This move will simulate an effective kickboxing guard and powerful arm strikes. Start in a high plank position with your feet together or hip width apart. Keep your shoulders stacked above your hands, and begin to lower yourself with control to the bottom of your Push Up. Make sure you keep your elbows tucked into your side, keeping your core tight. Return to high plank, then add your reach. Reach one arm out in front of you, extending your arm fully to engage your back and arm muscles, then return to high plank. Push Up, and switch arms. Your core and shoulders should remain engaged and level with each Push Up and plank, keeping your elbows from swinging out. Use your full range of motion to reach as far as you can into a deep Push Up.