The term “functional movement” has been thrown about something shocking the past few years, what with different international training organisations reinventing the “Fitness Attribute wheel” to the extreme; frankly, I’m sick of the term, particularly as that little phrase deserves an article onto itself, but I digress…
Part of this reinvention has included the advocacy of Kettlebells (KB) for everything from rehabilitation in sedentary people to sports-specific training in elite athletes. The question is though, are these recommendations warranted and evidenced by research? And moreover, are KB relevant to YOU and YOUR training goals? This, my friends, is what this little piece will hopefully address.
DISCLAIMER: Get comfortable as you’ll be here a while. Despite being on the edge of your seat if you DO read on, GSCPT waives any liability for your ar*e going numb.
I’m assuming if you ARE still reading, you have some experience with KB or you at least have an idea of a few techniques. The most commonly advocated techniques (and those that research has focussed on most) are the Double Hand KB Swing (DHKBS) and Single Hand KB Swing (SHKBS). These techniques involve explosively contracting muscles to accelerate the KB from the starting position, eccentrically slowing the KB towards the top of the swing (anywhere between shoulder height to directly overhead depending on what “school” of training you come under) and eccentrically controlling/ slowing the KB’s descent from top position back to the starting point. (Please see the attached promo picture for an example of the DHKBS).
With both exercises appearing simple in text and image, there’s a lot more to it than simply chucking it around. Variation exists in the actual swing technique itself i.e. the Squat vs. Hip-hinge method (for those out there who are familiar). A comparative analysis of each is also article worthy itself and will be left with their respective “schools of thought” for the time being. For you hardcore RKC/ Crossfitters etc out there, be aware that the specific swing technique in these studies haven’t been declared; so… um… make do and infer what you will. Now on to the research itself…
Despite KB common prescription and worldwide popularity, there’s not much at all. To date, there have been only 13 studies on KB use, comprised of:
– 1 Conference presentation
– 2 reviews
– 2 muscle activation studies (1 on low back loads)
– 5 muscular strength & power studies (vertical jump, power clean, back squat etc)
– 2 calorie expenditure studies and
– 1 musculosketal health study (low back pain)
Thankfully, there’s enough of the training spectrum there for us to sink our teeth into, from rehabilitation to developing athletic performance. What I’ll try to do is evaluate the findings for each topic and specific population AND, if you fall into that group, you can make up your own mind whether to “Swing it or Sling it?!” (See what I did there?)
NB. In my recommendations, “Swing it” doesn’t necessarily mean the swing exercise, rather, KB MAY be used with caution for that particular population.
Before we get stuck in, please be aware of some study limitations as identified by Campbell (2013):
– Most studies used a 16kg KB – is this mass relevant to your goals, ability and budget?
– Study participants were either trained (regular weeks/months/years exercise experience) or untrained (recreationally active/sedentary/ not active). What category do you fall under?
If you can’t decide what you fall under:
1: Check your pulse. Are you dead? If not, go to 2.
2: Have you been sedated for the past year of your life? What the hell have you been doing?!
3: What category do you fall under now? If you’re still unsure, go back to 1.
Topic 1: KB, Rehabilitation, “Prehabilitation” and Corrective Exercise
KB have been advocated by many for “corrective exercise” and injury rehabilitation e.g. Brumitt, Gilpin et al (2010) and Brumitt & Dale (2009)’s recommendation for rehabilitative use amongst golfers, particularly the “woodchop” exercise to replicate the back swing. The problem is, much of the research recommendations until now have been strictly anecdotal or opinion based. The best way to look at this is if we classify KB as a resistance exercise (which, technically being an object with a mass to be lifted, they are), then cross reference their potential use during the different stages of tissue healing following injury.
Acute Injury phase (1-4 days): If you’ve recently injured yourself – “SLING IT!” Careful prescription of exercise is required during this phase as to not damage the injured musculature and delay healing. Usually, isometric (static contraction exercise with no change in muscle length) is advocated. KB COULD be used in this manner, but does this undermine their purpose if other methodologies and equipment are preferred and available? With this in mind, in my opinion KB are NOT suitable for this phase.
