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- Alex Hutchinson (@sweatscience)
One of the most interesting developments in sports nutrition over the last few years is the “train low, compete high” concept — the idea that purposely doing some of your training when your glycogen stores (the main form in which your body stores carbohydrate for exercise) are low can boost your performance when you eventually compete fully loaded. An initial study in 2005 found that subjects doing half their training in the “low” state ended up with higher glycogen levels and longer time-to-exhaustion. But there were some questions about how well those results would translate to real-life — for example, whether trained athletes would experience same effects as the untrained volunteers in that experiment.
A new study [LINK FIXED] from Asker Jeukendrup’s group at the University of Birmingham, just posted online at Medicine & Science in Sports & Exercise, tackles some of these questions, with interesting results. The set-up was two groups of seven cyclists, training six days a week for three weeks. Both groups alternated 90-minute aerobic sessions with intense interval sessions of 8 x 5:00 with 1:00 rest. The control group did the sessions on alternate days, while the “low” group trained just three days a week, starting with the aerobic session to deplete glycogen, then doing the intervals an hour later without refuelling.
As hypothesized, the “low” group learned to burn more fat instead of carbohydrate — a physiological strategy that some experts think might allow your body to last longer before running out of glycogen. On the other hand, there was no difference in time-trial performance at the end of the study. You might think this means that the strategy was ineffective, but there’s an added wrinkle: not surprisingly, the “low” group managed a much feebler effort in their interval sessions (since they were so depleted), but still managed to improve by the same amount on the time trial. This means that the key variable in a training session isn’t how fast you go, but rather what stimulus signal you’re sending to convince your body to adapt.
In this regard [the authors write], we suggest that the additional “stress” of training with low glycogen compensates for a slight reduction in physical performance during training.
There was also a penalty to pay for the increased fat burning: the “low” group didn’t increase their carbohydrate-burning abilities as much as the control group:
This also suggests that training with low muscle glycogen may be counterproductive for athletes who compete in high intensity events where CHO oxidation plays a significant role in performance, and that this type of training may be more suited to preparation for ultra-endurance activities.
For now, it’s a case of “more studies needed” — although there’s no doubt that coaches and athletes are already experimenting with these ideas. It may be that trial and error will sort out some useful approaches before we really understand why they work.
[An unrelated note: I’m heading out on a hiking trip tomorrow morning, so I’m unlikely to be able to update the blog for the coming week. Next weekend, I’ll be watching the Sydney triathlon — the first stop on this year’s world championships series, and the first race on this course since Simon Whitfield’s immortal gold-medal performance in 2000. Can’t wait!]