Start marching in forearm plank position. The basic marching plank will challenge your core more thoroughly than the traditional plank, while also working your lower back, shoulders, and glutes.
Get into the forearm plank position so that only your forearms and your toes are touching the floor.
Lift your right foot off the floor, taking care not to shift your body weight at all as you do so. Lower your right foot back to the floor and lift your left foot. Lower your left foot back to plank. This is one repetition. Do 5 to 10 repetitions, breathing deeply and maintaining a solid plank.