Two Minute Tuesday: Using Fueling Requirements to Individualize Training

Welcome to our first Two Minute Tuesday, where each Tuesday we’ll take a quick look into one aspect of physiology and how it impacts training.

Athletes and coaches often talk about the need to individualize training programs based on an individual’s needs: their unique physiology along with their goal events.

One thing that’s often overlooked is the impact of fueling requirements, especially when comparing less powerful athletes to more powerful athletes. One-size-fits-all training isn’t ideal, and it’s even more risky when we base all our training zones as a percentage of FTP.

In our example today, we will use metrics from INSCYD to show carbohydrate combustion rate for two different athletes at 80% of their FTP. We’ve chosen this intensity because this represents the lower end of ‘tempo’ in the most commonly used training zones. Time limited athletes often think this is an ideal training intensity for endurance training when time limited, and it’s common to see athletes target 1.5-2 hour rides at this intensity. Here we illustrate how this can be acceptable for some athletes but problematic for others.

Carbohydrate usage at 80% of threshold for athlete with 350 watt threshold

Carbohydrate usage at 80% of FTP for athlete with threshold of 279 watts

Above, we can see that there are major differences in carbohydrate usage at this intensity level between our two athletes.

It’s important to realize that the top level of carbohydrate intake possible during endurance exercise is typically in the 90-100 grams of carbohydrate per hour range (irrespective of athlete size). So we can see that for the second rider, he can very nearly maintain glycogen stores while riding at this intensity. Meanwhile, our first rider will deplete his glycogen stores during a training session at this intensity even with perfect fueling.

The training session is very manageable in isolation for both athletes. However, within a training week a session like this could compromise the ability of our first athlete to do intensity training the next day. It also may become significantly harder after training that has led to depleted glycogen stores.

Meanwhile, our second athlete should be able to do this in the days before or after intense training, so long as he pays attention to fueling during the workout.

This simple example shows us that something as simple as a 2 hour training ride at 80% of threshold can have very different impacts on different athletes. This even applies to athletes of similar levels but different body types.