what is this workout accomplishing…
3x3x50
1 min rest between reps and 3 mins rest between sets
At what tempo?
done at 95-100%
Physiologically it would be a strong stimulus for mitochondria to grow around fibers called upon to do the work.
From CNS point, my take is it depends a lot on what kind of pace/effort You are actually able to hold with such short rests,and what kind of drop off You experience from bout to bout.
does anyone implement this into there program for short or long sprinters?
And if so, and the other day was special endurance woudl it be detrimental for pure accle/max v work to be ignored? i can see off season when 3 workouts are possible including all 3 but how about in comp when 2 workouts are begin used?
It sounds like a great workout when the track is congested and you are not sure what people are doing on the turns 
Nothing like flying around the bend and having to avoid someone in the sprint lane(s)
Agreed Chris 
Quik -
I would say that would be a speed endurance workout for a 100m sprinter and a lactate workout for a 400m sprinter. Anyone agree/disagree?
We do 3x3x50/60 with similar recovery intervals (in some cases 2 mins between sets 2 and/or 3) subsequent to period transition and prior to pre-competition phase. When performed on micro day 1, an SE (e.g. split 160s) work bout may be performed on day 4 following ET and neuromuscular recovery.
MaxV and acceleration work is not performed during this micro. In addition, we don’t work this session more than 2 consecutive micros and only twice during the training year. Speed endurance is the goal and results have been favorable with our group. Though demanding, we have sold the athletes on this work as a primer for extensive SE work to come.
The one caveat on doing this workout is, if the athlete meets test and evaluation goals prior to transition. If not, we typically work on those areas that are deficient, which may not require the session discussed here.
but if this type session is only worked on for 2 sessions per year how is an adaptation made? Or is it not supposed to be? and if an adaptation is indeed made then wouldnt not continuing that session have a negative effect on perfromance? (you lost what you have gained)?
Actually, the maximum use of this session is 4x during a training year. The split runs (80-90%) however, are the focus. Though longer in duration, the quality and confidence of work completion is enhanced with the demanding early-meso speed endurance (95%) work. Particularly with athletes competing in the 300/400 events.
Flying sprints (maxV) of shorter to greater duration replaces this session, as well as acceleration sessions, with longer recovery intervals. When we have extended the 3x3x50/60 throughout the meso, test and evaluation goals were subpar (given that everything else was the same).
At the percentage you state it is “cold climate” split rep special endurance - i.e. good for indoors.
Quik are you doing these from standing start, blocks or with a small run-in?
thanks
Chris
standing/falling start