Over the years I have had problems with my stride while running. When I run now, my left foot slaps against the ground after my heel makes contact.

Does anyone know what muscle controls this motion? What can I do to strengthen it?

Thanks.

Shin, calf and ankles. If you really concentrate effort into preventing the foot from slapping down, it will automatically work those muscles and get you into the habit of using better running form.

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Keep your body lean, your blood clean and your mind sharp. -Rollins

Are u sure u havnt jus got flat feet? It sounds odd to only have it in one foot, but u never know. =/

Do u walk around bare foot a lot? Or wear badly fittin shoes? There's other causes.... but im no doctor. =)

-Gaz