Most personal training clients arrive at the gym bright-eyed and full of energy, ready to start their day with a powerful strength-training session. However, some clients show up for training after an extended run or bike ride. In these cases, clients have used up a good amount of their bodies’ glycogen stores. As a result, unless these stores are properly refueled between training sessions, the resistance workout will suffer greatly. In this article, we discuss fueling strategies for double training days, focusing not only on timing but also on appropriate macronutrient intake, including how to pair protein with the right carbohydrates to ensure maximal energy availability for both workouts.
Understanding Glycogen Resynthesis
When you have double workouts in a single day, restoring muscle glycogen stores properly requires careful advance planning. Fueling for double workout days matters because the gap between sessions can fluctuate and serves as one’s only chance to rebuild the glycogen burned during the first workout. On a normal single-training day, an athlete has a full 24 hours to refill glycogen, so timing matters less. However, on a double-training day, the time between workouts may leave only 6 hours or less, which makes refueling the single most important factor in the efficacy of the second training session. The shorter the gap between the 2 training sessions, the more the between-session fueling matters.
During the first workout of the day, the body draws upon stored glycogen reserves. The refueling that follows must replace the energy already used; otherwise, the athlete will feel weak and perhaps light-headed or shaky relatively soon into the second workout. Some individuals mistakenly see this as a fitness-related problem, when in fact it almost always relates to a lack of proper refueling.
The Event Determines the Rate of Glycogen Loss
During intense, intermittent exercise, as on double training days, the body breaks down muscle glycogen. The freed glucose molecules are then oxidized by muscle cells through anaerobic and aerobic processes to produce adenosine triphosphate (ATP), which is essential for muscle contraction.
The rate at which muscle glycogen breaks down depends primarily upon the intensity of physical activity: the greater the exercise intensity, the faster the degradation. High-intensity activity, such as repeated bouts of wind sprints, lowers glycogen stores faster and in a shorter time, while an endurance athlete who trains for hours has a slower rate of breakdown. The end result remains the same: a marked decrease in available muscle glycogen.
How the Body Reacts to Double Training
In addition to merely depleting glycogen stores, “2-a-day” places a strain upon the body in ways similar to an intense workout, but often at more than double the toll. Fluids and electrolytes get quickly depleted, particularly on hot, humid days. For trail runners and cyclists, micro-damage to muscle tissue increases as well. Imagine a double-training day of eccentric riding/running and downhill on rough terrain, and you begin to understand the importance of fueling properly between events.
On the flip side, double-training regimens offer clear advantages. Some athletes support the practice, citing opportunities to increase training volume, improve the quality of each workout, and boost metabolism. Consider the following aspects of training twice in a 24-hour period:
- Makes each workout better: If an athlete attempts to run 12 miles all at once, the last few miles will probably end up with poor technique due to fatigue. This, in turn, often leads to injuries. If this process gets replaced by a longer run in the morning and a shorter workout in the evening, the second run will feel stronger with fresher legs, better technique, and perhaps occur at a faster pace.
- Mitochondrial adaptation: Training twice in the same day signals the muscles to boost the production of mitochondria – the cells’ powerhouse — thereby improving the body’s ability to burn fat and store glycogen.
- Allows for easier time management: For athletes with already busy schedules and family commitments, breaking up the day’s workouts into two shorter time slots often seems easier to fit into the day than committing to one very long session.
The 2-Phase Windows of Glycogen Replenishing
Glycogen synthesis after exercise takes place in two distinct phases. The so-called “rapid phase”, occurring anywhere from immediately post-workout up to 90 minutes later, reflects the time frame during which the permeability of muscle cell membranes to glucose increases dramatically. Carbohydrates consumed during this window get packed into the glycogen stores with the highest efficiency. The “slow phase”, lasting from the endpoint of the rapid phase until 12-24 hours later, describes the time when the body settles into a more gradual glycogen replenishment pace.
