By Chris Carmichael
Coaching is a push-and-pull between tradition and innovation, between “If it ain’t broke, don’t fix it!” and “Newer is better!”. During my coaching career I’ve been on both sides of that divide, always seeking innovation but wary that innovations that sound good don’t always lead to improved performance. Training when you’re low on carbohydrate (CHO) is getting a lot of attention right now, so let’s take a look at what it means for you.
The idea behind “Train Low” is to deliberately go out for a training session when you have partially-depleted CHO stores, when you’re low on CHO energy. But there are questions athletes need answers to:
Why Train Low?
The reason most cited for this approach is to increase an athlete’s reliance on fat for fuel, thereby forcing the body to improve its ability to burn fat for fuel. If you can burn a higher percentage of fat at all intensity levels your CHO stores will last longer during rides and competitions. That means you’d have more high-octane fuel (CHO) for high-power efforts when it counts. Sounds great!
How to Train Low?
There are a lot of ways to reduce carbohydrate availability during exercise, but the two that are most common are starting a workout without replenished CHO stores or not consuming carbohydrate during prolonged workouts. The first scenario can be achieved by exercising first-thing in the morning (before breakfast) or training twice in a day without replenishing CHO between workouts.
What happens when you Train Low?
Your power outputs during interval workouts will decline. A number of studies (including Yeo et al., 2008) have reported about an 8% decrease in power outputs during high-intensity intervals (5minute maximal efforts). When it comes to endurance rides you always slow down as the ride gets longer. With low CHO availability you will slow down sooner and more substantially. Your perceived exertion will be higher. Essentially, the end of a 3hr low CHO ride will feel like – and your muscles will be in a similar condition to – the end of a 5hr high CHO ride.
This somewhat logical consequence of training with low CHO availability has led to the idea of Train Low/Race High and subsequently Train Low/Train High methods where you do lower-intensity endurance rides with low CHO and prepare to perform interval workouts or race with high CHO availability.
But does it work?
Yes and no. For instance, Yeo in 2008 found that despite the lower power outputs during high-intensity intervals in a low CHO state, subjects experienced improvement in whole body fat oxidation and resting muscle glycogen storage.
If you are going to Train Low studies (Akerstrom et al., 2009; De Bock et al., 2008) found that training without consuming CHO during workouts doesn’t enhance the adaptations we would normally see from those workouts. This suggests that a lack of CHO replenishment prior to a workout is a more effective way to Train Low than restricting CHO feedings during a workout.
The bigger problem is that while Train Low philosophy has positive impact at the cellular level it’s impact on real-world performance is less certain. In short, it improves performance for some athletes and not others, because in the real world you compete with your whole body and performance is also influenced by the cardiovascular, central nervous, and endocrine systems.
So, WHO is Train Low recommended for?
Intuitively, athletes think that the fittest riders are the ones that would benefit from new techniques like tweaking CHO availability. Pros who are already close to their maximum potential and are looking for tiny advantages can benefit from Train Low methods. In fact, they were doing it long before it was cool!
The other group that could benefit from Train Low is less obvious: time-crunched athletes. This group typically has 2-3 interval workouts a week and a longer weekend endurance ride. There may be some benefit – and no real harm – to completing this longer weekend ride before breakfast (low CHO availability) for a few weeks. Just know you won’t feel great, your perceived exertion will be higher, and you should take food with you (remember, low CHO stores seem to be more important than low blood sugar). I still recommend completing weekday interval workouts with high CHO availability, however. Experiment with one portion of your overall training plan and stick with proven workouts for the rest of it.
I don’t recommend Train Low for elite amateurs (Cat 1 and 2 in Elites and Masters). It’s not because it won’t work, but rather because it introduces a lot of risk. They already have a very high workload and train 5-6 times a week. There isn’t a lot of room for error and they haven’t reached the point where all the fundamental aspects of performance are already optimized (like the pros). Time-crunched athletes can get away with it because their training load and workout frequency are lower so they can better absorb and recover from the mistake. When elite amateurs make mistakes with how and when Train Low methods are utilized, it often does more damage and is harder to recover from.