A Nonexercise Model to Estimate Cardiorespiratory Fitness in Individuals with Spinal Cord Injury

Purpose: Cardiorespiratory fitness (CRF), commonly assessed by peak oxygen uptake (VO2peak), is widely recognized as an independent predictor of cardiovascular morbidity and mortality.However, direct assessment is resource-intensive and may not be feasible in individuals with spinal cord injury (SCI).This study aimed to develop and validate an SCI-specific nonexercise model to estimate CRF.Methods: Thirty-seven individuals with SCI underwent direct CRF assessment using VO 2 peak measured during a graded arm-crank ergometer test with gas analysis.Estimated CRF was derived using multivariable linear regression.Candidate factors included demographic, anthropometric, physiological, injury-related, and physical activity variables.Agreement between measured and estimated VO 2 peak was evaluated using correlation and Bland-Altman analysis.Results: Participants (mean age, 46.7±9.2 years; 25 male and 12 female participants) had a mean measured VO2peak of 16.1±6.1 mL•kg -1 •min -1 .The final model included injury level, waist circumference, heart rate, and total physical activity, and showed moderate explanatory performance (adjusted r 2 =0.645, root mean square error=3.36).The resulting equation for estimating VO 2 peak was: VO 2 peak=17.80-7.26(tetraplegia)-0.11(waist circumference)＋ 0.12 (heart rate)＋ 0.19 (total physical activity).Estimated VO2peak was strongly associated with measured VO 2 peak (r=0.83,p＜ 0.001), and Bland-Altman analysis showed no clear systematic bias.Conclusion: This SCI-specific nonexercise CRF estimation model demonstrated moderate explanatory performance using clinically accessible variables.These findings suggest that the model may provide a practical approach for estimating VO 2 peak in clinical and rehabilitation settings when direct assessment is not feasible.