The Role of in Strength and Conditioning: A Review of the Literature

Chris Beardsley, MA (Hons)1 and Bret Contreras, MA2 1Strength and Conditioning Research Limited, Loughborough, Leicestershire, ; and 2School of and Recreation, Auckland University of Technology, Auckland, New Zealand

ABSTRACT and power, and whether they are useful measured by the half and counter- for improving aerobic fitness. Addition- movement jump. The subjects performed STUDIES SUPPORT THE USE OF ally, researchers have been interested in Pavel Tsatsouline’s Program Minimum KETTLEBELLS FOR IMPROVING several biomechanical factors (muscle protocol with 16-kg kettlebells for men POWER, ALTHOUGH EVIDENCE activity, ground reaction forces, lumbar over 70 kg of body weight and 12-kg FOR USING THEM TO IMPROVE motion, and spinal loading) associated kettlebells for men under 70 kg of body STRENGTH AND AEROBIC FITNESS with various movements, with weight (see Tsatsouline (20)). It was IS STILL EQUIVOCAL. STUDIES the kettlebell swing being the most com- found that both programs improved INVESTIGATING THE BIOMECHANI- monly researched exercise. maximum and explosivestrengthsignifi- CAL PROPERTIES OF KETTLEBELL cantly and to the same extent. It is pos- TRAINING HAVE BEEN FRUITFUL, sible that the positive results observed by CHRONIC EFFECTS OF AND IT MAY BE USEFUL FOR KETTLEBELL TRAINING ON the program implemented by Lake and DEVELOPING SPRINT RUNNING STRENGTH AND POWER Lauder (10) arose as a result of the PERFORMANCE AND FOR INJURY Several investigations have looked at heavier weights used, which may have PREVENTION. HOWEVER, WE STILL strength and power changes with resulted in a greater training stimulus DO NOT KNOW THE OPTIMAL chronic kettlebell training. Jay et al. and therefore more significant adapta- LOADS FOR MAXIMIZING SYSTEM (8) investigated the effects of kettlebell tions. Similarly, Otto et al. (16) compared AND JOINT POWER PRODUCTION, training on postural coordination and the effects of a 6-week, 2 days per week, HOW THE MECHANICS, JOINT countermovement jump height in weightlifting or kettlebell program on MOMENTS, AND ELECTROMYO- untrained subjects. They implemented maximum strength (as measured by the GRAPHIC ACTIVITY CHANGES AS a standard 8-week kettlebell training back squat) and explosive strength (as LOADS INCREASE DURING KET- program involving progressions from measured by the vertical jump and power TLEBELL SWINGS, NOR WHETHER the unweighted swing to the kettlebell clean) in resistance-trained subjects. The kettlebell group performed kettlebell KETTLEBELL TRAINING TRANSFERS , to the 2-handed kettlebell swings, accelerated swings, and goblet TO PERFORMANCE. swing, and finally to the 1-handed kettlebellswing.Malesubjectsuseda squats with a 16-kg kettlebell, whereas 12-kg kettlebell, and female subjects the Olympic-style weightlifting group INTRODUCTION used an 8-kg kettlebell. The program performed back squats and Olympic- he use of kettlebells in the did not significantly improve counter- style pull variations. Although both is a recent phe- movement jump height in comparison groups improved vertical jump similarly, T nomenon. As a result, research- with a control group. In contrast, Lake ers have just started to investigate the and Lauder (10) compared the effects of KEY WORDS: utility of kettlebells in strength and con- a 6-week program of kettlebell swing kettlebell swing exercise; sprint running; ditioning programs over the last few training with a similar program of jump horizontal jumping; hamstrings; gluteus years. Of primary interest is whether ket- squats in resistance-trained athletes on maximus; hip extensors tlebells can be used to develop strength maximum and explosive strength, as

64 VOLUME 36 | NUMBER 3 | JUNE 2014 Copyright Ó National Strength and Conditioning Association and both groups improved strength strength measures. Two of the studies a maximum kettlebell 5-minute measures, the group that performed compared kettlebell exercises with test, a maximum treadmill test, and weightlifting improved back squat and more traditional methods. One of these heart rate response and energy cost power clean by a greater amount than found that kettlebells produced similar during a less intense 20-minute kettle- the kettlebell group. This seems to sug- results, and the other found that kettle- bell workout. They found that tread- ̇ 21 21 gest that weightlifting leads to superior bells produced inferior results. Three of mill VO2max was 38.9 mL$kg $min , ̇ improvements in vertical sports-specific the 4 studies investigating power trans- whereas the kettlebell VO2max was 2 2 performance than kettlebell training. fer found that kettlebells improved 31.6 mL$kg 1$min 1, which was ̇ However, the weightlifting group per- measures of power. Two of these stud- 81.2% of the treadmill VO2max. During formed a greater volume of work and