Interview with Israel Halperin


I am very pleased to offer an interview with Israel Halperin, an athlete, trainer, and researcher with extensive knowledge about how to improve human performance. I have interacted with Israel over Facebook for quite a while, and really appreciate his expertise, open-mindedness, curiosity, and willingness to share information. I always find it interesting when people like Israel, who are true experts in their field, are more humble and curious than people with only a fraction of their knowledge (who are often convinced they are already know everything!)

Israel is one of the good guys, and you should include him in your sources of interesting, practical and reliable information. And he provided some awesome information in this interview.

Read below for Israel's thoughts on many interesting topics, such as: foam rolling, how to cue an athlete to maximize performance, how to use psychological tricks to improve endurance, some problems with Tim Noakes' central governor model for endurance, and a possible scientific explanation for the phenomenon of curling in the squat rack.

Q: Hi Israel, thanks for agreeing to do the interview. You've had the chance to examine human performance from many different perspectives – as an athlete, trainer, and even a scientist. And I know that you’ve worked with athletes from many different training cultures. Tell us a little bit about your background and what you are doing now.

It’s my pleasure, Todd, thanks for having me. My movement career began with a strong passion towards martial arts at a very young age, which is still ongoing to this day.

During my early to mid-twenties I dedicated my life to combat sports as a competitor. Throughout this period I travelled and competed in the U.S, Thailand, Israel, and Europe, where I was lucky enough to train at some of the best MMA and kickboxing gyms in the world.


After accumulating a number injures I reached a point where I felt I had enough. The next natural step for me was to train other combat athletes in kickboxing as well as run their strength and conditioning sessions.

During this period I also completed my B.Ed in physical education in Israel, which motivated me to pursue an academic career in human movement sciences. I then moved to Canada and completed an M.Sc in Exercise Physiology at Memorial University in Newfoundland.

At present I live in Australia studying for my PhD with the Australian Institute of Sport (AIS) in conjunction with Edith-Cowan University. I work at the AIS Combat Centre with a team of sport scientists trying to understand what leads to success in the Olympic combat sports (Judo, Boxing, Wrestling and Taekwondo). In my spare time I train a number of athletes in kickboxing, which remains my favorite combat sport.

Q: Let’s talk about foam rolling, because I know you have done some interesting research in that area. Tell us about it!

I completed my M.Sc under the supervision of Professor David Behm at Memorial University of Newfoundland in Canada. Professor Behm and others from the same department are leading the self-massage research and I was lucky enough to participate in the project.


Briefly, we compared the effects of self-massage using a stick roller to static stretching of the calf muscles. Both interventions improved range of motion to approximately the same degree. In contrast, while force production decreased with stretching, it remained unaffected and even slightly increased with the rolling. These results, confirmed by others, may be of practical value, especially for athletes in the warm up stage. Note, however, that the negative effects of stretching are negligible or nonexistent unless stretching is done too long, too intense, or too close to the next physical task.

Q: There is a lot of speculation out there about the mechanisms by which foam rolling works (assuming it works!). Some suggest that it works by melting fascia, or improving "tissue quality" or breaking adhesions. There are also speculations that it works by proprioceptive enhancement. My personal favorite explanation is that it activates descending inhibition of nociception. What are your thoughts?

First, my view of rolling is that if you like it and believe it can help you, then go ahead and roll. On the other hand, if you are not a fan and prefer doing something else instead, I am fine with that as well. Despite the growing popularity, I do not think it’s mandatory to roll.

Second, I mostly agree with your preferred explanation. That is, the improved range of motion is mostly due to central adaptions, specifically as a result of enhanced pain tolerance. However, I think that the immediate responses are also partly due to alternations in tissue stiffness. I do not know and would rather not guess which exact tissues are affected. I also speculate that slight improvements in force production after rolling may be due to greater activation of sympathetic tone as a result of varying levels of pain induced by the self-massage. However, to the best of my knowledge this issue remains to be addressed.

Q: Tell us about your research into the nature of fatigue and the role of the nervous system.

I take great interest in the causes of muscular fatigue and what leads to its perception. A specific theme I am currently exploring concerns non-local muscle fatigue (NLMF). This occurs when fatiguing one muscle group leads to fatigue in different, rested muscle groups.

For example, fatiguing the quadriceps in one side can lead to fatigue in the contralateral quadriceps. Interestingly, we recently found that NLMF predominately occurs in the lower limbs as compared to the upper limbs. That is, fatiguing any muscle group in the body seems to negatively affect the lower limbs (especially the quadriceps), whereas the upper limbs (especially the elbow flexors) seem to be immune to such effects. These findings could have some practical implications. Particularly, it may be beneficial to train the lower body before the upper body, which has better resistance to NLMF. This precise problem is a subject of my current work.

I am also interested in performance enhancement by tapping into muscular reserves. That is, finding ways to squeeze that extra bit from the athletes in spite of their perception that they are doing their very best. This can be achieved by manipulating psycho-physiological variables such as feedback, deception, knowledge of exercise endpoint, self-talk, and other tricky ways. Due to my background and my daily interactions with combat athletes, I am especially interested in exploring such strategies during the rest periods between the rounds of competitions. In fact, I recently used a Gatorade mouth rinsing technique with a kickboxer in between rounds of a professional bout.


Q: That is interesting that non-local muscle fatigue has more effect on the quads than the biceps. Perhaps this helps explain the phenomenon of curling in the squat rack. Can you elaborate on some of your strategies for "tricking" the athlete into working harder?

I think you are onto something with your squat rack curling hypothesis Todd. You gave me some good ideas for future studies.