Research done by sports nutrition scientists reveals that in order to maximize the rate of glycogen resynthesis after endurance training depletion, experts recommend ingesting 1.0-1.2 grams of carbohydrates per kilogram of body weight per hour for the first 4 hours post-exercise. Athletes should try to consume this in smaller, more frequent snacks rather than one large meal. Delaying this consumption by even 2 hours may potentially cut the rate of muscle glycogen storage from 7.7 down to 2.5 units per hour, a drop of ~ 66%.
For one reason or another, many athletes have adopted either a low-grain or gluten-free approach to eating. These meal plans can still offer ample carb sources, sufficient to meet even the most ardent recovery and glycogen resynthesis needs. Below are some healthy post-exercise ideas that easily fit into a gluten-free lifestyle.
- Smoothie
- 1 banana
- 1 cup mix of pineapple and mango chunks
- 1/2 cup coconut water
Total: ~56 g carbs
- Electrolyte Recovery Drink
- 1 cup orange juice
- 1/4 tsp salt
- 1 tbsp honey
- 1 cup water
Total: ~42 g carbs
- Dried Fruit/Nut Trail Mix
- 1/4 cup dried apricots
- 2 tbsp raisins or craisins
- 1 tbsp almond butter
Total: ~38 g carbs
- Rice Cakes with Nut Butter/ Honey
- 2 plain rice cakes
- 1 tbsp peanut, almond, cashew or sunflower seed butter
- 1 tsp honey
Total: ~36 g carbs
- Mashed Sweet Potato Treat
- 1 medium sweet potato
- 1 tsp maple syrup
- 1 tbsp nut butter of choice
Total: ~31 g carbs
When rapid resynthesis of muscle glycogen must drive an athlete’s recovery fuel, such as during 2-a-day training with a short window between sessions, or competitions requiring multiple games/matches during a single day, athletes should focus on consuming foods with a higher glycemic index.
Knowing When to Incorporate Protein with Between-Training Carbohydrates
Not all double-training days involve 2 distinct cardiovascular sessions. Athletes often split their training into a morning run and a strength workout later in the day. In this instance, protein serves a vital role as recovery fuel for two reasons:
- Protein intake supports the muscle repair from the first training session
- Protein helps rebuild glycogen when the athlete, for whatever reason, finds it challenging to meet the full recovery carbohydrate intake (consuming less than 0.8 grams per kilogram of body weight per hour)
When clients come to personal trainers with questions about this topic, we can help them understand that while the top priority remains refueling with enough carbohydrates, protein is a helpful add-on. A ratio of roughly 3 or 4 grams of carbohydrate to 1 gram of protein typically works very well.
Here we offer some easy-to-prepare meal options for refueling between morning cardio and afternoon resistance training:
- Gluten-Free Rice Bowl
Ingredients:
- 1 cup cooked jasmine or other fragrant rice
- 1/4 avocado
- 1 small grilled chicken breast
Total: ~45 g carbs, 20 g protein
- Scrambled Eggs with Yams
Ingredients:
- 2 eggs
- 1 cup diced, cooked yams or sweet potatoes
- 1 tsp olive or sesame oil
Total: ~30 g carbs, 12 g protein
Creatine and the Transport of Glucose
Personal trainers and serious bodybuilders often rely on creatine supplementation to enhance adaptations to resistance training. In addition, adding creatine to one’s training protocol may have a positive effect on muscle storage in the days following glycogen-depleting exercises like double training days.
Creatine does this by increasing the abundance of a glucose transporter called GLUT4, which in turn facilitates greater glucose uptake into muscle cells. It may also help reduce post-exercise inflammation; exercise-induced muscle damage (EIMD) can impede muscle glycogen replenishment for up to 10 days after the incident.
