If you're fit and run it at the correct effort, breathing should always feel easy and your HR shouldn't go too high. The only thing that might be tired would be your feet/legs after 8 miles or so, if you're not running in the pogo shoes
Doesn't Lydiard specifically prescribe these runs for once a week during base phase?
I think Daniels says there's no physiological benefit, but he says to do them once in a while for marathon training (although not other distances) for the psychological benefit as well as general practice at that pace.
He also amended the most recent additions of his book to include... you guessed it... 10 mile runs at M pace in his 5k plan.
Which book is this in? I have nearly all of them and have never seen this. And I'd known Arthur since 1977, exchanged e-mails and letters with him for stretches of time, have been to several of his talks, visited him in New Zealand,spent a weekend with him a month before he died, and never knew him to specify a particular pace, though he did at one time give those fractional efforts, 7/8 effort, 3/4, 1/4, etc.
To the OP's question as applied to Lydiard and to most of us from that era, all a steady run was is a run at a constant pace, i.e, not an interval or fartlek session. You can do them at any kind of pace or effort and you might pick the pace up as the run goes on or you might slow it a bit if you're struggling.
He also amended the most recent additions of his book to include... you guessed it... 10 mile runs at M pace in his 5k plan.
Which book is this in? I have nearly all of them and have never seen this. And I'd known Arthur since 1977, exchanged e-mails and letters with him for stretches of time, have been to several of his talks, visited him in New Zealand,spent a weekend with him a month before he died, and never knew him to specify a particular pace, though he did at one time give those fractional efforts, 7/8 effort, 3/4, 1/4, etc.
To the OP's question as applied to Lydiard and to most of us from that era, all a steady run was is a run at a constant pace, i.e, not an interval or fartlek session. You can do them at any kind of pace or effort and you might pick the pace up as the run goes on or you might slow it a bit if you're struggling.