Is Straight-back Lifting Really Better than Rounded-Back Lifting?

The traditional advice is “In occupational lifting, bend at your knees; keep the object close to your center of gravity; keep your back straight.” However, some authors have been questioning the traditional wisdom on this subject.^1,2 

The argument against this advice suggests that people who practice this advice are more likely to not trust their backs. This in turn can lead to not exercising and stretching the back. It may lead to more back pain through negative back beliefs. It’s always good to reconsider and re-evaluate long-held beliefs.

Some scientific evidence to help us consider the question comes from the USA’s National Institute for Occupational Safety and Health.⁴   The research team used electromyography (EMG) to evaluate seven workers while they performed eight lifting tasks with 10kg cables. An EMG-assisted model was used to calculate forces and moments acting on the lumbar spine.

Stooping while lifting consistently showed the greatest spinal loads. The authors recommended against stooping for lifting heavy objects at work, as it was associated with spinal loads that most exceeded what was considered safe. Interestingly, the posture associated with the lowest spinal load was having two knees on the floor while straight-back lifting. The kneeling and straight-back posture resulted in half the spinal load as the standing & stooped posture. 

References:

1. Nolan D, O'Sullivan K, Stephenson J, O'Sullivan P, Lucock M. How do manual handling advisors and physiotherapists construct their back beliefs, and do safe lifting posture beliefs influence them?. Musculoskeletal Science and Practice. 2019 Feb 1;39:101-6.
2. Brox JI. Lifting with straight legs and bent spine is not bad for your back. Scandinavian Journal of Pain. 2018 Oct 1;18(4):563-4.
3. Gallagher S, Marras WS, Davis KG, Kovacs K. Effects of posture on dynamic back loading during a cable lifting task. Ergonomics. 2002 Apr 1;45(5):380-98.