Monday, August 25, 2014

Research Review: Kettlebell Swings

It's been a while since we've posted an article on here, but it's been a very busy summer here with the opening of our new facility so that's our excuse and we're sticking to it.  Now that school is back in action, we'll be putting out content on a more regular basis, so hold on to your butts!



Our goal is to put out 2-articles each week, with one being a research breakdown and one being something a little more fun.  We've also gotten a few requests for article topics, which we will write about, so if you have a request, leave a comment or email us and we'll touch upon your request.

Research in Kettlebells

In our training we use kettlebell's quite a bit and it has slowly turned into one our favorite methods to teach the hip hinge and develop power.

In literature, the amount of quality research on kettlebell's is small.  There have been a few studies looking at the effect of KB's on strength and power (1-5) and the results of these studies have shown that KB training elicit similar results as traditional training and may have a stronger effect on the development on power over absolute strength.

When breaking down these research studies, it is clear there are some obvious drawbacks on the methods used.  In all the studies reviewed, you will only find one with the use of a KB over 16kg (6).  For anybody with experience in KB's knows this is a very light weight, and considering this light of a weight could stimulate such positive results, it makes you wonder what effects a heavier KB would have. 

Many of our youth athletes have the strength, control, and efficiency to use a 16kg KB, so for these studies to use this light of a weight with fully mature subjects is questionable.

I've seen seen athletes swing KB's of 70-100+lbs with no problem whatsoever.  This weight is 2-4 times more than the amount these studies use, and it would be very interesting to see the effects on strength and power with the use of these heavier bells.

Kettlebell Mechanics

We teach the KB swing as a hinge, not a squat.  We often explain it as a dynamic RDL rather than a dynamic squat.  When the swing is performed in this manner, high levels of posterior chain activation take place to control the rapid eccentric movement and greater emphasis on the stretch-shortening cycle takes place.

(photo credit: coreybeavinfitnessand.wordpress.com)


The mechanics of the swing also place greater emphasis on the medial hamstring group (semitendinosus) than the lateral group (bicep femoris) (7).  This is interesting because sprinting uses similar muscle patterns and places greater emphasis on the medial hamstrings (8).  This may give reason to the KB swing being a great exercise to train the medial hamstrings in a similar manner seen in sprinting.

The hip hinge swing also has a much higher proportion of horizontal forces compared to squats and jump squats (6).  This is a unique dimension of the KB Swing that can't be matched by traditional squats, deadlifts, or Olympic movements. The swing takes hip extension through a fuller range of motion and the path of the bell differs from traditional barbell movements.  This may also be interesting for athletes because recent research is showing the application of horizontal forces increases greater than vertical forces when accelerating to top-end speed (9).

Finally the impulses seen during the KB swing are huge (6).  Impulse is force x time, and this means the KB swing elicits of ton of force in a small amount of time.  This is important because the ultimate goal of athletic preparation is to produce higher forces is shorter times; this outcome is what leads to faster running speeds, higher jumping, increased power, quicker change of direction, and ultimately better performance.

There have been many who have claimed the benefit of KB swings on back pain and rehabilitation.  The exact reasons for these potential mechanisms are not known, but research by McGill et al (10) have shed some light onto some potential reasons.

The KB swing elicited compression forces peaking at 3195N and shear forces peaking at 461N, both seen at the bottom of the swing.  The low amount of shear forces is considered to be desirable and less strenuous on the spine.  The KB Swing also takes the spine through varying degrees of flexion and extension, and this movement is considered good for the spine.  As the saying goes, motion is lotion.

Recommendations

Everybody uses Kettlebell's differently and places different emphasis on them.  Like anything, they aren't an end all be all, but they can serve a purpose.

We at BBA do not program Olympic Lifts, for various reasons which we will touch upon in a future article, and KB Swings are part of our power development tool box we use instead of Olympic lifting.  I feel strongly as research continues to take place, we'll see the benefits of heavy KB swings being very similar to Olympic cleans and snatches, and in our opinion, with less the risk and learning curve.

