Acute Hormonal Response to Kettlebell Swing Exercise Differs Depending on Load, Even When Total Work Is Normalized

ABSTRACT

Raymond, LM, Renshaw, D, and Duncan, MJ. Acute hormonal response to kettlebell swing exercise differs depending on load, even when total work is normalized. J Strength Cond Res 35(4): 997-1005, 2021-This study examined the acute hormonal response to kettlebell (KB) swing exercise using 2 loads, but when total work was equalized. Ten strength-trained males (25 ± 6 years) completed 2 KB swing trials, with an 8- and 16-kg KB, respectively, in a counterbalanced order. Each protocol lasted 12 minutes comprising 30-second KB swings followed by 30-second rest. Swing cadence was manipulated in each trial to ensure that total weight lifted was the same across conditions. Heart rate (HR) and ratings of perceived exertion (RPE), using the Borg RPE scale 6-20, were taken at the end of each 30-second exercise period. Saliva samples (min 0.5 ml) were taken 15 minutes before, immediately after, and 15 and 30 minutes after each condition from which cortisol (C) and testosterone (T) were determined. Results indicated a significant main effect for load for C (p = 0.007) and T (p = 0.05) where higher values for both C and T were evident for the 16-kg load. There was also a significant main effect for time for T (p = 0.001), where T values were all significantly higher post-exercise compared with pre-exercise. For HR, there were significant main effects for load (p = 0.004) and time (p = 0.001) with higher HR seen in 16-kg load and significant increases in HR evident with increasing repetition, irrespective of condition (all p < 0.05). Rating of perceived exertion values increased with repetition for the 8-kg and 16-kg loads, but the increase was more marked for the 16-kg load compared with the 8-kg load (p = 0.002). The present findings suggest that KB swing exercise produces an acute increase in hormones involved in muscle adaptation, but that KB load influences this response, even when total work completed is the same.

Kettlebell training in clinical practice: a scoping review

BACKGROUND

A scoping review of scientific literature on the effects of kettlebell training. There are no authoritative guidelines or recommendations for using kettlebells within a primary care setting. Our review objectives were to identify the extent, range and nature of the available evidence, to report on the types of evidence currently available to inform clinical practice, to synthesise key concepts, and identify gaps in the research knowledge base.

METHODS

Following the PRISMA-ScR Checklist, we conducted a search of 10 electronic databases from inception to 1 February 2019. There were no exclusions in searching for publications. A single reviewer screened the literature and abstracted data from relevant publications. Articles were grouped and charted by concepts and themes relevant to primary care, and narratively synthesised. Effect sizes from longitudinal studies were identified or calculated, and randomised controlled trials assessed for methodological quality.

RESULTS

Eight hundred and twenty-nine records were identified to 1 February 2019. Four hundred and ninety-six were screened and 170 assessed for eligibility. Ninety-nine publications met the inclusion criteria. Effect sizes were typically trivial to small. One trial used a pragmatic hardstyle training program among healthy college-age participants. Two trials reported the effects of kettlebell training in clinical conditions. Thirty-three studies explicitly used 'hardstyle' techniques and 4 investigated kettlebell sport. Also included were 6 reviews, 22 clinical/expert opinions and 3 case reports of injury. Two reviewers independently evaluated studies using a modified Downs & Black checklist.

CONCLUSIONS

A small number of longitudinal studies, which are largely underpowered and of low methodological quality, provide the evidence-informed therapist with little guidance to inform the therapeutic prescription of kettlebells within primary care. Confidence in reported effects is low to very low. The strength of recommendation for kettlebell training improving measures of physical function is weak, based on the current body of literature. Further research on reported effects is warranted, with inclusion of clinical populations and investigations of musculoskeletal conditions common to primary care. There is a need for an externally valid, standardised approach to the training and testing of kettlebell interventions, which better informs the therapeutic use of kettlebells in primary care.