Sub-acute phase (4 – 30 days): If you’re up to it, “SWING IT!” with care and control. The goals during this phase are to decrease pain, increase joint range of motion, muscular flexibility and to restore/increase strength. Exercises chosen are based on patient diagnosis, their clinical presentation, the functional demands of their sport, exercise experience and/or post-surgical status and typically range from muscular endurance (>15 reps) to strength (4-6 reps) with eccentric exercises preferred to help direct muscle fibre alignment. Care is still required to avoid damage to newly deposited collagen fibres, however, as muscular asymmetries and weaknesses can be addressed, KB CAN be used in this phase, provided you/ your coach have an accurate knowledge of anatomy, physiology and exercise.
Remodelling phase (30 days- 1 year): My advice? If you know how, “SWING IT!” During this phase strength/power/ sports specific training may be developed. With this in mind, KBS (swings) may be appropriate for a transition from the sub-acute phase to power training prior to Olympic weightlifting techniques (this will be discussed in depth later).
Moving on to “Prehabilitation”: if you’re a competitive/elite female athlete or footballer, then “SWING IT!” A common injury in females athletes, particularly as they progress through the Long Term Athlete Development pathway, is that of ACL rupture (Hewett, Myer et al, 2005) caused by excessive knee joint valgus (legs moving toward midline of body) and decreased neuromuscular control (muscle activation). A study by Zebis, Skotte et al (2012) found that DHKBS activates the Semitendinosus (medial hamstring) 20% more than the Biceps Femoris (lateral hamstring) muscle. As the Semitendinosus and Semimembranosus PREVENT excessive knee valgus, performing DHKBS may help strengthen said muscles, increasing their ability to withstand knee valgus forces and thereby potentially prevent ACL injuries.
If you’re one of the four in five people in the UK currently suffering from Low Back Pain (LBP) (Palmer, Walsh et al, 2000), my advice to you is “SWING IT!” Research by Jay, Frisch et al (2011) has shown a decreased perception of Upper and LBP following 8 weeks of KB training in sedentary office workers. Concomitantly, a study by McGill and Marshall (2012) indicated safe, yet reasonably high activation in this region, with sheer forces (forwards and backwards motion) and compressive forces of the L4 on the L5 disc during SHKBS. Of note to Palmer, Walsh et al’s (2000) study, is that the control group did nothing at all, a common coping strategy for those who suffer from LBP (www.backcare.org.uk); hoping that the pain will go away itself and not wishing to aggravate it will not cure it. This may be the only time you’ll get to swing at the office, so best enjoy it!
Finally, if you suffer from muscle weakness in your glutes or posterior chain, “SWING IT!” McGill and Marshall (2012) also showed that SHKBS activate the Glute Max and Med by 76% and 70% respectively, that’s a bad a*s amount of activation right there (get it?). Interestingly, the Rectus Abdominus wasn’t as activate as anticipated during the swing, leading to possible implications for abdominal bracing techniques during heavier lifts/ swings.
