Effect of parameter selection on entropy calculation for long walking trials.
Jennifer M Yentes, William Denton, John McCamley and 2 others
PMID 29202357WHAT IT FOUND
Changing analysis settings can reverse which walking mode looks more regular in step-time entropy.
Tolerance settings changed which mode looked more regular. Do not compare entropy values across studies without identical parameters.
Key findings
01Approximate entropy results changed depending on the combination of tolerance, window, and data length.
02Sample entropy decreased as tolerance increased, and between tolerance values of 0.2 and 0.25 times SD the apparent order flipped.
03For sample entropy, when tolerance was fixed rather than scaled to SD, overground walking appeared more regular than treadmill walking.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
Read the rest of this summary
You get three full summaries a month, free, and we do not ask for a card. Search, the TL;DRs and your library stay unlimited either way.
What it does not show
Only 14 of the 21 participants had usable data, so the methodological findings rest on a small healthy young sample. The study analyzed only step time, one temporal aspect of walking, so it does not address other gait measures, spatial events, or continuous variables. Participants walked for one-hour, and fatigue was not measured, so fatigue could have influenced step-time patterns even though none reported it. Overground speed was not recorded, and treadmill speed can constrain natural speed fluctuations, so the two walking modes are not directly comparable clinically. The analysis depended on data resolution, and step time was calculated to five significant digits, so different precision could change entropy matches.
Declared interests
The authors have no conflicts of interest to disclose. The publication types list NIH extramural and U.S. government non-PHS research support.
The easy way to misread this
Do not conclude that treadmill walking is more regular than overground walking for patients. The apparent order changed with analysis settings, and the study tested healthy young adults, not a clinical population or treatment.