"I practice running at different tempos for different lengths of time"
Pretty much the same as singing - you learn all the paces and speeds and efforts - MacColl used Laben's scale of movement and applied them to singing brilliantly
A far as traditional singing, the old singers sang more or less as they spoke (barring old age, etc) and their enunciation and phrasing were as close to those used in speaking as the music and poetic rhythms would allow - the ones we interviewed described how they would put almost imperceptible notes or gaps in to maintain both the rhythm and the narrative sense - the old Clare farmer, Tom Lenihan (recognised locally as 'the traditional singer' went in great detail about this

One of the most important aspects of singing is learning to relax - tension can distort both voice production and breath control
Once you work out a technique for this you can apply it to almost anything - I use it all the time for driving, especially along narrow country lanes
Jim