If you've ever done one-too-many kettlebell swings, (or looked on with concern while somebody near you did!) you'll know that this exercise can either feel like your best friend, or your worst enemy. Whilst undoubtedly a great way of strengthening and lengthening the hamstrings and getting the glutes firing, it's all too easy to go just that bit too far, and spend the rest of the week walking like John Wayne...
And according to new research from the University of Central Florida, it's no wonder! They asked two groups of exercisers to complete either a warm-up alone, or a warm-up followed by eight short sets of kettle bell swings. They then used a handheld algometer to measure the exercisers' pain thresholds. They did this by applying pressure to key muscle groups in the lumbar and pelvic region, and asking them to indicate when the pressure turned from 'comfortable' to 'slightly unpleasant pain'.
Results suggested the group who had performed the kettle bell swings had significant reductions in muscle sensitivity; that's to say they could comfortably tolerate more pressure being applied to their low back and pelvis.
The authors acknowledge that the mechanism underlying this effect is not fully understood, though it is thought that the cyclic contracting and stretching of muscles helps clear muscle metabolites that cause discomfort if left to accumulate. I would also be interested to see a further study including an active control group (performing deadlifts, perhaps) to ensure these effects are specific to the kettle bell swing action, and not generalisable to any exercise that strongly activates the gluteals and low back.
Either way, the findings are certainly of interest, and should be interpreted with your workouts in mind. A higher pain threshold may be just the ticket for those rehabilitating from injury, or post-exercise muscle soreness, or conditioned athletes looking to push their performance to the next level. On the other hand, it may increase the vulnerability of those inexperienced with exercise, those with injury or weakness in any of the associated areas, or those planning to go on to lift more, heavy weights during the same session.
So what is the take home message here? When it comes to kettle bell swings, proceed with caution. Consult an expert to ensure good technique, and take care about what exercises you perform straight after your swings; your body's feedback mechanisms may be slightly off kilter.
With that in mind, have fun out there! Work hard and stay safe!
Beth Jones, PhD. xxx
Source: Kellman BM, et al. The short term effect of kettlebell swings on lumbopelvic pressure pain thresholds: a randomized controlled trial. J Strength Cond Res. 2016 Nov 19. [Epub ahead of print]