Either hard, or easy. No middle. This is the most useful way to train for the majority of people.
Either sprint, or jog.
Either do a pump routine, or a heavy routine.
The stuff in the middle, while it feels good, is usually a waste of time.
I think this is a misapprehension of a thing which is mostly true....
The missing factor is TIME.
Over the course of the year or the month or the whatever, the bulk of the energy is best spent training the ends and working towards the middle. Why? Because moving up your top top top end and moving up your baseline are the two things which take the longest to do, are often the most persistent adaptation and quite often (despite assertions to teh contrary) are the most compatible in terms of recovery over time for most people.
Heavy Squats and rucking play well together.
Sprinting and light jogging play well together.
High intensity Skill work (throws) and tonic low intensity movement (bikram, pilates) plkay well together.
Anaerobic and Lactate threshold work and volume squatting...does not play well together for very long.
High intensity circuits of weightlifting movements and 800 meter running...does not play well together for very long.
Crossfit...does not play at all for very long.
So given a set period of time, the bulk of your energy might be spent at teh ends of the spectrum and for distinct sharp blocks of limited time you work that middle ground very very hard.
8 Weeks Out from a SM contest
6 Weeks out from a fight