As seen in Night Stick the official publication for New Hampshire Police Association :Volume 77 Spring 2012 edition.

As your brain is your most important weapon, the effects of physical stress is often underappreciated for its effects on cognition for those who go into harms way, such military personnel, law enforcement, and other groups.

It’s been a generally held belief that cerebral blood flow (CBF) remains relatively steady during exercise, but recent studies (1,2) suggest that’s not the case. CBF appears to depend on a multitude of factors, including exercise intensity. With lower intensity steady state forms of exercise – all things being equal, such as hydration, etc, – CBF may increase, but during high intensity intermittent forms of exercise (like wrestling with another human being in a life or death struggle for example), appears to decrease. This may partially explain the cognitive decline people experience during high intensity exercise.


Sgt. Jim Vaglica ( sporting an OptimalSWAT shirt, takes his training very seriously


This information very much applies to law enforcement as it does for the military. Under psychological stress, demand for CBF increases, while supply may decrease, resulting in additional cognitive decline.

If a person has not experienced that cognitive decline under training conditions – and so has some experience and understanding of its effects – the results could prove fatal during a “real life” encounter.

If one has not experienced some job related stress training, they often find even simple directions difficult to follow during their first exposure to it. For example, simple directions regarding which targets to engage in which order, or other simple instructions, fail to happen…

Obviously, this will differ greatly with the persons experience, training, fitness, etc., but it’s well established that physical + psychological stress = decline in cognitive abilities and that’s old news for most and common sense.

The specific effects of stress, physical and psychological, on cognitive abilities is a large and growing topic of interest and research for the military and law enforcement.

Basic take home: some form of stress training, where higher intensity, intermittent, training combined with firearms- hopefully following some job/task relevant movement patterns – will help best prepare those who are likely to face violent encounters that require an ability to function under physical and psychological stress simultaneously.


Additionally, such training will add to an ability to physically deal with the effects of stress and will improve overall fitness and general physical preparedness (GPP) of law enforcement and mil populations.

Most people realize how physical and emotional stress will negatively impact performance, but few make the effort to utilize some form of stress training to help ‘inoculate’ the person to that stress, which could very well mean the difference between life and death in a highly stressful encounter not uncommon to law enforcement personnel.

For example, an article entitled “Assessment of Humans Experiencing Uncontrollable Stress: The SERE Course” by Dr. C.A. Morgan III and Major Gary Hazlett (3) goes into depth on the effects of stress on performance, and the importance of properly applied stress to help “inoculate” the individual to future stressors:

“Physical and psychological stress are unavoidable in military operations, yet the negative effects of stress can make it difficult or impossible for individuals or teams to operate effectively. Stress is an essential element of warfare, and individual responses to combat-related stress have often been the determining factor between victory and defeat on the battlefield.”


“Having recognized the effects of stress, the U.S. military designs its training scenarios to be both rigorous and realistic in their stress intensity. Rigorous training improves a person’s ability to perform on the battlefield, and exposure to realistic levels of stress can protect or “inoculate” a person from some of the negative effects of operational stress. The concept of stress inoculation is very much like the concept of preventing a particular disease through vaccination: When stress inoculation occurs, an individual’s performance will likely be better the next time he is stressed. Like immunization, which occurs only when the vaccine is given in the proper dosage, stress inoculation occurs only when the stress intensity is at the optimal level – high enough to activate a person’s psychological and biological systems, but low enough so as not to overwhelm them. If the stress level is not high enough, inoculation will not occur; if the stress level is too high, stress sensitization will occur, and the individual will probably perform less effectively when he is stressed again.”

The above is focused on the military specifically, but the same principles apply to other professions where a high level of physical and mental stress is likely to occur; such as law enforcement. The correct application of some form of practical job related stress training could pay long term dividends for the law enforcement community.

However, it needs to be designed with the population in mind (patrol LEO vs. Tactical LEO, mil, etc), and correctly applied to that population. Some in the LE tactical community have found my Practical Applied Stress Training (P.A.S.T) is a tool in the tool box that can help there.


(1) J Appl Physiol. 2009 Nov;107(5):1370-80.
Cerebral blood flow during exercise: mechanisms of regulation.

(2) Sports Med. 2007;37(9):765-82.
Regulation of cerebral blood flow during exercise.

(3) 2000 Edition of the The Professional Bulletin of the John F. Kennedy Special Warfare Center and School

  1. Robert Tapia 12 years ago

    I lost my password. I have been a subsciber with you for about 17 years. I have always supported you in all you do and believe in all the researh you have truly committed to giving all your subscribers. I was trying to buy your tactical book but cannot seem to get in due to no pass word in the system. I just want you to know that I support all you do and am pleased in the important info you research day in day out and am proud to know you even through e-mail. I don’t write you much but follow all you do and trust your info to be truth. Hope I can buy the book.
    best wishes,
    Bob Tapia

    • Author
      Will Brink 12 years ago

      Bob I’m unclear what the issue is. You don’t need any password to purchase any of my books. Link takes you directly to either the hard copy/print publisher, or e publisher (Amazon, etc) and does not require a password on this end.

  2. Alex 12 years ago

    Im not in the military or law enforcement but i can understand how physical demand can inpair your cognitive functions..
    I really can’t engage in a complex conversation when im working out and sometimes it is even difficuld to focus or remember anything else.. it happens during strength training and cardio too.
    Is there anything or some kind of exercise we can do to try to fix this ? i think that it would than be helpfull in real life situations and even performing better at work..

  3. scott 12 years ago

    perfect practice makes perfect

  4. Curt Bush 12 years ago

    Very interesting subject. You may be interested in a book that I think is rather relevant to this topic.
    It is “How We Decide “ by Jonah Leher. Published by First mariner Books 2010. Check it out.
    It has many examples of human reaction and performance under high levels of stress. I think you would enjoy it.

    • Author
      Will Brink 12 years ago

      I have heard of the book, but have not read it. Will look into it asap. Thanx

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