Saturday, May 3, 2008

Lactate threshold

At Berkeley I was associated with both the Environmental Science program and the Department of Integrative Biology. IB was an interesting department that included ecologists, evolutionary biologists, biomechanics, sports physiologists and others. Inevitably you learn a bit about what other people in a department do and I remembered this study from a couple of years back that may become relevant to our class, our lab session on Monday, or just for general interest or edification. But first a bit of background....

As you may know we have two modes of energy use - aerobic and anaerobic. Over short distances or time periods we can perform (run, swim, cycle etc) at high rates for short periods of time but this involves the build up of lactic acid. Sooner or later this will limit your ability to perform anaerobically and you switch to aerobic mode. The bad news is that your aerobic capacity is largely inherited and training can only increase it by 10-15%. The good news is that this so called 'lactate threshold' which is the pace or work rate when lactic acid begins to accumulate can be improved quite dramatically by training. So if you do interval training or other types of training to improve your lactate threshold you are improving your ability to clear lactate and your ability to work at a high level for longer. If you run, then a 5k or 10k pace should be slightly above your lactate threshold. That's why pacing is so important in these shorter races because if you go out too fast you are way above your lactate threshold and will never clear it. The aim is to slowly accumulate a manageable amount of lactic acid by the end of the race, and because the race is relatively short you won't have it for long. In longer races (half marathon and above) you cannot afford to have any lactate accumulation.

Anyway, what I thought was interesting was that in 2006 George Barlow at Berkeley showed that the much demonized lactic acid is actually used as a fuel and isn't just a waste product. This doesn't really alter any training advice but it's interesting and just goes to show you should always question the things that 'everyone knows'.

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