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Restoring Movement with Natural Physics

Guest post by Dr. Ben Fung, PT, DPT.

Dr. Fung is a licensed Physical Therapist in the state of California who earned his Doctor of Physical Therapy degree with honors, graduating at the top 99.95% of national academics.Dr. Fung’s thesis on kettlebell exercise was presented and published by the American College of Sports Medicine in 2010.  In addition to lecturing at national health conferences on the science of kettlebell exercise, Dr. Fung founded “Kettlebell and Physiokinetic Fitness” which went on to become a San Diego 2011 “Best Alternative Exercise Studio” Finalist in its opening year.

Kettlebell Therapy: Restoring Movement with Natural Physics

As a Physiotherapist, I have used kettlebells to rehabilitate and promote health in individuals with low back pain, shoulder impingement, ankle sprains, medial knee pain, myocardial infarction, mitral valve replacement, and much more. Who would have thought that a cast iron ball would be so clinically effective and versatile?

Like most people, when I first saw a kettlebell, I was simultaneously confused and amused.  My first exposure to kettlebells happened at a martial arts seminar in San Diego when one of the instructors lugged out a 53 pound iron-wrecking-ball with a handle fused to the top of it.  He called the object a “kettlebell” – it looks like a tea kettle and it swings like a church bell.  He began a demonstration and spoke on the benefits and martial arts applications of kettlebell exercise.  I had little interest in new trends and was much less inclined to try it out myself – that is, until I saw one of the seminar leaders struggle with the most basic and foundational exercise, the ballistic kettlebell swing.

Out of pride, I had to try it.  Sure enough, after only 10 repetitions I was winded with a decent heart rate response.  Curious about the scope of kettlebells, I attended an introductory kettlebell seminar where countless benefits were claimed by the kettlebell promoters.  Among the claims was a quick side note on the unique physics of kettlebell exercise.  Physics!?!  I would be the judge of that.  Little did they know, I had a degree in Bioengineering, and, I had yet to choose a topic for my doctoral thesis.

Finding no recent or accessible publications regarding kettlebell exercise, I decided to interview the available “kettlebell authorities”.  During the interviews, the authorities had many words in common, words such as: functional, core, power, martial arts, tactical, cardio, VO2 Max, flexibility, dynamics, and rehab potential.  Choosing to focus on the cardiovascular aspect of kettlebell exercise, the American College of Sports Medicine was kind enough to receive me as a presenter to their 2010 annual conference and published my work on kettlebell exercise.  The cardiovascular aspect was fairly self evident and scientifically supported1, 2, however, the clinical applications were not to end there. I quickly realized potential applications of kettlebells to sports and orthopedic rehabilitation.

Kettlebells have a distinct advantage to other modalities of exercise in that they are physically and naturally ergonomic.  As every earthbound human body is victim to gravity, every free body object manipulated by the human body physically acts like a kettlebell.  In terms of physics, a kettlebell essentially is a handle with a big heavy weight attached at the bottom of the handle.  There are infinite examples of how this is expressed in our daily lives: suitcases, bags, backpacks, shopping carts, door handles, buckets, chairs… the list goes on.  Due to gravity, no matter how one lifts a free body object, the point of grip/contact becomes the handle and the remaining mass becomes the big heavy weight at the bottom.  Realizing this concept, the first and most obvious rehab application was that of addressing low back injuries associated with lifting.

Physiotherapists treat innumerable amounts of back injures due to poor lifting mechanics. Part of the rehabilitation process is training a habit of proper lifting mechanics3, 4.   However, to effectively prevent further injury, one must not just train correct biomechanics; one must also strengthen beyond the functional needs via the overloading principles of exercise physiology.  Enter: the Ballistic Kettlebell Swing.  The swing is executed with centrifugal force by the simultaneous extension of the lower extremities, the maintained stable core, retracted scapulas, and a swinging pendulum action of the upper extremities free of forced shoulder flexion.

Due to the physics of the kettlebell, training with a kettlebell has good carryover to the many physically similar objects of daily function and makes it an ideal mode of exercise and training for body mechanics.  What is even more interesting than the physics of the kettlebell object itself are the ballisticexercises made available by the ergonomic properties of the kettlebell design.

One of the foundational exercises done with a kettlebell is the ballistic kettlebell swing.  The advantage comes from the physics of ballistic exercise.  Ballistics resides in the world of angular and centrifugal physics.  Since many of our major joints of movement are round in nature and not linear, ballistic physics work with our joints rather than against them.  Additionally, the ballistic kettlebell swing is done in a closed chain stance which offers many functional carryovers, and, protects our joints from shear forces and compression forces seen commonly in open chain gym machines as well as many traditional forms of resistance exercise.  Since the physics of our joints and the physics of kettlebell ballistics are similar in nature, the exercises become joint sparing and thus encourage natural movement.

