Start in pushup position with your arms straight and your hands gripping dumbbells. Lower your body to the floor to perform a pushup. Push yourself back up, then pull one dumbbell to the side of your chest. Pause, lower the dumbbell, and repeat on the other side. That's one rep.
Standing Cable Pullover
Stand in front of a lat pull-down machine, and grab the bar with an overhand grip with your hands slightly wider than shoulder-width apart. With your back and arms straight, pull the bar down in an arcing motion until it touches your thighs. Pause, then slowly reverse the movement to bring the bar back to its starting position.
Get your body into a press up position as if you are about to do a pushup. It should form a straight line from shoulders to ankles. Engage your core by sucking your belly button into your spine.
Hold a pair of dumbbells at arm's length next to your sides, with your palms facing each other. Raise your arms straight in front of you until they're parallel to the floor. Pause, then slowly lower the dumbbells back to starting position.