Don’t wait for a hamstring injury, avoid it by strengthening it. When you run, your hip-joint angle and knee-joint angle change simultaneously with each stride so the hamstring’s length doesn’t extend and contract much.

TRY THIS
Lie on your back with knees bent, feet flat on the floor and then lifting your hips up into a bridge while catching and throwing a medicine ball with a partner.
Make it tough
Once you’re in position, try and lift one foot off that ground. The aim is to maintain the exact same body position you were in previously (with the exception of one foot being raised off the ground).
Make it tougherTry raising and lowering your hips while keeping yourself balanced.

MAKE SURE to stretch afterwards, as strengthening your hamstrings can make them tighter after a workout. This is particularly important if your work requires you to be sitting in a desk chair for long periods as your hamstrings.