What it measures: Readiness to train; signs of overtraining
Why have it? Heart-rate variability (HRV) – the variation in the time interval between heartbeats – is increasingly being monitored in elite runners. ‘While genetic factors explain about 30 per cent of HRV, high variability has been shown to be associated with good health, low stress and adequate recovery,’ says Nigel Stockill, an exercise physiologist and performance director at HRV-testing company Firstbeat. ‘HRV fluctuates naturally – increasing during sleep and relaxing activities, when parasympathetic nervous system activation increases, and dropping during periods of physical or mental stress, when the sympathetic nervous system predominates. If the natural interplay between these two branches of the nervous system is disrupted by excessive stress or training overload, it causes the body to remain in a sympathetically dominant state.’
Daniel Plews, lead performance physiologist at High Performance Sport New Zealand (HPSNZ), was one of the earliest adopters of HRV monitoring at elite level. ‘It provides an objective marker that can be used to monitor an athlete’s training and how they are adapting,’ he says. ‘For certain training phases we expect HRV to behave in a certain way. If it isn’t responding as we expect, it can help ascertain whether they should do more or less training and allow the coach to adjust sessions on a day-to-day basis.’
In a study published in Medicine and Science in Sports and Exercise, researchers compared the effects of a HRV-guided running programme with a predefined training programme. In the first group, higher-intensity training was based solely on daily HRV readings. If a runner’s HRV fell outside their normal range, they skipped hard training and did easier workouts. After eight weeks, the HRV-guided training group had significantly improved performance over three kilometres despite performing fewer tough sessions than the predefined training group.
What’s it like? Firstbeat’s BodyGuard is a device consisting of two small electrodes worn constantly on the chest for three days to build up a picture of your daily HRV response. It’s easy to forget you’re wearing it, but don’t neglect the activity diary – the more detail you include, the more useful the resulting analysis. For example, my assessment – a nerd’s delight of graphs and data – showed I was getting the right balance of overload and recovery most of the time, but that a higher stress load one day, from a high-intensity run coupled with work and commuting, had affected my sleep quality.
Details: £300 for a 72-hour continuous assessment and follow-up coaching session from Firstbeat. Apps that couple finger sensors or chest straps with smartphone capabilities are also available, such as HRV4Training.