Kettlebell training: a superior alternative to conventional weights?

Andrew Hamilton looks at the recent research on Kettlebell training for sports performance: how effective is it and can the use of Kettlebells be superior to conventional weight training?

Kettlebells are cast-iron weights (resembling a cannonball with a handle) used to perform ballistic exercises that combine cardiovascular, strength and flexibility training. Unlike traditional dumbbells, the Kettlebell's centre of mass is extended beyond the hand, which facilitates ballistic and swinging movements. Although Kettlebell training was a staple of strength training in the old Soviet Union and Eastern-block countries, its popularity in the West is relatively recent and as such, there is comparatively little research on its efficacy in English-published journals. In the past decade however, that has changed and there have been a number of promising findings.

Explosive strength

In one study, a team of British scientists looked at the effects of Kettlebell training on maximum strength (assessed by half-squat 1-rep max [1RM]) and explosive strength (assessed by vertical jump height)⁽¹⁾. In this study, 21 healthy men who could perform a proficient half squat were tested for their half-squat 1RM and also their maximum vertical jump height, before a period of Kettlebell training and then again post-Kettlebell training. The period of Kettlebell training was also compared to a period of jump squat power training, which is known to improve 1RM in the half squat and also vertical jump height.

After their half-squat 1RM had been assessed, the subjects were randomly assigned to either a Kettlebell or jump squat training group both of which trained twice a week. The Kettlebell group performed 12-minute bouts of Kettlebell exercises (12 rounds of 30 seconds of exercise each round followed with 30 seconds of rest) using 12kg Kettlebells for subjects under 70kgs and 16kg Kettlebells for subjects over 70kgs. Meanwhile, the jump-squat training group performed at least four sets of three jump squats, using a load that maximised each subject’s peak power. The training volume of this group was also altered to accommodate the different training loads and ranged from four sets of 3 reps with heaviest load (60% 1RM) to eight sets of 6 reps with lightest load (0% 1RM).

When the results were analysed, they showed that maximum strength in the half squat improved by an average of 9.8% regardless of whether jump squat or Kettlebell training was undertaken. Meanwhile, explosive strength as measured by vertical jump height improved by an average of 19.8% following the training interventions, and analysis revealed that both types of training were equally effective in this instance also. The researchers concluded that six weeks of twice-weekly Kettlebell training provided a stimulus that was sufficient to increase both maximum and explosive strength and also that this mode of training was equally effective as the more traditional method of half squat power jump training.

Kettlebell training and aerobic power

Since energy is a measure of ‘force times distance’, the relatively large range of motion used in a Kettlebell swing results in a high energy expenditure and oxygen consumption; this has led some researchers to ask if Kettlebell swing training could be an effective method to improve aerobic fitness? In a US study on National Collegiate Division I soccer players, researchers compared Kettle training (Kettlebell snatches) to conventional circuit training exercises⁽²⁾. The soccer players were split into two groups:

• *Kettlebell training (20 minutes of Kettlebell snatching with 15 seconds of work and rest intervals)
• *Circuit training (multiple free-weight and dynamic body-weight exercises as part of a continuous circuit program for 20 minutes)

Both groups trained three days per week for four weeks; before this 4-week training period, and again afterwards, aerobic fitness levels were measured and compared. The results showed that in the Kettlebell-trained group, the average increase in maximum oxygen uptake was 2.3 ml·kg⁻¹·min⁻¹, or approximately a 6% gain. However, there was no significant change in the circuit-training group.

Oxygen consumption

In the same year, another group of US scientists compared a Kettlebell high-intensity interval training program to a standard sprint interval cycling program in terms of aerobic demands on the body⁽³⁾. Eight men completed two 12-minute sessions of Kettlebell and sprint-cycling intervals in a counterbalanced fashion. In the Kettlebell session, three circuits of four exercises were performed using a Tabata regimen (20 seconds hard/10 seconds of rest). In the sprint cycling intervals, three 30-second sprints were performed, with four minutes of recovery in between the first two sprints and 2.5 minutes of recovery after the last sprint.

