Jacob T Bonafiglia1, Nicholas Preobrazenski1, Hashim Islam1, Jeremy J Walsh2,3, Robert Ross1, Neil M Johannsen4,5, Corby K Martin5, Timothy S Church5, Cris A Slentz6, Leanna M Ross6, William E Kraus6,7, Glen P Kenny8,9, Gary S Goldfield3,8,10,11, Denis Prud'homme8,12, Ronald J Sigal8,9,13, Conrad P Earnest14, Brendon J Gurd15. 1. School of Kinesiology and Health Studies, Queen's University, Kingston, ON, Canada. 2. Department of Kinesiology, McMaster University, Hamilton, ON, Canada. 3. Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada. 4. School of Kinesiology, Louisiana State University, Baton Rouge, LA, USA. 5. Pennington Biomedical Research Center, Baton Rouge, LA, USA. 6. Duke Molecular Physiology Institute, Duke University School of Medicine, Durham, NC, USA. 7. Division of Cardiology, Duke University School of Medicine, Durham, NC, USA. 8. School of Human Kinetics, Faculty of Healthy Sciences, University of Ottawa, Ottawa, ON, Canada. 9. Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada. 10. Department of Pediatrics, University of Ottawa, Ottawa, ON, Canada. 11. School of Psychology, University of Ottawa, Ottawa, ON, Canada. 12. Institut du Savoir Montfort, Ottawa, ON, Canada. 13. Departments of Medicine, Cardiac Sciences and Community Health Sciences Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. 14. Health and Kinesiology, Texas A & M University, College Station, TX, USA. 15. School of Kinesiology and Health Studies, Queen's University, Kingston, ON, Canada. gurdb@queensu.ca.
Abstract
OBJECTIVE: This study tested the hypothesis that greater mean changes in cardiorespiratory fitness (CRF), in either the absence or presence of reduced interindividual variability, explain larger CRF response rates following higher doses of exercise training. METHODS: We retrospectively analyzed CRF data from eight randomized controlled trials (RCT; n = 1590 participants) that compared at least two doses of exercise training. CRF response rates were calculated as the proportion of participants with individual confidence intervals (CIs) placed around their observed response that lay above 0.5 metabolic equivalents (MET). CIs were calculated using no-exercise control group-derived typical errors and were placed around each individual's observed CRF response (post minus pre-training CRF). CRF response rates, mean changes, and interindividual variability were compared across exercise groups within each RCT. RESULTS: Compared with lower doses, higher doses of exercise training yielded larger CRF response rates in eight comparisons. For most of these comparisons (7/8), the higher dose of exercise training had a larger mean change in CRF but similar interindividual variability. Exercise groups with similar CRF response rates also had similar mean changes. CONCLUSION: Our findings demonstrate that larger CRF response rates following higher doses of exercise training are attributable to larger mean changes rather than reduced interindividual variability. Following a given dose of exercise training, the proportion of individuals expected to improve their CRF beyond 0.5 METs is unrelated to the heterogeneity of individual responses.
OBJECTIVE: This study tested the hypothesis that greater mean changes in cardiorespiratory fitness (CRF), in either the absence or presence of reduced interindividual variability, explain larger CRF response rates following higher doses of exercise training. METHODS: We retrospectively analyzed CRF data from eight randomized controlled trials (RCT; n = 1590 participants) that compared at least two doses of exercise training. CRF response rates were calculated as the proportion of participants with individual confidence intervals (CIs) placed around their observed response that lay above 0.5 metabolic equivalents (MET). CIs were calculated using no-exercise control group-derived typical errors and were placed around each individual's observed CRF response (post minus pre-training CRF). CRF response rates, mean changes, and interindividual variability were compared across exercise groups within each RCT. RESULTS: Compared with lower doses, higher doses of exercise training yielded larger CRF response rates in eight comparisons. For most of these comparisons (7/8), the higher dose of exercise training had a larger mean change in CRF but similar interindividual variability. Exercise groups with similar CRF response rates also had similar mean changes. CONCLUSION: Our findings demonstrate that larger CRF response rates following higher doses of exercise training are attributable to larger mean changes rather than reduced interindividual variability. Following a given dose of exercise training, the proportion of individuals expected to improve their CRF beyond 0.5 METs is unrelated to the heterogeneity of individual responses.
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