"Heavy lifting will hurt your back!"

Have you been told this? Maybe from a friend, a family member, maybe (hopefully not) from a healthcare professional?

And where did this idea come from?

There exists a body of evidence that shows when you continually flex specific segments of a cadaver spine (usually of pig origin) failure and including disc herniation can result (Callaghan and McGill. 2001; Busscheret al. 2009; Gallagher et al. 2006). Makes sense, take most things, clamp it then flex it continuously for 70,550 ± 29,477 repetitions and it will eventually fail! No surprises there.

Issues arise when we apply this data to living organisms and assume that loading these spinal structures will result in the same outcome, at some point structural failure. But it just does not work that way, that is far too simplistic and does not consider how amazingly adaptable our tissues truly are!

The data we have from living, breathing heavy lifting individuals paints a completely different picture. What do we see when we look at the spines of humans with a history of long-term resistance training? Well, we see adaptation of course! Granhed et al. (1987) notes higher bone mineral density of spinal segments when compared to matched controls 7.06 ± 0.87 g⋅cm2 versus 5.18 ± 0.88 g⋅cm2 when examined using dual-photon absorptiometry.

In this same study, they also found a significant correlation between bone mineral content and the amount of lifting the athlete had completed throughout the year i.e lifting more = HIGHER bone mineral content. In a similar fashion, Conroy et al. (1993) showed that in 25 elite junior weightlifters a higher 1RM squat was associated with greater L2-L4 bone mineral content. This all suggests that heavy lifting may be protective of spinal structures, if that is not confidence building, I am not sure what is!

But what about adaptation within the disc you say? Good news is that the strength of the ligaments surrounding the spine and the outer wall of the disc (anulus fibrosus) have been shown to be associated with the bone mineral content of the surrounding vertebrae (Neumann et al. 1993; Skrzypiec et al. 2007).

The key takeaways from this blog are that:

·       We are living adaptable organisms, when we apply loads to tissues, they adapt!

·       The vast majority of injuries associated with strength training are probably a result of doing too much too soon. ‍

‍

If you would like help introducing strength training to your daily exercise, we at The Biomechanics are here to help!

References:

Busscher I, van Dieën JH, Kingma I, van der Veen AJ,Verkerke GJ, Veldhuizen AG. Biomechanical characteristics of different regions of the human spine: an in vitro study on multilevel spinal segments. Spine 34:2858-2864, 2009.

Callaghan JP, McGill SM. Intervertebral disc herniation: studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force. Clin Biomech 16: 28-37, 2001.

Conroy BP, Kraemer WJ, Maresh CM, Fleck SJ, Stone MH, FryAC, Miller PD, Dalsky GP. Bone mineral density in elite junior Olympic weightlifters. Med Sci Sports Exerc 25: 1103-1109, 1993

Gallagher S, Marras WS, Litsky AS, Burr D. An exploratory study of loading and morphometric factors associated with specific failure modes in fatigue testing of lumbar motion segments. Clin Biomech 21: 228-234,2006.

Granhed H, Jonson R, Hansson T. The loads on the lumbar spine during extreme weight lifting. Spine 12: 146-149, 1987.

Marshall LW, McGill SM. The role of axial torque in disc herniation. Clin Biomech 25: 6-9, 2010.

Neumann P, Keller T, Ekström L, Hult E, Hansson T.Structural properties of the anterior longitudinal ligament. Correlation with lumbar bone mineral content. Spine 18: 637-645, 1993

Skrzypiec D, Tarala M, Pollintine P, Dolan P, Adams MA. When are intervertebral discs stronger than their adjacent vertebrae?. Spine 32:2455-2461, 2007.