Creatine can increase intracellular fluid volume by virtue of its inherent osmolarity. This benefits the body because scientists have identified cellular swelling as a potent stimulus for muscle glycogen synthesis. Although this benefit to glycogen storage may be slow, over a 5-day period it does not appear to have any effect within the 6-hour window immediately after exercise cessation.
One study found that a moderate carbohydrate intake after creatine loading could increase muscle glycogen stores by 53% compared with a high-carbohydrate diet alone, supporting the role of creatine in enhancing glycogen storage. The exact mechanism behind this remains unclear, but further studies may help clarify it. As an interesting aside, an individual’s training status may influence creatine’s efficacy regarding glycogen storage. Advanced athletes might experience less benefit than untrained individuals, since years of training have already optimized glycogen resynthesis after exercise.
Beyond Carbohydrates and Protein
Most data on double-training nutrition focuses on refueling with carbs and protein. While of course essential, coaches often fail to remind their athletes of other areas that demand attention in order to avoid undue fatigue and diminished output, namely the consumption of healthy fats, adequate sleep, and the manner in which overtraining diminishes the immune system.
Depending on the sport, some athletes eat very little fat, mostly to control weight. The end result? The hormones that support recovery and sleep don’t function properly. Healthy fat sources from nuts, avocado, olive oil, and fatty fish do not need to dominate recovery meals. However, because of their many benefits, athletes can feel comfortable including them in other meals throughout the day.
Sleep architecture may come in as a close second to fuel when discussing recovery from arduous exercise. Refueling for glycogen resynthesis may earn an A, but sleeping less than 5 hours a night will cut recovery efforts to a C- or D at best. A significant amount of slow-phase glycogen replenishment and muscle repair occurs while we sleep. Supporting one aspect of training while tearing another part down will not benefit the athlete, especially when working out twice a day. Coaches caution athletes not to schedule evening sessions too late in the day to avoid interfering with their regular circadian sleep cycle.
Excessively high training volumes day after day tend to suppress the body’s natural immunity. Consuming enough carbohydrates, distributing protein appropriately, and getting quality sleep will always be the best and most practical immune defense.
Biological Hunger versus Mechanical Refueling
Many athletes use 2-a-day training as a safe, efficient way to increase training volume. This energy output requires more refueling, as we discussed. Yet how that ties in with natural hunger cues may throw a wrench in an athlete’s plans.
While trainers and coaches might naturally encourage their athletes to trust and respond to what will probably amount to increased hunger cues, some individuals experience a decided drop in appetite or what they perceive as a delayed sense of hunger following a tough training session…let alone 2 in a single 24-hour period. While these individuals certainly need more calories on days of double workouts, whether cardio or strength training, they may not inherently crave additional fuel or even feel the need for it.
When this scenario does present itself, coaches may need to remind their athletes to rely on what they call “practical cues”, those which originate in the logical part of the brain. Paying attention to this logic will help them remain adequately fed and maintain sufficient glycogen synthesis. Trusting both biological and practical hunger cues takes time to cultivate, but ultimately it will serve athletes well.
When an athlete works out twice a day, refueling takes on a whole new level of importance. Whether one chooses to replenish glycogen stores with supplements, energy-packed shakes, or carefully crafted meals, the nutrition consumed in between workouts holds the power to take the athlete to new heights of strength and endurance. Personal trainers and coaches can help clients achieve their goals by explaining how proper nutrition can work to their advantage and keep them going strong.
References
pmc.ncbi.nlm.nih.gov/articles/PMC3905295/
runlovers.it/en/2025/training-twice-day-double-sessions/
ctyeh.com/articles/13536?lang=en
pmc.ncbi.nlm.nih.gov/articles/PMC6019055/
pubmed.ncbi.nlm.nih.gov/10444618/
pmc.ncbi.nlm.nih.gov/articles/PMC12297025/
jsperformancelab.com/blog/the-science-of-muscle-glycogen-replenishment-for-endurance-athletes
runnersconnect.net/running-questions/fueling-properly-for-double-workout-days/
