Biomechanics of the Spine in Sports

Does Overhead Squat Performance Affect the Swing Kinematics and Lumbar Spine Loads during the Golf Downswing?

The performance of the overhead squat may affect the golf swing mechanics associated with golf-related low back pain. This study investigates the difference in lumbar kinematics and joint loads during the golf downswing between golfers with different overhead squat abilities. Based on the performance of the overhead squat test, 21 golfers aged 18 to 30 years were divided into the highest-scoring group (HS, N = 10, 1.61 ± 0.05 cm, and 68.06 ± 13.67 kg) and lowest-scoring group (LS, N = 11, 1.68 ± 0.10 cm, and 75.00 ± 14.37 kg). For data collection, a motion analysis system, two force plates, and TrackMan were used. OpenSim 4.3 software was used to simulate the joint loads for each lumbar joint. An independent t-test was used for statistical analysis. Compared to golfers demonstrating limitations in the overhead squat test, golfers with better performance in the overhead squat test demonstrated significantly greater angular extension displacement on the sagittal plane, smaller lumbar extension angular velocity, and smaller L4-S1 joint shear force. Consequently, the overhead squat test is a useful index to reflect lumbar kinematics and joint loading patterns during the downswing and provides a good training guide reference for reducing the risk of a golf-related lower back injury.

Characterization and prediction of rate-dependent flexibility in lumbar spine biomechanics at room and body temperature

BACKGROUND CONTEXT

The soft tissues of the spine exhibit sensitivity to strain-rate and temperature, yet current knowledge of spine biomechanics is derived from cadaveric testing conducted at room temperature at very slow, quasi-static rates.

PURPOSE

The primary objective of this study was to characterize the change in segmental flexibility of cadaveric lumbar spine segments with respect to multiple loading rates within the range of physiologic motion by using specimens at body or room temperature. The secondary objective was to develop a predictive model of spine flexibility across the voluntary range of loading rates.

STUDY DESIGN

This in vitro study examines rate- and temperature-dependent viscoelasticity of the human lumbar cadaveric spine.

METHODS

Repeated flexibility tests were performed on 21 lumbar function spinal units (FSUs) in flexion-extension with the use of 11 distinct voluntary loading rates at body or room temperature. Furthermore, six lumbar FSUs were loaded in axial rotation, flexion-extension, and lateral bending at both body and room temperature via a stepwise, quasi-static loading protocol. All FSUs were also loaded using a control loading test with a continuous-speed loading-rate of 1-deg/sec. The viscoelastic torque-rotation response for each spinal segment was recorded. A predictive model was developed to accurately estimate spine segment flexibility at any voluntary loading rate based on measured flexibility at a single loading rate.

RESULTS

Stepwise loading exhibited the greatest segmental range of motion (ROM) in all loading directions. As loading rate increased, segmental ROM decreased, whereas segmental stiffness and hysteresis both increased; however, the neutral zone remained constant. Continuous-speed tests showed that segmental stiffness and hysteresis are dependent variables to ROM at voluntary loading rates in flexion-extension. To predict the torque-rotation response at different loading rates, the model requires knowledge of the segmental flexibility at a single rate and specified temperature, and a scaling parameter. A Bland-Altman analysis showed high coefficients of determination for the predictive model.

CONCLUSIONS

The present work demonstrates significant changes in spine segment flexibility as a result of loading rate and testing temperature. Loading rate effects can be accounted for using the predictive model, which accurately estimated ROM, neutral zone, stiffness, and hysteresis within the range of voluntary motion.

Biomechanics of the spine. Part I: spinal stability

Biomechanics, the application of mechanical principles to living organisms, helps us to understand how all the bony and soft spinal components contribute individually and together to ensure spinal stability, and how traumas, tumours and degenerative disorders exert destabilizing effects. Spine stability is the basic requirement to protect nervous structures and prevent the early mechanical deterioration of spinal components. The literature reports a number of biomechanical and clinical definitions of spinal stability, but a consensus definition is lacking. Any vertebra in each spinal motion segment, the smallest functional unit of the spine, can perform various combinations of the main and coupled movements during which a number of bony and soft restraints maintain spine stability. Bones, disks and ligaments contribute by playing a structural role and by acting as transducers through their mechanoreceptors. Mechanoreceptors send proprioceptive impulses to the central nervous system which coordinates muscle tone, movement and reflexes. Damage to any spinal structure gives rise to some degree of instability. Instability is classically considered as a global increase in the movements associated with the occurrence of back and/or nerve root pain. The assessment of spinal instability remains a major challenge for diagnostic imaging experts. Knowledge of biomechanics is essential in view of the increasing involvement of radiologists and neuroradiologists in spinal interventional procedures and the ongoing development of new techniques and devices. Bioengineers and surgeons are currently focusing on mobile stabilization systems. These systems represent a new frontier in the treatment of painful degenerative spine and aim to neutralize noxious forces, restore the normal function of spinal segments and protect the adjacent segments. This review discusses the current concepts of spine stability.

