Study: When is bending too much?

This recent study looked at sustained bending and the time it takes before our postural muscles give in and we begin to rely on our passive structures for support.

Alessa 2017

How long is too long, to be in a forward, bent posture? Many of us spend hours doing house chores; weeding, DIY, working on the car etc. Not to mention the time spent leaning over a computer desk or looking down at your phone.

Back pain

Your muscles play an amazing role of suspending us in these positions, but just like with exercise our muscles will reach a point of fatigue. When the postural muscles aren’t able to provide the support we then rely on “passive” structures like ligaments and fascia, which is not their primary role, eventually leading stress and increased risk of injury.

This study looked at 2 angles of the spine leaning forwards and found that within 40 seconds the participants transitioned from the support of postural muscles to the passive structures. While this was found to be a natural transition the prolonged strain on the passive structures has been shown to increase the risk of lower back pain as suggested in another study.

As mentioned in a previous blog, these positions are not “wrong” but it’s better for the overall health of the spine to regularly change position and break from sustained load on an individual structure to provide balance.

Abstract

Static trunk bending is an occupational risk factor for lower back pain (LBP). When assessing relative short duration trunk bending tasks, existing studies mostly assumed unchanged spine biomechanical responses during task performance. The purpose of the current study was to assess the biomechanical changes of lumbar spine during the performance of relatively short duration, sustained trunk bending tasks. Fifteen participants performed 40-s static trunk bending tasks in two different trunk angles (30° or 60°) with two different hand load levels (0 or 6.8 kg). Results of the current study revealed significantly increased lumbar flexion and lumbar passive moment during the 40 s of trunk bending. Significantly reduced lumbar and abdominal muscle activities were also observed in most conditions. These findings suggest that, during the performance of short duration, static trunk bending tasks, a shift of loading from lumbar active tissues to passive tissues occurs naturally. This mechanism is beneficial in reducing the accumulation of lumbar muscle fatigue; however, lumbar passive tissue creep could be introduced due to prolonged or repetitive exposure.

 

Alessaa F. et al (2017) Changes of lumbar posture and tissue loading during static trunk bending. Human Movement Science

Author: Graeme Lawson

With more than 13 years working both in the UK and New Zealand, Graeme offers a vast amount of experience and knowledge when treating musculoskeletal conditions. Being part of various clubs on the grass roots level to international with the England Volleyball team he has developed a broad skill set. His patient’s see exceptional results from a progressive blend of hands on manual therapy, education and exercise prescription. Catering from the home and work related injuries to athletes from novice to elite levels. Graeme’s outlook is the same with all who visit, that prevention is better than the cure. While providing a variety of hands-on treatments, he knows how important it is to offer education, preventative advice and tailored exercises to continue long after you have been discharged, helping avoid injuries in the future. For pastimes he has played basketball over the last couple of decades at different national levels. Graeme has also been doing CrossFit for 6 years. Having both the knowledge and ability of these technical movements provides athletes confidence with the advice they receive.

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