Tester and testing procedure influence clinically determined gait speed.
Stuart J Warden, Allie C Kemp, Ziyue Liu and 1 others
PMID 31491564WHAT IT FOUND
Different testers using stopwatches recorded gait speeds up to 0.095 m/s apart, and 16% of people showed differences greater than the 0.1 m/s threshold for clinical change.
Automated timing gates removed this tester effect. Dynamic starts also inflated speed.
Key findings
01Manual stopwatch timing introduced significant variability between testers, with the largest mean difference between testers being 0.095 m/s.
02Sixteen percent of participants had a difference in usual gait speed greater than 0.1 m/s between manual and automated timing, a magnitude considered clinically meaningful.
03Using a dynamic start (walking through the measurement zone) resulted in usual gait speeds 2.9% faster and fast gait speeds 6.3% faster than a stationary start.
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
The study included a wide age range (5 years and older) and mixed abilities (including those with assistive devices), so results may not apply uniformly to specific clinical subgroups. The authors note that the exact reason for tester discrepancies is unknown, though they suspect subtle differences in stopwatch triggering. The study did not test all possible variations in gait speed protocols, only those related to tester, timing method, and start condition.
Declared interests
The study was supported by the National Institutes of Health (Extramural). No other specific conflicts of interest or funding sources that designed the study were reported in the text provided.
The easy way to misread this
Do not assume that high reliability coefficients (ICC 0.93-0.97) mean manual timing is safe for detecting small changes. The limits of agreement were wide (±0.15 to ±0.20 m/s), meaning an individual patient's score could vary by more than the clinically meaningful threshold of 0.1 m/s depending on who holds the stopwatch.