So I got this on sale on Amazon the other day for 20$
https://www.amazon.com/gp/aw/d/B01GCA4BJC?psc=1#
For when it snows and they don't plow worth a ****, or if I don't feel like going to the gym, or wanting to switch my workout up for a week.
Do these things actually build muscle or will it be more of a flexibility thing?