Abstract
Background The effects of hardstyle kettlebell training are frequently discussed in the strength and conditioning field, yet reference data from a proficient swing is scarce. The aim of this study was to profile the mechanical demands of a two-handed hardstyle swing performed by a Russian Kettlebell Challenge (RKC) Instructor.
Methods The subject is a 44-year-old male, body mass 75.6 kg, height 173.5 cm, with 6 years of regular hardstyle kettlebell training since attaining certification in 2013. Two-handed hardstyle swings were performed with a series of incremental weight (8-68 kg) kettlebells. Ground reaction forces (GRFs) were obtained from a floor-mounted force platform. Force-time curves (FTCs), peak force, forward force relative to vertical force, rate of force development (RFD) and swing cadence were investigated.
Results Data revealed the FTC of a proficient swing were highly consistent (mean SD = 47 N) and dominated by a single force peak, with a profile that remained largely unchanged with 8-24 kg kettlebells. Pearson correlation analyses revealed a very strong positive correlation in peak force with kettlebell weight (r = 0.95), which increased disproportionately from the lightest to heaviest kettlebells; peak net force increasing from 8.36 ± 0.75 N.kg-1 (0.85 x BW) to 12.82 ± 0.39 N.kg-1 (1.3x BW). There was a strong negative correlation between RFD and kettlebell weight (r = 0.82) decreasing from 39.2 N.s-1.kg-1 to 21.5 N.s-1.kg-1. There was a very strong positive correlation in forward ground reaction force with kettlebell weight (r = 0.99), expressed as a ratio of vertical ground reaction, increasing from 0.092 (9.2%) to 0.205 (20.5%). Swing cadence exceeded 40 swings per minute (SPM) at all weights.
Conclusion Our findings challenge some of the popular beliefs of the hardstyle kettlebell swing. Consistent with hardstyle practice and previous kinematic analysis of expert and novice, force-time curves show a characteristic single large force peak, differentiating passive from active shoulder flexion. Ground reaction force did not increase proportionate to bell weight, with a magnitude of forward force smaller than described in practice. These results could be useful for coaches and trainers using kettlebells with the intent to improve athletic performance, and healthcare providers using the kettlebell swing for therapeutic purposes. Findings from this study were used to inform the BELL Trial, a pragmatic clinical trial of kettlebell training with older adults. www.anzctr.org.auACTRN12619001177145.
Competing Interest Statement
The primary author is a Physiotherapist and hardstyle kettlebell instructor, with an online presence as The Kettlebell Physio.