Page 2 of 6

54 Years of Misinformation: Squat Lifting is Still Not Safer Than Stoop Lifting

• May 31, 2024

Even more research has just confirmed that squat lifting (knees bent and back straight) techniques are no safer than stoop lifting (knees straight and back bent) techniques when picking up heavy objects. Both techniques pose a high risk of injury to the spine, regardless of posture. This confirms that lifting heavy objects from the ground can lead to back problems. The study found that both squat and stoop lifting techniques place a significant amount of strain on the spine, with squat lifting actually resulting in slightly higher forces. This debate over whether squat lifting or stoop lifting is safer has been ongoing since the 1970s. Research in the late 1990s did not find clear evidence favoring either technique for preventing back pain. Despite this, the use of proper lifting techniques in the workplace is still being discussed. 

New Data Confirms Squat Lifting Not Superior to Stoop Lifting 

Even though wearables that promote proper lifting posture are largely ineffective at reducing the load on a worker’s back, other wearable technology that focuses on the important aspects of lifting is highly effective. 

New wearable technology is being used to validate that lifting stress is best avoided in the following ways:

1. Limit the frequency of lifts (i.e., more lifts, the more risk).
2. Limit the weight of the object (i.e., it’s not a one-size-fits-all scenario).
3. Control the height at which the object is being lifted (i.e., worse on the ground or above the shoulders).
4. Monitor the capability of the person lifting (i.e., fitness, muscle strength, etc.)

Let’s take a look at some physiological and behavioral data collected from a research-grade wearable (smartwatch) to validate that lifting posture is irrelevant and that the four items listed above are most critical. 

Two important wearable outputs that can be used to determine lifting stress on the worker are:

1. Heart rate (BVP). Occupational heavy lifting is known to impose a high cardiovascular strain and can be measured by tracking BVP (Blood Volume Pulse).
2. Emotional response (EDA). Heavy lifting causes emotional responses in workers. These emotional responses can be measured using EDA (Electrodermal Activity). EDA is a measure of changes in the skin’s conductivity triggered by emotional responses.

Using a smartwatch to measure heart rate and EDA can determine the magnitude and duration of the body’s response to lifting various objects in the workplace.

Above: Data from a light 28-pound lift.

The heavier or more stressful the lift, the greater the initial spike from baseline for EDA and BVP. This gives two more important reference points for measuring lifting stress. 

Back to proving that squat lifting is no safer than stoop lifting, the data shows a healthy male who lifted 56 pounds for 5 seconds. The initial spike from baseline in emotional response (EDA) was very close for both stoop and squat (stoop was actually slightly better). The stress on the heart (BVP) was also very close for both stoop and squat (stoop performing slightly better again). 

That's more proof that lifting posture is not the most important aspect. So, what should be the focus? Performing the same analysis for the following criteria and the findings reinforce a focus on the following:

• Weight of the object. The weight of the object being lifted is very important with regards to stress on the worker. A healthy male was asked to lift a 56-pound load and then a 112-pound load. The 56-pound load is typically close to the maximum suggested load for men. The 112-pound load is significantly higher than the recommended load for the average man. When measuring EDA, the initial spike in emotional response was 5 times greater for the 112-pound load than the 56-pound load. Interestingly, for the 112-pound lift, the EDA did not immediately return to baseline after the lift was completed. Normally, the EDA returns to baseline almost immediately after the lift is completed. It took a significant amount of time for the EDA to return to baseline after finishing the lift, showing that this was beyond the comfort zone for this individual.

In addition, the initial spike in BVP showed that the strain on the heart was 2 times greater when comparing the two lifts.

• Height at which the object is being lifted. Additional experiments were conducted to compare lifting an object from ground level vs. waist height. The ground lift was 3 times higher for EDA and 40 percent higher for BVP than lifting an object from waist height.

New Research Conclusions

1. Lifting posture is irrelevant.
2. Focus on the following:
1. Limit the frequency of lifts (more lifts, the more risk)
2. Limit the weight of the object
3. Control the height at which the object is being lifted (worse on the ground or above the shoulders)
4. Monitor the capability of the person doing the lifting (fitness, muscle strength, etc.). Everyone’s capabilities are different.

With regards to using wearable tech for making sure employees are safe and don’t overexert themselves while doing lifting tasks, it’s important to select the right wearable technology to measure the criteria that is most important. The technology should focus on the things that matter most and be able to be “calibrated” to the specific worker using the wearable. Each worker has different capabilities for performing lifts regardless of what many consider to be safe lifting limits for male and female workers. 

