Home Forums April 2021 | Should we be coaching athletes to avoid spinal flexion while lifting?

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    Should we be coaching athletes to avoid spinal flexion while lifting?

    By Marc Chivilo and Linda Truong

    Introduction

    Low back pain (LBP) is a leading cause of disability worldwide and is prevalent among both athletes (Farahbakhsh et al. 2018) and the general population (Wu et al. 2020). Although lifting is a known risk factor for the onset and exacerbation of low back pain (Coenen et al. 2014), it is unclear whether increased spinal flexion during lifting is an independent risk factor. Current advice regarding the avoidance of spinal flexion is based on findings from cadaver studies indicating that the spine is more susceptible to injury with repeated flexion under low to moderate loads (Callaghan & McGill 2001) However, these findings may not translate to real-world settings.

    However, more recent biomechanical modelling has shown that anterior shear forces were increased at L4-5 and L5-S1 (where shear forces are greatest with lifting) when lifting with a more lordotic posture (Khoddam-Khorasani et al. 2020).

    What is this review about?

    A variety of psychosocial factors play a role in the development and persistence of LBP and help contribute to the global burden of LBP-related disability (Pincus et al. 2002). However, biological/biomechanical factors should also be considered in prevention and treatment strategies. Despite worldwide practice encouraging individuals to lift with a ‘straight back,’ there has not been a reduction in the rates of LBP (Martimo et al. 2008). The purpose of this review is to present  the evidence regarding whether avoiding/reducing spinal flexion during lifting is beneficial to prevent and/or treat LBP.

    The main findings

    A recently published systematic review (Saraceni et al., 2020) identified 12 independent studies (1 longitudinal and 11 cross-sectional, n=697 participants, average age >=18 years old) that measured lumbar spinal flexion that occurred while lifting an external load (from a pen to 12 kg box) in groups with and without LBP.

    Two separate meta-analyses were conducted based on the measurement technique used. The first meta-analysis included four studies that measured lumbar flexion using intra-lumbar angles, the gold standard for measuring spinal kinematics. The remaining studies used thoraco-pelvic angles to measure lumbar flexion, and were included in a second meta-analysis.

    • No differences in peak lumbar spine flexion while lifting in groups with and without LBP  in one longitudinal (95%CI: -0.7 to 3.7, p=0.19) and three cross-sectional studies (95% CI: -2.5 to 0.7, p=0.29) that measured flexion using intra-lumbar angles.
    • Individuals with LBP demonstrated 6 degrees less lumbar flexion than those without LBP  (95% CI: -11.2 to -0.89, p<0.01) in seven cross-sectional studies that measured flexion using thoraco-pelvic angles.
    • No included studies showed a statistically significant effect for lifting with a more flexed lumbar position being associated with LBP.
    • Overall, there was low quality evidence of no longitudinal or cross-sectional relationship between greater lumbar spine flexion during lifting and LBP onset or persistence or recurrence.

    The findings of this review does not support the near-universal recommendation from healthcare providers that avoiding lumbar spinal flexion under loaded conditions will prevent or minimize the occurrence or recurrence of LBP. However, this interpretation should be treated with caution as studies included in this review were observational, which makes it difficult to infer causation. Further, the quality of evidence is low with a high risk of bias within the individual studies included. Despite this, this review provides preliminary evidence that LBP is more complex and influenced by other factors beyond biomechanics.

    Another important limitation of this review is that none of the included studies had subjects lift loads that are considered to be “heavy”, with the loads lifted ranging from a pen to a 12 kg box. There are sporting and occupational settings in which the loads lifted will be far greater than 12kg, which makes these results difficult to apply in all situations. However, it is also important to note that many of the early in-vitro studies showed a disc injury mechanism under repeated low-moderate loads, and this systematic review shows that this may not be correlated with increased rates of LBP. Studying potential injury mechanisms under higher load conditions, as well as kinematic changes under higher loads, is certainly something that future research could investigate.

