The Cooper Institute
 

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH

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Recent Research on Kettlebells

Written by
Karyn Hughes, MEd
Posted in
Move more

Thursday, Aug 01, 2013

In recent years, there has been a large rise in the use of kettlebells in exercise training. Kettlebell classes are taught in YMCA’s, military bases, athletic conditioning rooms, and fitness centers just about everywhere. Personal trainers are using kettlebells with their clients to challenge them with whole body movements with the intention of achieving greater training results in a short period of time. The unique design of the kettlebell allows for a swinging motion which allows not only for a simulation of various Olympic lifts such as the snatch and clean and jerk but also is thought to allow movements that simulate movements in everyday life therefore creating functional benefits.  And while their popularity has risen over the past few years, it is actually a training form that originated in Russia in the 1700’s! Popularity is still growing as kettlebell sales continue to be on an upward trend. But how safe and effective are they? Are they safe even for the novice? Will they help us lose weight, and develop substantial strength?

Until recently kettlebell research studies were few and far between, but in 2012, three studies were published in reputable, scientific, fitness journals.  They investigated three major aspects of kettlebell training:

1)    Metabolic demand

2)    Training effect on strength, vertical jump, and body composition

3)    Safety of kettlebell training on the spine

Let’s take a look at what was found.

KB Training and Metabolic Demand

Hulsey et al. (2012) looked at kettlebell swings and treadmill running at equivalent ratings of perceived exertion rates. Researchers wanted to determine if continuous kettlebell swings would illicit an energy cost able to improve cardiorespiratory fitness.  Eleven male subjects used a 16 pound kettlebell (KB) and two female subjects used an 8 pound KB. They performed KB swings in a cycle of 35 second swing bouts followed by 25 seconds of rest, which equated to 22 to 25 swings per minute for a total of 10 minutes.  After 48 hours of rest, the same subjects ran on a treadmill (TM) for 10 minutes at a similar rating of perceived exertion as the KB swings which was a 15 which equated to running at above 85% of their age predicted max heart rate. During TM running, subjects had significantly higher oxygen consumption or 46.7 +/- 7.3 compared to the KB swings of 34.1 +/-4.7.  But the KB swings did produce enough of a physiological response that could for instance, assist in weight loss goals.

KB Training and Strength, Vertical Jump, and Body Composition

Otto III et al. (2012) studied thirty healthy male subjects with one year of resistance training experience but no KB training experience. The subjects were randomly assigned to a weightlifting group or KB group. The KB group used a 16 kg KB and completed KB swings, accelerated swings, and goblet squats with the total number of sets progressively increased over 6 weeks.  Emphasis was placed on proper form, speed, and technique. The weight lifting (WL) group performed high pulls, power cleans, back squats all in a linear periodization that closely replicated the number of sets and reps (volume) of the KB workout. Subjects maintained their normal diet during the 6 week study.

The WL group increased vertical jump about 2% while the KB showed no improvement. The WL group showed a 9% and a 14%increase on the power clean and back squat respectively while KB showed a 4.2% and a 4% increase. While this may not sound very impressive it should be noted that ultimately, even though volume was about the same, the actual workloads for the WL group were higher. In terms of body fat, neither group experience any changes. Overall the researchers did feel that the results of the study do indicate that power and strength benefits can be achieved through KB training.

KB Training and Spine Safety

 McGill & Marshall (2012) completed the first and so far only biomechanical study examining and quantifying spine loading during KB exercises using a 16 kg KB. Three dimensions of evaluation were used – electromyography, ground reaction forces, and 3D kinematic data. Results showed regardless of the swing or snatch, it appeared to create a hip-hinge squat movement patterns of rapid muscle activation-relaxation cycles that elicited considerable magnitudes of load on the spine. The KB swing appears to result in unique compression and shear load ratios in the lumbar spine. This may explain why it causes discomfort in the lower backs of participants who otherwise tolerate heavy loads.

Conclusions and Cautions

KB training certainly develops posterior power development, but at what costs?  Back problems are the leading cause of missed days at work after colds. Furthermore, disc degeneration is most often attributed to poor body mechanics, faulty loading during activities of daily living, and poor mechanics during physical activity.  The KB spine compression to shearing load ratio is a cause for serious concern.  Trainers need to ensure that core strength, proper progressions and appropriate loads are recommended.  Lastly, will we see a drop out trend in KB training due to low back claims or injury? Stayed tuned.  Additional research is definitely needed to provide further insights into this popular exercise trend.

References

Hulsey, C. (2012). Comparison of kettlebell swings and treadmill running at equivalent. J Strength Cond, 26(5), 1203-07.

McGill, S.M., Marshall, L.W. (2012). Kettlebell swing, snatch, and bottoms-up carry: back and hip muscle activation, motion, and low back loads. J Strength Cond Res, 26 (1), 16-27. doi: 10.1519/JSC.0b013e31823a4063.

Ott, W. (2012). Effects of weightlifting vs. kettlebell training on vertical jump, strength and body composition. J Strength Cond, 26(5), 1199-1202.