In a different thread (https://www.uphillathlete.com/forums/topic/30-30s-on-a-treadmill-at-incline/) Scott discusses what 30/30 session may target and stimulate.
Say you are a skier/runner, what do the following sessions stimulate:
1. 20x(30″ Z4 effort + 30″ coasting) — This one has already been answered
2. 20x(45″ Z4 effort + 15″ coasting)
3. 8x(60″ Z4 + 45″ Z4 + 30″ Z4 + 15″ Z4 with 15″ coasting in between)
4. 8x(30″ effort + 30″ rest), effort is close to all out (say 115% of your anaerobic threshold pace = Z4 but faster than effort in #1, #2, #3)
5. 8x(30″ effort + 90″ rest), effort is close to all out
#1, #2 and #3 have the same speed, but different duration of effort and rest
#4 and #5 are a bit faster, but have different recovery
There’s always these subtle differences (how fast you go, how fast and how long is your
recovery) that may completely change the stimulus.