Topic 2: KB and Body fat reduction, Calorie expenditure/ weight loss
Now THIS is where things get interesting…
Kettlebells burn fat, right? They must do. Sure they’ve been touted by NUMEROUS sources for body fat reduction and weight loss for the sedentary to elite athlete e.g. DragonDoor (2012), Bodybuilding.com (2012), Mens Fitness (2013), Women’s Health (2013) and by arguably the world’s LEADING organisation for kettlebell certification, the RKC (2012). With that in mind, here’s my recommendation:
For the purpose of body fat reduction via KB training, I advise you to “SLING IT!” Controversial, I know. But how could ALL these sources be wrong? Well, like I said in the intro, for years research recommendations have been based on anecdotal evidence and personal opinion… until now. Farrar, Mayhew et al (2010) compared 12 mins maximum effort DHKBS to a graded VO2 max test to exhaustion in recreational uni students, with expired gases (Respiratory Exchange Ratio- RER) and heart rate continually measured throughout (for those unfamiliar, RER indicates where expended calories are being metabolised from i.e. from fat or carbohydrate/ glycogen and is measured by an Oxygen Cart). Despite all subjects expending 120-160Kcal during the 12 min maximum effort DHKBS AND being in the “Fat burning zone” of > 65% VO2 max (Carey, 2009), the RER indicated that subjects metabolised carbohydrate ONLY during the 12 minutes i.e. not a SINGLE CALORIE from fat. So “SLING IT!” folks., there are more effective methods out there for metabolising body fat e.g. High Intensity Interval training (Talanian, Galloway et al, 2007), which brings me onto my next point…
Whilst KB may not metabolise body fat during max effort protocols, they’re effective for general weight loss/ calorie expenditure, right? They at least burn more calories overall when compared to something boring like treadmill running, don’t they? Nah, sorry, they don’t. If you want to use KB to burn more calories during your session, I’d advise you to “SLING IT!” Research by Hulsey, Soto et al (2012) compared 10 mins (35:25 secs work: rest) of DHKBS at 16/24kg in 13 moderately trained subjects to steady state treadmill running at the same Rate of Perceived Exertion (RPE), with both RPE and calorie expenditure measured constantly throughout. Whilst KB DID burn calories (12.5 Kcal per min), treadmill running at the same RPE was FAR more effective, burning 17Kcal per min – that’s 50% more calories during steady state running.
So there it is folks. KB do NOT metabolise body fat AT ALL during a 12 min max effort/ high intensity protocols, NOR are they superior to steady state treadmill running in an attempt to burn more calories per session. Those claiming that they do are unfortunately mistaken.
Topic 3: KB and Power, Strength
Power, who needs it? Well, arguably everyone, but athletes definitely do. Peak power is critical to athletic development- generating high or max forces FAST. In theory, power may be developed by explosively swinging the KB for a desired number of repetitions, whilst increasing the mass of the KB itself will increase the inertia (the accelerative force required to overcome gravity and the weight of the KB), thus requiring the athlete to generate more force. But, does research testify to this theory?
The one we’ve all been waiting on! Have all you RKC’s, Crossfitters etc out there crossed your fingers? Maestro, drum roll please!
… If you are new to exercise and have no previous weightlifting experience, I hereby declare that you “SWING IT!” Jay, Sundstrup et al (2013) found that 8 weeks of KB training improved vertical jump scores by 9% in sedentary office workers (why sedentary office workers NEED to vertical jump though, is beyond me).
If however, you are a competitive athlete or someone with KB or weightlifting (WL) experience, I hereby advise you to “SLING IT!” Lake, Lauder et al (2012) found no significant difference to vertical jump or half squat strength in weight trained males following KB training; likewise, Otto, Coburn et al (2012) found 6 weeks of weightlifting induced significantly greater improvements in strength (+13.5%) compared to KB training, with no significant difference on vertical jump performance or body composition. Lake, Lauder et al (2012) also found that DHKBS were inferior to the Back Squat (Peak force=80% RM) and Jump Squat (Peak power=0% RM) in producing peak force and power respectively in a strength & conditioning trained population. The ONLY study to date, which found KB training DID improve strength (3RM bench and Clean & Jerk) by Manocchia, Spierer et al (2013), has several limitations, namely using the KB similar to a dumbbell/ barbell which will undoubtedly have influenced strength results themselves. In closing, for the athletic population at least, there are more effective methods such as Olympic weightlifting, available for improving strength and power than KB.
And it is done. You are now familiar with all the facts to date regarding kettlebells and their training effects. Whether you “swing it” or “sling it” now is your prerogative, however, consider yourself warned, as your sessions may be more or less effective depending on your purpose of use. If you DO begin or continue to incorporate them into your training, remember there is no substitute for correct technique, so ensure you know what you’re doing, or at least seek out someone who does from a reputable training provider. Whichever one THAT is, I’ll leave to you hardcore KB fans to sling around. I’m off to the bar (bell).
We at Ireland Strength and conditioning would like to thank Gareth O’Neill for his brilliant guest blog.
