NON-EXERCISE EQUATIONS TO PREDICT VO2 PEAK IN HEALTHY COMMUNITY DWELLING OLDER ADULTS Bonita L. Marks Ph.D., FACSM1,2, Jessica Hawkins, M.A.1, Michael Babbitt M.A.1, and Laurence M. Katz M.D.1,2 Departments of 1Exercise and Sport Science and 2Emergency Medicine, University of North Carolina at Chapel Hill. Presented at SEACSM Conference, Feb 14-16, 2008, Birmingham, AL
INTRODUCTION Patients with functional limitations often cannot participate in peak aerobic capacity (VO2 Peak) testing. A non-exercise VO2 Peak prediction equation developed by Jackson et al. (1990)1 and expanded by Weir et al. (2006)2 suggested that using an estimate of percent body fat (%BF) derived from 3 skinfold sites3 as a body composition predictor variable produced valid VO2 Peak estimates (compared to VO2 Peak obtained from the Bruce treadmill (TM) test protocol) for average fit individuals over 50 years of age (women, n = 195, mean age = 38 yrs: triceps, suprailium, thigh; men, n = 1,814, mean age = 44 yrs: chest, abdomen, thigh; R = 0.81, SE = 5.3 ml.kg.min-1). Another prediction equation was developed using body mass index (BMI) instead of %BF (R = 0.78, SE = 5.6 ml.kg.min-1).1 In healthy subjects, substituting BMI as the criterion variable in the prediction equation of Jackson et al.1 resulted in less than 0.1 ml.kg.min-1 difference, but VO2 Peak estimates for those with positive stress tests or hypertension were under-estimated by 2.4 ml.kg.min-1 (p < 0.02). Furthermore, the original research which established the Jackson & Pollock 3-site formula3 also had a relatively limited older adult sample with women under-represented (men: n = 402,18 - 61 yrs, mean age 33 yrs; women: n = 283,18 - 55 yrs, mean age 32 yrs). Neither the Bruce TM test nor these commonly used skinfold equations are ideal for determining aerobic fitness and predicting %BF in persons exceeding 62 years of age for either gender.
PURPOSE This current study investigated whether substituting a %BF estimate derived from 4 skinfolds sites per Durnin and Wormersley (1974)5 and a less aggressive TM test protocol would yield similar estimates of VO2 Peak in community-dwelling, healthy older adults. References: 1. Jackson AS, Blair SN, Mahar MT, Wier LT, Ross RM, Stuteville JE (1990). Prediction of functional aerobic capacity without exercise testing. Med Sci Sports Exerc, 22:863-870. 2. Weir LT, Jackson AS, Ayers GW, Arenare B (2006). Non-exercise models for estimating VO2max with waist girth, percent fat, or BMI. Med Sci Sports Exerc, 38:555-561. 3. Jackson AS & Pollock ML (1985). Practical assessment of body composition. Phys and Sports Med, 13(5):75-89. 4. Baumgartner TA & Jackson AS (1995). Measurement for Evaluation in Physical Education and Exercise Science. Brown & Benchmark Publ., Madison WI p 289. 5. Durnin JVG & Womersley J (1974). Body fat assessed from total body density and its estimation from skinfold thickness: measurements on 481men and women aged 16 – 72 years. Br J Nutr, 31:77-97.
Subjects
Nineteen older adults between 60 - 76 years of age (11 males, 8 females) volunteered for this study. Subjects reported being highly active (more than 3 hr/wk for past 10 yr) or not very active at all (less than 90 min a week) All were healthy without cardiopulmonary, metabolic, or orthopedic limitations.
