I've found that for me running provides strong hamstrings but biking and weight training helps develop strong quads, providing balance and preventing injury. Find the steepest hill you can, hopefully off-road, and eventually build up to running 30 times up and down. The next year, we did plenty of hills, and did much better.
Weights are also excellent for the arms, too.
It is easier to keep form in a big race when you have been working your arms in the weight room. Many long-distance runners neglect the arms, to their detriment. I've found that for me running provides strong hamstrings but biking and weight training helps develop strong quads, providing balance and preventing injury. Find the steepest hill you can, hopefully off-road, and eventually build up to running 30 times up and down. The next year, we did plenty of hills, and did much better.