This small study of healthy volunteers explored differences in the coronal biomechanics of the trunk, pelvis, hip, and knee joints, as well as gluteus medius muscle activity during walking and step down tasks.

Komsak Sinsurin, Raul Valldecabres & Jim Richards (2020) An exploration of the differences in hip strength, gluteus medius activity, and trunk, pelvis, and lower-limb biomechanics during different functional tasks, International Biomechanics, 7:1, 35-43, DOI: 10.1080/23335432.2020.1728381

KEY POINTS: BIOMECHANICS OF FUNCTIONAL TASKS

• Functional impairment of glute med can lead to excessive lateral trunk bending, which is often observed in people with knee problems.
• During gait, the following was observed:
  • Increased contralateral pelvic drop and pelvic obliquity excursion, compared to step-down tasks.
  • Increased lateral bending versus step-down tasks.
  • Significantly greater knee adduction, compared to step-down tasks.
  • Peak hip...

This study compared various measures of lumbar trunk stability with a previously described unstable sitting task¹.

Larivière, Christian, Richard Preuss, Daniel Ludvig, and Sharon M. Henry. "Is postural control during unstable sitting a proxy measure for determinants associated with lumbar stability?" Journal of Biomechanics 102 (2020), 109581. doi:10.1016/j.jbiomech.2019.109581.

Of these measures, parameters of lumbar structural function and muscle activation and coordination were predictive for the unstable sitting task²:

• Angular kinematics of pelvis or lumbar spine following rapid arm movement.
• Lumbar intrinsic stiffness when resisting trunk perturbations.
• Thickness of perimuscular connective tissue around abdominal muscles.
• Onset of internal oblique/transverse abdominals and iliocostalis lumborum before rapid flexion/extension of a single arm.
• Percent thickness change of internal oblique and transverse abdominal muscles at rest...