after-week.

If you’re a “functional athlete” or someone training a variety of movements, energy systems, and intensities, then the ability to push hard in these workout sessions day-after-day comes down to your ability to recover.

If you’re not recovering, you’re not performing. No way around it. 

Today I wanted to provide some background on why proper rest day “fueling” (eating and hydration) is important, bring awareness to some flaws I’ve seen on rest day, and give you 5 tips for better fueling.

Keep in mind, the advice provided is general and based on athletes who are at least “moderately” trained (training >10 hours a week). Although most of the information can be applied to less trained athletes, please consult your health professional, doctor, nutritionist, or dietician prior to implementing any of the strategies below.

Also a rest day is defined as a day where you aren’t training, participating in planned physical activity, or performing a task that is more physically difficult than what you normally do.    

 

Why is rest day fueling important?   

As you may be aware, you need calories (or energy) for all your metabolic processes to take place aka living and functioning. 

You need energy to keep your body functioning at rest (breathing, tissue repair, digesting food) and you need energy when exercising. 

The exercise/physical activity you perform on a daily and weekly basis determines how efficient you will be and the specific energy requirements your body needs to operate optimally. 

For example, if you regularly perform aerobic exercise, your body is going to be better at utilizing fatty acids and glucose (simple sugar) for long duration tasks, think running 5 miles. 

Meanwhile, if you’re an Olympic lifter who doesn’t perform much aerobic exercise then your body will utilize a combination of the energy that’s readily available and ‘glycolysis’ for more energy production (more powerful short term, but not efficient long term). That’s why it’s optimal for powerlifters and Olympic lifters to take 2-5 minutes of rest between sets, it allows for better energy regeneration in the absence of oxygen.

You need fuel to function.

Regardless if you’re an aerobic based athlete or anaerobic based athlete (functioning primarily with and without oxygen respectively), you will almost certainly function better when your glycogen (carbohydrate) stores are full. Even if the athlete has trained on a low carbohydrate diet for some time, power and performance increase even more when utilizing glycogen aka carbs(1).

 

Storage 

That leads into my next point about rest day fueling with carbohydrate (glucose) sources. If you’re training moderately (~2 hours a day, 5 days a week), you’re going to need the fuel to continue to push through the following session. If you’re fairly well trained, you can even tell when you didn’t have enough carbs or simply enough calories the day before. That’s because you feel “off” and sluggish. You feel like you’re working harder and can’t apply the same power output you had previously managed. The muscles store glycogen and if you’re looking to make progress, you need to provide it.

So on your rest day and immediately following the previous workout session, ensure you’re taking in some carbohydrates of various forms and restoring those glycogen stores in the muscles. 

Also keep in mind, for the 3-24 hours that follow a single bout of exercise, you have an increase in GLUT4 protein expression (2,3). GLUT4 is the receptor responsible for bringing the glucose into the muscle cell. This is a fancy way of saying after you exercise, you are potentially more sensitive to uptaking glucose. Therefore, glucose for rest day fuel is strongly considered if you’re training at least moderately. More energy for the following session.

Repair

The second point I want to make is about tissue repair. Everytime you workout you are ripping apart your muscle cells. Yes, you have microtrauma to the muscles. Hence why you get sore and feel inflamed afterwards. 

Regardless of whether you are on a rest day or on a training day following a prior training session, you need to start the repair of the muscle tissue you broke down in order to continue to push at the levels you desire. Your body can’t do this as optimally if you’re limiting carbohydrates and/or protein intake. 

Everytime you perform a bout of exercise, more specifically resistance training, you get an increase in muscle protein synthesis (MPS) (4). This means your body starts making new muscle tissue by incorporating amino acids into the bound skeletal muscle proteins (5). 

Essentially, you’re building muscle.  

But what’s also true is that ingesting protein following this bout of exercise increases the rate of MPS (6,7). So it seems that when trying to repair muscle tissue, protein consumption post-exercise increases MPS and recovery.

In fact one study had shown 20g of high-quality protein ingested every 3 hours after exercise for a 12-hour window was more superior than 10 grams every 1.5 hours or 40g every 6 hours (8). This was limited to lower body exercise. Another study from 2016 had shown that among healthy resistance-trained men, ingesting 40g of protein following an acute bout of whole body resistance training can increase protein synthesis by 16% in a 5-hour recovery window compared to 20g (9). 

