How You Should Structure an Endurance Training Plan

Start with 80/20

The basic principle is the 80/20 rule: around 80% of your endurance training should be easy and around 20% should be hard.

Easy means Zone 2. Low heart rate, lots of volume, building your aerobic base. Hard means intervals, tempo sessions and some time in the higher zones.

Most people do the easy part too hard. Your pace looks shit on Strava, some old guy overtakes you, whatever. Who cares. Get a heart-rate monitor, slow down and build the aerobic base.

Work backwards from race day

Start at race day and work backwards.

You want two full taper weeks before the race, meaning your peak week should be three weeks before race day.

For a Half Ironman, aim for something around twice the actual race volume during peak week, spread across the week:

• around 4 km swimming
• around 40 km running
• around 180 km cycling

For a full Ironman, don't try to do twice the race distance in a week, that would be ridiculous. Something around 130–150% of race volume makes much more sense.

Once you know where you want to end up, work backwards by roughly 10% per week until you arrive at the amount of training you're doing today.

Three weeks up, one week down

Structure your training in blocks of three harder weeks followed by one easier recovery week.

During the three training weeks, increase your volume by roughly 10% each week. Then take an easier week, recover properly and start climbing again.

You don't need to hit 10% perfectly. The point is simply that the line should gradually go up instead of you randomly doubling your training because you suddenly got excited about your race.

This is basically what your Excel should look like

For a Half Ironman, do three running sessions, two swims and two bikes per week.

For running, do two longer easy runs and one interval session. I also don't really see the point of going out for a 4 km endurance run. Even at the beginning of the plan, you should be somewhere around 20–25 km running per week.

Also include brick sessions. Ideally one a week, minimum every other week. You need to get used to the slightly awkward feeling of getting off a bike and immediately trying to run.

A 12-week block could look roughly like this:

Don't get hung up on whether week six should be 33 or 34 km of running. It can be a bit messy.

The Excel is mainly there so you can zoom out and see that the volume is generally going up, you have recovery weeks, you're hitting the volumes you want before the race, and you're not still smashing yourself seven days before the start.

What does “intervals” actually mean?

Don't put “8 km intervals” into the spreadsheet. Just put “Intervals” into the cell and decide which session you're doing.

For marathon and full-Ironman preparation, these are examples of sessions you could use:

• 10–15 min warm-up + running ABC, then 12 x 1,000 m at around 4:25/km with 2 min easy jogging between
• 10–15 min warm-up, then 6–7 x 2,000 m at around 4:40/km with 2:30 min easy jogging between
• 4 x 4 km at around 4:50/km, getting closer to 4:45/km towards the end, with 5 min easy jogging between
• 8–10 km at around 4:50/km, 5 min easy jogging, then 6 x 1,000 m at around 4:35/km with 3 min easy jogging between
• 22–24 km alternating every kilometre between around 4:50 and 5:10/km
• 15–17 km at around 4:50/km, 5 min easy jogging, then another 5–7 km at around 4:45/km

Obviously don't copy those paces if they have nothing to do with your own running speed. The point is the structure.

For a Half Ironman, make the interval work shorter than some of the monstrous marathon sessions above.

You can use exactly the same logic for a marathon

There's nothing particularly triathlon-specific about the structure.

Race date → two taper weeks → peak week → work backwards by roughly 10% → recovery every fourth week.

For marathon training, simply remove the swimming and cycling columns and put more thought into your long runs and interval sessions.

The same logic works.

Don't forget the boring stuff

Do some strength work alongside all of this, and especially don't forget your tibialis.

It takes almost no time to train and your lower legs are going to take an absurd amount of repetitive load once the running volume gets high.

That's basically it.

Figure out where you need to end up, work backwards to where you are today, increase the volume slowly, take recovery weeks, do most of it in Zone 2, keep some proper hard sessions in there, add bricks, and taper before the race.

You can make it substantially more complicated than that.

For most people trying to finish an endurance race, I'm not convinced you need to.