(14) THE IMMEDIATE EFFECTS OF A STANDARDIZED KETTLEBELL SWING PROTOCOL ON LUMBAR PARASPINAL MUSCLE FUNCTION

Purpose: Tensiomyography (TMG) is a reliable, noninvasive, passive technique that may be used to examine muscular fatigue. Studies have shown that TMG is sensitive and can accurately assess muscular fatigue following various exercise protocols. Kettlebell swings are commonly utilized to target the lumbar erector spinae and lower body musculature. This exercise exhibits distinct loading properties that requires cyclical contraction of the trunk extensors and posterior chain, potentially explaining its novel influence on muscle contractility. The purpose of this study was to determine if a standardized kettlebell swing protocol influenced lumbar erector spinae contractility utilizing TMG.

METHODS: Forty-one healthy participants between the ages of 18 and 45 were recruited. Exclusion criteria included reports of low back pain, pre-existing injuries precluding performance of a kettlebell swing, and/or a positive response on the PAR-Q. Participants were randomly allocated to either a kettlebell swing group (KBS; n=21) or a control group (CON; n=20). Following a general warm up, participants in the KBS group performed a two-handed kettlebell swing using the interval training protocol 30 seconds of work, followed by 60 seconds of rest for a total of 10 intervals. Male participants performed the intervention with a 12kg kettlebell and female participants performed the intervention with an 8kg kettlebell.  Participants in the CON group performed a general warm up only and then sat still for approximately 5 minutes. Participants were assessed at baseline, post-intervention, and 24-hours post-intervention for bilateral erector spinae fatigue, measured by five TMG parameters: Maximal displacement (Dm), contraction time (Tc), relaxation time (Tr), delay time (Td), and sustain time (Ts).

RESULTS: Independent samples t-test revealed no significant differences in age (p=0.765), body mass (p=0.652), and height (p=0.234) between groups at baseline. A 2x3 (Group by Time) Repeated Measures Mixed ANOVA revealed no significant difference in lumbar erector spinae fatigue following the kettlebell swing protocol for any of the five TMG parameters (p > .05) in comparison to the control group.

CONCLUSIONS: A KBS protocol failed to produce significant differences in lumbar erector spinae fatigue in comparison to the control group based on the TMG parameters (Dm, Tc, Tr, Td, and Ts). Failure to produce lumbar erector spinae fatigue warrants further investigation into the nature of muscular contraction involved in the performance of a kettlebell swing. The result of this study suggests that the KBS protocol utilized in this study was not sufficient to induce meaningful changes to the lumbar erector spinae musculature contractility; however, further research should be conducted investigating alternate KBS protocols. Future studies may also consider measuring muscular fatigue of glutes and/or hamstrings, as these may have performed alongside or beyond participants’ erector spinae.

PRACTICAL APPLICATION: Use of TMG can help clinicians determine if therapeutic exercises selected to target the lumbar erector spinae induce fatigue and therefore promote training induced muscular adaptations.  The result of the current study suggests that the protocol implemented did not create meaningful changes in muscular contractility and alternate dosing strategies may be warranted.


Acknowledgements: None