Will 2015 Be the Year You Pick up The Kettlebells? Find Out If Your Strength, Fitness & Physique Would Benefit

2015 may offer a chance to get spice up your routine with kettlebells.

"Moderate evidence indicates that kettlebell training may be safe and effective for increasing certain functional strength and power measures and may show positive results with postural control in young, healthy populations," says a recent review of the literature in Physical Therapy Reviews (Girard. 2014) and does thus sound positively optimistic, but by far not as euphoric as some kettlebell warriors on the Internet.

Those of you who know me are probably aware that I am not a fan of kettle bells, but I am true to the motto of being open to good scientific evidence, like the one from the previously cited review by Girard et al. (2014).
Speaking of which, the previously cited review found only five studies satisfied the eligibility criteria and were included in this review. The populations studied age range was 18–72 years old. Methodological scores based on the PEDro scale ranged from 3 to 7 out of 10. In those studies, ...

[k]ettlebell training demonstrated improvements for a number of strength measures: time 6 group for bench press ( P < 0.05) and back extension (P = 0.053), main effect for clean and jerk (P < 0.05) and certain power measures such as improved explosive strength comparable to a jump squat control (19.8% increase). Improved postural control was demonstrated in one study (P = 0.04)" (Girard. 2014).

What the kettlebells did not do in any of the five studies by Otto et al. (2012), Manoccia et al. (2013), Lake et al. (2012) and Jay et al. (2011 & 2013) was to have an effect on aerobic endurance as measured by VO2 Max.
The non-significance of the oxygen uptake and thus the non-existence of conditioning effects may come as a surprise for those of you have already done kettlebell swings. Rightly so, as I would argue, because this result of the review is based mainly on the results of Jay et al. (2011) who invited 57 employees of a large pharmaceutical company for a physical examination. Of those only 43 showed up (motivation to work their assess off ↓) of whom 40 men and women in their mid-forties then trained for 20 minutes included a 5 –10 minute warm up and a 10–15 minute interval training consisting of 10 intervals of 30 seconds with rest period of 30–60 seconds which began with ZERO workload and was progressively intensified by the participants choice!

Kettlebell, weights, or ergometer, you have to work your ass off to make progress!

That's much in contrast to Fortner et al. (2014) who had their 14 young (18-25y), non-obese volunteers train three times a week for 8 weeks with 4.5kg and 8kg kettlebells for the female and male subjects, respectively in a "tabata style", i.e. at a twenty-second work to ten-second rest ratio and compared the VO2 response to a traditional protocol, consisting of four sets of work separated by ninety seconds of rest.

Figure 1: Subjective Borg RPE response to Tabata versus traditional kettlebell swing protocols in healthy, young adults. TAB- Tabata, TRADtraditional (left). % of peak VO2 value achieved during Tabata and traditional kettlebell swing protocols in healthy, young adults (right | Fortner. 2014).

As you can see in Figure 1 the response to the two different workouts was very different - despite the fact that the total number of swings from each individual's "tabata condition" (TBA) was equally divided into four sets for their "tradititional condition" (TRAD). From non-kettlebell studies, we know that training at an intensity like this, even if it's done for only a few minutes, will just as Fortner et al. say "safely and effectively provide multi-faceted exercise adaptations with a relatively short time investment" (Fortner. 2014) - an assumption that's backed by a 2011 study by Falatic et al. that used a 15s/15s protocol and elicited significant increases in VO2max in seventeen female NCAA Division I collegiate soccer players.

Figure 2: Energy expenditure during two-hand kettlebell exercise and graded treadmill walking (Thomas. 2014).

Furthermore, James et al.  (2014) were recently able to show that a KB routine consisting of 2-hand swings and sumo deadlifts with 3-minute rest periods produces similar metabolic responses to those of a moderate-intensity treadmill walking protocol designed for the improvement of aerobic fitness in 5 women, 5 men between 21 and 31 years of age - and, as you can see in Figure 2, it also burned a few extra calories.

A comparison with treadmill walking is yet not enough to confirm that kettlebell training is also superior to "regular" HIIT training. Personally, I suspect it isn't but it's at least a good way to diversify your training routines and create a new exercise stimulus that may even help you break through a plateau.
References:

• Falatic, Jonathan Asher. "The effects of kettlebell training on aerobic capacity." San José state University (2011).
• Fortner, Howard A., et al. "Cardiovascular and metabolic demands of the kettlebell swing using a Tabata interval versus a traditional resistance protocol." International Journal of Exercise Science 7.3 (2014): 2. 
• Greenwald, Samantha Leigh. The impact of an acute bout of kettlebell exercise on glucose tolerance in sedentary males. Diss. State University of New York at Buffalo, 2014.
• Jay, Kenneth, et al. "Kettlebell training for musculoskeletal and cardiovascular health: a randomized controlled trial." Scandinavian journal of work, environment & health (2011): 196-203.
• Jay, Kenneth, et al. "Effects of kettlebell training on postural coordination and jump performance: a randomized controlled trial." The Journal of Strength & Conditioning Research 27.5 (2013): 1202-1209.
• Lake, Jason P., and Mike A. Lauder. "Mechanical demands of kettlebell swing exercise." The Journal of Strength & Conditioning Research 26.12 (2012): 3209-3216.
• Manocchia, Pasquale, et al. "Transference of kettlebell training to strength, power, and endurance." The Journal of Strength & Conditioning Research 27.2 (2013): 477-484.
• McGill, Stuart M., and Leigh W. Marshall. "Kettlebell swing, snatch, and bottoms-up carry: back and hip muscle activation, motion, and low back loads." The Journal of Strength & Conditioning Research 26.1 (2012): 16-27. 
• Otto III, William H., et al. "Effects of weightlifting vs. kettlebell training on vertical jump, strength, and body composition." The Journal of Strength & Conditioning Research 26.5 (2012): 1199-1202.
• Thomas, James F., et al. "Comparison of Two-Hand Kettlebell Exercise and Graded Treadmill Walking: Effectiveness as a Stimulus for Cardiorespiratory Fitness." The Journal of Strength & Conditioning Research 28.4 (2014): 998-1006.