Cardiopulmonary Demand of 16-kg Kettlebell Snatches in Simulated Girevoy Sport

Chan, M, MacInnis, MJ, Koch, S, MacLeod, KE, Lohse, KR, Gallo, ME, Sheel, AW, and Koehle, MS. Cardiopulmonary demand of 16-kg kettlebell snatches in simulated Girevoy Sport. J Strength Cond Res 34(6): 1625-1633, 2020-Kettlebell lifting has become popular both as a strength and conditioning training tool and as a sport in and of itself: Girevoy Sport (GS). Although several kettlebell multimovement protocols have been analyzed, little research has attempted to quantify the aerobic stimulus of the individual events in GS, which could better inform kettlebell-related exercise prescription. The purpose of this study was to quantify the cardiopulmonary demand, assessed primarily by oxygen consumption (V[Combining Dot Above]O2) and heart rate (HR), of continuous high-intensity kettlebell snatches-under conditions relevant to GS-and to compare this demand with a more traditional graded rowing ergometer maximal exercise test. Ten male participants (age = 28.4 ± 4.6 years, height = 185 ± 7 cm, body mass = 95.1 ± 14.9 kg) completed (a) a graded-exercise test on a rowing ergometer to determine maximal oxygen consumption (V[Combining Dot Above]O2max) and maximal heart rate (HRmax) and (b) a graded-exercise test consisting of continuous 16-kg kettlebell snatches to determine peak oxygen consumption (V[Combining Dot Above]O2peak) and peak heart rate (HRpeak) during a simulated GS snatch event. Subjects achieved a V[Combining Dot Above]O2max of 45.7 ± 6.7 ml·kg·min and HRmax of 177 ± 8.3 b·min on the rowing ergometer. The kettlebell snatch test produced a V[Combining Dot Above]O2peak of 37.6 ± 4.4 ml·kg·min (82.7 ± 6.5% V[Combining Dot Above]O2max) and a HRpeak of 174 ± 10 b·min (98.0 ± 3.4% HRmax). These findings suggest that GS kettlebell snatches with 16-kg can provide an adequate aerobic stimulus to improve cardiorespiratory fitness in those with a V[Combining Dot Above]O2max of ≤51 ml·kg·min, according to aerobic training recommendations from the American College of Sports Medicine.

External kinetics of the kettlebell snatch in amateur lifters

BACKGROUND

Kettlebell lifting has gained increased popularity as both a form of resistance training and as a sport, despite the paucity of literature validating its use as a training tool. Kettlebell sport requires participants to complete the kettlebell snatch continuously over prolonged periods of time. Kettlebell sport and weightlifting involve similar exercises, however, their traditional uses suggest they are better suited to training different fitness qualities. This study examined the three-dimensional ground reaction force (GRF) and force applied to the kettlebell over a 6 min kettlebell snatch set in 12 kettlebell-trained males.

METHODS

During this set, VICON was used to record the kettlebell trajectory with nine infrared cameras while the GRF of each leg was recorded with a separate AMTI force plate. Over the course of the set, an average of 13.9 ± 3.3 repetitions per minute were performed with a 24 kg kettlebell. Significance was evaluated with a two-way ANOVA and paired t-tests, whilst Cohen's F (ESF) and Cohen's D (ESD) were used to determine the magnitude.

RESULTS

The applied force at the point of maximum acceleration was 814 ± 75 N and 885 ± 86 N for the downwards and upwards phases, respectively. The absolute peak resultant bilateral GRF was 1,746 ± 217 N and 1,768 ± 242 N for the downwards and upwards phases, respectively. Bilateral GRF of the first and last 14 repetitions was found to be similar, however there was a significant difference in the peak applied force (F (1.11) = 7.42, p = 0.02, ESF = 0.45). Unilateral GRF was found have a significant difference for the absolute anterior-posterior (F (1.11) = 885.15, p < 0.0001, ESF = 7) and medio-lateral force vectors (F (1.11) = 5.31, p = 0.042, ESF = 0.67).

DISCUSSION

Over the course of a single repetition there were significant differences in the GRF and applied force at multiple points of the kettlebells trajectory. The kettlebell snatch loads each leg differently throughout a repetition and performing the kettlebell snatch for 6 min will result in a reduction in peak applied force.

CrossFit® Instructor Demographics and Practice Trends

CrossFit^® is an increasingly popular exercise modality that uses high intensity power training. The literature to date regarding CrossFit^® has focused on its benefits to VO2 Max, body composition and the motivational variables of participants of CrossFit^®. A computerized survey was distributed to CrossFit^® instructors using Survey Monkey^® (Palo Alto, CA, USA). One hundred and ninety-three CrossFit^® instructors responded to the survey. Of these 86.6% (155/179) reported being a certified CrossFit^® instructor with 26.7% (48/180) having a bachelor’s degree in an exercise-related field. Instructors with a CrossFit^® certification have less bachelor’s (P=0.04) or master’s (P=0.0001) degrees compared to those without a CrossFit^® certification, more utilization of Olympic weightlifting (P=0.03), one-on-one teaching (P=0.0001), 1-RM max on snatch (P=0.004), 1-RM on clean and jerk or hang clean (P=0.0003), kettlebell use (P=0.0001) and one-on-one training (P=0.0001). Instructors report differences in their education and differences in use of weightlifting platforms and various types of footwear. Non-certified instructors differ from CrossFit^® certified instructors in regards to teaching of Olympic weightlifting and exercise programming.

