Kettlebells and suspension-aided training are new options for improving strength and cardiovascular gains
Back pain and poor abdominal muscle stability can complicate fitness efforts. Kettlebells and suspension-aided training are new options for improving strength and cardiovascular gains
If you take a stroll across your local park, most days you’ll notice an increasing array of intriguing gear being used by the personal trainers as they put clients through their paces. You may well wonder whether any of these fancy fitness toys actually make a difference.
Two of the most popular new fitness tools are the kettlebell and suspension training. Novel, with plenty of street cred, they are now used by just about every personal trainer, fitness studio and commercial gym. But what do they offer that other approaches can’t?
There is certainly a lot of evidence to support the use of kettlebells to develop strength and power across a number of different performance measures.
A 2011 study1 investigated the effectiveness of using kettlebell training to improve musculoskeletal health in adults from occupations with a high prevalence of reported musculoskeletal pain.
They measured the pain intensity of the neck/shoulders and low back and isometric muscle strength before and after a period of kettlebell training. They found pain reduction in the neck/shoulders and low back and improved muscle strength in the low back.
A study in the Journal of Strength Conditioning Research2 also found just six weeks of biweekly kettlebell training provided a stimulus that was sufficient to increase both maximum and explosive strength.
Other research in 20133 looked at whether kettlebell training transferred strength and power to weightlifting and powerlifting exercises, and improved muscular endurance. Thirty-seven participants were required to perform a barbell clean and jerk, barbell bench press, maximal vertical jump and 45-degree back extensions to volitional fatigue, before and after a 10-week kettlebell training program.
The results demonstrated kettlebells were an effective alternative tool to improve some performance in weightlifting and powerlifting, especially when traditional training methods were not convenient or accessible.
However, trainers may need to bear in mind specific training goals when choosing equipment.
Another study4 looked at the effects of weightlifting versus kettlebell on vertical jump, strength and body composition over six weeks. While short-term weightlifting and kettlebell training were both effective in increasing strength and power, the gain in strength using weightlifting movements was greater than that during kettlebell training. This indicated that although kettlebells were a viable training option, traditional strength training techniques should not be given away in favour of a shiny new tool.
Kettlebells and HIIT
A recent study in the Journal of Strength Conditioning Research5 examined the effects of a kettlebell training program versus a circuit weight-training program on aerobic capacity. The kettlebell group experienced, on average, a 6% gain in Vo2max, yet there was no change in the circuit weight-training group. This suggests that kettlebell training may offer an alternative way of maintaining or improving cardiovascular conditioning.
However, even if the aerobic benefits of kettlebell training are greater than that of circuit training, how do they stack up against more traditional forms of cardiovascular exercise?
Hulsey and his colleagues (2015)6 compared the metabolic demand of a kettlebell-swing routine with treadmill running at equivalent rating of perceived exertion. The subjects completed a 10-minute kettlebell swing routine consisting of 35-second swing intervals followed by 25-second rest intervals.
After 48 hours of rest the subjects completed a 10-minute treadmill run at equivalent rate of perceived exertions, as measured during the swing workout. According to the American College of Sports Medicine standards, this kettlebell drill could provide sufficient exercise stress to produce gains in aerobic capacity. But, it should be noted, the subjects were still likely to have higher oxygen consumption, work at a higher metabolic equivalent of task (MET) level, and burn more calories per minute during treadmill running.
Thomas et al (2014)7 conducted a similar study to determine whether continuous kettlebell exercise would produce similar cardiovascular stress to a brisk bout of graded treadmill walking. VO2, respiratory exchange ratio, kcal/min and blood pressure were similar for both forms of exercise, suggesting a kettlebell routine could produce similar metabolic responses.
However, rate of perceived exertion and heart rate were greater in the kettlebell group than the treadmill graded walking group. If the level of perceived exertion equated with participant discomfort, sustainability and adherence might be higher for the treadmill over kettlebell workouts, especially for the unfit or those new to exercise.
Sling suspension training
The use of ropes and slings to support and use body weight during exercise is called suspension training or TRX. A recognised approach to strength and resistance training, TRX allows a person to work against their own body weight to perform a variety of multi-planar, compound exercise movements.
TRX/sling-assisted exercises have been found to offer benefits to people with low back pain. A main benefit comes from the slings’ ability to stabilise the transversus abdominus muscles during exercise.
Research suggests that the transversus abdominis contracts prior to limb movement in healthy individuals, while the pre-activation is poor in those with low back pain. In particular, those who have faulty neuromuscular control, as opposed to true ligament instability, are thought to benefit from spine stabilisation exercises. Once the motor skill of ‘abdominal drawing in’ is learned it can be combined with varying postures and progressively unstable surfaces. The TRX/slings are a good option for achieving this.
Research in the North American Journal of Sports Physical Therapy 8 investigated whether transversus abdominis activation in individuals with low back pain is greater when performing bridging exercises on an unstable versus a stable surface. Fifty-one adults with stabilisation classification of low back pain were randomly assigned to either exercise progression using a sling bridge device or a traditional bridging exercise progression, each with four levels of increasing difficulty. Transversus activation ratio (contracted thickness/resting thickness) was measured using ultrasound imaging.
Results showed there was no significant difference between the groups with respect to their ability to perform the exercise or transversus abdominis activation ratio at the first three levels and
neither group experienced pain. However, at the fourth level, which involved hip abduction, 88% of the sling group could perform the exercise as opposed to 75% of the stable surface group.
