First, the results of the study: conventional weightlifting was superior to the kettlebell training.
Now, listen to how the results are described by the authors,
The principle finding of the present study was that short-term kettlebell training significantly increased vertical jump, and that the gain in vertical jump performance was equivalent to that achieved with a combination of [Olympic] weightlifting and traditional heavy resistance training exercises.
Both kettlebell and training and weightlifting increased back squat 1RM.
The results of the present study indicated that both weightlifting and kettlebell movements are effective in improving back squat and power clean 1RM as well as vertical jump ability; however, weightlifting exercises are more effective for strength development.Does this sound like the weightlifting was superior?
In all three tests (power clean and back squat 1RM and vertical jump) the conventional training produced larger gains. In the vertical jump and power clean the gains were close enough to each other that the differences were not statistically significant.
Which brings me to the next point: significance. The fact that the test for statistical significance was "passed" does not mean the results are significant in any other way. The increase in jump height for the KB group was less than 2mm. This is not telling, not meaningful, not important, not momentous, not compelling, or frankly even suggestive (yup, I used a thesaurus).
True, the conventional protocol produced jump height gains of just under a centimeter, so it wasn't any of those synonyms either.
On to the conversation! There have been numerous blog posts about this already. And there are two criticisms of the study that I've seen multiple times, so I'd like to address them.
A. The test procedures. Others have criticized the selection of tests on the grounds that they don't test what the kettlebell training trains or the tests are more similar to the weightlifting exercises so of course that group got better.
The tests selected for this study are standard tests. This has two advantages. First the results of this test can be compared to other studies that used the same test. Second, there is already a body of literature demonstrating that these tests correlate to actual measures of athletic performance. Both of these point are important for useful science.
If the conventional weightlifting exercises and tests are more similar, doesn't that tell us that the specificity of those exercises is higher? Remember, correlation between those test and athletic performance have already been demonstrated.
And while kettlebell exercises can be useful, one characteristic they don't possess is a high degree of movement specificity to many sport actions. (They are instead good for metabolic specificity etc.)
B. Another criticism was that the weights used for the KB protocol were too light. For the KB protocol everyone used a 16kg bell. For the conventional training 80% of 1RM was used, which was substantially higher. Some argued that the KB group should have used the same weight as the conventional group.
There are two problems with this criticism. The typical KB program uses the same weight or a narrow range and the objective is to increase reps not weight. The KB protocol used in this study looks like others I've seen suggested for kettlebell training.
But the sillier part is that the researchers couldn't have used kettlebells heavy enough for 80% of 1RM. They would have needed a set of KB's that went from around 60kg to 150kg. The largest I could find online was 48kg. And a blog post that a manufacture was planning to go up to 100 kg. So weights that size would've been impossible to get.
And why? Because KB training isn't done that way. The researchers compared a typical KB approach to a typical Olympic lifting approach. That's reasonable.
Lastly, a pet peeve of mind when it comes to discussing kettlebells. There were no kettlebell exercises done as part of this study. There were exercises done with kettlebells. All of the KB protocol could have been done with dumbbells. And for cheaper
1. Otto WH 3rd, Coburn JW, Brown LE, Spiering BA (2012). Effects of weightlifting vs. kettlebell training on vertical jump, strength, and body composition. Journal of Strength and Conditioning Research, volume 26(5),1199-202