James wrote this in response to a question asked on eliteft, it is more football based but maybe you can get some ideas out of his response.
"I actually address all of this in a manual that I am creating which illustrates numerous organizational strategies for managing various degrees of impact to the CNS.
Here’s the deal.
Charlie has stated that any running in excess of 75% and less than 90-95% of top speed for that distance is too slow to develop top speed and to0 fast/intensive to recover from in 48 hours. This 75-90%is the middle intensity zone which encompasses gassers, 300yd shuttles, etc.
So from a conditioning perspective the utilization of these medium intensity stressors may usefully be employed AS LONG as they are accounted for as CNS intensive and programmed so as to observe adequate recovery between like workouts/training days.
From a speed development perspective the medium intensity zone is lousy, especially when incomplete recoveries are utilized. The incomplete recoveries inhibit the performance of subsequent repetitions. Thus, the subject is unable to run at top speed for that distance for more than one or two repetitions.
Now, the key here is to contemplate your specific strategy for managing training. I favor the high/low approach in which CNS intensive stressors are consolidated to same training days and alternated with one or more low intensive day. (again this is entirely the basis of my upcoming manual)
Accordingly, if you wish to incorporate medium intensity drills (gassers, 300yd shuttle, metabolic patterns/sequences, etc) than you would be wise to treat these as CNS intensive and alternate these type of workouts/training days with either tempo work or rest.
I personally use my friday night (summer) conditioning workouts, with my high school football players, as metabolic patterns/sequences in which I construct various ‘fights’ using tires. The parameters consist of 4-15 second efforts followed by 20-60s second recoveries (on average). The type of drills which I set up closely approximate the type of fatigue the athletes will experience during actual competition. Here we see that this qualifies as medium intensity, however, the preceeding training day is tempo work and the two following days are rest/weekend. Thus, I have accounted for the CNS impact yielded by this event and adequate recovery is accomplished prior to the CNS intensive nature of Monday’s training which involves speed and/or agility work plus weight training.
So, yes you may incorporate lactic zone work so long as you account for this as CNS intensive in the weekly plan.
Speed and tempo alone, in my view, will not sufficiently condition a football player from a psychologica/physical/and tactical perspective. Their must be lactic energy system work either in the form of SPP drills/game simulation or drills such as the one that I outlined in which the athletes exert themselves ‘relatively’ maximally with incomplete recoveries between repetitions.
Perhaps the most significant component of the medium intensity drills is psychological in the mental toughness that it demands. Speed and tempo do not require this ‘will’ from the athlete. This is the unique aspect of demanding maximal efforts under conditions of fatigue. The way the athletes perform under these conditions will tell you a lot about what they are made of and strengthen their ‘will’.
IMPORTANT, remember that these types of drills MUST be accounted for as CNS intensive, even though they (because of incomplete recovery) do not allow the athletes to actually run at top speed or exert max force against the implements.
I also encourage coaches to do your best to consolidate ‘discipline’ drills to CNS intensive days (off season or in season). This is easier said than done, however it will pay off on game day."