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DEEP DIVE
I learnt the sprint training taxonomy in the UK, and the way it gets taught here is fairly clean. Speed, speed endurance, specific endurance, special endurance. Four buckets, each meant to train something different.
The system has been around for decades and it's the framework I still default to when I'm laying out a session plan or explaining what a workout is meant to deliver.
What I've noticed working with athletes, and talking to other coaches, is how often those terms get mixed up. Speed endurance and special endurance are the two that get confused most.
You'll hear one coach describe 3×200m at 95% with full recovery between reps and call it special endurance. You'll hear another describe 4×150m at race pace with shorter recoveries and call it the same.
Both coaches have track records, and both work with athletes who run fast. Neither is wrong inside the system they were trained in. They've just trained under different schools where the term points to different work.
The vocabulary mix-up isn't really the problem. The principle mix-up that tends to follow it is.
Because if you don't know what each of those sessions is actually doing physiologically and neurologically, the chances of you hitting the right adaptation in the right week of the year drop fast.
The principles are the thing. The names are just labels.
If you understand what each type of session is actually training, you can call them whatever you like. UKA names, Charlie Francis terminology, something you've made up yourself, it doesn't really matter. As long as you know which principle you're applying that week and why, the label is secondary.
Where it goes wrong is when the structure of the session has drifted away from the principle the label is supposed to represent. The label might say speed endurance while the session is built like special endurance, and the athlete adapts to the stimulus, not to the label.
Let me put some definitions to it, because once you separate the names from the work, the principles get easier to see.
Speed endurance is the one nearly everyone defines the same way. You're working at 95-100% with reps under 15 seconds and full recovery between reps. The goal is maintaining top-end speed mechanics under accumulating but not overwhelming fatigue.
For a 100m athlete this is your 60-100m repeats. For a 200m athlete it pushes out to 120-150m. Lactate does start to accumulate in the longer reps, but the goal of the session is the speed itself, not the burn that comes with it.
Special endurance is where the same name covers two different routes to the same destination.
In the Charlie Francis tradition, the high-intensity work that builds late-race holding ability uses long reps with full recovery between them. The lactic load comes from rep length and the cumulative volume across the session, not from compressed rest.
Each rep starts fresh, but the body has been taken deep into the lactic system by the time the set is done.
In the UKA and Soviet-derived schools, special endurance is built through reps with deliberately incomplete recovery.
The lactic load is the stimulus itself, and the session can be delivered through long reps or shorter split runs as long as the recovery stays short enough to keep lactate elevated across the set.
The body is being asked to maintain race-pace mechanics while the lactic system stays loaded the whole way through.
UKA actually splits these out further, reserving "specific endurance" for the full-recovery long-rep work and "special endurance" for the incomplete-recovery overload. That's the cleanest disambiguation in the literature I’ve come across, but most coaches don't carry that level of precision.
Whether the two routes produce the same adaptation is a debate that's never quite settled in the field.
They agree on the goal, which is the ability to hold race-pace mechanics under fatigue. They disagree on whether you need to train under accumulated lactic load to learn to hold form against it, or whether full-recovery long reps build that capacity on their own.
What's clear either way is that the two routes shape the rest of your training week differently.
This is your 200m, 250m, 300m, 350m work for a 400m runner. It's also where the 200m runner trains to survive the second half of their race, the part most 100m-leaning sprinters underestimate.
The difference matters because the two adaptations don't substitute for each other.
A 400m runner who only ever trains speed endurance arrives at race day with strong top-end speed and no ability to hold form through the final 150m.
A 200m runner who only ever trains special endurance loses the sharpness that makes the first 100m fast in the first place.
Clyde Hart's 400m programme at Baylor is one of the cleanest examples of how race-pace volume gets built across a season.
He coached Michael Johnson and Jeremy Wariner at Baylor, and worked with Sanya Richards-Ross professionally after she turned pro out of Texas.
The pattern across all of them was the same long-to-short progression.
Off-season volume built around 600m and 500m repeats, and as the calendar moved toward championships the rep distances shortened, with late-season weeks built around sessions like 4×300m, 3×350m and 2×450m, taking five to ten minutes of recovery between reps.
Total volume across these sessions typically lands between 800 and 1400 metres, run at controlled splits close to race effort rather than at maximum.
The progression isn't designed to make the athlete suffer. It's designed to teach the body to hold race-specific mechanics at incrementally sharper paces as the calendar moves toward competition.
Suffering is a by-product, not the target.
This is the part that gets lost when coaches treat special endurance as a generic high-lactate session.
The session that destroys you isn't the same as the session that builds the adaptation, because what drives the transfer is volume at race-pace intensity, not the depth of the burn. Throwing-up training, by itself, is just metabolic noise.
The same principle, applied wrong, looks completely different.
A 200m runner doing 4×100 at 98% with 12 minutes of recovery is doing speed endurance. The reps are short, the intensity is high, and the recovery is long enough that each rep is genuinely fast.
The same athlete doing 3×150 at race pace with 4 to 5 minutes of recovery is doing special endurance. The reps are longer, the recovery is shorter, and the lactic load builds across the session.
Swap one for the other without thinking about which is on the menu that week, and the training stops doing what it's meant to do.
For the athletes reading this, the practical version is straightforward.
If you're working with a coach, you should be able to ask what a given session is meant to train and get a clear answer. Not the name of the session. The principle behind it.
If your coach can't articulate that, it's a flag.
If you're self-coached, the work on this is mostly about being honest with yourself about what each session in your week is actually delivering.
A workout that drains you isn't automatically a workout that's productive. Intensity, duration, and recovery all need to line up with the adaptation you're trying to drive.
It's worth checking, occasionally, whether the sessions in a training log are still doing what the labels say they're doing.
Programmes drift.
The structure of a session moves a step away from the principle it was built to deliver, and unless someone is auditing it, the drift goes unnoticed because the label hasn't changed.
The label on the session doesn't match the stimulus the body is getting. And the wrong stimulus, repeated for long enough, doesn't just fail to deliver. It moves the athlete backwards.
The taxonomy I learnt in the UK is one framework. The American system has its own version. Coaches like Jim Hiserman split special endurance into I and II based on rep duration.
Mike Holloway slots it into the pre-competition week as the Friday session. Hart didn't carry that taxonomy at all, prescribing sessions by distance and pace target rather than by category name, but the principle behind what he was doing is the same.
What every one of those systems shares is a clarity about what each session is meant to deliver, and that's the thing worth taking from them. Not the labels.
For coaches, the test is whether you can sit down with your weekly plan and say out loud what each session is doing physiologically and why it sits where it sits in the week.
If you can, the label is yours to choose. If you can't, the label is hiding the fact that something in the programme hasn't been thought through carefully enough.
For athletes, the same test applies in a slightly different form. You need to know what your sessions are doing to you, in language a step deeper than the name on the page in your training log.
Because the body responds to the stimulus, not to the word.
The names may keep changing across coaches and across decades. The principles won't.