I know people that have gone through our fire/EMS academy in their upper 40's and one at 50. A fire academy is harder on the body than field EMS, so I'm sure you'll be okay. What will take you out is on the job injuries from lifting patients. I know many broken down medics and EMT's. Also, I might reconsider if you have a history of hypertension, a cardiac history, etc. EMT 's have died from cardiac related issues. Firefighters die every year responding to and returning from calls, and also dying in their sleep after a rough shift. I mention firefighters because they ride in emergency vehicles and respond just like EMS. The stress and adrenaline spikes, as well as the broken sleep and demands of going from "zero to 60" rapidly from a dead sleep can wreak havoc on the body. Discuss this with your physician.