Is there any benefit to deliberately training with low energy stores?
One of the hottest controversies in current sports nutrition was sparked by an unusual Danish study published in 2005. Volunteers performed a 10-week training program in which they exercised one leg every day and exercised the other leg twice as much every second day. That meant that the leg trained every other day did half of its workouts in a highly fatigued state, having been depleted of glycogen by the first half of the workout. By the end of the study, this leg had developed significantly greater endurance, giving rise to a new concept that was soon dubbed “train low, compete high,” in which athletes seek to do part of their training when their energy stores are greatly depleted (“training low”) so that they’ll perform even better when they’re fully fueled (“competing high”).
There’s no doubt that having full carbohydrate stores improves your endurance. In fact, that’s the point: “training low” is the nutritional equivalent of wearing a weighted vest to make your workout harder. There have long been rumors that athletes like Miguel Indurain, the five-time tour de France champion, tried this approach by doing some of his training in a fasted state. But there’s been little evidence that it actually works: even the Danish study had several flaws – notably that the subjects were untrained, which makes it much easier to observe improvements in the performance, and that “single-leg kicking” isn’t an activity that has any particular relevance to the real world.
Several recent studies have tried similar protocols with trained cyclists, and they’ve found that training low really does stimulate the body to adapt differently – but it doesn’t seem to produce any actual performance benefits. For example, a 2010 study at the University of Birmingham used highly invasive muscle biopsies and isotope tracers to measure the different muscular and metabolic changes produced by training high and training low. As expected, they found that training low taught the body to burn more fat instead of carbohydrate, which should theoretically improve endurance performance by allowing carbohydrate stores to last longer before running out. But in a one-hour time trial, there was no difference between the two groups.
This apparent contradiction is similar to discussions of the “fat-burning zone” for weight loss. In both cases, researchers have figured out how to make the body rely more on fat instead of carbohydrate – but you don’t lose more weight or bike faster, because the body seems to compensate for the change. In fact, there’s some evidence that in increasing your fat-burning abilities, you also harm your carbohydrate-burning capacity. It’s tempting to believe that this doesn’t matter in ultra-endurance events like marathons or 100-mile bike races, where fat-burning plays a major role. “However,” Australian institute of Sport nutritionist Louise Burke pointed out in a 2007 commentary, “the strategic activities that occur in such sports – the breakaway, the surge during an uphill stage, or the sprint to the finish line – are all dependent on an athlete’s ability to work at high intensities that are carbohydrate-dependent. “
`In practice, there are two approaches to training in a carbohydrate-depleted state. One is the approach used in the studies described above: deplete your muscle glycogen stores with 30 to 60 minutes of moderate exercise at about 70 percent of maximum effort. Then, without refueling, do some harder training. Alternatively, you can try working out first thing in the morning without eating anything first, possibly having eaten a low-carbohydrate dinner the night before, so that your whole body is low on glycogen. Both these strategies can be very stressful for the body and shouldn’t be attempted more than once or twice a week. Recovery afterwards is crucial, including lots of carbohydrates.
At this stag, although “train low, compete high” has become a popular buzz-phrase, the research remains highly uncertain. For most people, the best bet is to let others do the risky and often unpleasant experimentation – then, if it does turn out to provide measureable performance benefits, give it a try once the details have been workout out.