How to use heart rate variability to optimise triathlon training

Heart rate variability measurements can tell us a lot about our state of readiness to train and are central to optimising performance. James Witts explains…

Man checking his timer. Athletes in wet suits preparing for triathlon competition.

Heart rate variability training (HRV) looks at the heart rate variation from beat to beat. You see, even when heart rate is stable – say 60bpm – the gap between beats is not 1sec. It varies between beats. This is HRV.


“We’re interested in this because HRV links back to two important branches of the autonomic nervous system (ANS),” says Chelsea Sodaro‘s coach Dan Plews. “Greater variations between beats (i.e. increases in HRV) are associated with the parasympathetic activity (rest and digest/recovery), while reductions in the variations between beats (i.e. decreases in HRV) being associated with the sympathetic activity (fight or flight/stress).”

What influences HRV?

HRV’s influenced by everything – hydration, fuelling, sleep quality… – which is the beauty of HRV. Your autonomic nervous system regulates just about every organ in the body, so if something is wrong, your body will attempt to deal with the problem, which will affect your HRV.

It’s why HRV is a good metric to gauge state of readiness to train, or recovery. You have the figures at hand to see whether you’re stressed or prepared.

How to use HRV in training

But what about training? Can the results prescribe the intensity of a session a la power and HR training?

“No, it can’t prescribe within-session intensity,” Plews answers, “but it can possibly prescribe between sessions. For example, if you wake up one morning and HRV is substantially low and you planned a high-intensity session, you may decide to do a recovery/aerobic session instead. And vice versa.”

Like all training tools, HRV is certainly not the silver bullet and should be used alongside other variables to inform our decisions when it comes to training.

Other monitored variables may include performance, sleep quality, training load and motivation to train via commonly used tools like power meters.

What are the best tools to measure HRV?

As for the best tools to measure HRV, they’re pretty reliable on watches like Whoop or top-end Garmins and Polars. There are also some good appliactions for your smartphone that just require a morning press of the finger.

“The best apps are HRV4training and Elite HRV,” says Plews. “The two creators, Marco Altini and Jason Moor, have a good handle on HRV and understand its benefits and limitations.

“Their apps also include other metrics when it comes to making daily training decisions. Jason also offers an affordable course for people interested in learning more about HRV, called the Foundations in HRV Course.

How does HRV change in training? 

Plews is an HRV expert and is a pragmatist. He knows that HRV is part of the picture and not the whole picture.

“When it comes to HRV, we also have to understand that too much HRV can be just as bad as too little,” he says. “It’s all about establishing the optimal value for you. Part of the training response is for HRV to change, but what’s important is that it returns to within your individual range as you rest and recover.

“We also should consider HRV changes in the context of training. For example, the response of HRV after longer duration/low-intensity training will be different from short duration/high-intensity training.”


Top image credit: Getty Images