Start fast, pay the price

nyone who has staggered through the final miles of a poorly paced race knows the painful price that starting too fast can exact. Your muscles are tired, your energy reserves are low, and your morale is sapped by the stream of savvier runners passing you. But there’s also a more subtle factor at work, according to a new study from researchers at the Norwegian University of Science and Technology: your running economy – the amount of energy it takes to maintain a given pace – takes a serious hit.

The study, which was published in the Journal of Strength and Conditioning Research, involved a group of world-class endurance athletes who first ran on a treadmill to tire themselves out, then were allowed to recover for varying amounts of time. When their blood lactate levels were at 5 mmol/L , corresponding to the fatigue you’d typically feel while running a little faster than threshold (or half-marathon) pace, the runners were 5.5 per cent less efficient than when their lactate levels had declined to 3 mmol/L .

During a race, you seldom have a chance to slow down enough to let your lactate levels drop after an overly aggressive start. That means you’ll run most of the race with elevated lactate (which doesn’t actually cause fatigue on its own, but rises and falls in synch with other metabolites that combine to generate the sensation of fatigue). The resulting 5.5-per cent efficiency penalty, the authors calculate, could correspond to a loss of 30 seconds in a 10-minute run, or more than eight minutes in a 2:30 marathon. The takeaway? The longer the race, the smarter you need to be about your early pacing.

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