Rest days???

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So i've been walking now at a 3.5mph rate...slowly increasing the incline every 5 minutes, up to level 4, and then back down. Burning around 420 calories in 45 minutes. I'm wondering if people give their legs rest days. I also work on a very active dementia unit in a local LTC facility and my legs get a good work out through that as well. This is where i need the most work though...so i don't mind. I'm just wondering if I should give my legs rest days. And if I should...when? Should i work 3 days in a row then take a rest day or something like that? Any suggestions appreciated :)