When I had a regular exercise routine, I noticed a definite improvement in my fluency. I used to work out in the mornings for about an hour, always getting my heart rate above 130 and breaking a good sweat. On those days I was able to talk more smoothly. When I did stutter, my physical and emotional responses did not seem as bad either. For me, exercise intensity was key. On days when i didn't break a sweat and get my heart rate up, I did not see the same benefits.