This exercise targets the abdominals using body weight alone.

Here's how: Lie on your back with your feet on the floor. Place your hands across your chest and lift your torso 30 degrees. Try to avoid straining your neck muscles when you lift yourself upwards. Hold for a second, then slowly lower your torso to the ground, stopping just before your shoulders touch the floor. Repeat 15 times.

Raised push-ups

This exercise targets chest muscles, using body weight as resistance.

Here's how: With your hands against the edge of a desk or table, raise your body until just before your elbows fully lock, then slowly lower your body to desk or table level. Repeat for 15 reps.

Get ready

Before you do these exercises, Mr. Orvis recommends warming up with 5 to 10 minutes of walking, then doing a few reps of the exercises you'll do that day.

"Always cool down afterward with 5 to 10 minutes of stretching," says Mr. Orvis.