How We Coach, Part 6 of 10
Training Block Types: What Each Block Builds and How We Choose It
The short answer: A training block is a few weeks aimed at one main change in you. We use a small set of block types: Base and Durability, Aerobic Expansion, Build and Threshold, VO2 Max, Specificity, Hybrid and Rest. Each builds something different, each has a reason to come when it does, and each ends when its job is done. We choose your block from your race calendar, your fitness, your limiter, your history and your readiness, and we set the bike and the run separately. This article explains what each block is for, why we choose it, what goes wrong when the order is off, and how we used them for Holly Koksel, Katy Walmsley, Ben Creswick and Graham Lloyd.
The question every athlete should be able to answer: what is this block for?
Ask an athlete what their training is for and most will name their race. Ask what the next four weeks are for, specifically, and the answer often gets vague. That gap matters. Training that tries to build everything at once tends to build a little of everything and not much of anything.
Your body adapts to the stress you give it, and it adapts best when that stress has a clear aim and enough time to work. A block gives a few weeks to one main job, so the change has time to happen and we can see whether it did. When a block ends, the next one starts from a body that has absorbed the last.
So the question this article answers is: for each sport, what should the next few weeks build, why that and not something else, and how will we know it has worked?
How seasons are usually structured, and where that runs out
Two common patterns are a fixed march from base to build to peak, set months ahead, and a steady mix where every week has a bit of everything. Both are reasonable defaults.
A fixed march assumes every athlete needs the same blocks in the same order for the same length. An athlete whose threshold is already close to their ceiling keeps doing threshold work that has little room left to grow. An athlete who joins four weeks before a race is given a base phase there is no time for. The steady mix has the opposite problem. Every week is busy, but no single quality gets enough focused work to move.
We keep the idea of blocks and change how they are chosen. The block types are the same for everyone. The order, the length and which sport is in which block come from each athlete's season, and each sport gets its own block.
Three athletes' blocks across their seasons
What it measures. The blocks Katy, Holly and Ben trained in across the build to one of their big races, colored by block type.
The story at this point. Each of these athletes came to ANC with a different goal. Katy was building toward the Boston Marathon from a winter base. Holly had two races six weeks apart, the Anchor Down 6 hour ultra and IRONMAN Maryland. Ben joined in late August with a 70.3 and a marathon three weeks apart. Katy's bar runs from base to race specific work. Holly's has two race specific blocks with rest after each race. Ben's starts with testing and goes straight into race specific work, because his races were close.
How to read it. Each row is one athlete. Each colored section is one block, and the legend shows the block types. The label on the left is the race result the blocks were built for.
You might see this in your own training if your season has more than one important race. The blocks have to serve every race, in order.
Base and Durability: the block everything else stands on
What it builds. Your aerobic engine and your body's ability to handle training. Steady aerobic work across your sports, with strength training in the plan.
Why it comes first. Harder blocks ask more of joints, tendons and muscles, and those tissues adapt more slowly than fitness does. A base that is too thin can't carry the harder work, so the cost shows up later in the season as stalled progress or an athlete who can't absorb the next block.
When we use it. At the start of a season, when your next important race is far away, after the last race of a season, and whenever a sport's fitness is fragile. If your bike fitness is under 45 or your run fitness is under 35, that sport starts in Base and Durability whatever the calendar says.
An example. Holly started her season in May in Base and Durability. Anchor Down was more than three months away and IRONMAN Maryland more than four. With that much time, the right first step was the engine. Ben is in Base and Durability now in both sports, with his next A race about 30 weeks out. In his words, it is for "a bigger engine, more durability, and a higher ceiling for the hard work later."
Aerobic Expansion: raising the floor for long races
What it builds. A bigger aerobic floor. Longer steady sessions that widen what you can do at an easy, sustainable effort. It usually runs three to six weeks.
Why we use it. In long races almost all the work happens well below threshold. The higher that aerobic floor, the less each hour of race effort costs you, and the more you have left late in the day. For long races, it is often the most important block of the season. It also works as a bridge from base into harder work, so most of the stress stays aerobic while a smaller share moves up.
When we use it. When your aerobic floor sits too low under your threshold, or as a bridge.
