Does it really make any difference? If yes, then by what mechanism?
I pass gas frequently and have hard stools. I've read that walking helps with both these problems.
For example, on the Mayo Clinic site, one of the recommendations is
Get moving. It may help to take a short walk after eating.
That's all of it; there's no explanation why. I've seen similar advice on other sites as well.
Is there any truth to this? And how does exercise affect constipation?
This '05 study found a positive effect from exercise. Here middle aged (>45y) subjects with chronic idiopathic constipation had their Rome symptoms (straining, hard stools, and incomplete evacuation) improved by a 30 min cardio workout and 11 minute home programe.
On the other hand, this '98 study found there was little or no positive effect on patients with the same diagnosis, this study however, was smaller and of shorter duration.
However, I could find no study in favor (or against) of exercise helping occasional constipation. It is in the nature of this condition hard to gather subject for a controlled study, and we can assume the clinical support will stay at anecdotal level for some time being.
As exercise a lot of other benefits, it should in worst case be a harmless recommendation. Best case there is some effect that is not yet clinically documented.
As per vidstige's answer, it would probably only have minimal impact, although it is mentioned in some health articles, but usually not as the first item.
Hard stools or constipation can by understanding the causes of constipation addressed changing some habits for the most common causes. As per Causes of constipation
As per these articles Hard Poop, Constipation in adults the other first two are addressed by drinking more water, and changing your diet to include more fiber. If you are still getting hard stool after that, then also include some foods that have a laxative effect. e.g.
See Which foods are good for constipation? and just a Google Search for Laxative foods.
The delay one can be addressed by not waiting to go, and even if you feel you just need to pee, go and sit down on the toilet, this will sometimes trigger bowel movements.
Exercise would address #4
For #5 to #8, talk to a medical professional.