We stick to mostly KB Swings at our facility, and we really like them because of how quickly our athletes tend to pick up on the technique and how well they work at teaching hip hinging.  It's very rare to have an athlete NOT pick up and learn the technique after just a few sets of practice and specific cueing and coaching assistance.  We can get groups of athletes up and running with KB Swings the very same day we implement them, while it may take weeks and tons of time to teach a group of athletes to perform a "simple" hang clean.  This is a major reason we like them so much. 

With our swings, we program them in a variety of different methods.  We use them for power development, which we will program heavier swings or band assisted swings.  We also use them help teach and cement the hip hinge pattern.  For this we use lighter weights and coach assistance to help push the correct path.  Finally we use them as conditioning or specific metabolic work.  We love to use them with specific work to rest ratio's and hammer away at them during GPP or hypertrophy phases.  The added bonus is the emphasis it places on the posterior chain compared to many other conditioning methods. 

Finally like we touched upon, we teach a hip hinge type of swing and have the bell only travel up to chin level.  The American Swing popularized by Crossfit, in which the bell travels above the head is something you will never see at our facility.  In all honesty, this methods serves no benefit and only brings with it potential consequences.

Take a look at these swings and you'll likely see large amounts of lumbar extension, rib expansion, forward head position, and the fact that many are not suited for this type of loaded shoulder flexion.  Not to mention the effect this position has on the downward movement.  It's not uncommon to have the bell come down and all herky jerky and put massive strain on the shoulder and spine.  All in all, avoid the American Swing and stick to chin level.


Go Get 'Em!


References 

1. Jay K, Frisch D, Hansen K, Zebis MK, Andersen CH, Mortensen OS, Andersen LL. Kettlebell training for musculoskeletal and cardiovascular health: A randomized controlled trial. Scand J Work, Environ Health 37: 196–203, 2011.

2. Jay K, Jakobsen MD, Sundstrup E, Skotte JH, Jørgensen MB, Andersen CH, Pedersen MT, Andersen LL. Effects of kettlebell training on postural coordination and jump performance: A randomized controlled trial. J Strength Cond Res 27: 1202–1209, 2013.

3. Lake JP, Lauder MA. Kettlebell swing training improves maximal and explosive strength. J Strength Cond Res 26: 2228–2233, 2012.

4. Manocchia P, Spierer DK, Lufkin AK, Minichiello J, Castro J. Transference of kettlebell training to strength, power and endurance. J Strength Cond Res 27: 477–484, 2013.

5. Otto WH III, Coburn JW, Brown LE, Spiering BA. Effects of weightlifting vs. kettlebell training on vertical jump, strength, and body composition. J Strength Cond Res 26: 1199–1202, 2012.

6. Lake JP, Lauder MA. Mechanical demands of kettlebell swing exercise. J Strength Cond Res 26: 3209–3216, 2012.

7.  Zebis MK, Skotte J, Andersen CH, Mortensen P, Petersen HH, Viskær TC, Jensen TL, Bencke J, Andersen LL. Kettlebell swing targets semitendinosus and supine leg curl targets biceps femoris: An EMG study with rehabilitation implications. Br J Sports Med 2012.

8. Jönhagen S, Ericson MO, Nemeth G, Eriksson E. Amplitude and timing of electromyographic activity during sprinting. Scand J Med Sci Sports 6: 15–21, 2007.

9.  Randell AD, Cronin JB, Keogh JW, Gill ND. Transference of strength and power adaptation to sports performance-horizontal and vertical force production. Strength Conditioning J 32: 100–106, 2010.

10.  McGill SM, Marshall LW. Kettlebell swing, snatch, and bottoms-up carry: Back and hip muscle activation, motion, and low back loads. J Strength Cond Res 26: 16–27, 2012.

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