Strained hamstrings with weak hamstrings. To be effective, strength training needs to be done every other day. The above listed exercises will take a maximum of 10 minutes. Not much to ask of yourself if you want to add that little something to your running, and help you keep injury free. As we get older our bones lose minerals.
Runners lose less in their legs than others.
But they lose it up top. You will increase the mineral density of your upper body.