Gareth O’Neill is a graduate in BSc (Hons) Applied Sports Sciences with Coaching, accredited Strength Conditioning coach and REPS Level 3 Advanced Personal trainer. Following 4 years experience working in Sports Science support/ Strength Conditioning roles in semi-professional and representative level sport, he has returned to Belfast and is currently studying Physiotherapy at the University of Ulster.
Gareth O’Neill BSc(Hons) ASSC, BSc(Hons) Physiotherapy
Biography
Gareth is a graduate in BSc(Hons) Applied Sports Sciences with Coaching, an accredited Strength Conditioning coach, REPS Level 3 Advanced Personal trainer and Olympic weightlifting coach. With 5 years experience working abroad in Sports Science/ SC roles, he has returned to NI and is currently studying Physiotherapy at the University of Ulster.Gareth combines his qualifications, experience and academic position to apply current research, knowledge and evidence-based methodologies to practice, aiming to surpass training expectations and get the best results from your goals.
Outside of S&C and academic study, Gareth enjoys spending time with his partner Rachel, his two young nephews and friends, playing acoustic guitar and game and coarse fishing (when he can find the time… and the fish!) Finally, he enjoys working with young people and aiding in their sporting and personal development as a teaching assistant for A-Level PE.
References
www.backcare.og.uk [Accessed 28/07/13] Page available at http://www.backcare.org.uk/factsandfigures
Bodybuilding.com (2012) “Swing for the fences: Kettlebell training – burn fat and build muscles”. Available from http://www.bodybuilding.com/fun/swing-for-the-fences-kettlebell-training.html. Accessed 29.07.2013
Brumitt J, Dale RB. (2009) Functional rehabilitation exercise prescription for golfers. Athletic Ther Today. 14(4):8–12.
Brumitt, J. Gilpin, H.E. Brunette, M. Meira, E.P. (2010) INCORPORATING KETTLEBELLS INTO A LOWER EXTREMITY SPORTS REHABILITATION PROGRAM. North American Journal of Sports Physical Therapy; 5(4): 257–265
Campbell, B (2013) The benefits and drawbacks of using Kettlebells in a training program. Presented at NSCA Personal trainers’ Conference.
Carey, DG (2009) “Quantifying differences in the “fat burning” zone and the aerobic zone: implications for training. Journal of Strength Conditioning Research, 23 (7): pg. 2090-5.
DragonDoor (2012) “Kettlebell training for full body fat loss!” Available fromhttp://www.dragondoor.com/articles/kettlebell-training-for-full-body-fat-loss/. Accessed 29.07.13
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Lake, JP. Lauder, MA. (2012) Kettlebell swing training improves maximal and explosive strength. Journal of Strength Conditioning Research, 26 (8): pg. 2228-2233
Manocchia, P. Spierer, DK. Lufkin, AK. Minichiello, J. Castro, J (2013) Transference of kettlebell training to strength, power and endurance. Journal of Strength and Conditioning Research, 27 (2): pg. 477 – 484
Mens Fitness (2013) “The 20 minute Fat-burning Kettlebell complex”. Available from http://www.mensfitness.com/training/lose-weight/the-20-minute-fat-burning-kettlebell-complex. Accessed 29.07.2013
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Talanian, J. Galloway, S. Heigenhauser, G. Bonen, A. Spriet, L (2007) “Two weeks of high intensity aerobic interval training increases the capacity for fat oxidation during exercise in women”. Journal of Applied Physiology, 102 (4): pg. 1439 – 1447
Women’s Health (2013) Total body toning with kettlebells: Drop the dumbbells and burn calories and fat with kettlebells”. Available from http://www.womenshealthmag.com/fitness/kettlebell-workout. Accessed 29.07.13.
Zebis, MK. Skotte, J. Andersen, CH. Mortensen, P. Petersen, M. Viskaer, TC. Jensen, TL. Bencke, J. Andersen, LL (2012) Kettlebell swing targets semitendinosus and supine leg curl targets biceps femoris: an EMG study with rehabilitation implications. British Journal of Sports Medicine: July 6 (Epub ahead of print)
Ireland Strength and Conditioning 
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