Abstract: medRxiv preprint doi: https://doi.org/10.1101/2021.02.25.21252451; this version posted March 1, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license . PHYSICAL ACTIVITY AND COVID-19 HOSPITALIZATION 1 Muscle Strength Explains the Protective Effect of Physical Activity against COVID-19 Hospitalization among Adults aged 50 Years and Older RUNNING HEAD: PHYSICAL ACTIVITY AND COVID-19 HOSPITALIZATION Silvio Maltagliati1*, Stephen Sieber2, Philippe Sarrazin1, Stéphane Cullati3,4, Aïna Chalabaev1, Grégoire P. Millet5, Matthieu P. Boisgontier6,7, Boris Cheval8,9* 1 Univ. Grenoble Alpes, SENS, F-38000 Grenoble, France. 2 Swiss NCCR “LIVES–Overcoming Vulnerability: Life Course Perspectives”, University of Geneva, Geneva, Switzerland. 3 Population Health Laboratory (#PopHealthLab), University of Fribourg, Fribourg, Switzerland. 4 Department of Readaptation and Geriatrics, University of Geneva, Geneva, Switzerland. 5 Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland. 6 School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa, Ottawa, ON, Canada. 7 Bruyère Research Institute, Ottawa, ON, Canada. 8 Swiss Center for Affective Sciences, University of Geneva, Geneva, Switzerland. 9 Laboratory for the Study of Emotion Elicitation and Expression (E3Lab), Department of Psychology, University of Geneva, Geneva, Switzerland. NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice. medRxiv preprint doi: https://doi.org/10.1101/2021.02.25.21252451; this version posted March 1, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license . PHYSICAL ACTIVITY AND COVID-19 HOSPITALIZATION * 2 Corresponding authors: S. Maltagliati, 1741 Rue de la Piscine, UFR STAPS, 38041, Saint Martin d’Hères, France. Email: silvio.maltagliati@univ-grenoble-alpes.fr, @Maltagliati_S. B. Cheval, Campus Biotech, Chemin des mines 9, 1202, Genève, Switzerland. Email: boris.cheval@unige.ch, @ChevalBoris. Words: 2755 Figures: 3 Tables: 3 Supplementary material: 3 tables. medRxiv preprint doi: https://doi.org/10.1101/2021.02.25.21252451; this version posted March 1, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license . PHYSICAL ACTIVITY AND COVID-19 HOSPITALIZATION 3 Abstract Objectives. Physical activity has been proposed as a protective factor for COVID-19 hospitalization. However, the mechanisms underlying this association are unclear. Here, we examined the association between physical activity and COVID-19 hospitalization and whether this relationship was explained by other risk factors for severe COVID-19. Method. We used data from adults aged 50 years and older from the Survey of Health, Ageing and Retirement in Europe. The outcome was self-reported hospitalization due to COVID-19 measured before August 2020. The main exposure was usual physical activity, self-reported..