Sure these are only a couple studies, but there is numerous data that have studied the improvements of MPS when ingesting protein post-exercise following both aerobic and resistance exercise. Skeletal muscle can stay in a heightened anabolic state following a bout of resistance training when protein is available in the diet for 24 (10) to 48 (11) hours post exercise. 

Bottomline, eat your protein after you exercise, especially when you complete a more “resistance-heavy” exercise bout. That continual protein ingestion over the next 24-48 hours can potentially improve recovery and the following training session.  

 

Hydration

We all know drinking water is a good thing, but how much is essential and how do we optimize a proper level of hydration? 

This is all determined by your pre-exercise hydration status, your body composition, the temperature of the environment, the humidity level, what you’ve eaten/ingested, etc. There’s a ton of factors that play into it but let’s keep it simple, we’ll focus on water and electrolytes during your period of recovery. 

One important point to remember is that the human body is 50-70% water, depending on the body composition and mass of the specific individual (12). Therefore the body requires a certain amount of water to operate its normal day to day functions. If you have too much water or too little water, this will be detrimental to function and performance. Hence the importance of rest day hydration. But it’s not as simple as “just drinking water” throughout the day. Although that’s beneficial, there are some other key points to be noted as well.  

Plain water is good at restoring the volume of water in the blood, but it's not as efficient as improving rehydration status after exercise. Basically, you won’t be driving water into the muscle cells so easily. In fact, plain water by itself can decrease the relative concentration of electrolytes (sodium in particular in the blood, which comes with its own issues). So to help drive more water into the cell, sodium and carbohydrates in particular, can help to optimize this process. When sodium is in a higher concentration outside the cell, it will flow into the cell carrying water with it. Sodium is also the number one electrolyte lost in sweat during an intense workout and has a large effect on plasma osmolality (the relative amount of particles in your blood) (13). A study by Sheriffs et al. demonstrated proper hydration was achieved after the volume of fluid ingested was greater than that lost and when the drink sodium concentration was higher than that of sweat (14). So the pairing of the sodium and water had a greater rehydration effect. 

Another important point to consider is that carbohydrates can deliver a similar effect of restoring rehydration. Evans et al. found that drinking a 10% glucose solution immediately post-exercise resulted in greater fluid retention at the end of a 6-hour recovery window compared to a 0% glucose drink (15). The amount of fluid in those drinks was 150% of the fluid lost during exercise. Another similar study concluded that 4 hours after exercise, the water retention was greatest when drinking a 6% and 10% glucose drink (16). The fluid volume in these drinks was equal to 100% of what was lost during exercise.

It appears that the greatest ability to promote rehydration after exercise where fluid loss is high, is sufficient fluid paired with sodium and carbohydrate. This results in greater fluid retention. However, just remember more is not always better. A 10% glucose drink is already on the higher end of consumption status. Sure the carbs help with energy here, but in terms of osmolality, they may not necessarily be promoting greater rehydration status. That’s why some commercial “rehydration” drinks may not be optimally rehydrating you because the concentration of glucose (sugar) to water is a bit too high and may be pulling water from other tissues to follow the glucose concentration in the lumen aka your ‘gut’. 

So to jump start your recovery day fueling, it makes sense to rehydrate initially with a sodium and simple carbohydrate drink, then transition to more complex carbs after the first few hours following the exercise. Remember, if the exercise is not intense enough, you may not even need that much sodium and carbohydrate solution. The hydration amount depends on variables such as environment (humidity, altitude, temperature), work intensity, prior hydration status, and body composition. Those need to be accounted for first before choosing a specific drink mixture.   

Hormonal Changes

When talking about exercise and rest day fuel, we have to remember that some hormones can be produced and released as a result of the training session intensity and volume. These hormones are notably testosterone, IGF-1 (insulin growth-like factor), and growth hormone (GH). Much is still not fully understood about their effects and how much of a role they play in recovery acutely and chronically. However, exercise does induce a cascade of reactions in the body, specific to the individual and exercise type, that can enhance the effect of the given hormone. This is true for males and females.  Whether the signaling and hormone release is present over a period of time, it is important to ensure proper nutrition and food intake after a workout to enhance the overall effect of the hormones and their ability to promote a greater environment for recovery and future performance (16).

