Bad Form: Arching your back will end up loading your lower back instead of your buttocks.
Good Form: Bend your knees to form a 90° from the floor, and raise your pelvis up without arching your back. You'll also need to contract your abs and squeeze your buttocks while holding this position.
Bad Form: If you bend your knees at an acute angle and lean too far forward, your knees and spine will become overloaded.
Good Form: Don't raise your pelvis, and keep your back flat. Keep your knees bent at right angles while performing squats.
Bad Form: Not keeping your back straight will negate many of a plank's benefits.
Good Form: Keep your whole body in a straight line, with your arms at right angles. You also shouldn't bend your neck.
Bad Form: You can hurt your back badly if you let your knees go beyond your toes. This is because you'll end up rounding your back and laying the barbell on your neck, which shifts all of your weight to your toes.
Good Form: Ensure that the barbell is in line with the center of your feet. Don't lift your heels off the floor and make sure you arch your back. Never squat deeper than necessary, and make sure to keep your thighs parallel to the ground.
Bad Form: Standing too far away from the platform will put too much pressure on your knees.
Good Form: Squeeze your shoulder blades together and straighten your back. Then, slightly arch your back and move closer to the platform, keeping your knee in line with your foot.
Bad Form: Keeping your knee twisted could end up inflicting some nasty physical trauma.
Good Form: Keep your knee in line with your foot and bend it at a right angle when moving forwards.
Bad Form: Rounding your shoulders and back is just asking for an injury. You also won't be able to squat deep enough in this position.
Good Form: Straighten up and pull your shoulders back. Then, squat low enough so that your thighs are parallel to the ground.
Bad Form: If you raise your head, you'll end up arching your back involuntarily.
Good Form: Ensure that your body is entirely straight from top to bottom.
Bad Form: Gripping the dumbbell from its handle will load your joints instead of your muscles.
Good Form: Hold the dumbbell in both hands with your palms facing the ceiling. Keeping your shoulders steady, press your elbows as close to your head as possible. Then, just raise the dumbbell over your head, before lowering it gently back down.
Bad Form: Keeping your feet halfway or mostly on the platform, and not aligning them with your shoulders.
Good Form: Keep just a third of your feet on the platform, making sure that they're in line with your shoulders. Then, lift your heels as high as possible, and hold for a few seconds. Finally, lower your heels gently until they're slightly below the platform.