Body Composition Assessment Body Mass Index (BMI): Height and weight was measured without shoes using a Detecto balance-beam scale with a height rod. BMI was calculated from the formula: BMI = weight (kg) ÷ height (m2). Percent Body Fat (%BF): Fatfolds were measured on the right side of the body in a rotational fashion 3 times using a Lange skinfold caliper (Cambridge, MD) at the following anatomical sites for both genders: tricep, bicep, suprailium, and subscapula. Percent body fat estimates were obtained from age and gender specific tables originally created by Durnin & Womersley (1974) from linear regression equations of body density based upon a sample population of men (n = 209) and women (n = 272), ranging in age from 16 – 72 yrs (n = 24 for men aged 50 - 72 yrs; n = 37 for women aged 50 - 68 yrs).5
This research was approved by UNC’s Biomedical Institutional Review Board for Human Subjects, Study #05-3151. Funding was provided by the Biomedical Research Imaging Center (BRIC), School of Medicine, University of N. Carolina at Chapel Hill.
Descriptive Characteristics (Means ± SD) Variable Males (n = 11) Females (n = 8) Total (n = 19) Age (yrs.) 66.5 (5.3) 65.5 (6.5) 66.1 (5.7) Height (cm) 173.9 (5.4) 159.5 (4.5) 167.9 (8.8) Weight (kg) 75.6 (9.1) 72.5 (10.9) 74.3 (9.7) 24.9 (2.9) 28.7 (4.7) 26.5 (4.1) BMI (kg.m2) VO2Peak(Parvo) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXxx (ml.kg-1.min-1) 36.6 (8.0) 23.4 (7.1) 31.0 (10.0)
Scatterplots Comparing Predicted vs. Actual VO2 Peak (n = 19)
Subjects underwent a physician-supervised, ECG-monitored ramped exercise stress test on a treadmill utilizing the Modified Pepper Protocol, a progressive walking protocol developed at Duke University’s Center of Aging. The protocol begins at 1.5 mph and gradually progresses to 3.3 mph while the grade increases from 0 to 20%. Oxygen consumption was measured using the PARVO TrueMax VO2 Metabolic Cart System (ParvoMedics, Salt Lake City, Utah ). Blood pressure and ratings of perceived exertion were also recorded. The test was terminated when the subject requested to stop or the physician deemed it appropriate to stop the test. All tests were completed without incident with subjects attaining or slightly exceeding their age-predicted maximum heart rates.
VO2 Prediction Equations
VO2%BF ~ 50.513 + (1.589 * PAR ) - (0.289 * age) - (0.552 * %BF) + ( 5.863 * gender) VO2 BMI ~ 56.363 + (1.921 * PAR ) - (0.381 * age) - (0.754 * BMI) + (10.987 * gender) Gender: 0 = women; 1 = men PAR4 : Physical Activity Rating from 0 to 7 ( mean = 4) No regular participation in recreational sport or heavy physical activity (0 or 1) Regular participation in recreation or work requiring modest physical activity (2 or 3) Regular participation in heavy physical exercise (4 to 7)
r = 0.87 p = 0.01
r = 0.89 p = 0.01
VO2Peak Assessment
Where:
ACKNOWLEDGEMENTS
RESULTS
METHODS
†
VO2Peak VO2%BF VO2 BMI
† Fitness
Low Fit (n=9) 23.2 ( ± 5.7)* 16.6 ( ± 5.1) 17.0 ( ± 6.6)
Average Fit (n=9)
†
VO2 = ml.kg.min-1 (Means ± SD)
High Fit (n=1)
†
36.3 ( ± 5.1) 32.2 ( ± 4.8) 33.7 ( ± 3.6)
category assigned per the VO2Peak (Parvo) values;
54.35 41.38 38.59 *p < 0.001,
Paired T Tests
CONCLUSIONS Within groups, VO2Peak estimates were not significantly different (p =0.18). Low Fit Group (VO2 < 30 m.kg.min-1) had significant under-estimations of VO2 Peak using either predictor variable (BMI or 4-site %BF), however both did estimate the subjects to be in a low-fit category. Either predictor variable was adequate for the Average Fit Group: VO2: 30 to 50 ml.kg.min-1 (per PARVO measurements) Durnin & Womersley 4-site skinfold %BF estimate5 appears to be a suitable substitute for the J&P 3-site skinfold %BF estimate.1,3 Neither predictor variable appeared adequate for the High Fit subject.
