This is the kind of training you need to improve your marathon endurance

At the 2012 Madrid Marathon, Spanish researchers tested 40 runners just before the race and again within minutes of finishing. The goal was to learn why so many marathon runners fade in the final miles. None of the usual suspects – low blood sugar, dehydration and so on – indicated which runners faded the most. Instead, the best gauge was muscle damage.

With each stride, your quads and calf muscles undergo ‘eccentric’ contractions: momentum forces the muscles to lengthen, even as you try to shorten them to push off again. This produces a steady accumulation of microscopic damage to the muscle fibres. This causes that next-day soreness after a marathon, but the study showed it can also hobble you during the race. Runners whose pace dropped by more than 15 per cent from the beginning to the end of the race had levels of creatine kinase and myoglobin – by-products of muscle damage – that were 53 and 112 per cent higher, respectively, than those who maintained a steadier pace.

It’s tempting to assume the faders simply didn’t train as much as the maintainers, 
but age, experience and training were not able to explain the differences. In research published this year, the study’s lead author, Juan Del Coso, and his colleagues showed that genes play a role in how susceptible you are to muscle damage. Still, he says, there are some measures that can help protect your leg muscles before a long race.

Go far

One benefit of a regular long run is that it generates the kind of damage you want to avoid in a race. Thanks to a phenomenon called the ‘repeated bout effect’, triggering muscle damage even once leaves those muscles less susceptible to damage the next time. But Del Coso believes you need to include at least one long run at close to marathon pace – and a half marathon isn’t long enough. Do a 30K (18.6-mile) run about four weeks before a marathon, or a long warm-up followed by a 13.1-mile run (or an extended cool-down after, if the logistics are easier).

Go heavy

Another way to build up your ability to tolerate eccentric muscle damage is with resistance training. Do lower-body strength exercises such as squats twice a week during your training cycle, cutting back to once a week during your taper. For maximum protection, Del Coso suggests including weights of at least 80 per cent of the heaviest load you can lift – but be sure that you’ve mastered the correct form before you attempt anything this heavy.

Go downhill

If you’re preparing for a long trail race, you’ll face distance and descents, which amplify the damaging effects of eccentric contractions. Levels of creatine kinase after the 103-mile Ultra Trail du Mont Blanc, for example, averaged more than 13,000 units per litre, compared with 564 in the ‘high damage’ group at the Madrid Marathon. In addition to resistance training, run plenty of downhills, simulating the gradient, distance and pace of the race to come. Experiment with your stride to find ways of descending as lightly as possible, perhaps by increasing your cadence.