How should you pace yourself through a time trial or sportive?
Tearing off like a bat out of hell might get you a good time for the first few miles, but as the expenditure catches up with you, you’ll pay the price later.
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However, setting a leisurely pace that enables you to feel good right to the end might leave you wondering just how much faster you could have gone if you’d pushed harder earlier on.
There’s no one right answer to this question because the distance, terrain and wind conditions of an event all pay a part in determining the best pacing strategy. Now, two new studies suggest that something called ‘gross efficiency’ — basically how efficiently your muscles convert chemical energy released during aerobic exercise into forward motion on the bike — is also critical for determining your best pace.
In the first study, the researchers looked at whether gross efficiency (GE) changed after time trials of different distances. To do this, cyclists completed GE tests, consisting of sub-maximal exercise performed before and after time trials of different length: 500m, 1km, 2km, 4km, 15km, and 40km. What they found surprised them.
Previously a cyclist’s GE was thought to be constant, only changing gradually in response to weeks or months of training. However, the GE of the cyclists was significantly lower immediately after the time trials compared to before.
In the shorter time trials, the drop in GE was linear, while in the 40km time trial, it dropped linearly at first before stabilising later in the time trial.
Why does this matter? Well, a lower GE means that muscles become less efficient at producing energy aerobically, which (for a given pace) means that the proportion of energy produced anaerobically has to increase. But more anaerobic energy means more fatiguing by-products, which means that the original pace may no longer be sustainable over longer distances.
In a follow-up study, the proportion of anaerobic work was calculated in 18 trained competitive cyclists over four time trial distances: 500m, 1km, 2km, and 4km. The results showed that the rapid drop in GE over shorter distances meant that the cyclists were having to derive 30 per cent more energy from their anaerobic energy systems than had originally been calculated from pre-exercise measurements.
The bigger picture
What does this mean for cyclists seeking the best pacing strategy? Well, a steady drop in GE as distance covered increases means that a sustainable pace over, say, 2km will be even less sustainable over 10km than you might otherwise assume.
This is because fatiguing by-products will accumulate even more rapidly in the later stages of the distance as GE declines – i.e. in a non-linear way. However, once you’ve covered around 15km or so, your GE begins to stabilise, which means that if you can sustain a given pace at, say, the 10-mile mark, there’s a good chance you will be able to maintain the same pace for longer distances.
Applying the science
– For short time trial distances under 10km, the decline in GE is significant, which means you might get better results by slightly reducing your initial pace.
– Your heart rate is an excellent indicator of how anaerobic your pace is (when you start to accumulate significant levels of lactate, you’ll notice a sudden increase in heart rate). For this reason, heart-rate monitors provide better pacing feedback than speed or power meters.
– Regardless of time trial distance, in undulating conditions you should allow your effort to increase by up to 10 per cent on the uphill sections and drop a similar amount on the downhills, as research demonstrates this strategy is likely to produce a faster time (1). The same applies (to a lesser degree) in headwinds and tailwinds respectively (2).
Int J Sports Physiol Perform. 2014 Jun 6. [Epub ahead of print]
1. Int J Sports Med. 2011 Feb;32(2):132-6
2. Ergonomics. 2000 Oct;43(10):1449-60
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