“And what made these workouts, in my humble opinion, so intriguing and successful? If the repeats were run at the proper pace (not too hard), and since they were of a short duration (usually about 150 yards), they allowed the runner to accomplish the 3 most important things in ONE workout:
“1) working the aerobic system, ie, not going past (or heavily past) the Anerobic Threshhold (again, this was possible because the repeats were so short, and the breaks so frequent), but not dropping the HR's too low either (ie, too easy)
“2) overall minutes in Aerobic zone could be high(ie, good volume. How? Again, see above: one backs off continually just before Heart Rate reaches higher levels, and recovery jog/walk quickly returns HR to lower levels)
“3) SPEED. ALL the running in these workouts are at a faster pace than one would do if they were running the same, let's say, 60 minutes steady.
“What is better? A 60 minute steady run averaging a Heart Rate of 155, (and let's say run at 6:15 pace) OR.....
A 60 minute effort, broken up into LOTS of 25-30 second "bursts" of 5:00 pace, where the HR reaches 165 briefly at the end of each repeat (but is still within the Aerobic zone), then drops to 140 during recovery jog/walk (done at about 9:00-10:00 pace), and again the overall HR of the workout averages 155 ?
“…And let me repeat, such workouts can STILL be a below threshold effort, despite the faster paced repeats.
“And as far as risk of muscle pulls or whatever from the faster paces, one last time, these are NOT all-out sprints being done. That is not what the workout is for (of course they can done in all-out manner also later on, and I am sure Igloi had his runners do those all-out workouts too, but that is for later on and for a different purpose).
“In order to run a LONG, AEROBIC workout, something MUST be sacrificed (if not, the run will be too hard, ie, anerobic, or too short). Therefore your two choices are:
•The 60 minute STEADY aerobic effort, which sacrifices speed , because it contains no breaks (or very easy sections)
•The 60 minute Igloi/Schul aerobic workout, which sacrifices steadiness (consistency of pace, because it allows breaks/very slow parts). But of course what you get in return for that "sacrifice" is LOTS of faster paced running.”