8 Underrated Body-Weight Exercises Personal Trainers Love

While most personal trainers will agree that training with weights is a surefire way to build muscle, they're not the only tools worth using. Your own body weight is more than enough resistance to strengthen your body from head to toe.

And just when you thought you'd exhausted the library of body-weight exercises, three personal trainers want you to give their favorite, most underrated equipment-free moves a try.

1. Start by standing tall with your feet at shoulder-width apart.
2. Explosively drive your right knee up toward your chest as you bring your left elbow forward.
3. Quickly switch sides, bringing your right foot down and driving your left knee up.
4. Alternate side as quickly as possible, using the momentum from your arms to drive your legs high.

"I like this movement and think it's pretty underrated because you choose how challenging it can be," Mathew Forzaglia, certified personal trainer, tells LIVESTRONG.com. "This can be done as a max-effort exercise or at a low to moderate intensity."

1. Lie on your back with your arms extended overhead and legs out straight.
2. Using your core, lift your head, shoulder blades and legs off the ground. Keep your biceps by your ears and actively press your lower back into the ground to ensure you're engaging your abs throughout the entire exercise.
3. Hold this position and remember to breathe.

Although the hollow body hold is becoming somewhat trendy, it's amazing for core strength and stability, K. Aleisha Fetters, CSCS, tells LIVESTRONG.com. Make sure to keep your breath consistent and steady.

1. Start standing with your feet hip-width apart.
2. Step a few feet forward with your left foot.
3. Lower into a lunge until both knees are bent to 90 degrees. Your back knee should hover just above the ground, and your front knee should be stacked over your ankle.
4. Hold for a beat before pushing through your front foot to step forward with your left leg.
5. Drop into another lunge with your left leg in front.
6. Continue this pattern as you walk forward.

Lunges are a single-leg exercise, which means they'll not only improve any muscle imbalances you may have between your left and right sides but they'll also fire up your core. Plus, you can easily make these more challenging by adding a pulse (a small bounce up and down at the bottom of the lunge), Carolina Araujo, certified personal trainer, tells LIVESTRONG.com.

1. Start by lying on your stomach with your hips rooted into the ground, arms extended out from your your chest like a T.
2. Squeeze your glutes and shoulder blades, lifting your quads and chest off the floor.
3. Hold this position for a few moments.
4. Slowly release back to the ground.

"I think these don't get much attention, and they're super important to balance out the body and improve posture," Forzaglia says. "Most body-weight workouts are heavily [front-of-body] focused, so we need to activate [the back of our bodies], too."

1. Stand tall with your feet hip-width apart.
2. Bend your knees slightly and push your hips back.
3. Lean your torso forward slightly so that your torso is at a 45-degree angle to the floor.
4. Bring your arms up parallel to the floor, thumbs facing up. This is the starting position.
5. Bring both arms up, biceps in line with the ears, forming an I shape.
6. Return to the starting position.
7. Bring your arms up to a 45-degree angle with your neck, forming a Y shape.
8. Return to the starting position.
9. Finally, raise your arms up straight out to the side, forming a T shape.
10. Lower to the start and repeat the sequence.

"The upper back needs a lot of love, and it's the most challenging area of the to hit with your body weight and zero gear," Fetters says. This exercise will do the trick.

1. Start in a high plank with your body in a straight line from head to hips to heels.
2. Squeezing your elbows close to your ribs, bend your elbows and lower your body until your chest hovers just above the floor.
3. Press into your palms and use your triceps to press back into the high plank.

1. Start standing with all your weight in your left leg and a soft bend in the knee.
2. Hinge at the hip and reach your arms forward, biceps in line with your ears. Drive your right heel straight back behind you.
3. Try as best as you can to create a straight line from your fingertips to your back heel.
4. Pause here for a few moments, then return to a standing position.

"These are extremely beneficial for everyone but especially runners," Forzaglia says. "Single-leg Romanian deadlifts build strength in the hamstrings and glutes but also improve stability in the ankles, knees and hips, promoting better balance."

1. Start standing, feet hip-width apart.
2. Extend your arms out in front of you and slowly bend your knees as you push your hips back to squat down. Focus on lowering your body as if you were going to sit on a chair.
3. Squat down until your thighs are parallel with the floor, or as low as you can go comfortably while maintaining good form. Your knees should be over your toes and your gaze should be straight ahead.
4. Pause for a moment at the bottom of your squat.
5. On an exhale, reverse the motion by pressing through your heels to return to standing. As you stand, lower your arms back to your sides.

Although body-weight squats have a reputation for being an easy exercise, they're rarely done with great form, Fetters says. "If you really dial in on them, they can be very challenging, and they are foundational to your overall fitness."