    Another aspect of this discussion that needs to be considered is whether spinal flexion can be avoided during various sporting activities. Kinematic analyses have been performed with various lifts and movements and consistently show that it is not possible to keep the spine in a neutral position when performing these movements. During barbell squats and deadlifts, subjects were shown to use an average of 64.2% and 76.76% of their maximal voluntary flexion respectively (Edington 2018). Rowers have been shown to use 113% of their pre-test maximal lumbar flexion during ergometer rowing, and 104% during boat rowing (Wilson et al. 2011). Subjects performing a kettlebell swing, which is thought to keep the spine relatively neutral, were shown to have peak lumbar flexion of 26⁰ (McGill & Marshall 2012), which equates to nearly half of maximal flexion in healthy individuals (Dvorak et al. 1991). What all these movements have in common is that subjects are flexing their spines well outside of what would be considered a “neutral” position (Yamamoto et al. 1989). Certainly from a performance aspect, spinal flexion is necessary in some sports. Given that there is little evidence to support spinal flexion leads to LBP, reassurance can be given to athletes that these movements are safe on their spine once they have built the capacity and endurance to handle these movements.

     

    Application to clinical practice

    1. Explain to athletes that flexing the spine under loaded conditions is safe, and may offer some performance benefits

    There continues to be a lack of in-vivo evidence demonstrating that increased lumbar spine flexion is directly associated with increased injury risk. Explain that lumbar spine flexion outside of a neutral position is unavoidable during many tasks, and that moderate amounts of spinal flexion may optimize biomechanical variables resulting in improved lifting performance.

    1. Consider psychosocial factors

    Psychological factors such as negative back pain beliefs and fear avoidance are better predictors of the development of chronic low back pain after an acute episode compared to any physical/biomechanical variables (Pincus et al. 2002). It is recommended that clinicians screen for these variables using validated tools and provide positive education regarding the robust nature of the spine and its capacity to withstand loading. Clinicians should avoid suggesting that the spine is fragile or needs to be protected, as this may help to develop/reinforce negative beliefs about back pain.

    1. Follow good training principles

    Prescribing lifting exercises to athletes is likely to help build load-bearing capacity in the spine. It may be beneficial to expose athletes to a variety of lifting postures in order to improve the robustness of the spine under different conditions. This can be achieved by prescribing a variety of lifting exercises that differ in the amount of spinal flexion utilized during the lift. It is also important to allow adequate time for recovery between training sessions, and to avoid increasing training loads too quickly.

    1. Consider using cues to attenuate spinal flexion under certain conditions.

    Given the lack of evidence of spinal flexion under high load conditions, it may be reasonable to use cues to help avoid end-range spinal flexion when lifting heavy loads. Using various techniques to attenuate spinal flexion may also be useful in individuals with back pain who are aggravated by more flexed positions, especially if this results in the individual being able to continue their desired activity.

    1. Reassure athletes that most episodes of acute low back pain are likely to resolve on their own without any specific intervention.

    It is important to reassure athletes that most episodes of acute low back pain are not related to any structural failure of the spine (Maher et al. 2017), and over 90% of cases resolve within six weeks, regardless of treatment (Van Tulder et al. 2006). Most forms of treatment for acute low back pain have small clinical effects, and the only strong recommendations in NICE guidelines for non-pharmacological intervention are to provide advice and information regarding the nature of low back pain, self-management strategies, and encouragement to resume normal activities.

    Resources:

    NICE Guidelines: Low back pain and sciatica in individual aged  16 and over: assessment and management

    https://www.nice.org.uk/guidance/ng59

     

    Infographic on lifting:

     

     

     

    References

    Beach, Tyson A.C., et al. “Using Verbal Instructions to Influence Lifting Mechanics – Does the Directive ‘Lift with Your Legs, Not Your Back’ Attenuate Spinal Flexion?” Journal of Electromyography and Kinesiology, vol. 38, 2018, pp. 1–6., https://doi.org/10.1016/j.jelekin.2017.10.008.

    Callaghan, Jack P, and Stuart M McGill. “Intervertebral Disc Herniation: Studies on a Porcine Model Exposed to Highly Repetitive Flexion/Extension Motion with Compressive Force.” Clinical Biomechanics, vol. 16, no. 1, 2001, pp. 28–37., https://doi.org/10.1016/s0268-0033(00)00063-2.

    Coenen, Pieter, et al. “The Effect of Lifting during Work on Low Back Pain: A Health Impact Assessment Based on a Meta-Analysis.” Occupational and Environmental Medicine, vol. 71, no. 12, 2014, pp. 871–877., https://doi.org/10.1136/oemed-2014-102346.