Here are some more examples of what kettlebells can do for rehabilitation, and, promotion of health and wellness:

To address knee instability5, 6: the Ballistic Kettlebell Swing.

The ballistic swing is a dynamic closed chain co-contractive exercise which strengthens the muscles of the knee both anteriorly and posteriorly.  Since kettlebells are used ballistically, the explosive nature of the muscle contractions target type II muscle fibers which is a focus for sports rehab.  As technique and form are a natural part of kettlebell exercise, proprioceptive training is also garnished for each repetition of the swing to ensure proper squat mechanics at the foot, ankle, knee, and hip.

To address hip abduction5, 6: High Knees.

Recent trends of knee health have focused on closed chain strengthening of the Gluteus Medius muscle.  In addition to strengthening hip abduction, the “High Knees” exercise has the additional benefit of balance training and core awareness.  High Knees strengthen the stance limb by applying force downwardly through the contralateral limb. This is done by hooking the contralateral forefoot and dorsiflexing the ankle to create a “grip” under the handle of the kettlebell.  The kettlebell then is to be lifted by the contralateral lower extremity in a quick motion into hip flexion and knee flexion.  The kettlebell then is to be lowered to the ground for another repetition.  The downward force is resisted in the same closed chain eccentrics of which the gluteus medius naturally functions on the stance limb during gait and other functional single stance and transitional weight bearing activities.  Additionally, High Knees bypass the competitive and typically tonic Tensor Fascia Latae muscle which has been associated with impairments at the knee and hip.

To promote dynamic scapular retraction7, 8: once again, the Ballistic Kettlebell Swing.  

While shoulder health is remarkably complex, many experts agree that there must be a focus on scapular stabilization.  One of the advantages of the Ballistic Kettlebell Swing is that it also targets scapular retraction dynamically.  As the kettlebell accelerates and decelerates during each swing repetition, the scapular stabilizers must adapt to the changes in demand multi-dimensionally and infinitesimally.  Without scapular stabilization, the upper extremities would protact anteriorly causing instability at the thoracic spine, inability to maintain form of exercise, and result in termination of exercise due to compounding physics.  This natural safe guard is another benefit of exercising in natural physics.  When done correctly, the training effect from the dynamic stability seen in the Ballistic Kettlebell Swing can carry over to a wide array of function surpassing uni-dimensional linear activities.

To address osteoporosis: All kettlebell exercises.

A recent meta-analysis reinforced the importance of resistance exercises and impact loading to reduce bone loss9.  All kettlebell exercises by nature are resistance exercises.  A prescription of proper intensities, loads, and progressions can bolster a physical defense against osteoporosis.  Additionally, since the physics of the kettlebell reinforces good body mechanics and postural correction, one can encourage the favored upright extended postures easily avoiding dreaded spinal flexion postures during exercise.

Restoring Movement with Natural Physics

Restoring, optimizing, and maintaining movement and function are central goals for Physical Therapy and rehabilitation.  By using functional movements combined with physics which are natural to our body, kettlebells offer a mode of exercise with rehab applications and restorative qualities limited only by ones ingenuity and willingness to think outside the box.


1. Fung B, Shore S. Aerobic and Anaerobic Work During Kettlebell Exercise: A Pilot Study. Medicine and Science in Sports and Exercise, Volume 42:5 Supplement: S588-S589. June 2010.

2. Farrar RE et al. Oxygen cost of kettlebell swings. J Strength Cond Res. 2010 Apr;24(4):1034-6.

3. Berrios-Lopez Y et al. Effectiveness of a back school program in the application of body mechanics principles. P R Health Sci. J. 2009 Mar;28(1):48-53.

4. van Middelkoop M et al. Exercise therapy for chronic nonspecific low-back pain. Best Pract Res Clin Rheumatol. 2010 Apr;24(2):193-204.

5. Howard JS et al. Structure, sex, and strength and knee and hip kinematics during landing. J Athl Train. 2011;46(4):376-85.

6. Finnoff JT et al. Hip Strength and Knee Pain in High School Runners: A Prospective Study. PM R. 2011 Sep;3(9):792-801. Epub 2011 Aug 6.

7. Baskurt et al. The effectiveness of scapular stabilization exercise in patients with subacromial impingement syndrome. J Back Muscuolskelet Rehabil. 2011 Jan 1;24(3):173-9.

8. Phadke V et al. Scapular and rotator cuff muscle activity during arm elevation: A review of normal function and alterations with shoulder impingement. Rev Bras Fisioter. 2009 Feb 1;13(1):1-9.

9. Martyn-St. James M, Carroll S. A meta-analysis of impact exercise on postmenopausal bone loss: the case for mixed loading exercise programmes. Br J Sports Med. 2009 Dec;43(12):898-908. Epub 2008 Nov 3.

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