Research library
The studies behind it
Plain-English summaries, a link to the original, and the limits stated honestly. Small studies and models are leads, not proof.
Spine shape
Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position
The paper behind the four spine types. Types are set by sacral slope, measured on X-ray.
Biomechanical responses of human lumbar spine and pelvis according to the Roussouly classification
Computer models of each type: the Type 3 model was most stable; the straighter Type 1 and 2 models balanced and bore load less well. Models, not people.
Running
The evolution and function of human lumbar lordosis variability
Lower-back curve had no effect on shock absorption when walking, but a strong effect when running. A thesis, not a peer-reviewed paper.
Effects of step rate manipulation on joint mechanics during running
Raising step rate 5–10% reduced vertical bounce and the energy absorbed at the knee. Healthy runners, single session.
Altering cadence or vertical oscillation during running: effects on running related injury factors
A “less bounce” cue lowered loading rates and peak impact force more than a cadence cue did. Single session.
The effect of trunk flexion angle on lower limb mechanics during running
More forward trunk bend: +29% loading rate, +20% impact peak, +70% hip extensor moment.
Biomechanical consequences of running with deep core muscle weakness
Weakening the deep core in a simulation raised lower-spine loading by up to about 15%. A computer model, not a trial.
The metabolic cost of human running: is swinging the arms worth it?
Running with the arms held still cost 3–13% more energy and increased torso rotation.
Relation of anterior pelvic tilt during running to clinical and kinematic measures of hip extension
Less hip extension went with more forward pelvic tilt when running. A correlation, not cause.
Sitting
Posture of the trunk when sitting on forward inclining seats
Forward seat tilt increased the lower-back curve, about two-thirds of it from the hips. Small study, healthy subjects.
Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain
A rear seat that drops away cut lower-back muscle activity 6–24% and moved seat load forward onto the thighs. Flat backs not tested.
Where the sciatic nerve runs between the sit bone and the hip (cadaver study)
The nerve runs through the middle third of the gap between the sit bone and the outer hip bone.
A chair with a flexible four-segment seat pan
Better comfort and less back-muscle fatigue, in healthy students only. Two authors work for the chair’s makers.
Chairs for low back pain (summary of Andersson 1979, Snijders 2004, Van Veelen 2000)
Sitting reduces the lower-back curve; support low at L5 prevents the slump hinge; leave shoulder space above the lumbar support.
Intradiscal pressure in daily life (Wilke et al. 1999, summary)
Slouching gave the lowest disc pressure; sitting up straight actively raised it by about 10%. One person.