Defining the lumbar and trunk-thigh neutral zone from the passive stiffness curve: application to hybrid sit-stand postures and chair design

Traditional versus dynamic sitting: Lumbar spine kinematics and pain during computer work and activity guided tasks

Dynamic sitting may mitigate low back pain during prolonged seated work. The current study compared pelvis and lumbar spine kinematics, pain, and work productivity, in traditional and dynamic sitting. Sixteen participants completed three 20-min blocks of computer work and activity guided tasks in a traditional office chair or backless and multiaxial rotating seat pan while kinematics were measured from accelerometers on the low back. Pain ratings were recorded on a visual analogue scale every 10 min. Similar pelvis and lumbar kinematics emerged when performing computer work in traditional and dynamic sitting. Pelvis and lumbar sagittal and frontal plane shifts and fidgets were largest for dynamic sitting in the activity guided tasks. Buttocks pain was higher in dynamic sitting, but low back pain and work productivity were unaffected. Dynamic sitting increased spine movement during activity guided tasks, without negatively impacting lumbar kinematics, low back pain, or productivity during seated computer work.

An Assessment of Back and Shoulder Postures in Single-Handed Exertions: Expanding Ergonomic Reaching Guidelines to Consider Lumbar Spine Axial Twist

Occupational applicationsAcross a series of standing single-handed exertions performed at different lateral angles, distances, heights, and loads, lumbar axial twist exceeded an angular threshold of 9° in select exertions. Specifically, 9° of rightward axial twist was exceeded for all exertions performed laterally (90° from the body midline). Additionally, for those at the body midline, 9° of leftward axial twist was exceeded for upward exertions and exertions performed at far distances (tertiary reach envelope). Further, the data supports that for many exertions, lumbar flexion-extension and shoulder elevation would be unlikely to increase the potential for injury as angles remained within the in vivo lumbar neutral zone and were not considered overhead. Given the relationship between lateral hand exertions and lumbar axial twist, it is generally recommended that standing single-handed exertions not be performed beyond 60° from the midline. In addition to the current recommendations related to reach distance, future ergonomic reach envelope guidelines could benefit from incorporating recommendations on reach angle from the body midline.

Hamstring and knee injuries are associated with isometric hip and trunk muscle strength in elite Australian Rules and Rugby League players

OBJECTIVES

This study investigated relationships between isometric trunk and hip extensor strength, lumbar muscle morphology, and the risk of hamstring and knee ligament injuries in Australian Football League and National Rugby League players.

DESIGN

Prospective cohort study.

METHODS

Trunk and hip extensor strength, multifidus and quadratus lumborum cross-sectional area were measured during the 2020 pre-season. Logistic regressions and decision trees were employed to explore associations between maximum strength, strength endurance, multifidus and quadratus lumborum cross-sectional area, age, previous injuries, and hamstring and knee ligament injury risk.

RESULTS

Greater strength endurance [odds ratio = 0.42 (0.23-0.74), p = 0.004] and maximum strength [odds ratio = 0.55 (0.31-0.94), p = 0.039] reduced hamstring injury risk. Increased risk of knee ligament injuries was associated with larger multifidus [odds ratio = 1.66 (1.14-2.45), p = 0.008] and higher multifidus to quadratus lumborum ratio (odds ratio = 1.57 (1.13-2.23), p = 0.008]. Decision tree models indicated that low strength endurance (< 99 Nm) characterised hamstring strains, while high (≥ 1.33) multifidus to quadratus lumborum ratio mitigated risk. Knee ligament injuries were associated with larger (≥ 8.49 cm2) multifidus, greater (≥ 1.25) multifidus to quadratus lumborum ratio, and lower maximum strength (< 9.24 N/kg).

CONCLUSIONS

Players with lower trunk and hip extensor maximum strength and strength endurance had increased risk of hamstring injuries, while knee ligament injury risk was elevated with larger multifidus cross-sectional area, higher multifidus to quadratus lumborum ratio, and lower maximum trunk and hip extensor strength.

A Conceptual Model for the Impact of Occupational Standing on Enterprise Outcomes Using an Inductive Content Analysis of California Lawsuits

OCCUPATIONAL APPLICATIONSIn this paper, we provide a framework for practitioners when (re)designing tasks that historically have required standing in the workplace. While the goal is not to remove standing from all jobs, practitioners must work with management to align health and safety outcomes related to standing at work with the enterprise's main outcomes. Practitioners should also be made aware that in many of these jobs, standing has been required because, in the enterprise's judgment, it improves performance and customer service. Understanding common beliefs about customer interactions and job performance in the workplace will be vital to implementing changes that have previously been difficult to navigate.