The shockingly simple math behind fueling your workouts

The basic equation for calculating calories burnt is as follows:

Calories = Watts * TimeInHours * 3.6 

The 3.6 at the end is just a way for us to convert units since there are 3600 seconds in an hour. But here's what this tells us: riding at 200w for one hour results in approximately 720kcal burnt. Where does this come from? 

Glycogen stores

Your body can store roughly 15g per kilogram of body weight in glycogen, which is simply glucose that your body stores in the liver and muscles. This means that a 70kg person (155lb) can store nearly 4200kcal worth of glycogen in their body. The liver can store roughly 400kcal of glycogen, and the rest is stored in the muscles. The glycogen in the muscles is unable to travel between muscles so your leg muscles can only use the glycogen stored in the legs. All this to say that we realistically only have roughly 1100-1500kcal of glycogen in our muscles that we can use to propel us forward - assuming our glycogen stores are full. This is why carb-loading helps athletes perform better - it tops up their glycogen stores.

Endurance Ride Example

Let's play out a scenario where you go out and do a 4 hour ride at 200w. This means you'll burn approximately 2900 calories. 

2900kcal burned - 1600kcal in our muscles + liver = 1300kcal deficit

With that 1300kcal deficit, we can calculate your hourly deficit: 

1300kcal / 4 hours = 325kcal/hr deficit

In order to overcome that 325kcal deficit, you'll need to provide your body with 81g of carbs per hour (1g of carbs is ~4kcal). This gets you back home without a calorie deficit but you'll also need to replenish the 1600kcal of glycogen that you used from your muscles and liver, so eat up when you get home! If you're able to consume even more while you ride, you will have less of your glycogen stores to refill. 100g of carbs per hour will fuel your ride and give you a 300kcal head start on refilling your glycogen stores for your next ride.

Hard Interval Ride Example

The math for a 1 hour hard ride (250w average) looks like this:

900kcal burned - 1600kcal in glycogen store = 700kcal surplus

While you could do this ride without consuming any calories, this still means that your glycogen stores are short 900kcal for your next workout. If you consumed 75g of carbs during this ride, you'd only need to replenish 600kcal before your next ride to be topped off. 

Conclusion

So, what does all this mean for you? By understanding your body's energy needs and fueling strategies, you can avoid the dreaded bonk and optimize your performance. Here's a quick recap:

• Fueling is crucial: Whether you're pushing through a long ride or hammering a hard interval session, proper fueling keeps your energy high and prevents your body from dipping into its limited glycogen reserves.
• Plan your intake: Calculate your estimated calorie burn based on intensity and duration. Aim to consume enough carbs during your activity to minimize the deficit and maintain energy levels.  Long efforts at low intensity and short efforts at high intensity both require high amounts of carbohydrates while exercising.
• Listen to your body: Experiment with different fueling strategies during training to find what works best for you. Don't wait until you're feeling sluggish to refuel.
• Refill after activity: Even if you fueled well during your workout, you'll still need to replenish your glycogen stores afterward. Focus on a balanced meal rich in carbs and protein to aid recovery.

Our recommendation: 1½-2 scoops of Monolith Endurance Mix per hour of activity. As you train your body to process more carbs per hour (which we'll discuss in another article), you should plan to take in 75-100 grams of carbs per hour to perform at your best and promote recovery so you can do it again tomorrow. 

By following these tips and understanding your individual needs, you can conquer any distance or intensity and reach your full potential!