Squats

In strength training and fitness, the squat is a compound, full body exercise that trains primarily the muscles of the thighs, hips and buttocks, quadriceps, hamstrings, as well as strengthening the bones, ligaments and insertion of the tendons throughout the lower body. Squats are considered a vital exercise for increasing the strength and size of the legs and buttocks, as well as developing core strength.

Isometrically, the lower back, the upper back, the abdominal, the trunk muscles, the costal muscles, and the shoulders and arms are all essential to the exercise and thus are trained when squatting with the proper form.

Form

The movement begins from a standing position. Weights are often used, either in the hand or as a bar braced across the trapezius muscle or rear deltoid muscle in the upper back. The movement is initiated by moving the hips back and bending the knees and hips to lower the torso and accompanying weight, then returning to the upright position.

General Squat form guidelines:
Stance - Squat with your heels shoulder-width apart. Put your heels under your shoulders.
Feet - Turn your feet out 30°. Keep your whole foot flat on the floor. Don’t raise your toes or heels.
Knees - Push your knees to the side, in the direction of your feet. Lock your knees at the top of each rep.
Hips - Bend your hips and knees at the same time. Move your hips back and down while pushing your knees out.
 Lower Back - Squat with a natural arch like when you stand. No rounding or excess arching. Keep your back neutral.
Grip - Squeeze the bar hard. Let your upper-back carry the bar.
Grip Width - Your hands should be outside your shoulders.
Bar Position - Put the bar between your traps and rear shoulders (low bar) or on your traps (high bar). Center the bar.
Upper back - Arch your upper-back to create support for the bar. Squeeze your shoulder-blades and raise your chest.
Chest - Raise your chest before you unrack the bar. Keep it up and tight by taking a big breath before you Squat down.
Head - Keep your head in line with your torso. Don’t look at the ceiling or at your feet. Don’t turn your head sideways.
Back Angle - Not vertical or horizontal but diagonal. The exact back angle depends on your build and bar position.
Way Down - Bend your hips and knees at the same time. Hips back, knees out. Keep your lower back neutral.
Depth - Squat down until your hips are lower than your knees.
Way Up - Move your hips straight up. Keep your knees out, your chest up and your head neutral.
Bar Path - Move the bar in a vertical line over your mid-foot. No horizontal movement.
Breathing - Big breath at the top. Hold it at the bottom. Exhale at the top.

Squat variants

Back squat – Bar is held on the back of the body at the base of the neck or lower across the upper back. In powerlifting the barbell is often held in a lower position in order to create a lever advantage, while in weightlifting it is often held in a higher position which produces a posture closer to that of the clean and jerk. These variations are called low bar (or powerlifting squat) and high bar (or olympic squat).

Sumo squat - The barbell is rested on the shoulders in the usual squat position. The legs should be slightly wider than shoulder width apart and the feet should be pointed outwards. when squatting, you should feel a stretch on the adductor longues and adductor magnus muscles which are found on the inner thigh.

Box squat – At the bottom of the motion the squatter will sit down on a bench or other type of support then rise again. The box squat is commonly utilized by power lifters to train the squat. Pausing on the box creates additional stimulus in the hips and gluts. Some people believe this form of isometric training allows for greater gains in the squat compared to a traditional Olympic style squat, while others contend that the increased spinal loading creates more opportunity for injury.

Front squat – Weight is held in front of the body across the clavicles and deltoids in either a clean grip, as is used in weightlifting, or with the arms crossed and hands placed on top of the barbell.

Hack squat – Barbell is held in the hands just behind the legs. It is also called a "rear deadlift".

a) Hack squat with barbell

b) Hack squat with machine 

Overhead squat – Barbell is held overhead in a wide-arm snatch grip. However, it is also possible to use a closer grip if balance allows.

Zercher squat – Barbell is held in the crooks of the arms, on the inside of the elbow.

Goblet squat – Squat performed while holding a kettlebell next to chest and abdomen with both hands.

Sissy squat – Squat with several sorts (dumbbell, weight plate, Smith machine, barbell, bodyweight). In the most common variant, a dumbbell is held behind the legs while the heels are lifted off the ground and the torso remains flat while the lifter leans backwards. Sometimes done with a plate held on the chest and one arm holding onto a chair or beam for support.

Face the wall squat – Performed with or without weights. It is primarily to strengthen the vertebrae tissues. Toes, knees and nose line up almost touching the wall.

Hindu squat – Done without weight where the heels are raised and body weight is placed on the toes. The knees track far past the toes.

Jump squat – Plyometric exercise where the squatter engages in a rapid eccentric contraction and jumps forcefully off the floor at the top of the range of motion.

Pistol squat – Body weight single leg squat done to full depth, while the other leg is extended off the floor. Sometimes dumbbells, kettlebells or medicine balls are added for resistance.

Shrimp squat - Also called the flamingo squat, a version of the pistols squat where instead of extending the non-working leg out in front, it is bent and placed behind the working leg while squatting, perhaps held behind in a hand.