“Heart rate recovery” and acute vs. chronic training fatigue


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- Alex Hutchinson (@sweatscience)


I had a chance to see an interesting study in progress a few days ago, during my visit to Cape Town, which prompted me to look up a paper that appeared earlier this year in the European Journal of Applied Physiology. It’s a case study of an elite Dutch cyclist being monitored with something called the Lamberts and Lambert Submaximal Cycle Test (LSCT), which was first described last year in a British Journal of Sports Medicine paper.

The gist is as follows: to warm up before a hard workout, you do a specific 15-minute protocol (6min at 60% of max heart rate, 6min at 80%, and 3min at 90%). You measure your power output and perceived exertion during these three stages, and then you measure how much your heart rate decreases during the 90 seconds after the test. Doing the test frequently (it’s not too strenuous, so you can do it as a warm-up before pretty much every workout) gives you objective data that tells you whether you’re fresh or tired, and whether your training is making you faster or slower.

Just as a sample, here’s a snippet of data, showing the power (at a fixed heart rate) for the first stage of the test, compared to the weekly training load. Pretty clear correlation:

lsctYou can see a gradual increase in power as the training cycle progresses, indicating that the cyclist is getting fitter. But you can also see big spikes in power during the heavy training weeks — that’s not because he was “fitter,” but because the acute training-induced fatigue meant he had to work harder (and thus produce more power) in order to get his heart rate up to 60% max. The mechanism has to do with decreased sympathetic nerve activity and increased parasympathetic nerve activity — and what’s most interesting to me is that the exact opposite happens in the case of chronic training-induced fatigue.

The same pattern can be seen in the heart rate recovery data:

lsct2During the heavy training weeks, the athlete’s heart dropped more quickly than during the other weeks. So he was tired from the dramatic increase in training load — but the test suggests that he was what the researchers call “functionally overreached” as opposed to “non-functionally overreached.” Had he persisted with the extreme training load for too long, his heart-rate recovery would have started to dip down instead of up, indicating overtraining. In other words, the researchers conclude:

This suggests that training-induced acute and chronic fatigue are reflected differently in the LSCT, which has important practical applications for monitoring.

Obviously this test is best suited to cycling, since you can precisely measure your power output. But I wonder whether a simplified version of the test, where you just exercise (run, row, whatever) at a set submaximal heart rate and then measure your heart rate recovery, would provide any meaningful information.

Oh yeah, the study I saw in progress: two groups of cyclists, each doing two (I think) hard workouts a week. One group does them on set days, come hell or high water; the other group does the LSCT three times a week, and determines whether or not to work out that day depending on the results. The hypothesis is that working out when your body is ready to go, and resting when it’s not, will lead to greater gains in fitness and performance. It’ll be interesting to see the results.

4 Replies to ““Heart rate recovery” and acute vs. chronic training fatigue”

  1. Alex, I’m not sure I quite get how these graphs relate to actual training. Could you give an example of how one might incorporate this theory in running training? Would it be something like: 1) you do the test. 2) check HR recovery time 3) if HR drops fast, then you are good to go, if it takes longer, maybe take an easy day?

    Sorry if this sounds like a stupid question, but I’m not really a science guy so I don’t know if I’ve correctly translated what you’ve got here…

  2. @John Lofranco
    Hey John — yeah, the post is a bit of mish-mash of info! Sorry about that. First of all, I should say that this Lamberts and Lambert test is quite sophisticated and produces a bunch of data. I’m just cherry-picking a few interesting points here, and it’s not really clear whether we can meaningfully talk about HR recovery without also considering the other pieces of data like power output.

    Subject to that caveat, the basic gist is exactly what you said: do the test, check HR recovery, then decide whether today is a good day to go hard.

    The key point is that HR recovery is a complex marker. As you get fitter, you expect it to gradually recover more quickly. However, if you do a big training week (as shown at weeks 2 and 6 in the above graphs), it will recover MUCH more quickly after a constant-HR protocol. That doesn’t mean you’ve suddenly got fitter, it means you’re tired — and it’s a signal to back off.

    On the other hand, if you’re becoming chronically overtrained, the HR recovery will likely slow down. That’s a very bad sign, and requires immediate action.

    So (a) slight increase in recovery means fitness is improving; (b) sharp increase in recovery means you’re fatigued, so should be cautious in training; (c) decrease in recovery means you’re overtrained, and need immediate rest.

    Of course, there’s lots of potential for ambiguity — for instance, a slight increase in recovery could signal a slight increase in fatigue rather than fitness. I suspect this is why you also need the power data to get a more accurate assessment.

  3. I also like heart rate monitor watches that upload the information to your notebook so you can follow your progress and stats.but I am a nerd for things like that

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