Fuelling for Endurance Sport - A comprehensive guide

Part 1 - Training

Strategies to fuel for endurance training and competitions typically revolve around ensuring adequate carbohydrate (CHO) availability to support the demands of training and competitions (1). For exercise that lasts longer than 90 mins at submaximal intensity, or intermittent, high-intensity exercise of more than 90 mins, CHO availability is important as an energy source for the muscles and central nervous system (2). Endogenous carbohydrate stores within the body are finite, and can not fuel the demands of athletes desirably without replenishment (2). In an overly general sense, for most athletes, timing of CHO consumption shouldn’t matter. As long as total CHO and energy intake needs are being met, consumption can be used as fuel or to recover from training sessions, suiting the athletes individual eating preferences (3).

General recommendations of carbohydrate intake are below (2):

5-7g/kg/day for general athlete training demands, e.g. <1hr of low-moderate intensity training per day
7-10g/kg/day for increased endurance athlete training demands, e.g. 1-3hr of moderate-high intensity training per day.

For context, it’s a lot of carbs. Here’s the amount of carbs alone a 75kg athlete would need to consume to hit their daily goals (based on ~525g CHO per day):

2 Slices Helgas Multigrain Bread
1 Tablespoon Honey
2 x Bananas
200g Wheat Pasta
2 Cups Brown Rice
2 x Bagels
1 x Cup Orange Juice
1 x Blue Powerade
1 x Chobani Fit

It is suggested that the diet of the general population comprises around 55-65% of energy from CHO, whereas CHO should make up around 60-70% of total energy for endurance athletes (2). Where this can become a problem is when elite athletes have huge energy expenditures (think the Tour De France, or Crossfitters who may consume >4000-5000 kcals/day) and will have absolute CHO requirements of 650-900g/day, at 65-70% of their total diet. This number may be enough to exceed glycogen storage requirements and may be unnecessarily bulky or impractical for athletes to consume. In these cases, reducing CHO intake may be more practical. Another tip is to add around 20g protein when refuelling, which will not only aid muscle recovery but also enhance glycogen storage (3).

Part 2 - Pre-Event

Nutrition pre-event for endurance sport largely focuses on CHO consumption to maximise muscle glycogen storage in the days and hours leading into an event. It is suggested that for events of less than 90 mins, muscle glycogen stores can be maximised in a 24hr period when CHO consumption is around 7-12g/kg, and there is no muscle damage present, or the athlete is rested (3).

That means that the day before an event of <90mins, an athlete should be well rested and carb load with around 7-12g/kg of CHO. For events with a longer duration of >90mins, this carb load period should be increased to 36-48hrs pre-event. CHO consumption should also be at a higher amount of 10-12g/kg/day (3).

Want to know what ~700g of CHO looks like, to adequately fuel and carb load for a ~70kg person? It’s a s*** load of carbs.

This is by no means a meal plan, but an indication of the volume of food required to consume this amount of carbohydrates. You’ll also see some easy wins such as lollies and gatorade included, as these are simple ways to increase carbohydrate consumption without contributing significant volume and fibre to the diet.

Carbohydrate loading for a 70kg person based on 10g/kg/day:

Orange Juice - 1 cup
Chobani Greek Yogurt Lemon - 170g
Oats - 35g
Blueberries - 1 cup
Low Fat Milk - 2 cups
Honey - 1 Tablespoon
Helgas White Bread - 2 slices
Steamed vegetables - 1 cup
White Rice - 2 cups
Greenseas Tuna Salsa - 1 small can
Blue Powerade - 3 bottle
Weetbix - 3 Biscuits
1 potato
Rice Pudding - 113g
White Bagels - 2 bagels
Strawberry Jam - 2 tablespoons
Allen’s Snakes - 6 snakes

When looking at food consumption in the hours leading up to an event, the goals should be to continue to fuel muscle glycogen, top up liver glycogen, ensure blood glucose availability, prevent hunger, limit GI distress and ensure the athlete is in a good psychological state to perform.

A meal with 1-4g/kg of CHO should aim to be consumed around ~4hrs pre-event. At this point the food choices should be lower in fibre to aid digestion and limit the chance of GI distress. Around 4 hrs out some protein and fat may be consumed, but after this all protein and fat should be removed as they may increase GI distress. Typically the timing should dictate the food volume, with volume decreasing as the event draws nearer:

3-4h before event: Large meal
2-3h before event: Small meal
1-2h before event: Liquid meal/snack
<1h before event: Small snack

Lower GI foods may be slightly more beneficial as a pre-event fuel, when foods can not be consumed during the event.

Finally, pre-race nutrition is going to be influenced heavily by the preferences of the athlete, as it should be. Remember to practice new dietary approaches in training to ensure there are no unexpected hiccups on event day.

Part 3 - During Event

The good news for those of you who don’t like consuming anything during exercise is that for events lasting less than 60 minutes, there is no need to fuel during the event (4).

For events lasting longer than 60 minutes, carbohydrate (CHO) consumption is generally recommended to provide the body with accessible CHO. Typically, CHO consumption of around 30-60g per hour is recommended for events lasting 1-2.5 hours, and up to 90g per hour for events lasting longer than 2.5 hours (4). CHO absorption is more effective when CHO sources are mixed, such as combining glucose/fructose mixtures as opposed to consuming a single CHO source. This approach should also improve tolerance and decrease the risk of any dreaded runner's gut symptoms (4).

