The Goal

The Goal

Monday, 25 April 2016

The effect of heart rate on shooting - Part 1

Quite a long time ago now, I noticed that the beating of my heart appeared to slow when I was in the aim. I remarked as such to a medically-qualified friend, who replied that he was not in the least surprised as it is known that it is possible to consciously slow heart rate*. Having recently bought myself a Garmin 225 GPS watch combined with a heart rate monitor as a training aid for running, I decided that it would be interesting to see what results I got when measuring my heart rate during a SCATT session.

The Effect of Heartbeats on Aim
It's logical that heart rate (and possibly strength of heartbeat) will have an effect on aim. The hydrostatic pressure of the surge of blood around the body will disturb the fine aiming required to shoot a rifle accurately, either as it passes through the organs of the body or through the major blood vessels of the upper limb**. Indeed, the disturbance caused by heartbeats can be observed using a SCATT as is shown in the diagram below.

Fig 1.0 - The effect of heartbeats on SCATT traces. The notation indicates the heartbeat number in sequence and the time before the shot broke.

What is perhaps less logical, or at least less well known, is that it is possible to consciously control heart rate to some degree. By extending this, maybe it's possible that some people can subconsciously control their heart rate under circumstances or, to put another way, do I subconsciously decrease my heart rate while shooting?

The Measurement of Heart Rate
I bought my watch primarily for running, as my pace judgement isn't great and this is critically-important when running long distances. Go out 15 seconds per mile too fast in a marathon and the last 10k is likely to be deeply unpleasant, not to mention very slow. The watch that I bought also has an integrated heart monitor, which works by detecting colour changes under the skin of your wrist when bloodflow increases. Once an activity is recorded, the data can be viewed through the Garmin website or through a 3rd party app like Strava. The plan is simple, start the heart rate monitor and then correlate the heart rate output with shots from SCATT.

Fig 1.1 - Strava output for my last 5k parkrun. The red line is heart rate.

Experimental Conditions
I fired a good 10 shot group using my SCATT wearing the heart monitor. I was careful to try and do this as close to normally as I was able using my normal kit and technique. I switched on the heart rate monitor after warming up, but before I got down to shoot.

Fig 1.2 - SCATT results.

Heart rate monitor results
The heart rate trace yielded some great results and demonstrated exactly the effect I wanted to observe; however it also yielded something rather unexpected. Given that my resting heart rate is somewhere around 50bpm*** I was expecting to see my heart rate decrease to around that level or possibly lower while in the aim, and it to increase moderately when back out of the aim to, say 90bpm. The raw graph looks not dissimilar to this expectation.

Fig 1.3 - Heart rate results. Note the average heart rate of 90bpm.

When I superimposed the shots on the graph, as is shown below and then actually looked at the specific heart rate numbers I was rather surprised to see that the average during shots was 60-65bpm and between shots it went as high as 130-135bpm,which is approximately the same as when I run at a 9 minute mile pace on a flat course.


Preliminary conclusions
It is clear from the result that I am subconsciously controlling my heartbeat when doing SCATT sessions; however the range of heart rates was much broader than was expected. In the next article, I'll have a crack at explaining what might account for this variation and whether there's any way of using it to our advantage.

* Vid. http://www.ncbi.nlm.nih.gov/pubmed/22744827
** It is worth noting at this point that at least two aspects of shooting technique are aimed at diminishing the effect of heartbeats on aim: The modified Estonian position is supposed to reduce the effect of bloodflow through your guts on aim, and correct positioning of the sling on the upper arm reduces disturbance from the brachial artery.
** Average for a 40 year-old man is something like 70bpm according to http://www.topendsports.com/testing/heart-rate-resting-chart.htm but I've been running for few years now, which has had a significant effect.

13 comments:

  1. Excellent start to a very interesting subject, looking forward to seeing more on this.

    Thanks Gaz

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    1. Thanks Oli. I need the time to do a bit more experimentation and work is getting in the way a bit at the moment. I should have a bit more time once my current project goes live.

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  2. Whilst at a corporate medical c2004 i did the aerobic bike test & was ok - on the wind-down after the test with a 120-130bpm rate i started my relaxation techniques squeezing may hands & toes in time to breathing rate & then extending that to other muscles to the core & slowing it all down with pauses & concentrating on my breathing. My heartbeat dropped to 30-40bpm for a few moments & set off all the cardiac alarms! the doc/nurse were bricking it thinking i was keeling over post test (you have to sign a waiver to do the test in case you do snuff it!), it came back up & i was able to repeat the ex & scare them some more, the over all effect was accelerated relaxation & recovery but post test exhaustion because it burns out the adrenalin in the system. I use the same techniques to day (but less effective) its called autogenic relaxation & it took me about 2 years to train my body to react that way. It counteracted the bad effect of coffee & fags till I gave up, kept me competitive in smallbore for a while, now gives me a means to relax quickly on the FP or to calm the F down rapidly after a near miss / scare :-)

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    1. Hi Phil, great to meet you face-to-face in the Slurry on Sunday night after the ATSC Open. I've heard of autogenic training but never looked it up, but it sounds like it could be worth investigating!

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  3. OK so Physiology 1ZB was a long long time ago - when one is on final aim and not breathing, would blood CO2 rise quickly enough to cause an increase in heart rate ?

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  4. Malcolm Cooper was well known for being able to drop his heart rate while in the aim and demonstrated this on a live TV show (was it presented by Michael Buerke?).

    I find I can feel a pulse in my cheek - likely to affect aim more than other parts of the body if you are resting too hard on the butt.

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    1. Hi Charles, I suffer from pulse beat occasionally but it seems to be related to muscular tension in my case. If I focus on relaxing specific muscles it seems to go away,or at least reduce. I do have quite a heavy cheek pressure and wonder if it's related to that though. Could be time for another controlled experiment.

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