ies compared kettlebells with more tra- the standard 20-minute workout, they trained with greater specificity to ditional methods and both found that found that heart rate averaged 164 6 these 2 tests. Manocchia et al. (12) kettlebells produced similar results to 15 beats per minute, which equated to investigated the carryover of kettle- traditional methods of power develop- 93 6 4.5% of maximum heart rate. Farrar bell training to strength and endur- ment. Although the evidence is still et al. (3) also measured oxygen cost and ance on traditional lifts compared very sparse, it seems that kettlebell the heart rate response during a com- with a nontraining control group training is more likely to demonstrate monly used 12-minute kettlebell exercise using a 10-week periodized program useful improvements in power than in routine and compared the results with ̇ training twice per week in resistance- strength, however it is noted that in all the VO2max and heart rate response trained subjects. The workouts com- of these studies, very light weights measured during a maximal treadmill prised a wide range of exercises and were used, and it is likely that different test. The researchers found that during included non-kettlebell exercises such results might have been achieved using the kettlebell exercise bout, the oxygen 2 2 as push-ups. The kettlebell group heavier loads. cost was 34.3 6 5.7 mL$kg 1$min 1, improved their 3 repeti- which was 65.3 6 9.8% of the measured ACUTE AND CHRONIC EFFECTS OF ̇ tion maximum (RM) and their clean VO max during the treadmill test. The KETTLEBELL TRAINING ON 2 and jerk 3RM significantly in compar- CARDIOVASCULAR MEASURES measured heart rates were similar to ison with the nontraining control, Several investigations have looked at those reported by Schnettler et al. (19) 6 thereby demonstrating increases in either chronic changes in cardiovascu- at 165 13 beats per minute, which was 6 both strength and power. Finally, lar fitness or the acute physiological 87 6% of maximum heart rate. Husley Jay et al. (7) performed a study com- responses to kettlebell training. Jay et al. (6) examined the oxygen consump- paring the effects of 3 days per week et al. (7) performed a study comparing tion and the heart rate response during of kettlebell interval training over 8 the effects of 3 days per week of kettle- a typical 10-minute kettlebell swing rou- weeks with a control for improving bell interval training over 8 weeks with tine and compared it with a treadmill run measures of back, neck, and shoulder a control for improving measures of at an equivalent rating of perceived exer- pain, as well as back extensor strength back, neck, and shoulder pain, as well tion (RPE). The researchers observed in untrained subjects. The pain inten- as aerobic fitness in untrained subjects. that oxygen consumption was signifi- sity of the lower back and the muscu- They did not notice any change in aer- cantly higher for treadmill running 6 $ 21$ 21 lar strength of the back extensors obic fitness in relation to a control (46.7 7.3 mL kg min )than 6 improved more in the intervention group over the 8-week period. How- for kettlebell swings (34.1 4.7 21 21 groupthaninthecontrolgroup. ever, the workouts used began with pro- mL$kg $min ). In fact, the average In summary, to date, we have found 5 gressions from the unweighted swing to oxygen consumption during the ket- studies that have investigated the the kettlebell deadlift, then to the tlebell workout was 73% of the oxygen effects of kettlebell training on meas- 2-handed kettlebell swing, and finally consumption during the treadmill ures of strength and power (Jay et al. to the 1-handed kettlebell swing. Male workout at the same RPE. In regards (8), Lake and Lauder (10), Otto et al. subjects used a 12-kg kettlebell, and to heart rate response, Husley et al. (6) 6 (16), Manocchia et al. (12), and Jay female subjects used an 8-kg kettlebell. found that heart rate averaged 89 et al. (7)). Four of the studies investi- The use of unloaded progressions to 5.3% of age-predicted maximum for gated the effects on power production begin with and the relatively light loads the kettlebell workout and was similar 6 (Lake and Lauder (10), Otto et al. (16), in comparison with other studies may for both kettlebell (180 12 beats 6 Manocchia et al. (12) and Jay et al. (8)), have resulted in inadequate training per minute) and treadmill (177 11 and 4 of the studies investigated the stimulus to produce any adaptations. beats per minute) workouts. effects on strength (Jay et al. (7), Lake Three studies have investigated the In summary, only 1 study (Jay et al. (7)) and Lauder (10), Otto et al. (16), acute physiological responses to ket- so far has investigated the effect of a ket- Manocchia et al. (12)). All 4 studies tlebell training. Schnettler et al. (19) tlebell program on aerobic fitness and ̇ investigating strength transfer found investigated VO2max, heart rate found that it had no measurable effect. that kettlebells did in fact improve response, and energy cost during Three studies (Schnettler et al. (19),

