Check the results then discuss the study. Years ago a study showed that HIT on Nautilus machines did not fit well into what was defined as aerobic exercise (failed). The HITTER’S discussed and complained, but no real conclusions were arrived at. Let’s see where this leads regarding kettlebells.
Cardiorespiratory Responses to Kettlebell Training Exercise
Medicine & Science in Sports & Exercise. 37(5) Supplement:S219, May 2005.
Bishop, Emmett; Collins, Mitchell A. FACSM; Lanier, Angela B.

(E. Bishop, Dragon Door Research Grant Recipient.) <------- Although resistance training using Kettlebells™ is not new, the popularity of Russian Kettlebell™ training has recently grown in the U.S. due to promotion by Pavel Tsatsouline. However, at the present time there appears to be little scientific literature on Kettlebell™ exercise. PURPOSE
Therefore, the purpose of this study was to describe the cardiorespiratory responses to a typical 30-minute bout of Kettlebell™ training.

Five males and five females (24-58 yrs) were recruited to participate in the study. Each performed five sets of ten repetitions for three Kettlebell™ exercises each separated by 1 minute of rest. The exercises consisted two-arm swings, one-arm snatches (half performed with each arm), and one-arm clean and presses (using right and left arms). The females used a 4 or 8 kg Kettlebell™ based on strength and the males used an 8, 12, or 16 kg Kettlebell™. The cardiorespiratory responses to the exercise were measured using a Parvo Medics TrueMax™ 2400 metabolic system. The data were analyzed using simple descriptive statistics.

The cardiorespiratory responses varied greatly among the subjects and were related to the size Kettlebell™ each used. After the intial adjustment to exercise, ventilation (BTPS) ranged from about 24-39 L/min. This corresponded to tidal volumes and respiratory rates from 0.9-1.4 L/br and 24-41 br/min. Oxygen consumption values were from 0.65-1.28 L/min or 9.7- 18.0 ml/kg/min. Respiratory exchange ratios were from 0.88-1.07 with values typically below 1.0. Exercise heart rates were found to be between 101-143 bts/min and mean (±SEM) blood lactates following exercise were 4.3±1.8 mmol/L.

The cardiorespiratory responses to Kettlebell™ exercise were relatively low. The values were less than reported for traditional weight training exercise performed at 40% of one-repetition maximum. The low response found for Kettlebell™ exercise was probably due to the incorporation of momentum in Kettlebell™ training along with the size of Kettlebell™ used by the subjects.

Energy Cost Of A Basic Kettlebell Training Protocol
Medicine & Science in Sports & Exercise. 37(5) Supplement:S51, May 2005.
Lanier, Angela B.; Bishop, Emmett; Collins, Mitchell A. FACSM

Kettlebell training is a relatively ancient form of strength training that has been highly regarded among the Russian military and Eastern European power lifters for many years. Most recently, it has gained popularity among athletic strength coaches and recreationally active individuals as a novel way to enhance functional strength and positively impact cardiovascular endurance. However, to our knowledge this form of training with handheld weights has not been systematically investigated.

The purpose of this pilot study was to assess the energy cost and intensity of a basic Kettlebell training protocol.

Ten subjects, mean age 30.2 ± 10.6 years, participated in a maximal treadmill test to assess VO2max. Participants subsequently performed 5 sets of 10 repetitions of two-armed swings, snatches, and clean and presses using a 4, 8, 12 or 16 kg Kettlebell. Metabolic data were collected by a metabolic measurement system. The data were analyzed using simple descriptive statistics.

Training intensity in metabolic equivalents (METS) was 4.9 ± .88. The mean caloric expenditure and oxygen uptake values were 4.97 ± 2.02 kcal/min and 14.25 ± 3.08 ml/kg/min. Total energy expenditure during the session was 297.91 ± 121.13 kcal. Associated heart rate response during the training session was 122.08 ± 21.13 bpm that corresponded to 64.29 ± 11.74% of maximal heart rate. The training intensity relative to VO2max was 32.96 ± .08%.

Although intensity as assessed by heart rate appeared to be high enough to improve cardiovascular fitness pursuant to the ACSM recommendation, the training stimulus of 32% of VO2max was less than the ACSM recommendation of ± 55%. However, a basic Kettlebell training protocol may be an alternative activity for achieving the Surgeon General’s recommended amount (150-200 kcal/day) and intensity (3-6 METS) of physical activity for improving health.