How we know it is done. Your fitness has held steady for a couple of weeks at the current volume, your long steady sessions are under better control, and your body has handled all of it.
An example. For a 6 hour race and an IRONMAN, Holly's aerobic engine was the main event. Her Aerobic Expansion block ran from mid June into July and included her biggest rides.
Holly's weekly hours by sport from May to August
What it measures. Holly's training hours each week from May to early August 2026, split into run, bike and swim.
The story at this point. Holly also coaches with ANC, and she was preparing for two very different races. Her hours moved up and down with her blocks. They reached their peak, about 13.7 hours, in mid July during Aerobic Expansion, when her long rides were at their biggest. Then they came down through Specificity and into her race week for Anchor Down in early August.
How to read it. Each bar is one week. Orange is run, navy is bike and grey is swim. Watch how much of the big weeks is bike time.
You might see this in your own training if you are training for a long run or ultra and still riding a lot. For many athletes the bike can carry aerobic work that would cost the legs far more on foot.
Her longest run all summer was about two and a half hours. On race day she ran for five and a half, in record heat, and won the women's race. The engine her rides built carried her far past her longest training run.
Build and Threshold: making race effort cost less
What it builds. Your threshold, the hardest effort you can hold for a long time. Sweet spot and threshold sessions.
Why we use it. A higher threshold means any steady race effort is a smaller part of what you can do, so it costs less and you can hold it longer.
When we use it. When your aerobic floor is in good shape and your threshold is what holds you back. Doing threshold work on a thin base tends to produce tired weeks without much gain.
An example. Holly's Build and Threshold block ran from late May to mid June. Katy spent February in a Build block before her Boston race work.
VO2 Max: raising the ceiling so the threshold can rise again
What it builds. Your ceiling. Short, very hard efforts, two to four weeks of them, with plenty of freshness around the key sessions.
Why we use it. Your threshold can only rise so close to your ceiling. Once it is near the top, more threshold work has little room to grow into. Raising the ceiling makes room, and then we build underneath it again.
Our rules. No VO2 Max block without a recent test, because targets set slightly too high turn into sessions you can't finish. No VO2 Max work in a taper or once Specificity has started, because it costs freshness the race needs.
An example. Katy's VO2 Max block ran from March 1 to 22, between her Build block and her marathon specific work. Three weeks later she ran a half marathon best of 1:34:09. "That was hard but I felt really strong!" she wrote.
Specificity: turning fitness into race fitness
What it builds. Race fitness. Sessions that look like your race, at race effort, in race conditions, often late in a long session when you are already tired.
Why we use it. Fitness and race fitness are related and different. Holding race effort for hours, fueling at race pace and staying patient when tired are skills, and they need rehearsal.
When we use it. We propose it about six weeks before an important race, and it runs two to six weeks. The taper weeks count inside it. Bike and run each get their own Specificity date.
An example. Holly's Specificity block ran from late July to her race week. Her long runs became race rehearsals, with the work late in the run. It also mixed in race intensity bike work for Maryland. When she saw the intensity she wrote, "I'm definitely not doing an ultra at that pace haha." Angela explained: "It's more the block type you're in which is a hybrid approach."
Katy's weekly run miles and longest run from December to April
What it measures. Katy's total running miles each week from December 2025 to Boston, with a marker for her longest run each week.
The story at this point. Katy came to ANC wanting her running hours to count. Her run miles grew steadily from her December base, averaging about 21.5 miles a week, to about 33 in January and February and about 36 in March. Her biggest weeks reached about 39 miles. Her longest run, 17 miles, came in early April inside her marathon specific block. Then her miles dropped for the taper.
How to read it. The bars are weekly miles. The dots are the longest single run that week. Look at how the weekly total levels off from January while the longest run sits around 12 to 15 miles, then jumps to 17 in early April. That long run was the big rehearsal inside her marathon specific block.
You might see this in your own training if you are building for a marathon with limited time. A steady weekly total can still hold one or two key long runs where they matter most.
She ran Boston in 3:28:46, a marathon PR.
