Reliability of kettlebell swing one and five repetition maximum

Abstract

Background Research into the kettlebell swing has increased in the last decade. There has been a paucity of literature assessing an individual’s ability to perform the kettlebell swing exercise. The purpose of this study was to determine the test-retest reliability of the one and five repetition maximum (1RM and 5RM) kettlebell swing. Materials & Methods Twenty four recreational resistance-trained participants performed an isometric mid-thigh pull (IMTP) and two familiarization sessions followed by three test sessions for each RM load approximately one week apart, using a custom-built plate-loaded kettlebell. On each test occasion, subjects completed a series of warm-up sets followed by 3–4 progressively heavier kettlebell swings to a standardized height until 1RM or 5RM was reached. Test-retest reliability was calculated using the intra-class correlation (ICC) and typical error was represented as the coefficient of variation (CV%) with 90% confidence limits (90% CL). The smallest worthwhile change (SWC%) representing the smallest change of practical importance, was calculated as 0.2 × between-subject standard deviation. The relationship of kettlebell swing performance and maximum strength was determined by Pearson correlation with ±90% CL between the absolute peak force recorded during IMTP and 1RM or 5RM. Results Results demonstrated a high test-retest reliability for both the 1RM (ICC = 0.97, 90% CL [0.95–0.99]; CV = 2.7%, 90% CL [2.2–3.7%]) and 5RM (ICC = 0.98, 90% CL [0.96–0.99]; CV = 2.4%, 90% CL [1.9–3.3%]), respectively. The CV% was lower than the SWC for both the 1RM (SWC = 2.8%, 90% CL [1.9–3.5]) and 5RM (SWC = 2.9%, 90% CL [1.9–3.6]) kettlebell swing. The correlation between IMTP absolute peak force and the 1RM (r = 0.69, 90% CL 0.43–0.83) was large and very large for the 5RM (r = 0.75, 90% CL [0.55–0.87]). Conclusions These results demonstrate the stability of 1RM and 5RM kettlebell swing performance after two familiarization sessions. Practitioners can be confident that changes in kettlebell swing 1RM and 5RM performance of >3.6 kg represent a practically important difference, which is the upper limit of the 90% CL.