As a fitness tool, kettlebells have a devout following. For some strange reason, people who use kettlebells often seem to only want to use kettlebells. This tendency is strong enough that Steve Cotter – a well-known kettlebell instructor – attempted to curb the urge in one of his DVD sets. In it, Steve indicated that kettlebells are not ideal for every goal. But as a coach myself, I often get questioned as to whether or not high-rep kettlebell work can substitute for cardio. This topic was addressed recently in the Journal of Strength and Conditioning Research.

I have gotten the question about kettlebell cardio often enough that I actually came up with a standard answer for it - no. I’m a purist when it comes to cardio, and if the effect of the exercise is the only concern, then I think the traditional cardio training is universally the best. However, admittedly, there wasn’t much actual science on the topic of kettlebell-based cardio.

Notice I said “if” the effect of exercise was the only concern. Some may wonder what other concerns there could possibly be. Rate of perceived exertion (RPE) is one important factor because it modulates the actual likelihood of performing an exercise. This is the important bit for the kettlebell enthusiasts. When you enjoy doing something, you’ll do it more often and with more vigor, which will help results tremendously. Because of its role in how enjoyable exercise is, RPE is a factor we want to look at.

In this study, the researchers compared thirty minutes of kettlebell work (specifically, they combined swings and deadlifts) to treadmill walking at a slight incline. They looked at how each workout affected respiration, heart rate, calories burned, and RPE. The kettlebell cardio and treadmill cardio had similar VO2, blood pressure, and calorie burn markers, but the kettlebell workout had a higher RPE and heart rate. The researchers concluded that kettlebell exercise shows promise as a method for developing cardio.

However, there were a few finer points that need to be discussed here. The participants were all novices in kettlebells, which could have altered the results. The kettlebell work was also performed before the treadmill work, which could have created a substantial order effect. This means we have no idea if the treadmill cardio was altered by the kettlebell work in an important way. These are two major weaknesses in this study’s design.

Further, the respiratory and calorie results were similar, but this is to be expected because the two methods were matched for VO2. The researchers altered the treadmill speed so that the participants would have the same VO2 max that they had for the kettlebell cardio, making the results the same. However, the RPE was higher for kettlebells, which means it feels a lot harder to do than treadmill walking, for no added benefit other than a higher heart rate.

If anything can be gleaned from this study, it’s that my original recommendation was probably accurate. Traditional means of cardio tend to give the greatest benefit relative to how hard they feel, especially running. Nevertheless, RPE is probably also lower when you love what you’re doing. If you’d love to do low-intensity kettlebell work for thirty minutes straight, you can rest assured that you’ll get at least a modest cardio benefit.