When the subjects performed the Kettlebell intervals, their total caloric expenditure was found to be significantly higher, as were their oxygen consumption levels. This was despite the lower duration of training. The researchers concluded that intense interval training using Kettlebells could be a very effective alternative to sprint cycling intervals, as well as providing much-needed variety - along with flexibility of use (no bike needed!).

Kettlebell training and musculoskeletal health

Another aspect of Kettlebell training worth mentioning is muscle activation and injury. When performing Kettlebell swings, the dynamic muscle-activation patterns are markedly different to those of conventional resistance training, where the trunk is relatively static. This has led some researchers to suggest that Kettlebell training may be a useful component of injury prevention and/or rehab programs. Indeed, there is some evidence that Kettlebell training can reduce the occurrence of back and neck pain in those whose jobs involve heavy manual lifting⁽⁴⁾, those with chronic low-back pain⁽⁵⁾, and those with a history of knee and hamstring injury⁽⁶⁾.

Sports performance: conventional weights vs. Kettlebells

So far, so good – but how effective is Kettlebell training in terms of actually improving sports performance? And more to the point, how does it stack up against conventional heavy-weight training, which has been shown to improve a number of parameters of sports performance. This is where things become a little murkier because despite some of the undoubted physiological benefits of Kettlebell training, there’s little evidence of its superiority over conventional resistance training.

In a 2016 study on sprinting performance published by US scientists, researchers compared Kettlebell training to conventional stiff-legged deadlifts with free weights⁽⁷⁾. Although both interventions produced gains in vertical jump height, neither resulted in gains in sprint performance.

Another study published earlier this year investigated whether the enhanced muscle activation patterns produced in Kettlebell training could be used pre-training to enhance sprint performance⁽⁸⁾. The results showed that pre-sprinting Kettlebell exercises produced no benefits. Indeed, they were no better than a passive warm up – ie no warm up at all!

There’s very little data involving a direct comparison between Kettlebell training and conventional weight training. However one study did directly compare the effects of heavy resistance weightlifting versus Kettlebell training on vertical jump, strength, and body composition⁽⁹⁾. Thirty fit men were randomly assigned to one of two groups:

• *Conventional weightlifting
• *Kettlebell training

Both groups trained twice per week for six weeks, following programs that were progressed throughout the period (load/reps increased to allow for the subjects’ increased fitness as time progressed). The results showed that while both groups experienced similar gains in vertical jump height and lean muscle mass, the strength gains in the conventional weight-training group were significantly greater than those in the Kettlebell group.

This is an important finding because recent research has demonstrated that strength gains resulting from heavy resistance training leads to improved ‘muscle economy’, which means less energy/oxygen consumption is required to sustain a given pace/power output. Moreover, research has concluded that high levels of muscle economy are a key determinant of athletic performance – particularly endurance performance (see this article for a more in-depth discussion of this topic).

Conclusion and practical implications for athletes

What should sportsmen and women make of the research on Kettlebell training? Overall, the evidence suggests that using Kettlebells as part of a training program can deliver significant benefits. These include:

• *Training for explosive power
• *As an alternative mode of intense interval training
• *As part of an injury rehab/prevention approach in certain musculoskeletal conditions

However, when it comes to the benefits for sports performance, there’s no real evidence that Kettlebell training is superior to a conventional heavy resistance program. And when it comes to the development of sports-specific strength, conventional weight training may have the edge. Having said that, remember the old adage that ‘variety is the spice of life’. Adding some Kettlebell training to your regular strength training program could be a great way to make it more enjoyable and rounded, while still obtaining physiological benefits – and who could complain about that!

References

1. J Strength Cond Res. 2012 Aug;26(8):2228-33
2. J Strength Cond Res. 2015 Jul;29(7):1943-7
3. J Strength Cond Res. 2015 Dec;29(12):3317-25
4. Scand J Work Environ Health. 2011 May;37(3):196-203
5. J Strength Cond Res. 2012 Jan;26(1):16-27
6. Br J Sports Med. 2013 Dec;47(18):1192-8
7. Int J Exerc Sci. 2016 Oct 1;9(3):437-444
8. Sports (Basel). 2019 Feb 10;7(2). pii: E36
9. J Strength Cond Res. 2012 May;26(5):1199-202