These three arm exercises have two things in common: They all start with a push-up, and they all guarantee total-body toning

If there were ever a multitasking move, it would be the push-up. If you think it's just an arm exercise, think again: not only does it work your shoulders and triceps, but it will also tone your back, chest, and-if you do it correctly-your abs. (It's why they're one of the Best Exercises for Women.) And since you don't need any equipment, no place is off-limits. Now, drop and give us 20! Just kidding. Instead, let's try a few variations that will hone your form and build up to a total-body toning experience.

Start with a Half Push-Up-from a modified push-up position with knees on the ground and hands directly under shoulders, slowly lower your chest towards the ground. Push back up to starting position and repeat. Continue for 30 seconds, then take a 15-second rest. The get back at it-you've got two more rounds to complete.

Once you've nailed that variation, move on to the Push-Up Shuffle. Start in a plank position, hands directly under shoulders. As you lower into a push-up, reach the right hand sideways, so arms are wider-apart when your body nears the ground. As you push back up to starting position, bring the hand back to center. Repeat on the opposite side, then continue alternating.

Bring your leg muscles into the move with Spider Push-Ups. Start in a plank position, hands directly under shoulders. As you lower your body, try to touch your right knee to your right elbow. Reverse the movement while pushing your body back to the starting position. Repeat on the opposite side, then continue alternative.

Watch Seattle-based trainer Jennifer Forrester as she walks through the moves above. Her secret to that rock solid form? Never stop engaging your core! (Next up, we dare you to try our 30-Day Push-Up Challenge!)