Personal Trainer Demographics, Current Practice Trends and Common Trainee Injuries

Increasing emphasis on maintaining a healthy lifestyle has led many individuals to seek advice on exercise from personal trainers. There are few studies to date that evaluate personal trainer education, practice trends, and injuries they have seen while training clients. A survey was distributed to personal trainers using Survey Monkey® (Palo Alto, CA, USA) with 605 personal trainers accessing the survey. An exercise related bachelor’s degree was held by 64.2% of survey participants and a certification in personal training by 89.0%. The most common personal trainer certifications were from American College of Sports Medicine (59.2%) and National Strength and Conditioning Association (28.9%). Only 2.9% of all personal trainers surveyed had no exercise-related bachelor’s degree and no personal trainer certification. The most common injuries seen by personal trainers during sessions were lumbar muscle strain (10.7%), rotator cuff tear/tendonitis (8.9%), shin splints (8.1%), ankle sprain (7.5%), and cervical muscle strain (7.4%). There is variability in the practices between different personal trainers when analyzing differences in collegiate education, personal trainer certifications, and strength and conditioning certifications. The clinical implication of the differences in practices is unknown as to the impact on injuries or exercise prescription effectiveness.

Comparison of Cardiorespiratory and Metabolic Responses in Kettlebell High-Intensity Interval Training Versus Sprint Interval Cycling

The purpose of this study was to determine the effectiveness of a novel exercise protocol we developed for kettlebell high-intensity interval training (KB-HIIT) by comparing the cardiorespiratory and metabolic responses to a standard sprint interval cycling (SIC) exercise protocol. Eight men volunteered for the study and completed 2 preliminary sessions, followed by two 12-minute sessions of KB-HIIT and SIC in a counterbalanced fashion. In the KB-HITT session, 3 circuits of 4 exercises were performed using a Tabata regimen. In the SIC session, three 30-second sprints were performed, with 4 minutes of recovery in between the first 2 sprints and 2.5 minutes of recovery after the last sprint. A within-subjects' design over multiple time points was used to compare oxygen consumption (V[Combining Dot Above]O2), respiratory exchange ratio (RER), tidal volume (TV), breathing frequency (f), minute ventilation (VE), caloric expenditure rate (kcal·min), and heart rate (HR) between the exercise protocols. Additionally, total caloric expenditure was compared. A significant group effect, time effect, and group × time interaction were found for V[Combining Dot Above]O2, RER, and TV, with V[Combining Dot Above]O2 being higher and TV and RER being lower in the KB-HIIT compared with the SIC. Only a significant time effect and group × time interaction were found for f, VE, kcal·min, and HR. Additionally, total caloric expenditure was found to be significantly higher during the KB-HIIT. The results of this study suggest that KB-HIIT may be more attractive and sustainable than SIC and can be effective in stimulating cardiorespiratory and metabolic responses that could improve health and aerobic performance.

A Comparison of the Effect of Kettlebell Swings and Isolated Lumbar Extension Training on Acute Torque Production of the Lumbar Extensors

The aim of this study was to use a fatigue response test to measure the muscular fatigue (defined as a reduction in torque production) sustained by the lumbar extensors after a single set of kettlebell swings (KBS) in comparison with isolated lumbar extensions (ILEX) and a control condition (CON). The purpose of which is to measure the physiological response of KBS against an already established modality. Subsequent data provide insight of the efficacy of kettlebells swings in strengthening the lumbar muscles and lower back pain treatment. Eight physically active males participated in a repeated measures design where participants completed all conditions. There were statistically significant reductions in maximal torque, reported as strength index (SI), after both KBS and ILEX exercise. A statistically significant difference was found for reductions in maximal torque between CON and both KBS (p = 0.005) and ILEX (p = 0.001) and between KBS and ILEX (p = 0.039). Mean reduction and effect sizes were -1824 ± 1127.12 (SI) and -1.62 for KBS and -4775.6 ± 1593.41 (SI) and -3.00 for ILEX. In addition, a statistically significant difference was found between KBS and ILEX for rate of perceived exertion (p = 0.012). Data suggest that both KBS and ILEX were able to fatigue the lumbar extensors. Isolated lumbar extension was able to generate a greater level of fatigue. However, contrary to previous research, the KBS was able to elicit a physiological response, despite the lack of pelvic restraint supporting the potential to strengthen the lumbar extensors.