Training for a race? How to prime your muscles with carbs

July 17, 2017 in Leslie's Featured Content

Training for a race? How to prime your muscles with carbs

Athletes who are serious about their sport know that everything they eat counts.  Calories, carbohydrate, protein, fat and fluids are precisely measured and timed to give athletes a competitive edge.

That’s particularly true for athletes competing in triathlon, marathon, road cycling and race walking, endurance events that require the right fueling tactics to keep on going. One such tactic: carbohydrate-loading (carb-loading) to prepare muscles for sustained exercise.

The practice involves more than simply loading up on bagels and pasta, though. And if done effectively, the high-carb regime can boost performance by 2 to 5 per cent. 

Whether you’re a recreational half-marathoner or a competitive triathlete, properly topping up your carbohydrate stores will help you avoid hitting the “wall”.

Your body can store only enough glycogen, your muscle’s primary energy source, to fuel 90 minutes of exercise. Once that glycogen is used up, performance can suffer.

To sustain longer bouts of exercise, loading up on carbohydrates prior to race day saturates muscles with extra glycogen so you can run, bike or swim for longer.

Muscles can draw energy from body fat, but the process is less efficient than burning glycogen.  In other words, your body has to work harder to turn fat into muscle fuel. (Unless you train and eat differently, perhaps. More about that later.)

How to carb-load

Carbohydrate-loading typically starts two to three days before competition, although some athletes begin 24 hours prior to race time. 

The goal: to increase the proportion of carbohydrates in your diet while scaling back on exercise (tapering). Doing both allows muscles to tuck away more glycogen. Too much training will tap into the glycogen you’re trying to increase. 

The idea isn’t to eat more calories.  Instead, it’s about getting more of your daily calories from carbohydrate-rich foods and less of them from fat and protein.

A regular training diet for moderate exercise should contain 5 to 7 g of carbohydrate for every kilogram you weigh.  Intense training (one to three hours a day) boost carbohydrate needs to 10 g/kg body weight per day.

While carb-loading, carbohydrate intake increases to 10 to 12 g/kg per day (about 70 per cent of daily calories). For a 160 lb. (73 kg) triathlete, for example, that means eating 730 to 876 g of carbohydrate per day, two days prior to competition. 

If that sounds like a lot of carbs, it’s because it is. Consider than four cups of cooked pasta contain 155 g, one-fifth of a day’s worth.

For some people, it’s more palatable consume up to half of their daily carbohydrates from sports drinks and fruit juices. Keep in mind, though, that guzzling too much fruit juice (and eating too much fruit) may cause diarrhea.

Expect to gain weight while carb-loading. Your body stores three grams of water with every gram of muscle glycogen.  The extra water weight will be gone at the finish line, though.

Diet mistakes to avoid

Instead of eating three supersized meals piled high with carbs, eat five or six smaller meals to prevent feeling stuffed (and bloated). The day before the event, consider eating a bigger breakfast and lunch and lighter dinner to allow ample time for digestion.

Stay clear of foods high in fibre and fat, which slow digestion and fill you up faster. Too much fibre can also spell trouble on race day.

Avoid high protein meals, too. Eat smaller portions of meat, chicken and fish to accommodate the extra carbohydrate. 

Pulses such as black beans, chickpeas and lentils supply protein along with starchy carbohydrates. Don’t go overboard, though. Pulses are high in fibre; eating too many can cause digestive upset.

Forget the pre-race pasta dinner?

Not all experts agree that filling up on a big bowl of pasta the night before a race is the way to go. Some believe that sports performance depends on training your muscles to burn fat for energy.

A low carbohydrate diets prompt muscles to use fat, but it lacks the energy that’s needed to train hard. Enter what’s called a “sleep-low” sports diet, a regimen that skips carbohydrate at dinnertime (but not at breakfast or lunch).

According to a study published in Medicine & Science in Sports & Exercise (2016), compared to eating the traditional high carbohydrate dinner, a sleep-low diet enhanced triathlon performance and also reduced body fat.

The researchers tested the diet in 21 competitive male triathletes. Half of them ate a typical sports diet that included carbohydrate at each meal and after workouts. Those assigned to the sleep-low diet group consumed the same amount of carbohydrate each day but none of it at dinner.

For four consecutive days a week, for a three-week period, participants performed high intensity interval training in the afternoon designed to strip away muscle glycogen.

The next day before breakfast, the athletes completed a low intensity cycling workout. At this point, the those that didn’t eat carbs the night before were burning fat.

At the end of the study, the sleep-low group cycled stronger and ran faster than they did at the start of the study. They also lost 1.1 per cent body fat. The control group did not improve.

By manipulating the timing of carbohydrate intake in relation to exercise, the sleep-low protocol is thought to activate biochemical changes that allow muscles to adapt to burn fat for fuel.

Integrating this strategy into training requires starting a few weeks before an event and then tapering in the few days before, while loading up in carbohydrates.

Bottom line

You won’t benefit from carbohydrate-loading, or the sleep-low diet and training protocol, if you aren’t training for an endurance event. 

If you are, whichever method you choose to prime your muscles for prolonged exercise, practice well before you use it on race day.

All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.