 

Rest Day Fueling Flaws

There is a ton of misleading information out there about training and proper recovery fueling. This information can lead to poor choices in particular fueling strategies which can create a negative result in performance. Here are some flaws that are common.

Undereating - Of course if an athlete or individual is in a fat loss phase then ‘undereating’ or eating in a calorie deficit is essential. How much depends on that individual. However, this can unfortunately be a problem for performance athletes. If fat loss is not the primary goal, then the athlete has to ensure they’re taking in sufficient calories to fit their performance needs. If you’ve been training long enough, you’ll know your maintenance calories more or less. Remember the body is building itself back up during those recovery days and needs sufficient fuel for repair on top of normal metabolic processes. So the amount of energy you’re using for these rest days during a normal training week should be above baseline calorie levels. If you do not know your daily maintenance calories, it’s best to meet with a nutritionist or dietician who can help you find an optimal calorie intake. There’s also a ton of free resources out there in the forms of apps and databases that can help you troubleshoot this as well. But undereating on your recovery day is setting you up for failure on the following session and leading to less-than-optimal muscle building effect.

Lack of nutritional variety - This one is just about getting your micronutrition. Think veggies and other real foods. Performance, sleep, recovery can all be benefitted from ensuring proper nutritional variety when ingesting a mix of amino acids, vitamins, grains, fats, etc. Ensure you’re taking in a variety to promote greater performance and overall health.

Poor hydration - The organs, and in particularly the nervous system, need water to function optimally. Let’s also not forget the human body is made up of 50-70% water. If you’re not hydrating during that recovery day, the next session is going to be a smack in the face. The water you drink the day before your next workout can make a ton of difference in performance. Subtract 1-2 coffees and instead add 12-16 oz of water, your body will thank you.

5 Tips to improve Rest Day ‘Fueling’

1) Eat above maintenance

• You’re going to need the extra calories for repair of the damaged muscle tissue, replace glycogen stores, and increase anabolic hormone signaling.

2) Eat complex carbs for fuel

• If your recovery day is a complete “rest” day then eat more complex carbohydrates (oats, brown rice, quinoa, barley, sweet potatoes). These will take longer to digest and won’t have as powerful an effect on insulin secretion and blood sugar. Save the “insulin spikes” for the simple sugars needed around your actual workout.

3) Eat sufficient protein

• Aim for .8g/lb - 1g/lb of lean body mass. This will ensure you’re covering your bases when trying to maximize muscle repair or protein synthesis.

4) Hydrate properly and utilize sodium and carbohydrates

• Ensure immediately after an intense workout that your drink has a combination of carbohydrates and sodium. A glucose/dextrose 6% drink is sufficient (Gatorade is about 8-9% depending). The drink sodium concentration doesn’t have to be crazy high since most first world diets already have an abundance, but adding some sodium via a pinch of salt or supplementation can help shuttle more water into the muscle cell. This is more of an issue if you are sweating a lot. If you have salt sensitive hypertension (high blood pressure), consult your Doctor first before adding salt. 

5) Break up your meals throughout the day

• Take your time on rest day. Sometimes athletes try to do longer fasting periods on rest day which can place stress on the GI system if the meal is too large or your body is simply not adapted to this habitual type of eating. So spread out those meals and let your digestive system take its time digesting those nutrients. 

Hope this helps! For any questions or comments regarding any of the above, please comment below or reach out to the E26 Team at support@element26.co.

 

Written by: Phil Gauthier 

Phil is a Doctor of Physical Therapy and Certified Strength and Conditioning Specialist.

He is also an Owner and Co-Founder of the performance gear company, Element 26 (E26).

E26 prides itself on developing functional gear for the functional athlete to help you "Destroy Your PR's, Not Your Body." 

To reach Phil or any member of the Element 26 Staff, please email us at: support@element26.co and we will respond to you ASAP!

