Strengthening your core will help reduce your risk of several common running and walking injuries. Start with 1 set and gradually work up to 3 sets. Plan to do these twice a week on your cross training days. Warm up by walking for at least 5 minutes prior to doing these exercises.
Start on your hands & toes in a plank position. Hands should be a bit more than shoulder width apart. Engage your core by pulling your bellybutton towards your spine. Keeping your body straight, lower your body until you are about 4 inches from the ground and then raise it back up. Modified push-ups are done the same way but with your weight on your hands and knees. If you are not able to do these, consider doing push-ups with your hands on a raised surface like a chair or table.
Lift yourself off the ground with your weight on your forearms and toes. Engage your core and keep your body straight. The goal is to work up to at least a 30 second hold.
Stand with your feet shoulder width apart. Lower your body as if you are going to sit in a chair. Keep your weight on the heels of your feet. Arms can be in front of you for balance. Raise yourself back to standing and repeat. Once you have mastered squats, you can move on to doing single-leg squats which is done on one leg while the other leg is lifted off the ground.
Start on your hands and knees. Keeping your knee bent, lift one leg out to the side. Make sure you engage your core to keep your torso still and keep your arms fully extended. Slowly raise and lower your leg and then switch sides.
Lay on your side with your legs stacked. Your head can rest on your hand or arm. Engage your core to keep your torso still. Slowly raise and lower the top leg while keeping it straight.
Lay on your side with your leg stacked. Bring your knees forward so you have a slight bend at the hips and a 90-degree bend at the knees. Engage your core so you keep your pelvis still. Keeping your feet together, lift the top leg up and then slowly lower it. If this is too easy, use a resistance band around your knees to increase the resistance.
Lay on your back with your knees bent. Lift your pelvis until your knees form a straight line to your shoulders. Squeeze your glutes at the top of the bridge and then slowly lower pelvis back to the ground.The video shows how to do the glute (supine) bridge and how to progress to a single-leg bridge.
Take a big step with your right foot. Lower your left knee to the ground. Contract the muscles in your right leg to lift your body back to standing. Now step with the left foot and repeat. Contract your core to keep your pelvis stable and keep your torso upright. The website shows how to properly do a walking lunge and offers variations of the lunge.
Start on your hands and knees. Keep your back neutral (engage your core to keep it straight and stable). Slowly extend one leg until it is parallel with the floor. Slowly return to the starting position and then repeat. Once you can do these well, you can also extend the alternate arm at the same time.
Stand on one leg with the other leg in the air behind you. Keeping your back straight, and engaging your core, hinge forward and reach your hands toward the ground. Activate your glutes to return to the upright position and then repeat.