It’s important to take breaks from running, even while training. This can reduce risks of overuse and, ultimately, injury. Corkum suggests continuing aerobic exercises, like swimming, cycling, or rowing. These activities give the body a break from the motion of running, she explains, while continuing to elevate the heart rate and strengthen the lungs. For those who don’t have access to gym equipment or cardio machines, she recommends going for a walk. 

“Not all runners need aerobic cross-training,” she says, “but every runner should be doing some sort of strength training, yoga, or stretching practice to keep the body balanced and strong head to toe.”

https://www.mindbodygreen.com/articles/how-to-train-for-a-5k