References:

1. Hearris MA, Hammond KM, Fell JM, Morton JP. Regulation of Muscle Glycogen Metabolism during Exercise: Implications for Endurance Performance and Training Adaptations. Nutrients. 2018;10(3):298. Published 2018 Mar 2. doi:10.3390/nu10030298

2. Kraniou GN , Cameron-Smith D , Hargreaves M. Effect of short-term training on GLUT-4 mRNA and protein expression in human skeletal muscle. Exp Physiol 89: 559–563, 2004.

3. Kraniou GN , Cameron-Smith D , Hargreaves M. Acute exercise and GLUT4 expression in human skeletal muscle: influence of exercise intensity. J Appl Physiol 101: 934–937, 2006. 

4. Phillips SM, Tipton KD, Aarsland A, Wolf SE, Wolfe RR. Mixed muscle protein synthesis and breakdown after resistance exercise in humans. Am J Physiol Endocrinol Metab 273: E99–E107, 1997.
   
   
5. Witard, O. C., Bannock, L., & Tipton, K. D. (2022). Making Sense of Muscle Protein Synthesis: A Focus on Muscle Growth During Resistance Training, International Journal of Sport Nutrition and Exercise Metabolism, 32(1), 49-61. 

6. Biolo G, Maggi SP, Williams BD, Tipton KD, Wolfe RR. Increased rates of muscle protein turnover and amino acid transport after resistance exercise in humans. Am J Physiol Endocrinl Metab 268: E514–E520, 1995.

7. Biolo G, Tipton KD, Klein S, Wolfe RR. An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. Am J Physiol Endocrinol Metab 273: E122–E129, 1997.

8. Areta JL, Burke LM, Ross ML, Camera DM, West DW, Broad EM, Jeacocke NA, Moore DR, Stellingwerff T, Phillips SM, Hawley JA, Coffey VG. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J Physiol 591: 2319–2331, 2013. doi:10.1113/jphysiol.2012.244897.

9. Macnaughton LS, Wardle SL, Witard OC, McGlory C, Hamilton DL, Jeromson S, Lawrence CE, Wallis GA, Tipton KD. The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiol Rep 4: e12893, 2016. doi:10.14814/phy2.12893.
   
   
10. Burd NA, West DW, Moore DR, Atherton PJ, Staples AW, Prior T, Tang JE, Rennie MJ, Baker SK, Phillips SM. Enhanced amino acid sensitivity of myofibrillar protein synthesis persists for up to 24 h after resistance exercise in young men. J Nutr 141: 568–573, 2011. doi:10.3945/jn.110.135038.

11. Churchward-Venne TA, Burd NA, Phillips SM. Nutritional regulation of muscle protein synthesis with resistance exercise: strategies to enhance anabolism. Nutr Metab (Lond) 9: 40, 2012. doi:10.1186/1743-7075-9-40.

12. Evans GH, James LJ, Shirreffs SM, Maughan RJ. Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration. J Appl Physiol (1985). 2017 Apr 1;122(4):945-951. doi: 10.1152/japplphysiol.00745.2016. Epub 2017 Jan 26. PMID: 28126906.

13. Baker LB, Barnes KA, Anderson ML, Passe DH, Stofan JR. Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. J Sports Sci 34: 358–368, 2016. doi:10.1080/02640414.2015.1055291. 
    
    
14. Shirreffs SM, Taylor AJ, Leiper JB, Maughan RJ. Post-exercise rehydration in man: effects of volume consumed and drink sodium content. Med Sci Sports Exerc 28: 1260–1271, 1996. doi:10.1097/00005768-199610000-00009.

15. Evans GH, Shirreffs SM, Maughan RJ. Postexercise rehydration in man: the effects of osmolality and carbohydrate content of ingested drinks. Nutrition 25: 905–913, 2009. doi:10.1016/j.nut.2008.12.014.

16. Kraemer WJ, Ratamess NA, Hymer WC, Nindl BC, Fragala MS. Growth Hormone(s), Testosterone, Insulin-Like Growth Factors, and Cortisol: Roles and Integration for Cellular Development and Growth With Exercise. Front Endocrinol (Lausanne). 2020;11:33. Published 2020 Feb 25. doi:10.3389/fendo.2020.00033