Triathlon
How to balance swim, bike and run training
There is no fixed rule for sharing your hours, but most triathletes put about half their training time into the bike and divide the rest between run and swim, weighted towards their race and their weakest sport.
The run usually sets the ceiling on everything else, because it is the hardest of the three to recover from.
At a glance
| Lever | Why it matters | Pushes time towards |
|---|---|---|
| Race time | The bike is the longest leg in standard triathlons, roughly half the race | Bike |
| Your limiter | Where extra hours buy the biggest gain in your overall time, which isn't always your weakest sport | Wherever time pays back most |
| Recovery cost | Running's impact makes it the slowest to bounce back from | Away from the run |
| Technique | Swim speed depends heavily on skill, which needs frequent practice | More, shorter swims |
Where should you start?
Start from the race, then adjust for you. In sprint and Olympic distance triathlon, and in half and full Ironman distance (70.3 and 140.6 miles), the bike takes up roughly half the race time, the run most of the rest, and the swim the smallest share. That is the natural starting point for sharing out your training time too.
Then shift it towards wherever extra hours will make you faster overall. That isn't always the sport you think of as your weakest.
Should you train your weakest sport the most?
Sometimes, but your real limiter may not be the sport you feel weakest at. If you're starting out and one sport is clearly behind the other two, closing that gap is often worth the time. A balanced athlete is set up to race well in a multisport event, and a big weakness costs time and confidence on race day.
Once the gaps are smaller, the question changes from "what am I worst at?" to "where does an extra hour make me faster overall?". Taking a minute or two off your swim split can need a lot of extra pool time. The same hours spent on the bike or run, which make up most of the race, might save you far more, even if you already think of yourself as a strong cyclist or runner.
Your limiter is the sport where extra training buys the biggest improvement in your finish time, given what you can recover from. For many triathletes that is the bike or the run, not the swim.
Example: a 10-hour week
One common shape for an age-grouper building towards a half-distance race. It's an illustration, not a prescription.
| Sport | Sessions | Time |
|---|---|---|
| Swim | 3 × 45 min | 2:15 |
| Bike | 2 × 60 min, 1 long ride of 2:45 | 4:45 |
| Run | 2 × 45 min, 1 long run of 90 min | 3:00 |
| Time by sport | Swim / bike / run | 22.5 / 47.5 / 30% |
Three sessions per sport keeps each one ticking over. One ride can finish with a short brick run, and strength work adds a little on top.
Why does the run set the limit?
Running loads your muscles, tendons and bones in a way cycling and swimming don't. That impact is why running injuries are common in triathletes, and why the run is usually the first sport where adding volume goes wrong.
Cycling builds a lot of the same aerobic fitness at a lower mechanical cost, and the physiological overlap between the two sports is well studied in triathletes. It isn't a full substitute, though: your legs still need running to adapt to running. Many triathletes protect the run by building its volume gradually and putting more of their moderate work on the bike.
How much should you swim?
For most age-groupers, more often beats longer. Swim speed depends heavily on technique, and technique responds to frequent practice. For the same total time, three shorter swims usually do more than one long one. That's coaching practice rather than a hard rule, but it holds for most adult swimmers. The swim is also the shortest leg, so time saved there is time you can spend on the bike or run, once you're comfortable and efficient in the water.
Where do bricks and strength fit?
Treat both as parts of the week, not extras on top of it. A brick is a run straight after a ride. It trains the awkward first kilometres of the race run, and it doesn't need to be long to be useful. Strength work supports the run in particular, and a couple of short sessions a week is common. Both use up recovery, so count them when you plan the week rather than squeezing them in afterwards.
Should you trust your time by sport?
Plan the week first, then use the time by sport to check it. The percentage of hours you give swim, bike and run tells you how your week was shared out. It can't tell you whether they were the right sessions, so it is a useful check on a week and a poor way to design one.
What time by sport gets right
- It shows drift. Most triathletes slowly overdo their favourite sport and avoid their weakest. Tracking hours by sport makes that visible.
- It connects training to the race. Comparing your hours by sport to how the race time actually divides is a quick sense check.
Where it falls short
- An hour is not an hour. An hour of running and an hour of swimming differ in training stress, recovery cost and injury risk. Counting them all as hours treats them as equal.
- It hides intensity. Two weeks with the same hours by sport can contain completely different sessions.
- Elite ratios don't transfer. Professionals train two or three times a day with full recovery around it. Copying their proportions at a third of the hours, with a job, rarely works the same way.
- Combined numbers mislead. Totals that add all three sports together can show you're building while one sport stands still. See Fitness, Fatigue and Form.
- It ignores your life. Pool times, daylight, travel and family decide what's possible in a given week more than any ratio does.
How to use it anyway
Plan the week from your race, where extra time pays back most, and what you can recover from, then look at your hours by sport afterwards to see if anything has drifted. Check each sport's progress on its own, not just the total.
Common questions
Should I train my weakest sport the most?
Not always. If one sport is far behind the other two, closing that gap is often worth it. Once you are more balanced, put extra hours where they will improve your overall time most. Taking a minute off a swim split can cost many pool hours that might save more time on the bike or run.
Does cycling fitness help my running?
Partly. Cycling builds much of the same aerobic fitness at lower impact, but your muscles, tendons and bones still need running to adapt to running. It supports the run rather than replacing it.
How often should I swim?
For most age-groupers, about three times a week works better than one or two long swims of the same total time, because swim speed depends heavily on technique and technique improves with frequent practice.
What is a brick session?
A brick is a run done straight after a ride, sometimes a swim straight into a ride. It trains the transition and the heavy-legged first part of the race run, and it does not need to be long to be useful.
Related
Sources
- Millet GP, Vleck VE, Bentley DJ. Physiological differences between cycling and running: lessons from triathletes. Sports Medicine. 2009;39(3):179–206.
- Friel J. The Triathlete's Training Bible, 4th edition. VeloPress, 2016.