Outbreaks　of　respiratory　infectious　diseases　have　often　been　reported　in　fitness　centers,　likely　attributed　to　high　population　density,　extensive　shared　surfaces,　and　elevated　metabolic　equivalent　(MET)　levels.　This　study　analyzed　the　behaviors　of　30　gym　attendees　to　establish　a　connection　between　exercise　intensity　and　virus　exposure.　Close　interactions　among　participants　were　tracked　using　self-developed　wearable　devices　that　utilized　computer　vision　technologies,　while　surface-contact　behaviors　were　recorded　using　video　cameras.　A　multi-route　transmission　model　for　respiratory　infectious　diseases　was　subsequently　created,　integrating　the　observed　behaviors.　The　Omicron　variant　of　COVID-19　served　as　a　case　study　to　evaluate　infection　risk　via　various　transmission　routes　and　to　assess　the　efficacy　of　interventions.　The　METs　during　physical　activity　were　about　3.5　times　higher　than　those　recorded　at　rest.　The　average　interpersonal　distance　during　close　interactions　in　the　gym　was　measured　at　0.82　m,　with　36.7　%　of　interactions　occurring　face-to-face.　On　average,　the　participants　made　contact　with　surfaces　770.3　times　per　hour,　with　517.5　of　these　contacts　involving　public　surfaces.　The　hourly　infection　rate　was　calculated　at　18.5　%,　with　long-range　airborne　transmission　and　close　contact　accounting　for　70.1　%　and　28.5　%　of　the　cases,　respectively.　To　mitigate　transmission　risk,　several　intervention　scenarios　were　modeled.　These　included　(1)　100　%　mask-wearing　with　N95　masks　and　occupancy　reduced　to　62　%　(25　m2/person);　(2)　100　%　mask-wearing　with　surgical　masks　and　occupancy　reduced　to　26　%　(59.6　m2/person);　(3)　no　mask-wearing,　with　occupancy　reduced　to　18　%　(86.1　m2/person).　All　scenarios　fulfilled　the　criteria　for　achieving　an　Rt　below　1,　indicating　that　under　these　conditions,　gyms　could　be　reopened　safely.　©　2024　Elsevier　Ltd