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Farrar et al. (3), and Husley et al. (6)) femoris (long head), a lateral hamstring. injury prevention, although further investigated oxygen cost and heart rate Unfortunately, they did not specify research is required in this area to con- response acutely during kettlebell whether a certain type of swing was man- firm this suggestion. workouts in comparison with treadmill dated nor which type of swing was actu- In a second study exploring EMG running. In general, in these studies, the ally used. They found that there was oxygen consumption during kettlebell greater activation of the semitendinosus activity, McGill and Marshall (14) workouts was found to be less than that than of the biceps femoris (long head) investigated the muscle activation observed during treadmill running at during kettlebell swings. This finding of various trunk, leg, and back muscles similar intensities. However in these may have relevance for sports-specific during several kettlebell movements, studies, heart rate response was found training because sprint running including the kettlebell swing, kettle- to be similar in kettlebell training to involves greater medial than lateral bell swings with kime, kettlebell ̇ snatches, the kettlebell bottoms-up that in treadmill running. The VO2max hamstring activation, as Jo¨ nhagen values observed during the more chal- et al. (9) and Higashihara et al. (5) carry, and the kettlebell racked carry. lenging kettlebell workouts, which have shown. Exercises such as the According to McGill and Marshall lasted between 5 and 20 minutes were kettlebell swing, which activate the (14), “kime” is a technique that in- ̇ volves a brief muscular “pulsing” at higher than 60% VO2max, which would medial hamstrings by a greater classify them as “hard” exercise accord- amount than the lateral hamstrings, the top of a kettlebell swing in an ing to the definitions used by the Amer- may therefore be useful for inclusion attempt to train rapid muscle ican College of Sports Medicine [see in a sprint running training program. contraction-relaxation. In this study, Pollock et al. (17)]. However, no studies Zebis et al. (23) also reported that although the researchers did not as of yet have been able to demonstrate the kettlebell swing activated the explicitly refer to the possibility of improvements in aerobic fitness as hamstrings at high degrees of hip flex- 2 types of swing being used, they did a result of kettlebell training. ion. This may suggest that the kettle- note that the subjects began the bell swing could lead to improvements swings in a squat position, and there- THE BIOMECHANICS OF in strength and hypertrophy in differ- fore it seems likely that a squat- KETTLEBELL TRAINING ent parts of the hamstring muscles dominant swing was adopted. McGill There are 2 main styles of kettlebell compared with exercises that activate and Marshall (14) found during the swing: the hip-dominant swing and the hamstrings most strongly at low kettlebell swing and the kettlebell the squat-dominant swing. In a previous degrees of hip flexion such as the Nor- swing with kime that the gluteal acti- review comparing these 2 swing types, dic hamstring curl (Zebis et al. (23)). vation peak occurred late in the swing Matthews and Cohen (13) suggested Using magnetic resonance imaging cycle and was closely associated with that hip-dominant kettlebell swings are (MRI) scans, Mendiguchia et al. (15) the final degrees of hip extension. This an excellent alternative to traditional found that the signal intensity in var- was an interesting finding as Worrell hamstring exercises such as the ious regions of 3 different hamstring et al. (22) reported in a dynamometer Romanian deadlift. They proposed that muscles differed depending on the experiment that the mean percentage hip-dominant kettlebell swings are par- exercise selected. This phenomenon of gluteus maximus EMG was highest 8 ticularly useful for strength and condi- can be observed in other muscle in full hip extension (0 ) compared 8 tioning coaches because they place groups also. Wakahara et al. (21) with that reached at 30, 60, or 90 of a greater emphasis on rapid eccentric reported that the muscle activation hip flexion. Whether the kettlebell control of the hamstrings in stretch- in different regions of the triceps dur- swing involves maximum gluteus shortening cycle movements than more ing resistance training is associated maximus activity at the degree of traditional exercises and also allow train- with regional hypertrophy in those hipflexionwheregluteusmaximus ing of the hamstrings at more sports- same