Dougherty RJ; Lindheimer JB; Stegner AJ; Van Riper S; Okonkwo OC; Cook DB.

Journal of Alzheimer’s Disease. 61(2):601-611, 2018.
VI

Cardiorespiratory fitness (CRF) is routinely investigated in older adults;
however, the most appropriate CRF measure to use for this population has
received inadequate attention. This study aimed to 1) evaluate the
reliability and validity of the oxygen uptake efficiency slope (OUES) as a
sub-maximal measurement of CRF; 2) examine demographic, risk-factor, and
exercise testing differences in older adults who satisfied standardized
criteria for a peak oxygen consumption (VO2peak) test compared to those
who did not; and 3) determine the difference between directly measured
VO2peak values and OUES-predicted VO2peak values. One hundred ten
enrollees from the Wisconsin Registry for Alzheimer’s Prevention
participated in this study. Participants performed a graded maximal
exercise test and wore an accelerometer for 7 days. For each participant,
the OUES was calculated at 75%, 90%, and 100% of exercise duration.
VO2peak was recorded at peak effort, and one week of physical activity
behavior was measured. OUES values calculated at separate relative
exercise durations displayed excellent reliability (ICC = 0.995; p <
0.001), and were strongly correlated with VO2peak (rrange = 0.801-0.909; p
< 0.001). As hypothesized, participants who did not satisfy VO2peak
criteria were significantly older than those who satisfied criteria (p =
0.049) and attained a directly measured VO2peak that was 2.31 mL.kg.min-1
less than the value that was predicted by OUES VO2peak (p = 0.003). Older
adults are less likely to satisfy VO2peak criteria, which results in an
underestimation of their CRF. Without adhering to standardized criteria,
VO2peak measurement error may lead to misinterpretation of CRF and
age-related associations. Here, we conclude that OUES is a reliable, valid
measurement of CRF which does not require achievement of standardized
criteria.