Kettlebell exercise is gaining popularity with the U.S. military, athletes, and even celebrities. The commercially lauded benefits of kettlebells have yet to be scientifically evaluated.
PURPOSE: This study examined the aerobic and anaerobic work during kettlebell exercise.
METHODS: 8 healthy subjects (25- 33 y.o.) participated in a maximal kettlebell stress test and a standard kettlebell workout on 2 separate days. Prior to testing, all subjects completed a medical history screening questionnaire and signed voluntary consent forms approved by the Institutional Review Board of Azusa Pacific University. VO2, VCO2 were recorded with the VO2000 (MedGrapics). Maximum exercise protocol consisted of progressive 3 minute stages starting with an 8 kg bell, adding 4 kg per stage until exhaustion. Kettlebell workout consisted of three 6 minute cycles using kettlebell "snatch", "clean" to "press", and "swing" per Russian Kettlebell Challenge, Level I. Exercise during both the maximum and workout tests was performed in intervals of 30 seconds work followed by 30 seconds rest.
RESULTS: Average heart rate (HR) during the maximum stress test reached 95% of age predicted maximum with a RPE of 17/20. Maximum VO2 reached only 26.6 + 5 ml/kg/min while VCO2 measured 32 + 6 ml/kg/min. RQ in the final minute was 1.2 + 0.08. Subjects reported that grip strength was the limiting factor. During the workout session, at steady state, HR averaged 88% of age-predicted maximum, with RPE at 15/20. VO2 was 23.8 + 0.9 ml/kg/min (90% of kettlebell maximum) and VCO2 was 26.7 + 1.1 ml/kg/min (84% of kettlebell maximum). RQ measured 1.1 + 0.06.
CONCLUSION: Kettlebell exercise is high intensity work that is slightly more anaerobic than aerobic as seen by RQ > 1. However, during the workout VO2 averaged 6.3 METS consistent with moderately hard aerobic work. Thus, the standard kettlebell workout taxes both aerobic and anaerobic systems. During exercise the RQ remained < 1 as long as kettlebell weights were less than or equal to 13% of body mass. Therefore, for a workout which stresses the aerobic system, kettlebell weight should be kept below this level of resistance. The maximum protocol was limited by grip fatigue, reaching only 95% of age predicted max HR. Future studies should vary the styles of grip throughout testing in order to reach true maximum.