Deadlift
The deadlift is a weight training exercise where one lifts a loaded barbell (or, in the case of the trapbar deadlift, a loaded trapbar) off the ground from a stabilized bent-over position. It is one of the three gauges of powerlifting, and is an excellent exercise for overall body development if done properly.

# Overview
The deadlift is a compound movement that works grip strength, and the primary muscles used in the deadlift are the erector spinae, the gluteus maximus, adductor magnus, hamstrings and the soleus. 
The remaining muscles are involved in stability control. It is, in a sense, the purest single event test of strength because it is one of the few lifts of dead weight (weight lying on the ground).  In most other lifts the weight changes direction or starts in the air and several other athletic skills such as balance, coordination are emphasized.  For example, both Olympic weightlifting events require a great deal of athletic skill in addition to strength.  In addition, it is commonly believed to be the oldest test of strength dating back to cultures who competed at lifting the heaviest stones.

# World records
The record under official powerlifting rules is 455 kg (1003 lb) by Andy Bolton.
The record for a strongman-style deadlift, with a longer bar and from a greater height, is held by Benedikt Magnusson, who deadlifted 500kg (1100 lb). This feat was a Tire Deadlift at the Arnold Classic in Columbus Ohio 2008. Sigmarsson deadlifted 523 kg from the knees in 1987.

# Muscles involved
- Torso
Front
Abdomen
Rectus abdominis (under aponeurosis)
Obliques
Abdominal external oblique muscle
Back
Iliocostalis
Intertransversarii laterales lumborum
Latissimus dorsi
Levator scapulae
Longissimus
Quadratus lumborum
Rhomboideus major
Serratus posterior superior
Serratus posterior inferior
Splenius cervicis
Teres Major
Trapezius muscle
- Front
Abdomen
Rectus abdominis (under aponeurosis)
Obliques
Abdominal external oblique muscle
- Abdomen
Rectus abdominis (under aponeurosis)
- Rectus abdominis (under aponeurosis)
- Obliques
Abdominal external oblique muscle
- Abdominal external oblique muscle
- Back
Iliocostalis
Intertransversarii laterales lumborum
Latissimus dorsi
Levator scapulae
Longissimus
Quadratus lumborum
Rhomboideus major
Serratus posterior superior
Serratus posterior inferior
Splenius cervicis
Teres Major
Trapezius muscle
- Iliocostalis
- Intertransversarii laterales lumborum
- Latissimus dorsi
- Levator scapulae
- Longissimus
- Quadratus lumborum
- Rhomboideus major
- Serratus posterior superior
- Serratus posterior inferior
- Splenius cervicis
- Teres Major
- Trapezius muscle
- Legs
Quadriceps
Rectus femoris
Vastus lateralis
Vastus intermedius
Vastus medialis
Hamstrings
Biceps femoris muscle, long head
Biceps femoris muscle, short head
Semitendinosus
Semimembranosus
- Quadriceps
Rectus femoris
Vastus lateralis
Vastus intermedius
Vastus medialis
- Rectus femoris
- Vastus lateralis
- Vastus intermedius
- Vastus medialis
- Hamstrings
Biceps femoris muscle, long head
Biceps femoris muscle, short head
Semitendinosus
Semimembranosus
- Biceps femoris muscle, long head
- Biceps femoris muscle, short head
- Semitendinosus
- Semimembranosus
- Hips
Gluteal muscles
Gluteus maximus
Gluteus minimus
Piriformis
Superior gemellus
- Gluteal muscles
Gluteus maximus
Gluteus minimus
- Gluteus maximus
- Gluteus minimus
- Piriformis
- Superior gemellus
- Forearms
Flexor digitorum profundus
- Flexor digitorum profundus

