Kettlebells and the Heart – an interview with Dr. Eddy Crendal

What are your major interests?

-My personal interests revolve around strength training. I am very passionate about the art and science of strength and conditioning, along with nutritional and supplemental strategies for supporting progress. I am hoping to compete in Powerlifting again this year.

My professional interests involve research and clinical practice in cardiology. I believe the heart is one of the most complex and fascinating organs we have, and it is also one of the most adaptable. Heart disease is still the number one killer world-wide, and as such, I feel like I am in a domain where I can potentially make a difference to the community.


What is your current professional role?

-Having just finished my PhD, I decided to take a step back from the research world, and become involved in clinical practice. I am currently employed as a Cardiac technologist at the St Vincent’s Hospital. My roles involve analysing and fitting 24 hours Holter monitors, monitoring patient ECGS during Stress echocardiograms, and eventually conducting echocardiograms on both outpatients and inpatients. I really enjoy rubbing shoulders with top Cardiologists in Melbourne, and picking their brains on various topics!


Tell us about your PhD research?

-In a nutshell, my research (entitled Myocardial Mechanics in Metabolic Syndrome and Aging Populations) involved the use of cardiac ultrasound techniques to monitor subtle changes occurring in the myocardium (heart muscle) under pathological metabolic conditions, such as metabolic syndrome and diabetes, as well as in the normal process of aging.

We found some very interesting results, with commonalities in both populations (metabolic syndrome and aging). Specifically, while certain functions of the heart deteriorated (longitudinal deformation), other functions (circumferential deformation) increased, in a kind of compensatory manner. It proved again just how adaptable our hearts are!


Can you go into a bit of detail about the little case study we did?

-Sure. For about six months leading up to a data collection phase of my research, I practiced as much as possible with the cardiac ultrasound, to improve my accuracy and skill. Being a tall, fit, and lean subject- you were perfect to practice on, since you are what we call echogenic (easy to acquire good images on). I remember assessing your heart at several points in time, and coincidentally, I measured some variables of your heart structure/function before and after a 12 week Kettlebell training program you performed.

Now obviously, we must interpret this with caution, as it is only a case study, and morphological changes in the heart vary amongst individuals, and typically occur over longer periods of time. However, what I saw was quite remarkable…

You see, the heart can adapt in several ways in response to stress. For instance, its walls can thicken, without any changes in ventricular cavity dimensions. This is typically seen in hypertensive subjects (due to greater peripheral resistance in the vasculature), and strength athletes (due to the peripheral resistance generated from the Valsalva manoeuvre). This is called concentric hypertrophy. On the other hand, the heart chambers can also increase in dimension, or dilate, without any changes to the walls. This is usually called eccentric remodeling, and is more common in endurance athletes (helping to improve stroke volume and preload).

Interestingly, your heart structure and function changed a bit following those 12 weeks of Kettlebell training, and involved both some aerobic and strength adaptations!


What measures changed?

-The main thing I noticed was an increase in left ventricular diameter, accompanied by improved diastolic function (measured as the ratio of early to late diastolic filling velocity). Additionally, both your diastolic and systolic tissue velocities increased at the septum and lateral wall of the left ventricle. These changes are indicative of more efficient pumping capacity of the heart, usually related to improved cardio-respiratory capacity. But it didn’t end there; your septum and lateral wall thickness also increased slightly, and as mentioned above, your systolic tissue velocity augmented. These indicated adaptations to strength training- i.e. the heart remodels itself to contract more powerfully to overcome the greater peripheral resistance generated from Valsalva manoeuvres.


Are these changes good for aerobic performance?

-Eccentric remodeling (left ventricular dilation) is often seen in elite athletes. For example, elite cyclists are known to have some of the biggest hearts in the population. One of my colleagues (Andre La Gerche) has extensively researched this phenomenon, and found that this remodeling may sometimes even be detrimental to health. I guess there is such thing as too much of a good thing!

The increased chamber size, accompanied by the more compliant tissue and greater diastolic filling equate to a much more efficient heart. This is why these cyclists often have ridiculously low heart rates. Their hearts are machines! They are able to supply oxygen to their working muscles more efficiently during stress, and withstand the stress for longer!

Thus, these changes are indeed absolutely good for aerobic performance!


What can we take away from this?

-I would say this shows how versatile Kettlebell training can be. Not only did you get stronger throughout your training cycle, with your heart showing evidence of some strength adaptations, but we also saw how your heart adapted for improved cardio-respiratory performance!

Kettlebell training may thus be a useful tool for athletes seeking both aerobic-conditioning and strength gains- a kind of double whammy, bang for your buck training approach. It would be interesting to also investigate how clinical populations respond to Kettlebell training, i.e. could Kettlebell training be an efficient mode of exercise for managing and improving type-2 diabetes status?


Would you expect to see other changes over time? Also, what are other changes that could be interesting to investigate, which could help with aerobic performance?

-I think it would have been really interesting to assess your heart with the more sophisticated technology I used in my research; namely speckle tracking echocardiography. We didn’t use this in our little case study, as I was still learning how to implement it at the time.

Briefly, speckle tracking imaging allows the direct measurement of contraction and relaxation of myocardial tissue in the longitudinal and circumferential axes (see picture below). Additionally, it also permits the measurement of left ventricular twist. Did you know that when the left ventricle contracts, it twists, a little like the wringing of a towel? Left ventricular twist often increases when other functions deteriorate, in order to maintain an adequate ejection fraction. It is a good indicator of ventricular filling and ejection capacity, and thus could be read as a marker of cardio-respiratory performance.

Wouldn’t it be interesting to see how the twisting action of your left ventricle responds to a Kettlebell training macro-cycle? Maybe next time..!

Thanks for your time Dr Crendal!


My name is James Ross, I’m a qualified personal trainer, strength & conditioning coach and sports scientist. I am a founder and coach at The Richmond Gym in Melbourne and started the website

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