Thursday, July 27, 2017

Quit Playing Games with My Heart

Have you seen this chart, or have you heard about the topic it describes?

(Scroll to the very bottom of the post for TL;DR if you like!)

From "On Combat", as rendered by Amazon.com. Not for commercial use.
In brief, as I have heard it taught and as this chart explains, the higher your heart rate, the worse your physical performance. This idea has implications for anyone in a physical confrontation, where an increased heart rate seems to mean an inability to perform self defense actions.

When I first encountered this concept, it did not make sense to me. In my teens I was a high school cross country and track runner, and I frequently elevated my heart rate over 200 bpm. I did not encounter these symptoms. In my twenties and thirties I played men's league ice hockey and managed to perform complex motor skills such as skating, puck handling, and shooting, all while my heart was racing. 

Now, encountering this chart and its ideas as a martial artist, I'm learning that I should be experiencing tunnel vision and racing to the bathroom when my heart rate is high. Could there be more to this phenomenon?

The chart appears in On Combat: The Psychology and Physiology of Deadly Conflict in War and in Peace by Lt. Col. David Grossman and Loren Christensen, published in 2004, but it derives from a 1997 article Grossman wrote with Bruce K. Siddle titled Psychological Effects of Combat, for the Academic Press Encyclopedia of Violence, Peace, and Conflict. 

In On Combat, the authors write:

"There is a zone that exists, generally between 115 and 145 beats per minute (bpm), where you are at your optimal survival and combat performance level... Starting at about 115 bpm, your fine-motor skills begin to deteriorate."

The authors caveat these statements:

"We should be cautious about fixing specific heart rate numbers (or any other precise measures of physiological arousal) on Condition Yellow, Red, or Black. The impact of these Conditions can vary greatly depending upon training, physical fitness, and other factors. Also, it must be understood that these heart rates apply only to survival stress or fear induced heart rate increases. You can so a set of wind sprints and get your hear rate to 200 bpm, but the effect of this exercise induced heart rate increase will not be the same as when fear or survival stress causes the increase." (emphasis added)

You can download a .pdf version of the chart with similar caveats added to the bottom.

Apparently my earlier examples involved exercise without survival stress or fear, so I did not experience the negative effects inherent in the chart. But what is the source of these statements?

The authors state later in the book: 

"The linking of specific heart rate with task performance was pioneered by Bruce K. Siddle, author of the excellent book Sharpening the Warrior's Edge, and one of the great pioneers in the field of 'Warrior Science (TM).'"

I happen to be reading Siddle's book now. On pages 48-49 he writes:

"Levitt and Gutin (1971) studied the performance of a five-choice reaction time task and found that the ideal resting heart rate performance is at the rate of 115 heart beats per minute... After the heart rate increased above 115 bpm, the subject's performance began to deteriorate, with the worst performance at 175 bpm. 

Similarly, Levitt (1972) examined the affects (sic) of various stress levels induced by exercise, on tasks varying information-processing demands... He found a clear Inverted-U effect, with optimal performance at the heart rate of 115 to 145 bpm. His students' performances were clearly less effective at heart beats of 80 and 175 bpm."

Siddle repeats these findings using different wording on page 79.

I find three flaws with the heart rate theory at this point.

First, as far as I can tell, Siddle did no research on his own, as he has no training or expertise in this area. Despite this problem, Grossman and Christensen refer to "Bruce Siddle's research" as if Siddle conducted original work. Siddle's "research" consists of citing two papers by Levitt, one of which had a co-author, Gutin. That's it. Siddle built his whole theory around two studies, and Grossman and Christensen then built then theory on top of Siddle.

Second, Grossman and Christensen's caveats noted "these heart rates apply only to survival stress or fear induced heart rate increases." I believe they added these caveats to address criticism such as those I listed earlier. However, the caveats are inconsistent with the research Siddle cites to support his heart rate theory.  Levitt's 1972 research involved subjects on treadmills, not fighters in stressful situations. According to the caveats, this exercise-induced heart rate elevation should not have caused degraded performance. However, Levitt's research did cause degraded performance. Which is it?

Third, more recent research shows that conclusions by Siddle, Grossman,Christensen are no longer tenable. For example, a 2007 paper by police officer Kathleen Vonk titled Police Performance Under Stress (pdf) stated:

"Although the Inverted-U theory is well-known within the police training arena, many essential components have unfortunately been omitted or forgotten over the years. Siddle included these components in his book Sharpening the Warrior’s Edge, however much of the information has been left behind. For example, even in basic psychology text books both task complexity characteristics and personality characteristics are mentioned as affecting one’s performance, relating these characteristics to an individualized Inverted-U. Rarely, if ever, are these mitigating factors even mentioned in defensive tactics programs...

Since human beings are so different and complex, attempting to categorize or generalize an optimal performance zone to one specific heart rate range would be virtually impossible. Rather than trying to reinvent the wheel, the police profession may be better off looking to the athletic profession in terms of improving physical and mental skills under elevated stress levels." (emphasis added)

Vonk (who has a BS in exercise science) then describes the results of six years of research where her consulting firm collected heart rate data of police officers in a variety of situations, from training to field operations. I recommend reading her paper to better understand her suggested approach, one that abandons heart rates as factors causing stress responses.

My take-away from investigating the Siddle-Grossman-Christensen heart rate theory is that you cannot make any predictions about individual performance based on heart beats per minute. Martial arts instructors should be very careful how they approach this topic with students.

Unfortunately, we cannot seem to excise this theory from popular or martial culture. For example, consider this 2013 Art of Manliness article: Managing Stress Arousal for Optimal Performance: A Guide to the Warrior Color Code. The authors of that article are also confused about Jeff Cooper's color codes, but that's a topic for another post!

If you would like to read a lengthy criticism of the heart rate theory and chart, see this blog post by police officer and trainer W. Hock Hochheim titled Death to the Heart Rate Chart. Stu Marshall, an anaesthetist (a doctor that administers anaesthesia) calls Siddle's work an urban myth

TL;DR: There is little to no science behind the theory that increased heart rates degrade performance. Multiple other factors appear to be responsible, i.e., read Vonk's paper.

What do you think of the heart rate theory? Is it bogus, benign, or beneficial? Let me know here or respond to me on Twitter!

Stay informed of new blog posts by following me on Twitter @rejoiningthetao.

No comments:

Post a Comment