# Variations
The Romanian deadlift is commonly used by Olympic Weightlifters.  This variation puts more emphasis on the hamstrings and glutes.  To perform them, unlock the knees and let the weight descend until knee level by bending from the hips.
The Sumo deadlift is a variation of the deadlift whereby the legs are spread far apart to the sides (arms reaching down inside of legs), mimicking a sumo stance, hence the name. This variation changes the emphasis of the lift to the legs and glutes instead of the back. The sumo deadlift is purported to be easier for those with large waists as well as those with relatively long torsos and shorter arms.  However, the sumo technique may place greater stress on the hips and hamstrings, as well as the connective tissues of the pelvic bone.
Deadlifts can be performed using dumbbells or barbells, with one hand or two hands & with one leg or two legs. Variations are only limited by the athlete's imagination.  Other variations are the side deadlift or suitcase deadlift, deadlift from a box, rack pulls, deadlift lockouts, and "Kuck pulls"
The archaic "dead weight lift", or "dead weight lift with lifting bar" involved a T-bar with weight loaded on it while the lifter stood on sturdy chairs or other such platforms. A remarkably heavy amount of weight could be lifted in this manner due to its short range of motion; the main limitations are in the grip. This lift is similar to the modern day rack pulls, where a heavy amount of weight is lifted deadlift style a short distance in a power cage or squat rack.
Typically, there are two grips used: overhand, or pronated,  and a mixed overhand-underhand (supinated) (sometimes called "offset," "staggered," "alternating", or "mixed") grip. Dependent on forearm strength, the overhand grip may result in the bar potentially rolling about. Some argue the mixed grip is capable of neutralizing this through the "physics of reverse torsion." The mixed grip also allows more weight to be used for this reason.
In order to prevent the bar from rolling out of the hands, some lifters have been known to use an Olympic lifting technique known as the "hook" grip. This is similar to an overhand grip, but the thumbs are inside, allowing the lifter to "hook" onto them with the fingers. The hook grip can make it easier to hold heavier weights using less grip strength, and keeps both shoulders and elbows in a symmetrical position. While it theoretically takes much of the stress off of the joints which might be created by the twisting of a mixed grip it has the disadvantage of being extremely uncomfortable for the thumbs, something which those who advocate it says will pass once a lifter becomes accustomed to it. Another, but rarely used method is a combination of the mixed overhand-underhand grip and the hook grip, preferred by people who lift heavier weights than their grip can handle, but who don't want to rely on lifting straps or other supportive gear.
You will find that many powerlifters adopt the overhand grip for their lower weight sets and move to the mixed grip to lift larger weights so they can achieve their one rep max.
The trapbar deadlift is a variation of the deadlift using a special U-shaped bar (a trapbar).  This allows more clearance for the knees to pass "through" the bar. To perform the trapbar deadlift, one loads the bar, steps inside the hollow portion of the bar, bends down, grasps the handles, stands erect, then lowers the bar to the ground in the exact opposite path. Proponents of trapbar deadlifts include Hardgainer Magazine, Bob Whelan, the Cyberpump website, and Dr Ken Leistner and iron-game writer Paul Kelso.
Snatch-grip deadlift.  Deadlifts from a platform.

# Dangers
Improper form can precipitate new conditions, aggravate existing ones, and possibly cause injury, especially the heavier the weight one lifts. Failure to keep the back straight during the movement causes undue stress to the spinal discs, by pinching the front and leaving a gap at the back, forcing the internal fluids to compress towards the back, and potentially causing a herniated disc. This is especially true of the lumbar region of the spine, which bears the bulk of the compressive forces on the upper body.
In addition, the compression can squeeze the spinal roots of the spinal cord, causing nerve-conditions like lumbago or sciatica.
It is important that those executing a deadlift be proficient in the recruitment (voluntary activation) of the deep abdominal and trunk muscles. In particular, it has been suggested that recruiting the Transverse Abdominus muscle provides a natural corset-like brace around the trunk, helping to protect against injury. A good method to help achieve this and avoid lower back injuries is to keep the abdominals braced using the Valsalva maneuver.  This will build anterior support for the spine. However, as a cautionary note, this technique can drastically increase blood pressure during the exercise and should not be performed by people with known or suspected heart conditions.
Some weightlifters use special belts to keep their lower back stabilized. Whether or not these belts actually prevent injuries is debated but evidence shows using the belt moves the concentration of pressure within the abdomen towards the anterior, taking pressure off of the spine. Conversely, one school of thought suggests that the use of belts should be minimized, as it does not allow for the development of one's "stabilizer muscles", thereby increasing the potential of serious injury.
Using an underhand grip is potentially hazardous on heavy deadlifts as a supinated grip shortens the biceps muscle and increases the load on it, possibly leading to a rupture of the muscle or connecting tendons.  The risk is most notable in individuals without full flexibility in the elbow joint.