Ventilatory threshold may be a more specific measure of aerobic capacity than peak oxygen consumption rate in persons with stroke.
Pierce Boyne, Darcy Reisman, Michael Brian and 5 others
PMID 27454553WHAT IT FOUND
The breathing threshold measure was less tied to walking speed than peak oxygen use in 59 people with chronic stroke.
This may mean it reflects aerobic capacity more specifically. Peak oxygen use can look artificially low when walking is impaired. The rating method was reliable.
Key findings
01After adjustment, VO2-VT was less strongly related to comfortable gait speed than VO2-peak (r=0.37 vs r=0.52; difference r=-0.16, p=0.02).
02VO2-VT ratings were reliable across three raters, including one novice: means were 10.5, 10.7 and 10.6; overall ICC 0.93 (95% CI 0.89 to 0.96).
03OUES did not show significantly lower motor-function correlations than VO2-peak (r differences -0.08 to 0.18, p=0.17 to 0.84).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
This was a cross-sectional correlation analysis, so it cannot show that VO2-VT is more specific than VO2-peak or that motor function causes the difference. There is no gold-standard aerobic capacity measure for persons with stroke, so the researchers had to adjust indirectly for possible confounders. Physical activity history was missing for many incline GXT participants (17 of 33), and the sensitivity analysis used only 43 of 59 participants. The data combined two studies with different GXT protocols and eligibility criteria; the speed protocol was partly based on each participant's gait speed, which may have inflated the correlation between VO2-VT and walking speed. The main finding was not consistent across protocol subsets: in the speed GXT subset, VO2-VT and VO2-peak had similar correlations with walking speed (p=0.69). The OUES result was unclear: residual confounding appeared when steps per day were adjusted (differences 7 to 20%), and OUES differences from other measures were not statistically significant (p=0.17 to 0.84). The reliability sample was smaller than the main analysis (44 participants), and some GXT files were not in the required software format.
Declared interests
The authors declared no conflicts of interest. Publication metadata indicates NIH extramural and non-U.S. government research support.
The easy way to misread this
Do not conclude that VO2-VT is a proven replacement for VO2-peak in stroke assessment. This was a cross-sectional analysis without a gold-standard aerobic capacity measure, and the advantage was not consistent across treadmill protocols.