Interval training for triathletes

Using interval workouts in training can lead to huge improvements in race performance, says tri coaching legend Joe Friel. Here he explains how…


Using interval workouts in training can lead to huge improvements in race performance, says tri coaching legend Joe Friel. Here he explains how…


What are the benefits of interval training?

Would you like to improve your race performance by at least 3%? Of course you would. We all want to improve, yet such speedy gains are uncommon in experienced athletes. But it can be done…

That might not sound much, but it’s the equivalent of going from a 2:30hr Olympic-distance finish to a 2:25hr. For an Ironman, a 3% improvement on a 16hr time would put you at the finish line 30 minutes sooner! And the key to such gains? Intervals.

As it happens, 3% is a relatively conservative estimate based on research that has looked at the benefits of interval training. Some studies put the performance benefits as high as 6% so, if you put the work in, you might be able to double those time gains described above.

Most studies for monosport athletes found the benefits occurred with only one interval session per week. That’s just four workouts per month in order to become at least 3% faster.

So for triathletes, the same would apply if you were doing one interval workout in each sport weekly during the build period of their season. The build period starts about 11 to 12 weeks before your first A-priority race of the season and then ends two or three weeks before.

Most triathletes tell me they do intervals. But I’ve found very few self-coached athletes who know what the various types of intervals are, how to choose the right one for their needs and how to blend them into a comprehensive training programme.

Unfortunately, most triathletes do a workout I call “intervals till you puke”. These are intervals done as fast as possible with no thought as to what the pace or power should be, how long the fast portions should be, or how much recovery should be taken between the fast portions.

Then there are athletes who don’t do intervals at all. They dislike the agony and are more likely to swim, bike and run at moderate efforts – a lot. This is three-zone training and has little benefit once you leave the base period of your season, unless you’re training for half Ironman or Ironman-distances raced at moderate effort.

For the shorter distances, three-zone workouts aren’t hard enough to produce the physiological benefits necessary to race faster, but are hard enough to leave you feeling tired and in need of some down time to recover – which is quite simply the worst of both worlds.

What are intervals?

Let’s get the language of intervals straightened out first. The word ‘interval’ actually refers to the rest time between the hard portions of training. But since nearly everyone uses the word ‘interval’ to mean the hard portions, it probably would help to eliminate confusion if we call the hard portion the ‘work interval’ and the easy portion the ‘recovery interval’.

The three most critical components of an interval workout are the intensities of the work and recovery intervals, the durations of the work and recovery intervals and the total time spent at the work interval intensity within the workout.

By changing each of these parts the benefits of the workout are changed. The most common mistakes made by self-coached athletes are to make the work intensity too great and the recovery interval too long.

Can you overdo interval training?

How to start interval training

The table below offers one example of a simple interval workout for each discipline of Ironman-distance racing. Each of these sessions may be done once a week for each sport during the build period of your season.

Start at the lowest number suggested and increase by one work interval (one rep) each week over a four or five-week period. When this period ends, maintain the highest level for an additional three to four weeks.


Venues for these workouts are pool for swimming, road or indoor trainer for cycling, track or other soft surface for running. For variety, add uphill work intervals or rolling courses for bike and run. Put in the work and watch your race performance improve!

Running: what are the advantages of interval training?

Free 2-week swim interval training plan for beginners