Well, the mouth rinsing technique that I just described is an interesting case. Basically washing your mouth with a sugary drink for a few seconds and then spitting out the liquid tends to enhance performance. These positive effects seem to be related to activation of specific receptors found in the oral cavity which may directly activate reward centers in the brain thereby increasing motivation to complete the task with extra effort.

Positive self-talk is another strategy supported by recent research. Choosing 2-3 short positive sentences and repeatedly saying them to yourself (e.g. “I will win”) before and/or during exercise can be quite helpful. For instance, a competitive kickboxer I work with who struggles with the high intensity portions of training found this technique helpful to counter his negative thoughts. This strategy can be helpful prior to and between the rounds of competitions. The positive effects seem to stem from either increasing motivation and/or reducing the sensation of effort.


Q: Researcher Tim Noakes has sought to explain why these tricks work in reference to a “central governor.” As you know, his basic idea is that fatigue is an emotion created by the brain to protect the body from perceived threat related to continued energy expenditure. Thus, when we quit exercising from fatigue, it is not because the local muscles have exhausted their energy reserves, but because some central system has analyzed all the available evidence related to the threat of continued performance, and then decided to shut down the exercise to protect the body. What do you think of Noakes’ central governor idea? Can you compare it to the ideas of Samuel Marcora? The distinction may sound like semantics to some readers, but I find the topic interesting!

Overall I definitely agree with the gist of the Central Governor Model (CGM) and other models stating the exercise is mostly regulated by the brain. However, other than this general agreement I find this topic to be complex and confusing with case dependent conclusions.

To begin, I will briefly share my thoughts on the CGM. Professor Noakes deserves a lot of credit for his pioneering work and for raising awareness to this topic. However the CGM can be criticized for a number of reasons, which some may think are just semantic.

First, if the governor regulates exercise, then who regulates the governor? This little man inside the man is also known as the homunculus fallacy and can be quite problematic as the loop continues forever without truly explaining the effects.

Second, if the governor regulates performance as a function of available energy resources and to avoid physical harm, as proposed, then psychological interventions should not influence performance as they have no direct or indirect effect on either. This contradicts experimental observations. For example, while positive self-talk should not influence the calculations of the governor with regard to available energy resources or potential physical harm, it was nevertheless shown to enhance performance. This, I find, cannot be adequately rationalized by the CGM.

These issues are better dealt with by the psychobiological model of exercise performance proposed by Professor Samuel Marcora. In contrast to the CGM, Marcora’s model relies heavily on psychological research. For exercise sciences this I think is a novel and an important step in the right direction. Specifically, Marcora proposes that exercise regulation is the result of an interplay between motivation to complete the task and perception of effort during the activity. His model can rationalize the effect of different interventions including psychological ones and the homunculus fallacy is not an issue. For these reasons, I currently prefer the psychobiological model over the CGM.

However, often the brain vs. muscles debate turns into a false, either/or dichotomy. On one hand, I believe that the “continuation vs. stopping of the exercise” question is answered (regulated) in the brain. On the other hand, power output can also decrease during exercise solely due to muscular alternations despite high levels of motivation. For example, I doubt that many 100 meters sprinters regulate or hold back during competitions either consciously or subconsciously. However, in my opinion the decrements in speed are due mostly, if not exclusively, to peripheral changes. Indeed, there are persons who can fully activate their muscles, as demonstrated by electrical twitch studies, just as there are ones who cannot. This last example illustrates the uncertainties involved with this topic. The question if exercise is regulated depends on many different factors such on the type, intensity and duration of the activity, as well as the identity of the participants and their perception of the event and its importance. Despite the great progress made in recent years, we are still a long way from having definitive answers.

Q: Can you describe your research on the effects of internal versus external focus on performance?  

In a recent pilot study we found that both kicking and punching speed and impact forces were enhanced when the instructions were “When you kick/punch, focus on hitting the pad as fast and as forcefully as you possibly can” (external focus) compared to “When you kick/punch, focus on moving your arm/leg as fast and as forcefully as you possibly can” (internal focus). While these two sentences may seem alike, the external focus instructions led to 3-6% improvements in speed and force off punches and kicks. Considering that the participants were elite boxers and Taekwondo athletes, these effects are quite large.


Q: Very cool. Isn’t it true that many martial arts traditions often advocate internal focus at times? Is there ever a role for a more internal focus, or do you try to ensure that your athletes always have external focus?

You are absolutely right about the common usage of internal focus of instructions in martial arts: “lift your hands”, “move your feet”, “turn your hip”, “extend your elbow”, etc. Based on the results of my research and that of others which have conclusively demonstrated the inferiority of internal focus in regards to movement related outcomes, I try not to use internal instructions. I wrote “try” as it is quite difficult to avoid it.

I also emphasized the inferiority of internal cues rather than the superiority of external ones. While in my research I found that external cues are more effective, they afford only marginal advantage over the control instructions which did not refer to either internal or an external point of reference. On the other hand, the negative effects of internal cues were strong. Now, there may be some cases in which internal instruction may be beneficial, such as activating a specific muscle group. However, with some creativity, one can also find a way to achieve the same goal with external cues, which would probably be more effective. With the athletes I work with I try to only use external instructions in training, and especially in competitions. Most importantly, I do my best to avoid using internal cues.

Thanks for the interview Israel, I really appreciate your knowledge and willingness to share. Best of luck.

Thanks Todd, my pleasure.

Well that's it. Click here to keep track of Israel's research, or follow him on Twitter. (And stay tuned for a blog from Israel in the near future.)