Forget about dehydration, glycogen depletion, overheating and all the other perils that marathoners worry about. When Spanish researchers ran a study at the Madrid Marathon a few years ago to see which factors would predict how much a runner would slow down in the final miles of the race, the most important contributor was muscle damage. Levels of creatine kinase and other markers of muscle damage that circulate in the blood were highest in the runners who hit the wall hardest.
The same researchers, led by Juan del Coso of Camilo José Cela University, have now published a further analysis in PLoS ONE showing that levels of muscle damage during a marathon are partly predicted by seven different gene variants. That led to some predictably overeager headlines, like Reader’s Digest ’s “Avid Runners Are Genetically Gifted to Feel Less Pain.” But the differences were actually quite subtle, with a “gene score” of 5.2 out of 14 for the runners with the least muscle damage versus 4. 4 in those with the most damage. And the finishing times and post-race soreness in the two groups weren’t significantly different.
The takeaway? Muscle damage in the legs, from the accumulated pounding of about 30,000 landings per marathon, is a significant problem for some runners. But don’t just blame your genes. Instead, make sure your training includes some long, hard runs – a marathon-pace 30k, like Hamilton’s classic Around the Bay race before a spring marathon, is ideal, del Coso says. And lower-body strength exercises such as weighted lunges and squats can also help damage-proof your muscles.
Alex Hutchinson is a senior editor and science columnist for Canadian Running. He’s considered one of the most respected sports science journalists in the world.