Herniated lumbar disc surgery in triathlon athletes with intraoperative neurophysiologic monitoring

Intraoperative neurophysiologic monitoring was performed in a patient by somatosensory evoked potential, motor evoked potential and free-running electromyography with intraoperative stimulation. It was verified that after decompression, there was an increase in the amplitude of motor evoked potential responses, showing an immediate improvement of the treated levels. Intraoperative neurophysiologic monitoring for surgical lumbar disc herniation in an athlete allowed a dynamic neurophysiological diagnosis, differentiation of the involvement of compression at the central or foraminal levels, and clinical awareness of the iatrogenic damage, thereby increasing safety.

The lumbar spine and low back pain in golf: a literature review of swing biomechanics and injury prevention

BACKGROUND CONTEXT

The golf swing imparts significant stress on the lumbar spine. Not surprisingly, low back pain (LBP) is one of the most common musculoskeletal complaints among golfers.

PURPOSE

This article provides a review of lumbar spine forces during the golf swing and other research available on swing biomechanics and muscle activity during trunk rotation.

STUDY DESIGN

The role of "modern" and "classic" swing styles in golf-associated LBP, as well as LBP causation theories, treatment, and prevention strategies, are reviewed.

METHODS

A PubMed literature search was performed using various permutations of the following keywords: lumbar, spine, low, back, therapy, pain, prevention, injuries, golf, swing, trunk, rotation, and biomechanics. Articles were screened and selected for relevance to injuries in golf, swing mechanics, and biomechanics of the trunk and lumbar spine. Articles addressing treatment of LBP with discussions on trunk rotation or golf were also selected. Primary references were included from the initial selection of articles where appropriate. General web searches were performed to identify articles for background information on the sport of golf and postsurgical return to play.

RESULTS

Prospective, randomized studies have shown that focus on the transversus abdominus (TA) and multifidi (MF) muscles is a necessary part of physical therapy for LBP. Some studies also suggest that the coaching of a "classic" golf swing and increasing trunk flexibility may provide additional benefit.

CONCLUSIONS

There is a notable lack of studies separating the effects of swing modification from physical rehabilitation, and controlled trials are necessary to identify the true effectiveness of specific swing modifications for reducing LBP in golf. Although the establishment of a commonly used regimen to address all golf-associated LBP would be ideal, it may be more practical to apply basic principles mentioned in this article to the tailoring of a unique regimen for the patient. Guidelines for returning to golf after spine surgery are also discussed.

Bilateral Strength Comparisons among Injured and Noninjured Competitive Flatwater Kayakers

Context:

Anecdotal evidence suggests a relationship between strength imbalances and injury incidence.

Objective:

To examine the relationship between bilateral strength imbalance and incidence of injury.

Participants and Design:

Thirty national- or international-standard flatwater kayakers were classified as noninjured, trunk injured, or upper-limb injured based on the number of days lost from training over the last 6 months. Bilateral strength imbalance was measured using a kayak ergometer, producing data for peak force and force impulse for each side of each stroke. Bilateral strength imbalance was then compared between the noninjured, trunk-injured, and upper-limb-injured groups by means of 2 one-way ANOVAs. No participants reported training days lost through lower-limb injury.

Results:

A significantly elevated bilateral peak-force strength imbalance was observed between the upper-limb-injured and the noninjured groups.

Conclusion:

These data support the existence of a relationship between strength imbalance and incidence of injury.

Epidemiology of juvenile low back pain: a review

Studies show that the cumulative prevalence of low back pain (LBP) in juveniles was close to 30%. The majority of the LBP was mild. Of those with LBP approximately 8% sought medical treatment. Chronic or recurrent LBP averaged 8.1% of the adolescent populations studied. The cumulative prevalence of LBP increased with age. One study showed a cumulative prevalence of LBP of over 70% by age 15. A potential link between the adolescent growth spurt and the increased prevalence of LBP was proposed. Asynchronous bone growth resulting in skeletal malalignment was proposed as a possible cause of LBP. Immaturity of the vertebral bony structures was thought to increase the risk of pars defects. Correlations between anthropometric measurements of height and weight were inconclusive. The role of decreased muscle flexibility in LBP was also inconclusive. Some researchers found a correlation between age, gender, height and LBP. Disc degeneration and spondylolytic symptoms were also noted as sources of LBP. However, not all cases of disc degeneration (DD) or spondylolysis were symptomatic of LBP. It was noted that the prevalence of DD was rare in adolescents. Disc protrusions were more common in LBP groups than in non-LBP groups, and females with LBP had more disc protrusions than males with LBP. Risk factors for spondylolysis and spondylolisthesis included genetics, the growth spurt, repetitive stresses and sports participation. Within competitive sports, age and training more than 15 hours/week correlated with the incidence of spondylolytic changes. Participation in sports as a risk factor for LBP was reported. A familial tendency for LBP was noted in one study in which the child had an increased incidence of reported LBP if one or both parents had a history of LBP.