Kettlebell swings are a very popular choice when it comes to circuit classes. They're typically selected because they require you to perform lots of repetitions and therefore effective for getting your heart rate elevated.
From experience, most people perform them incorrectly unless taught otherwise.
Without trying to turn this into post into a rant, I am still seeing 'trainers' teach kettlebell swings to their clients and class members incorrectly.
I am trying so hard to resist naming names, but I see videos being published on social media daily, demonstrating trainer's lack of understanding. Even those without the relevant certification could spot poor execution of this exercise.
Fortunately, these technical errors often mean that the weights selected are fairly light and therefore severe injury is unlikely, however I've known many people to complain of lasting back ache after doing so with a kettlebell as light as 4kg.
How should we do them then?
Firstly, it is important to understand that these are primarily a hamstring exercise.
You are not supposed to squat and then raise the Kb with your shoulders. The knees should hardly bend at all.
The overall movement pattern of this drill is a hip hinge, performed almost identically to a stiff-leg or Romanian deadlift.
With a relatively wide stance, knees soft but not bent, and the kettlebell held with two hands in and around the groin area, you are to push your hips rearward until you feel a significant stretch in your hamstrings. Visualise yourself closing your car door with your bum.
The subsequent loading of your hamstrings should result in you being able thrust your hips explosively in order to return them to full extension, to which point the kettlebell should feel weightless and therefore no need to raise it with your shoulders, or any other upper-body musculature for that reason.
This movement should not feel slow and 'flowy', rather you should aim to snap your hips back to full extension with extreme effort. Of course, your back should remain flat or neutral, but there should be no need to focus on this matter if you are capable of ensuring that it is your hamstrings and hips that are doing all of the work.
Not just for circuits?
Whilst I do use them for clients wishing to reduce body fat, I do not select this exercise because of their higher rep ranges. In fact, I'd rather a client put more effort in to using heavier loads and therefore be required to perform less reps than your typical circuit training methods.
For me, weight is important. There are far more benefits outside of energy expenditure / burning calories:
* Because of the stance used, the medial hamstrings (semitendinosus) are activated to a greater extent than the lateral hamstrings (semimembranosus). This may be helpful for sprinters as the medial hamstrings are involved in running more than the lateral hamstrings.
* Swings produce greater horizontal:vertical ground reaction forces compared with squats or jump squats. Important for sports involving horizontal propulsion, or more specifically acceleration during sprinting.
* Effective at improving the stretch shortening cycle of the hamstrings. Useful for sports involving explosive changes of direction and sprinting.
* Swings produce more hamstring activation at higher degrees of hip flexion (bent hips) compared with other hamstring exercises such as the Nordic hamstring lower which produces greatest activation at full hip extension. This is useful for injury prevention as swings can be used to supplement other exercises in order to target the muscles at various muscle lengths and produce strength and size gains across the whole muscle evenly.
* Swings create peak glute activation at near full hip extension. Useful for training the strength and power of the glute muscles when combined with exercises that produce greater glute activation in hip flexion such as squats and deadlifts.
* Swings performed with moderate loads produce similar power outputs to jump squats with conventional loads (%1RM) and therefore can be used as an additional tool to help develop power, particularly when training horizontal propulsion is required.
It is important to understand that 4, 8 or even 12kg kettlebells are unlikely to be adequate in helping with the above. Once you can perform them correctly, try using a kettlebell that weighs at least 20kg or more before working up to heavier loads by using two kettlebells at a time.
Try combining them with other lower body strength movements such as squats, jump squats, glute ham raises and leg curls to help reduce your chances of hamstring and knee injury, develop strength, power and size of the hamstrings as well as improve sporting actions linked with sports that involve sprinting.
* Further reading: Chris Beardsley & Bret Contreras, 2014. Strength & Conditioning Journal.