Studies like this show that overexertion activities like lifting, carrying and pushing items have been a leading cause of injuries in the U.S. for years. Businesses spend billions on overexertion injuries, showing a significant financial impact. Lifting heavy things at work is a major cause of injuries. Many people suffer from back injuries due to these activities, which can be painful and reduce quality of life. It's a big problem because a lot of people are affected, and it's one of the most common health issues people face. 

Companies need to adjust their strategy to reduce Musculoskeletal Disorder (MSD) risk. Ask most safety professionals to describe the most important aspects of safe lifting and 9 times out of 10 will yield the same answer: knees bent and back straight (i.e., squat lift). So, if research continues to show that this criteria is unimportant, why keep reinforcing this outdated, unscientific method of lifting?

What the Standards Say and What Needs to Change

The Occupational Safety and Health Administration (OSHA) has not established a specific ergonomics standard. However, a great deal of scientific research has been conducted to investigate the link between ergonomic risk factors and the likelihood of injury. Many of these programs utilize anthropometric data for male and female populations while incorporating force, distance, angles and frequency to generate potential risk categories. The success of this approach is limited because it doesn’t fully capture all the necessary physiological and behavioral information needed to evaluate risk. The NIOSH Revised Lifting Equation (NRLE), Rapid Upper Limb Assessment (RULA) and the American Conference of Governmental Industrial Hygienists Hand Activity Level (ACGIH HAL) are tools with limited success in reducing lifting risk. They are referenced by many clients. These tools are stagnant and not specific to each individual. 

The biomechanical approach of reducing risk by categorizing risk based on a set of statistical parameters is limiting. The long-term success of these programs is based on the fact that the job and employee don’t change. If the work environment is appropriately modified and the worker is trained and conforms anthropometrically to a desired risk table, the risk of injury is low. Age is often used in those calculations as a generic contributor to risk calculation. The physiological sensor output (i.e., respiration, oxygen saturation (OS), pulse, emotional response) will be different from one person to another despite their identical age, height, sex and size.

The human body is dynamic, and each individual is constantly changing and adapting physiologically and emotionally each day. A wearable device monitoring biometric data is able to detect when the human body is stressed. This provides essential insights into risk with lifting that is not captured on a statistical chart. The NRLE doesn’t capture all of the risks. When performing a lifting task, an employee may fit the demographics for low risk according to the NRLE; however, the captured biometric data during the same task indicates the fluctuation in pulse, an emotional response or other biometric data changes, which indicates the employee is struggling with the lift. With the chart showing from 2011 to 2018, health and safety professionals still have a lot of work to do to reduce the risk of MSDs.

Every person is unique. And, many factors affect a person’s ability to lift objects safely. Some of these factors include a person’s:

• Gender
• Physical size
• Physical well-being
• Fitness level
• Predispositions
• Lifting habits

The muscles are strengthened and conditioned over time through repetitive motions. MSD claims increase when a worker’s lifting technique is modified without a work-hardening program implemented at the same time. Change is change, and when one incorporates new biomechanical techniques, different muscles are used which can increase the risk of injury. So changing a worker’s lifting technique from what they are used to (stoop to squat) can actually cause an injury.

Interestingly, the human body is fully capable of warning when it’s well and when it is at risk. The physiologies react in ways that tell when there is a potential problem. Each time a worker lifts an object, bodies go to work and there is measurable data that can indicate lifting risk both physically and emotionally. These changes are personal and provide an excellent source of information for assessing risk and preventing injuries.

For assessing employee lifting, lowering, pushing, pulling and carrying, collecting and analyzing physiological and behavioral data is essential to further reducing the risk associated with lifting and carrying. The old philosophy of squat lifting (using the legs and keeping the back straight) is not the optimal solution. The best solution involves monitoring each worker’s physical and emotional effort required to perform and sustain safe lifts. By doing this, risky situations can be identified and improvements can be made to:

1. Help workers understand their lifting limitations
2. Improve workplaces to help avoid risky lifts
3. Provide lifting aids when needed

Data alone will not keep workers safe. But data used to make improvements in workplace procedures and methods offers the best scenario for preventing workplace injuries and accidents. Companies are searching for a proactive tool to reduce risk. Human beings are complex and diverse. These new technologies becoming available are giving people in this profession real insights into risk on a personal level. This is the tool EHS professionals have been looking for. 

So What Should Be Done?

First, educate people about the risks of lifting a heavy object from the ground, no matter the lifting technique used.

Second, understand that providing lifting technique training or wearables that promote proper lifting posture are not effective at reducing spinal loads, and it does little to reduce the risk of LBDs. 

Lastly, and most importantly, know that the only way to reduce the risk of LBDs is to implement engineering controls to raise the hand working height, reduce or eliminate the weight of the object (which also reduces force) and limit the number of lifts in a typical working day.