The kettlebell has seen increased popularity in recent years. 108 A kettlebell is a cast-iron weight shaped like a ball with a handle which ranges from 4 kilograms (kg) and upwards to over 40kg. Clinically, the kettlebell is used for strength training, dynamic flexibility and power training. 109
The double handed KBS is one of the foundational and most utilised exercises and forms the technical foundation to most other kettlebell exercises. 110 The aim of the KBS is to improve flexibility, strength and power to the posterior chain and deep core muscles in a repetitive dynamic motion throughout a full ROM in the sagittal plane. 110
Mathews, 108 described two main variations of KBS: the hip-hinge swing and the squat-dominant swing. The biomechanics of these two types of swing is thought to differ in respect of the involvement of the lower body muscles. The hip-hinge swing has a similar muscular recruitment …show more content…
24 The distinctive quality of the KBS, compared to other posterior chain exercises, is “inertia and centrifugal forces” causing a posterior shear force on the lumbar vertebrae differing to the anterior shear forces experienced during the above mentioned posterior exercises. 24, 86 The contraction-relaxation cycles of the KBS are thought to act as a flushing mechanism allowing an increase of blood and clearing metabolites, which is thought to aid in LBP recovery. 24
The KBS shear forces measure no more than 460 N, 69 and compression up to 3,195 N, well within the maximal SPL. If there is true instability of one or more vertebral segments, according to McGill’s data, those exposed to posterior shear loads could potentially have an intolerance performing KBS. Although these types of cases are uncommon, it is an important point raised in the study.