Why You SHOULD Use Your Back as a Crane

by Mia Inman, PhD, SSC | January 05, 2017

In the 1980s, the New Zealand Accident Compensation Corporation (ACC) began a campaign to prevent lower back injuries in the general population. A central tenet of the ACC campaign was the phrase “Don’t Use Your Back like a Crane”. While this phrase is not as well known among younger people [1], those of us who are older had it drilled into us via TV, print media, at school and at home. This phrase is still used around the world today, and the underlying principle is still being followed, although alternative phrases such as “Lift with your legs” or “Bend at the knees” may also be employed.

The main directive from the “Don’t Use Your Back Like A Crane” campaign was to avoid bending over at the hips to reach down to pick up a load, and was accompanied by illustrations showing a person bending over with a flexed lumbar (and often thoracic) spine. The belief was that such a practice would result in injury. Lifting a heavy weight with a flexed spine does, in fact, predispose the person to a back injury. This is true whether this person is bending over at the hips, or even squatting down. However, this principle does not apply to a crane, as a crane does not use a flexed “spine” to lift a load. In other words, unless something is seriously wrong, you don’t see a crane that looks like this:

not a crane

As an alternative, people were taught to bend their knees and squat down to the load, keeping the back as vertical as possible while standing up with the load. The problem with squatting down to lift a heavy weight is four-fold:

It results in an increased level of stress on the knees, which do not have a large amount of surrounding muscle to provide support to the joint.
The relatively small amount of musculature involved in the lift limits the amount of weight that can be safely lifted.
It is physically impossible to squat down with an upright back to a load on the floor in front of your feet without some degree of spinal flexion [2].
This lifting advice implies that the back is an inherently weak part of the body.

More specifically, the Lift-With-Your-Legs technique implies that you should compensate for the “weaker” areas of the body (the back) by employing the “stronger” areas of the body (the legs). However, if we only lift heavy weights using our “stronger” leg muscles while leaving the back weak, over time the back becomes predisposed to injury. A better solution would be to strengthen the “weaker” areas (the back) to improve the body’s overall capability. And that is best done, as will be shown below, by using a crane-like lifting technique that is known as a Deadlift.

While the intention to reduce the occurrence of back injuries is admirable, the analogy used by the “Don’t Use Your Back like a Crane” campaign was misguided, because a crane is a very mechanically efficient tool for lifting heavy loads. Furthermore, crane mechanics apply equally to the human body lifting a heavy weight by bending at the hips with a straight back, i.e. using a deadlift technique – both systems are examples of a Class 1 Lever. A Class 1 Lever places the fulcrum between the load and the force that moves the load, with the rigid member being the segment that transmits the force.

The table and figure below compares these two systems: a tower crane and a schematic representation of the human body in the setup position of a deadlift. In a tower crane, the fulcrum is the tower, a counterweight is placed at the end of a “counter-jib” segment on one side of the fulcrum, and the load being lifted is located on the other side of the fulcrum, somewhere along the length of the “jib” segment. A crane can lift a heavy load without mechanical failure because the jib is designed to maintain rigidity along its length by resisting bending forces, specifically by the use of reinforcing struts along the length of the segment.

	Tower Crane	Human Body/Deadlift
Fulcrum	Intersection of the tower and the jib	Hips
Rigid member	Jib	Spine held in normal anatomical arch
Rigid member	Support Structures Struts	Spinal Erectors
Load position	Somewhere along the length of the jib	In the hands directly below the scapulae
Opposing force	Counterweight/pulley	Hamstring/Adductors/Glutes

A tower crane is, in part, a Class 1 lever. Unlike the human body, the rigid member (the jib) does not move, instead the load is raised by pulleys attached to the jib. However, for the purposes of this discussion, this simple analogy is useful.

crane vs deadlift

[Enlarge image]

Similarly in the human body in the start position of the deadlift, the fulcrum is the hip joint, the opposing force or “counterweight” is provided by the hamstrings, glutes and adductors pulling down on the inferior-posterior side of the pelvis (purple arrows), the spine is the rigid member, and the load being lifted hangs from the arms directly below the scapulae (grey arrow), near the other end of the spine. This opposing force around the hip fulcrum can be effectively and efficiently transmitted to the load hanging from the arms if the spine is held rigidly in its normal anatomical arch throughout the lift.

The human spine is comprised of interlocking vertebrae that are supported by the spinal erector muscles (green lines) that originate on the pelvis and attach to each vertebra. Isometric contraction of the spinal erectors, assisted by a big held breath and braced abdominal muscles, will hold those vertebrae in a relatively neutral position throughout the lift, and also hold the lumbar spine in the desired neutral position relative to the pelvis. This prevents flexion of the spine and maintains normal anatomical position, thereby decreasing the chance of injury.

Furthermore, by preventing lower back flexion relative to the pelvis, this position keeps the hamstrings, adductors and glutes in maximum tension, and they can therefore contribute more force on one side of the fulcrum to better lift the load on the other side. Lifting in this manner puts the bulk of the stress on the structures and musculature along the posterior chain (up the spine, around the hips, and down the back of the legs), not around the knee joint as in the Lift-With-Your-Legs technique.

This does not mean that you should attempt to lift a heavy weight without having prepared to lift that weight. A human spine, in an untrained or detrained state, can only maintain isometric contraction of the spinal erectors, i.e. maintain the normal anatomical spinal arch, while lifting a relatively small load. In order to lift heavier loads, the musculature around the spine must and can be trained and strengthened.

People who are unfamiliar with the deadlift technique may be concerned about the stress being applied to the spine and spinal erectors during the deadlift, in terms of the aforementioned isometric contraction. This is a benefit of this lifting technique, not a detriment. We want an appropriate level of stress applied to the spinal erectors that increases over a series of training sessions, in order to progressively strengthen them. This will allow us to lift more weight and get stronger over time.

It’s really very simple: you should use your back like a crane, since a crane is a mechanically efficient system that is specifically designed and built to lift a heavy load. However, while the human spine and the associated musculature are designed to lift a heavy load, you should also do the work necessary to build and strengthen that musculature to support the spine under heavy loads.

Furthermore, you have to learn proper lifting mechanics [3,4,5], whether you’re lifting a loaded barbell or a bag of groceries. You need to learn to hold your lower back in normal anatomical arch throughout the lift. You need to take a big deep breath [6] and hold it to stabilize the spine under heavy loads. You need to keep the load as close as possible to the balance point over the middle of your feet during the lift. Once you have learned the correct lifting mechanics, you have to train the musculature around the spine, and the best way to do that is by deadlifting with correct form and progressively increasing the load over successive training sessions.

Strengthening your back and learning proper lifting mechanics will not only decrease the chance of a back injury, but will also increase your physical capability and make your life easier.

Get to work.