Hybrid and Rest: when one direction isn't enough, and when the job is recovery
Hybrid builds two things at once, for the case where an athlete genuinely needs both. Most of the emphasis stays on the main need, and a smaller share goes to a second one that can't wait. We use it for experienced athletes with a clear split need, such as a long race and a shorter one close together, or a strong sport and a rebuilding one. We never use Hybrid to avoid making a decision, because a block that aims at everything drifts back into the steady mix that builds little. No Hybrid block starts without a recent test.
Graham Lloyd moved into Hybrid work in early August, about six weeks before the IRONMAN 70.3 World Championship in Nice. His bike was strong and his run was still rebuilding, so his needs were genuinely split between his two sports. Katy is moving into Hybrid work now for La Quinta 70.3 on December 6.
Rest builds recovery: a short reset after a race, so the next block starts from a body that has absorbed the last one. Skipping it usually means the next block starts tired and lands poorly. It comes after every important race, sized to the race. An IRONMAN or marathon gets a flexible week, then a lighter Base and Durability block. A 70.3 or half marathon gets a similar pattern or a few days off or light. Shorter races need a day or two. Holly had a short rest after Anchor Down, then a return to Specificity for IRONMAN Maryland six weeks later. Ben's week after the Victoria Marathon was a Big Pull Back before his winter base.
How we choose your next block, and why in this order
We use the same order for every athlete, for every block.
1. Overrides. Life events and anything Angela flags.
2. Timeline. How far away your next important race is. Inside about six weeks, Specificity.
3. Numbers. Your fitness by sport, against the floor, and your recent tests.
4. Limiter. The thing holding you back most right now.
5. History. What has worked for you before.
6. Readiness. Whether you are ready to absorb the block.
Timeline comes early because some choices simply run out of time. Six weeks from a race there is no longer room to build a new base, and rehearsal matters most. Numbers come before limiter because a sport below its floor needs its base whatever its limiter says. Limiter comes before history because what is holding you back now is what the next block has to change.
Tests usually sit in the week after a block's final week, with easy days between them. They show whether the block did its job and set the numbers for the next one. Blocks end on evidence. When the gains flatten, the block has done its work and we move on.
Ben's season shows the timeline deciding. He joined in late August with IRONMAN 70.3 Tri Cities four weeks away. There was no time for a long base, so after his test week he went straight into Specificity. His limiter was execution, and race specific work taught him to hold back. He placed third in his age group. Right after Tri Cities, his sports split. His run went into a marathon specific block for Victoria. His bike went back to base, because his next bike race was eight months away. Three weeks later he ran 2:46:42, third of 299 in his age group.
How the block choice changes with your situation
Your race is more than three months away and your fitness is fragile
Base and Durability first, as with Holly in May and Ben this winter.
Your race is long and your aerobic floor is low
Aerobic Expansion, often the biggest block of the season for long course and ultra athletes.
Your threshold has moved close to your ceiling
A short VO2 Max block after a recent test, then back to building underneath it, as with Katy in March.
Your race is about six weeks away
Specificity, with the taper inside it, set separately for bike and run.
One sport is strong and the other is rebuilding, close to a race
A Hybrid block, as with Graham before Nice.
What blocks can't do, and what they need from you
A block sets direction. It doesn't decide how much load each week carries. That is the weekly call, covered in Load and Recovery. A good block with the wrong weekly dose still goes badly, which is why we keep the two decisions apart.
Blocks also need honest signals to end at the right time: sessions that feel controlled when they do, short checks, tests done on the days planned, and comments that tell us when a block's work has started to feel different.
To put blocks in a few lines: each block has one main job, each sport gets the block it needs, the order follows your race, your numbers and your limiter, and every block ends when the evidence says it is done.
What this means for you
What this means for you
When you train with us, you will always know which block you are in and what it is for. A good check for your own training: can you name what your current block is building in each sport, and what would tell you it is done?
Keep reading in the How We Coach series
- StressLogic: how we decide your training
- Part 3: Setting your Critical Power and Critical Speed
- Part 5: Adjusting as you go
- Load and recovery
Athlete stories from this article:
Coaching built around you
If you would like every block in your season to have a clear job, start at angelanaethcoaching.com.
Tell us your goal race and the hours you really have. Or see our online marathon coaching or online 70.3 coaching.