After a long run or a difficult workout, walking around on sore feet for the rest of the day is the worst. By massaging your feet with a roller like this one, you promote circulation and prevent soreness & cramps.
Things like these are ridiculously expensive to buy–go to any specialty running store and you'll find something exactly like this for $25. Printing this will only set you back about $5 or less in filament costs.
Simply print one of each part–I printed the sleeve in PLA and the core in PETG to give it some strength and durability–and assemble by fitting the sleeve onto the core and screwing on the cap. It's very easy.
The rest of my RECOVER series will also focus on providing affordable alternatives to otherwise expensive exercise and muscle therapy equipment–come back to my page to see!