There was also a significant increase in transversus abdominis activation ratio in the sling-based exercise group compared with the traditional exercise group. The researchers concluded that while both types of exercise activated transversus abdominis, sling-based combined with dynamic movement resulted in a thickness change without volitional contraction of the abdominal musculature. Since the role of local stabilisers was reflexive in nature, the hope was that use of exercises which activate these muscles, without conscious contraction, might translate to other functional activities.
Further research in the Journal of Science and Medicine in Sport9 using surface EMG to measure the activity of core muscles during a five-second hold of four exercises (hip abduction in plank, hamstring curl, chest press and 45-degree row) confirmed suspension training generated relatively high levels of core-muscle activation when compared with that among previous studies of core exercises on stable and unstable support surfaces. Like Saliba, they found hip abduction in plank with suspension offered the strongest potential strengthening of core muscles.
There are many studies involving abdominal activation and instability devices such as the Swiss ball, but there is minimal research comparing them with a suspension device. Research by Snarr and Esco10 measured the electromyographical activity of the rectus abdominis, external oblique and erector spinae while performing five different plank exercises, with and without multiple instability devices, such as a Swiss ball.
Results indicated that planks performed with the instability devices increased superficial musculature when compared with traditional stable planks. Therefore, a traditional plank performed on a labile device might be considered an advanced variation and appropriate for use when greater challenge was warranted.
However, caution should be taken for those individuals with a history or weakness in the lumbar region due to the increases in erector spinae activation during instability planks.
Similar in case to kettlebells, research into suspension training highlights the need to consider the primary training goals when choosing equipment. Research in the Journal of Sports Science and Medicine12 analysed upper extremity and core muscle activation when performing push-ups with different suspension devices. Suspended push-ups increase core activation. However, a stable push-up, or parallel system provided greater increases in deltoid and pectoral muscle activation, so might be preferable to those attempting to increase upper body strength.
Research to date would appear to suggest that both kettlebell and suspension training offer effective new training. However, they are additions, rather than replacements, to current tools. Choices must be based on target response and participants’ abilities. Kettlebell exercises involve a learning curve to acquire proper and safe technique, but offer potential gains. Suspension movements are great core activators, but can be challenging and may not suit everyone.
Rachel Livingstone is Director, The Health Hub, Sydney
- Jay K, Frisch D, Hansen K, Zebis MK, Andersen CH, Mortensen OS, Andersen LL. Kettlebell training for musculoskeletal and cardiovascular health: a randomized controlled trial. Scand J Work Environ Health. 2011 May;37(3):196-203. doi: 10.5271/sjweh.3136. Epub 2010 Nov 25.
- Lake JP, Lauder MA. Kettlebell swing training improves maximal and explosive strength. J Strength Cond Res. 2012 Aug;26(8):2228-33. doi: 10.1519/JSC.0b013e31825c2c9b.
- Manocchia P1, Spierer DK, Lufkin AK, Minichiello J, Castro J. Transference of kettlebell training to strength, power, and endurance. J Strength Cond Res. 2013 Feb;27(2):477-84. doi: 10.1519/JSC.0b013e31825770fe.
- Otto WH, Coburn JW, Brown LE, Spiering BA. Effects of weightlifting vs. kettlebell training on vertical jump, strength, and body composition. J Strength Cond Res. 2012 May;26(5):1199-202. doi: 10.1519/JSC.0b013e31824f233e.
- Falatic JA, Plato PA, Holder C, Finch D, Han K, Cisar CJ. Effects of Kettlebell Training on Aerobic Capacity. J Strength Cond Res. 2015 Jul;29(7):1943-7. doi: 10.1519/JSC.0000000000000845.
- Hulsey CR, Soto DT, Koch AJ, Mayhew JL. Comparison of kettlebell swings and treadmill running at equivalent rating of perceived exertion values. J Strength Cond Res. 2012 May;26(5):1203-7. doi: 10.1519/JSC.0b013e3182510629.
- Thomas JF, Larson KL, Hollander DB, Kraemer RR. Comparison of two-hand kettlebell exercise and graded treadmill walking: effectiveness as a stimulus for cardiorespiratory fitness. J Strength Cond Res. 2014 Apr;28(4):998-1006. doi: 10.1519/JSC.0000000000000345.
- Saliba SA, Croy T, Guthrie R, Grooms D, Weltman A, Grindstaff TL. Differences in Transverse Abdominis Activation with Stable and Unstable Bridging Exercises in Individuals with Low Back Pain. N Am J Sports Phys Ther. 2010 Jun; 5(2): 63–73.
- Mok NW, Yeung EW, Cho JC, Hui SC, Liu KC, Pang CH. Core muscle activity during suspension exercises. J Sci Med Sport. 2015 Mar;18(2):189-94. doi: 10.1016/j.jsams.2014.01.002. Epub 2014 Jan 30.
- Snarr RL, Esco MR. Electromyographical comparison of plank variations performed with and without instability devices. J Strength Cond Res. 2014 Nov;28(11):3298-305. doi: 10.1519/JSC.0000000000000521
- McGill SM, Cannon J, Andersen JT. Analysis of pushing exercises: muscle activity and spine load while contrasting techniques on stable surfaces with a labile suspension strap training system. J Strength Cond Res. 2014 Jan;28(1):105-16. doi: 10.1519/JSC.0b013e3182a99459.
- Calatayud J, Borreani S, Colado JC, Martín FF, Rogers ME, Behm DG, Andersen LL. Muscle Activation during Push-Ups with Different Suspension Training Systems. J Sports Sci Med. 2014 Sep; 13(3): 502–510 published online 2014 Sep 1.