CHO mouth-rinsing is an interesting phenomenon that also shows promising evidence in aiding performance for endurance events (5). Mouth rinsing involves rinsing the mouth with a CHO solution for 5-10 seconds and then spitting the solution out. It may be beneficial for shorter events of less than 60 minutes or when gastrointestinal distress limits the opportunity to ingest CHO (5). It is important to note however, that for longer events the full ingestion of CHO is required (6). CHO solutions usually consist of approximately 6-8% glucose, similar to the ratio found in standard sports drinks such as Gatorade or Powerade. The mechanism explaining the benefit of mouth rinsing is not yet fully understood, but it is believed to be related to the activation of oral receptors and the stimulation of pleasure/reward brain areas (6).

Putting the above recommendations into practice could look something like the following on race day:

Event shorter than 60 minutes: 1-2 x Gatorade mouth rinses at the 30-minute and 45-minute marks
1-2.5 hour event: 1-3 sports gels per hour (or every 15-30 minutes), to equal 30-60g per hour of CHO
2.5 hour+ event: 2-3 sports gels per hour (or every 15-30 minutes), to equal 60-90g per hour of CHO

It’s incredibly important to remember that fuelling strategies are hugely dependent on individual preferences, particularly as they relate to an athlete's ability to tolerate the consumption of CHO during exercise. It is always recommended that athletes practice their fueling strategies during race/competition simulations, gradually increase food and fluid consumption, and even train their gut to tolerate higher amounts of carbohydrates over time.

Part 4 - Recovery

Endurance exercise can be intense, hard work on your body, and proper recovery nutrition is essential for replenishing energy stores, repairing muscles, and ensuring you're ready for your next workout (7). In this post, we'll deep dive on the key components of recovery nutrition, focusing on carbohydrates (CHO) and protein. We'll break down short-term and long-term recovery strategies and provide practical tips to help you bounce back after intense training sessions.

After a grueling endurance workout, your body is in a state of depletion. Muscle and liver glycogen stores are often exhausted, and your muscles need repair (7). Effective recovery strategies help you replenish these stores and facilitate muscle repair, positioning you to adapt to training and improve performance over time. Let's dive into the specifics.

Carbohydrates: Short-Term Recovery (Training Again Within 8 Hours)

When you're planning to train again within a short window (4-8 hours), there’s a couple of tools that can be used to give you the best chance at proper recovery (7-9). Here's what you need to know:

Evidence suggests that glycogen resynthesis is greatest in the first 1hr post-exercise, although this is less important for long-term recovery (7, 9). Get some CHO in ASAP!
Consume 1-1.2g/kg/hour of CHO for the first 4 hours after exercise. This helps maximize glycogen replenishment, ensuring your energy stores are ready for the next session (7-9).
Incorporate protein to aid in glycogen resynthesis and muscle repair. Particularly when your CHO intake is suboptimal, adding protein can enhance recovery (7, 8).
Opt for moderate to high GI foods. These foods are digested quickly, providing easier absorption and use of CHO than low GI foods (8, 9) .

Carbohydrates: Long-Term Recovery (8-24 Hours or More Between Sessions)

If you have a longer recovery period, the initial one-hour window is less critical, but maintaining a carbohydrate-rich diet is still essential (7):

Follow CHO loading principles, consuming 7-12g/kg/day of carbohydrates. Adjust based on the intensity of your training and your individual tolerance or needs (7).
Stick to endurance training nutrition guidelines for ongoing recovery. This ensures your body remains fueled for both training and everyday activities (7).

Protein: Essential for Muscle Recovery

While protein isn’t a primary source of energy during endurance exercise, it's vital for muscle remodelling and repair. Adequate protein intake supports muscle recovery and synthesis, helping you adapt to training stress (7, 8):

For short-term recovery, consume at least 0.25g/kg of high-quality protein immediately after training. This promotes muscle protein synthesis and aids recovery (7).
For long-term recovery, continue consuming at least 0.25g/kg every 3-4 hours. Immediate post-exercise consumption is less crucial if you meet your total daily protein needs (7).
Otherwise, aim for around 1.2-1.6g/kg/day of protein as per standard training protocols, depending on your training volume and individual circumstance (7, 8).

Practical Applications for Recovery: 70kg Athlete

Let's put these guidelines into practice for a 70kg athlete. Imagine you've completed a tough morning workout and have an easy 60-minute recovery run in the afternoon. Here's your recovery nutrition plan:

Carbohydrates: Consume 1-1.2g/kg (70-84g) of CHO per hour for the first 4 hours post-exercise.
Protein: Consume minimum 0.25g/kg (17.5g) of high-quality protein immediately after your morning session.

After these initial recovery steps, revert to your usual nutrition plan to ensure you stay fueled for your next workout and training plan.

An Analogy: Refueling Your Body Like a Bank Account

Think of your body's energy stores like a bank account. Imagine you get paid every Thursday night, so you spend your remaining savings on Thursday afternoon and indulge in some sweet retail therapy on a Friday morning after your pay lands. But what if the pay doesn't come in on Thursday night? You'd find yourself without funds on Friday morning.

Proper nutrition for recovery is just like this scenario. If you don't replenish your energy stores and provide fuel for adaptation (akin to not getting your pay), you'll be running on empty for your next workout. Over time, this lack of recovery can lead to poor performance, increased risk of injury, and slower progress.

Recovery nutrition is a vital part of any endurance athlete's routine. By focusing on carbohydrates and protein, you can effectively replenish glycogen stores, repair muscles, and prepare your body for the next training session. Whether you're facing a short recovery window or have more time to refuel, these strategies will help you get the most out of your workouts and support long-term performance improvements.

Remember, the athlete who recovers best is the one who adapts and improves the most. So, treat your recovery nutrition as seriously as your training sessions, and your performance will benefit.

References