The Best Multi-Joint Exercises...

The squat exercise is an effective exercise that works almost every muscle group. Your lower-body muscles and hip flexors work to bend and extend your hips and knees. Your core muscles contract to maintain spinal alignment. Stand with your feet slightly more than shoulder width apart, with your arms bent, palms forward, holding a barbell or pair of dumbbells on your shoulders. Begin the exercise by bending your hips and knees, lowering your body until your thighs are parallel to the floor. DO NOT allow your knees to extend past your toes! Think "butt out and down" as you complete the movement on the way down. Continue by contracting your thighs and buttocks to lift your body back up to the starting position. (Hint: Push down on your heels!) Contract your abdomen to avoid overarching your back. Complete three to four sets of 12 to 15 repetitions.

Deadlifts -- of which the barbell deadlift is only one of many variations -- are one of the most comprehensive compound exercises working the most muscles at once in a single movement. Stand with your feet hip-width apart under the bar. Squat and grasp the bar with your hands shoulder-width apart. Lift the barbell by straightening your legs. When you're fully standing with the barbell in your hands, pull your shoulders back. Return and then repeat until fatigued.

The bench press is one of the best core exercises for upper-body strength gains. The shoulder and elbow joints move to perform the chest press. The chest contracts to move the shoulder joint, and the triceps work to extend, or straighten, the elbow. Lie on a flat bench with your arms extended toward the ceiling, gripping a barbell or a pair of dumbbells. Begin the exercise by bending your elbows, lowering the weight to just above your chest. Continue the exercise by extending your arms back up to the starting position. Complete three to four sets of 10 to 12 repetitions. If using a barbell, be sure to have a spotter! (When you have mastered this, you can then add both the incline and decline bench press exercises using both the barbell and dumbbells.)

The shoulder press exercise strengthens your upper body muscles and core, which includes the abdominals and lower back muscles. Your shoulder muscles move your shoulder joint, and your triceps extend your elbows. Stand with your elbows bent and your palms facing forward, gripping a barbell or dumbbell in front of you at shoulder height. Begin the exercise by pressing the weight overhead toward the ceiling until your arms are fully extended. Hold, then slowly lower the weight back to the starting position. Contract your abdomen, using your core muscles to avoid arching your back! Complete three to four sets of 10 to 12 repetitions.