Triathlon training: Bike HIIT interval workouts improve cycling and running performance in triathletes

HIIT cycling workouts are one of the most effective ways to improve cycling time trial performance. Not surprisingly cycling intervals form a key part of successful cycle training. Whilst we know a lot about structuring cycling intervals, less in known about the best approach for cycling intervals for triathletes. This is especially true, when considering how HIIT cycle workouts affect both cycling and subsequent running performance in triathlons.

What's the best cycling HIIT workouts for triathletes?

Firstly, the length of your target triathlon is a key consideration – clearly, your training approach for a sprint distance triathlon, will be very different to a middle or long distance triathlon. Having said that, HIIT cycling workouts should form a key part of triathlon training whatever your target race distance.

Whilst research in this area is still quite limited; we can draw some conclusions from a study published in the European Journal of Sport Science (Etxebarria et al., 2013). In this study, researchers looked at how different cycling intervals affect triathlon performance. So, how did they do this? During the study, researchers compared the effects of short sprint intervals (9-11 x 10, 20, and 40s intervals) and long cycling intervals (6-8 x 5 min intervals) on cycling and running performance.

What did the researchers find? The main finding was: not only do bike intervals improve cycling performance, they can also improve running performance. In fact, high intensity cycling intervals improved 5km running performance by just over 1 minute, during a 5km time trial (completed after 60minutes of triathlon specific cycling). And here’s the thing: the length of the cycling interval was a key factor affecting subsequent running performance.

Cycling interval length and triathlon cycling and run performance

So how did cycling interval length affect cycling and running? Firstly, interval length and intensity didn’t appear to affect cycling performance amongst the group of moderately trained triathletes. In fact, both short and longer intervals led to similar improvements in VO2peak (~7%) and mean power (~10%); as well as reducing heart rate, blood lactate and the rate of perceived exertion during the 60minute cycle.

The effect of the different cycling intervals became more obvious when the triathletes completed a 5km running time trial, immediately after the 60minute cycle. Here’s where the research becomes more interesting: it was only the long interval group that demonstrated a significant improvement in 5km running time, with an average improvement of just over 60seconds.

From this, the researchers concluded that longer cycling intervals are more likely to benefit 5km running performance than shorter intervals. So, if you’re a triathlete looking to optimise training time; longer cycling HIIT intervals can be an effective way to improve both cycling and triathlon running performance. Here it’s worth noting, that the shorter intervals also appeared to have a positive effect on running performance, albeit to a much lesser extent.

Training implications for triathletes

The researchers used 6-8 x 5min intervals, which is in line with previous research looking at optimum interval length for improving cycling time trial performance.

Due to the large volume of intervals (30-40mins total interval time), the intensity of the intervals shouldn’t be maximal. In fact, during this study, interval intensity was set to 80% of maximal aerobic power (MAP), combined with a short (60second) recovery.

Depending on your current level of conditioning, you may need to adjust the intensity level. With this in mind, highly trained triathletes will benefit from completing these at a slightly higher intensity. For me, I would tend to complete these at an intensity that’s close to functional threshold power (FTP).

cycling hiit intervals 6 x 5mins

Depending on your conditioning, this would normally correspond with 80-90% of your maximum heart rate. And to gain the greatest training effect, keep the recoveries should (~60-90seconds), and the intensity at 50% (or below) of interval intensity.

Below is an example of a 8 week progression, building from 6 x 5mins off 90 seconds recovery, up to 8 x 5mins off 60 seconds recovery**

16 x 5mins @ FTP power90 seconds easy
26 x 5mins @ FTP power80 seconds easy
36 x 5mins @ FTP power70 seconds easy
46 x 5mins @ FTP power60 seconds easy
57 x 5mins @ FTP power75 seconds easy
67 x 5mins @ FTP power60 seconds easy
78 x 5mins @ FTP powe75 seconds easy
88 x 5mins @ FTP power60 seconds easy

Ideally your heart rate should be lower for the first couple of intervals, to avoid a drop off in power over the later intervals.

Further considerations for triathlon training:

One important point here: to get the most out of cycling training, it’s vital to include some shorter sprint cycling intervals. In fact, the researchers suggested that triathletes would benefit from a combination of both long and short intervals. So, whether your focus is cycling or triathlon, aim to include both shorter sprint intervals and longer aerobic intervals.

Another, key point to consider is the length of research – the research was relatively short, with just 6 training sessions, completed over a 3 week period. So, why does that matter?

Firstly, it demonstrated just how effective these sessions can be; making these a great way to boost cycling and running performance in the build up to key triathlon races. Secondly, because the training block was relatively short it’s harder to draw conclusions about the best long term approach. Why is that?

Simply put, just because one type of training yields quicker results; that doesn’t always equate with greater long term improvements. Having said that, it’s clear that using longer cycling intervals – especially when used in the build up to important races – are a very effective way to improve triathlon performance. I just think it’s wise to also include short sprint intervals.


Etxebarria N, Anson JM, Pyne DB, Ferguson RA. (2013) High-intensity cycle interval training improves cycling and running performance in triathletes. European journal of sport science. 10.1080/17461391.2013.853841.

**As is the case with any high intensity interval training program it is important that you have a sufficient level of fitness before undertaking any interval program and seek medical advice if you are unsure.

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