Your non-running days are quietly doing a lot of the work, so it's worth using them well. Two of them are for cross-training or strength, and they're where you build the resilience that keeps you running.
For cross-training, anything low-impact that gets you moving counts: an easy bike ride, a swim, a rowing session, or a brisk walk. The goal is gentle aerobic movement that supports your fitness without pounding your legs the way running does. If you enjoy pushing your aerobic base a little, our tips on how to increase your VO2 max at home offer some approachable options, though a relaxed spin or swim is more than enough.
Strength work is the other piece, and it matters more than many beginners realize. In addition to aerobic activity, the American Heart Association suggests adults include muscle-strengthening activities at least two days a week, and simple body-weight moves fit the bill perfectly. A short circuit of squats, lunges, glute bridges, planks, and calf raises, done once or twice a week, targets the muscles that stabilize your stride.
This isn't just about health in the abstract, either. Research on distance runners suggests that those who stick with a couple of strength sessions a week tend to complete their events at higher rates and pick up fewer minor injuries along the way, a pattern documented in a review of running injuries and prevention. No gym or heavy weights required, just your own body and a bit of floor space.