Kettlebell Research: What Science Says

Kettlebells have enjoyed growing popularity as a full-body training tool for improving cardiovascular health and musculoskeletal fitness. Yet for all the enthusiasm among personal trainers, experimental research on the effects of KB training was scant until last year, when studies began showing up in peer-reviewed journals. Here are the recent research findings on KB training.

Study 1. Metabolic Demand of Kettlebell Training

Hulsey, C.R., et al. 2012. Comparison of kettlebell swings and treadmill running at equivalent rating of perceived exertion values. Journal of Strength and Conditioning Research, 26 (5), 1203–07.

Experimental question. The two-handed KB swing is generally viewed as a foundational training approach for KB training. Researchers wanted to determine whether performing continuous KB swings would create an energy cost capable of improving cardiorespiratory fitness. To find out, they compared the metabolic demand of KB swings to treadmill running at equivalent ratings of perceived exertion (that is, subjective assessments of exercise intensity).

Subjects. Thirteen subjects (11 male, 2 female, average age = 21.4, average height = 69 inches, average weight = 170 pounds, average BMI = 23.5) volunteered for the study. All were deemed moderately trained and had no KB experience. Prior to testing, a certified KB instructor familiarized them with the two-handed KB swing exercise.

Study procedures. In the first experimental trial, subjects performed 10 minutes of two-handed KB swings, alternating 35-second swing bouts with 25 seconds of rest. The men used a 16-kilogram KB, and the women an 8 kg KB. Subjects were encouraged to maintain a steady swing count averaging 22-25 per minute. A certified KB instructor gave continuous feedback, helping subjects maintain correct swing execution and posture.

After 48 hours of rest, study participants returned to the testing lab and completed a 10-minute treadmill run at a subjective intensity (RPE of 15.3-15.5 on a 6-20 scale) equivalent to what they experienced during the KB swing trial. An automated metabolic gas analysis system commonly used in exercise studies measured oxygen consumption and kilocalorie expenditure. The final 7 minutes of each work bout were used for data analysis.

Results and discussion. Table 1 compares key cardiovascular and metabolic values obtained in this investigation. At an equivalent subjective RPE, subjects had no significant difference in heart rate. Oxygen consumption and calorie expenditure were significantly higher for treadmill running than they were for KB swings. However, it should be noted that subjects completed both 10-minute exercise bouts at above 85% of their age-predicted maximum heart rate. Thus, KB swings, albeit for just 10 minutes in this investigation, did elicit a physiological response necessary for improving cardiorespiratory fitness.

The study did not determine an optimal KB workout duration or a weekly frequency necessary to obtain a meaningful improvement in cardiorespiratory fitness; further research is needed to answer those questions. However, the kilocalorie expenditure (375 kcal) obtained from this study suggests that KB training is a viable exercise option for inclusion in a weight loss program.

To read additional studies, please see “Kettlebell Research Update” in the online IDEA Library or in the January 2013 issue of IDEA Fitness Journal.