Attend to your trunk
At foot strike, your spine firms up so that you can transfer forces effectively to the ground and propel yourself forward. It almost immediately relaxes enough to rotate a bit as your legs and pelvis go through the gait cycle.
Said another way, you need stability so that your spine is rigid at foot strike and mobility so that your pelvis and trunk can rotate as your legs are moving you forward.
Try braiding to the left for a minute, then to the right for a minute at the end of a run this week. We called it karaoke in high school for some reason; it’s also known at grapevine. Because we’re doing it for mobility, do it slowly with exaggerated arm swing. Big and slow!
Then drop down and do a prone plank for a minute! Although it’s a static exercise, it has a place in your stability routine.
Happy Running!