Get on your hands and knees (hands directly below your shoulders, knees directly below your hips).
Keep your back straight (flat) throughout the exercise.
Slowly lift up your right leg backwards, and your left arm forwards (so they are parallel to the floor).
Hold for 5 seconds and relax.
Repeat with the opposite arm and leg.
Repeat the whole process 5 times.
Progress by holding it for longer each time, aim for 10 seconds.
Tips: You'll feel the pressure mainly in your lower back and bottom. Remember to focus on your core and keep balanced by working your abs too. Don't let your hips tilt to one side whilst moving your legs. Keep breathing steadily, never hold your breath.
Bird Dog Exercise Variation
Advanced Half Bird-Dog
This exercise is harder than the one above. It will show you how much your core muscles are involved, even when your arms and legs are doing most the work.
Get into the push-up position (arms straight), with a straight line from your shoulders to ankles.
Keep focused on your core muscles throughout.
Slightly lift your right arm for 2 seconds (weight is on your left arm and both feet), and relax.
Then slightly lift your left foot for 2 seconds (weight is on your right foot and both arms), and relax.
Repeat with your left arm and then right foot.
Progress by lifting each arm and leg higher and for longer, aim for 5 seconds each.
Tips: You'll feel the pressure mainly in your arms and legs. As you develop core strength, you'll find it easier to hold this exercise for longer, even though your arms and legs are taking most the weight. Keep breathing steadily, and never hold your breath.