Hi Barson,
That's an excellent question! The basic reason is because you're not using as many muscles, and therefore energy, as you would be without the support of the walker or grocery cart.
When our body requires more effort than usual just to breathe, anything we can do to conserve elsewhere will save energy. So, by supporting yourself as you walk or even by stopping to rest periodically, you're conserving energy and are able to get farther than you would have without the added assistance.
So, next time you're somewhere and have the option to use a supportive device - do it! You'll get farther with less spent energy.
Warm Regards,
Lyn (site moderator)