An Objective Method to Accurately Measure Cardiorespiratory Fitness in Older Adults Who Cannot Satisfy Widely Used Oxygen Consumption Criteria

Article type: Research Article

Authors: Dougherty, Ryan J.^{a; b; c} | Lindheimer, Jacob B.^{a; b; d} | Stegner, Aaron J.^{a; b} | Van Riper, Stephanie^{a; b} | Okonkwo, Ozioma C.^{c; e; f} | Cook, Dane B.^{a; b; *}

Affiliations: [a] William S. Middleton Memorial Veterans Hospital, Madison, WI, USA | [b] Department of Kinesiology, University of Wisconsin School of Education, Madison, WI, USA | [c] Wisconsin Alzheimer’s Disease Research Center, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA | [d] Department of Veterans Affairs, New Jersey Healthcare System, War Related Illness and Injury Study Center, East Orange, NJ, USA | [e] Geriatric Research Education and Clinical Center, William S. Middleton Memorial Veterans Hospital, Madison, WI, USA | [f] Wisconsin Alzheimer’s Institute, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA

Correspondence: [*] Correspondence to: Dane B. Cook, PhD, Department of Kinesiology, University of Wisconsin, Madison, WI 53706, USA. Tel.: +1 608 262 7737; E-mail: dane.cook@wisc.edu.

Abstract: 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 (V̇O2peak) test compared to those who did not; and 3) determine the difference between directly measured V̇O2peak values and OUES-predicted V̇O2peak 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. V̇O2peak 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 V̇O2peak (rrange = 0.801–0.909; p < 0.001). As hypothesized, participants who did not satisfy V̇O2peak criteria were significantly older than those who satisfied criteria (p = 0.049) and attained a directly measured V̇O2peak that was 2.31 mL·kg·min-1 less than the value that was predicted by OUES V̇O2peak (p = 0.003). Older adults are less likely to satisfy V̇O2peak criteria, which results in an underestimation of their CRF. Without adhering to standardized criteria, V̇O2peak 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.

Keywords: Alzheimer’s disease, cardiopulmonary exercise testing, maximal exercise test, oxygen consumption, oxygen uptake efficiency slope, sub-maximal exercise test

DOI: 10.3233/JAD-170576

Journal: Journal of Alzheimer's Disease, vol. 61, no. 2, pp. 601-611, 2018