Time-integrated propulsive and braking impulses do not depend on walking speed.
Joan E Deffeyes, Denise M Peters
PMID 34139632WHAT IT FOUND
How you calculate walking forces changes the results.
Time-integrated impulses show propulsion stays constant regardless of speed. Peak force measures falsely suggest propulsion drops when walking slows, potentially mislabeling slow walkers as having gait deficits.
Key findings
01For healthy subjects, time-integrated propulsion and braking impulses did not change with walking speed, whereas peak force and percent-stance integration methods showed significant changes with speed.
02In patients with lower-limb pathology, the less affected leg produced similar propulsion to healthy controls only when using time-integrated impulses; other methods incorrectly showed reduced propulsion.
03Lower peak propulsive forces in slow walking are not inherently pathological; they are offset by longer stance times to maintain the same total impulse.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
Actual walking speed for each trial was not recorded, only group averages, so variability within subjects may mask subtle speed dependencies. The study did not normalize for leg length, which could affect the comparison between subjects of different statures. The speed range tested (0.98 to 1.55 m/s) was narrow; faster walking speeds were not examined. Patient groups differed from controls in age, sex, height, and weight, which may influence propulsion independent of pathology.
Declared interests
The authors declared no conflicts of interest. The work was supported by the National Institutes of Health (N.I.H., Extramural).
The easy way to misread this
Do not assume a patient has a propulsion deficit just because their peak propulsive force is low. If they are walking slowly, their total impulse may be normal because they apply force for a longer time. Check the integration method used in the assessment.