    Dvorak, J, et al. “Functional Radiographic Diagnosis of the Lumbar Spine.” Spine, vol. 16, no. 5, 1991, pp. 562–571., https://doi.org/10.1097/00007632-199105000-00014.

    ​​Edington, Corey. “Lumbar Spine Kinematics and Kinetics during Heavy Barbell Squat and Deadlift Variations.” University of Saskatchewan, 2018.

    Farahbakhsh, Farzin, et al. “Prevalence of Low Back Pain among Athletes: A Systematic Review.” Journal of Back and Musculoskeletal Rehabilitation, vol. 31, no. 5, 2018, pp. 901–916., https://doi.org/10.3233/bmr-170941.

    Khoddam-Khorasani, P., et al. “Effect of Changes in the Lumbar Posture in Lifting on Trunk Muscle and Spinal Loads: A Combined in Vivo, Musculoskeletal, and Finite Element Model Study.” Journal of Biomechanics, vol. 104, 2020, p. 109728., https://doi.org/10.1016/j.jbiomech.2020.109728.

    Low back pain and sciatica in over 16s: assessment and management. National Institute for Health and Care Excellence. 30 November 2016.

    Maher, Chris, et al. “Non-Specific Low Back Pain.” The Lancet, vol. 389, no. 10070, 2017, pp. 736–747., https://doi.org/10.1016/s0140-6736(16)30970-9.

    Martimo, Kari-Pekka, et al. “Effect of Training and Lifting Equipment for Preventing Back Pain in Lifting and Handling: Systematic Review.” BMJ, vol. 336, no. 7641, 2008, pp. 429–431., https://doi.org/10.1136/bmj.39463.418380.be.

    McGill, Stuart M, and Leigh W Marshall. “Kettlebell Swing, Snatch, and Bottoms-up Carry: Back and Hip Muscle Activation, Motion, and Low Back Loads.” Journal of Strength and Conditioning Research, vol. 26, no. 1, 2012, pp. 16–27., https://doi.org/10.1519/jsc.0b013e31823a4063.

    Pincus, Tamar, et al. “A Systematic Review of Psychological Factors as Predictors of Chronicity/Disability in Prospective Cohorts of Low Back Pain.” Spine, vol. 27, no. 5, 2002, https://doi.org/10.1097/00007632-200203010-00017.

    Saraceni, Nic, et al. “To Flex or Not to Flex? Is There a Relationship between Lumbar Spine Flexion during Lifting and Low Back Pain? A Systematic Review with Meta-Analysis.” Journal of Orthopaedic & Sports Physical Therapy, vol. 50, no. 3, 2020, pp. 121–130., https://doi.org/10.2519/jospt.2020.9218.

    Van Tulder, Maurits, et al. “Chapter 3 European Guidelines for the Management of Acute Nonspecific Low Back Pain in Primary Care.” European Spine Journal, vol. 15, no. S2, 2006, https://doi.org/10.1007/s00586-006-1071-2.

    Wilke, Hans–Joachim, et al. “New in Vivo Measurements of Pressures in the Intervertebral Disc in Daily Life.” Spine, vol. 24, no. 8, 1999, pp. 755–762., https://doi.org/10.1097/00007632-199904150-00005.

    Wilson, F., et al. “Kinematics of Lumbar Spine Motion in Rowing during a Fatiguing Protocol: A Comparison of Ergometer and Boat Rowing.” British Journal of Sports Medicine, vol. 45, no. 4, 2011, pp. 383–383., https://doi.org/10.1136/bjsm.2011.084038.208.

    Wu, Aimin, et al. “Global Low Back Pain Prevalence and Years Lived with Disability from 1990 to 2017: Estimates from the Global Burden of Disease Study 2017.” Annals of Translational Medicine, vol. 8, no. 6, 2020, pp. 299–299., https://doi.org/10.21037/atm.2020.02.175.

    Yamamoto, Isao, et al. “Three-Dimensional Movements of the Whole Lumbar Spine and Lumbosacral Joint.” Spine, vol. 14, no. 11, 1989, pp. 1256–1260., https://doi.org/10.1097/00007632-198911000-00020.

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