RELIABILITY AND PRECISION OF TWO METHODS FOR DETERMINING THE VENTILATORY THRESHOLD IN SEDENTARY BONE MARROW TRANSPLANT RECIPIENTS. Rick Wilson*1; Candi Ashley2 1. School of Physical Therapy, University of South Florida, Tampa, FL; 2. School of Physical Education, Wellness and Sports Studies, University of South Florida, Tampa, FL PURPOSE: The reliability and precision of 2 methods of determining the ventilatory threshold were assessed in the context of screening participants for a pilot study of a home-based aerobic exercise intervention for sedentary adult cancer survivors. BACKGROUNDS/SIGNIFICANCE: Diminished aerobic capacity appears to be one plausible mechanism of fatigue and physical disability in adults diagnosed with cancer. The ventilatory threshold represents the maximum sustainable aerobic exercise intensity and has been shown to occur at energy requirements required to perform activities of daily living in adult cancer survivors treated with hematopoietic stem cell transplantation. This suggests that sedentary adult cancer patients may not have the ability to sustain physical activities at even slightly higher energy requirements. Physiological indexes of aerobic impairment and oxidative metabolic dysfunction might provide quantitative evidence for fatigue-related disability in bone marrow transplant recipients. Several techniques may be used to determine the ventilatory threshold but their measurement properties have been studied in this population. SUBJECTS: Seventeen cancer survivors (mean age=48.9 years, SD=10.9, range=27-64) treated with hematopoietic stem cell transplantation at least six months prior to recruitment who participated in leisure time physical activities less than 20 minutes per day and fewer than 3 times per week. METHODS AND MATERIALS: Oxygen uptake at the ventilatory threshold (VO2vt) was measured on 2 occasions prior to initiating a 12 week home- based aerobic exercise program. Two blinded raters used 2 methods (V-slope and ventilatory equivalents) to assess VO2vt using open circuit spirometry data obtained during submaximal graded exercise tests. ANALYSES: Interrater reliability, test-retest reliability, and standard errors of measurement (SEM) were determined for both methods. RESULTS: Average VO2vt values obtained using the Veq method (1068+295 ml/min) were higher (paired t-test; p<.01) than those obtained with the V-slope method (839+216 ml/min). The intraclass correlation coefficient for interrater reliability was .94 for the V-slope method and .86 for the ventilatory equivalents (Veq) method. Intraclass correlation coefficients for test-retest reliability were .78 for the V-slope and .65 for the Veq method. The SEM at an interval of 1 week was 114.6 ml/min [95% CI: 91.2;153.9] for the V-slope and 162.0 ml/min [131.5; 213.2] for the Veq method. CONCLUSIONS: Compared to the V-slope method, the Veq method demonstrated a positive bias as a measure of VO2vt. Both the V-slope and ventilatory equivalent methods appeared to be highly consistent between raters but only moderately stable at a measurement interval of 1 week. The V-slope method appeared to be a more conservative and precise method for determining aerobic fitness in this sample. FUNDING SOURCE: This study was funded in part by a Linda Crane Research Award from the Florida Physical Therapy Association. KEYWORDS: aerobic exercise, measurement, cancer, physical fitness, fatigue Comparison of events at the ventilatory threshold.* * Tabled values represent mean (SD) for each method. Copyright 2009 by the American Physical Therapy Association. Requests for reprints should be directed to the corresponding author of the article. Educators, students, and other academic customers may receive permission to reprint copyrighted material from Physical Therapy (ISSN 1538-6724) by contacting the Copyright Clearance Center Inc, 222 Rosewood Dr, Danvers, MA 01923. Other types of customers who want permission to reprint should contact the APTA Editorial Office, Attn: Physical Therapy.