areas. Bloomquist et al. (1) used EMG is maximal is uncertain. How- specific speeds. Unfortunately, where re- MRI scans to record the differences in ever, the findings of McGill and searchers have investigated the biome- hypertrophy after programs of either Marshall (14) suggest that the peak chanics of the kettlebell swing, they have deep or shallow back squats in the ham- is not in high degrees of hip flexion. not always specified exactly whether 1 strings and anterior thigh muscles. Dif- This may make kettlebell swings a use- type of swing was mandated for the sub- ferent types of squats led to varying ful complement to movements that jects or which was generally used. degrees of hypertrophy at each point involve maximal hip extension torque Two studies so far have investigated elec- measured along the proximal to distal in high degrees of hip flexion such as tromyographic (EMG) activity during length of the thigh. Strength and condi- squats and . McGill and kettlebell movements. Zebis et al. (23) tioning coaches could therefore use ket- Marshall (14) also noted that the addi- investigated the relative muscular activity tlebell swings in combination with other tion of kime to the swing mostly of the hamstring muscles by measuring exercises to create an even development affected the abdominal muscles, with the EMG activity of the semitendinosus, of strength and size at all points along the largest increases in activation a medial hamstring, and the biceps the hamstring muscles. This may aid occurring in the external oblique

66 VOLUME 36 | NUMBER 3 | JUNE 2014 muscles (101% increase in the right effects of kettlebell training on maximal aerobic fitness, and most studies have external obliques and 140% increase strength discussed above. However, concentrated on standard low-load in the left). Overall, although the Lake and Lauder (11) also found that kettlebells weighing up to 32 kg. snatch and the swing seemed to be power outputs were similar in jump However, the majority of studies sup- very similar, the researchers noted squats and kettlebell swings, particu- port the use of kettlebells for improv- some differences in muscle activation, larly with the 32-kg kettlebell. They ing power, the evidence for using in that the snatch displayed greater therefore suggested that kettlebell them for improving strength and aer- activity in the right external obliques, swings might be appropriate for inclu- obic fitness is still equivocal. Studies the right rectus femoris, and the left sion into a power-based program. investigating the biomechanical prop- internal obliques. There was little Again, this is consistent with the erties of kettlebell training have been activity in the trunk, leg, and back results of studies investigating the pos- more fruitful. Researchers have so far muscles noted during the 2 types of itive effects of kettlebell training on found that kettlebell swings in partic- carries. McGill and Marshall (14) also explosive strength discussed above. ular have certain features that may reported on shear and compressive Lake and Lauder (11) also noted that make them useful for training ath- lumbar joint loads. They found that the relative contribution of the hori- letes. The summary of these findings both shear and compressive loads zontal and vertical components of and their practical implications is were the highest at the beginning of ground reaction forces during kettle- shown in Table 1. the swing. Compressive loads were bell swings was different to that during 3,195 N at the bottom of the swing, squats. They observed that kettlebell DIRECTIONS FOR FUTURE whereas shear loads were 461 N. Add- swings had a much higher proportion KETTLEBELL RESEARCH ing kime to the swing had little effect of horizontal forces. They suggest that There remain many gaps in kettlebell except at the top of the swing, where this is because the kettlebell is actively research at the moment. However, both shear and compressive loads re- projected forwards by hip extension. research involving kettlebells is a rap- mained high, whereas they reduced Additionally, the highest net impulse idly growing area, so by the time this significantly in comparison at the that they recorded during their study article is published, some of the infor- same point during normal swings. was produced by the kettlebell swing mation below could be outdated. $ McGill and Marshall (14) commented with 32 kg (276 N s), which was Below, we offer our suggestions to that less shear loading is considered to greater than the largest impulse future researchers, separated into 9 be more optimal. There was little dif- recorded in the back squat, using different categories. $ ference in spinal loads between the 60% of 1RM (183 N s)andinthe LOADING snatch and the swing. However, spinal jump squat, using 40% of 1RM back $ loads were found to be significantly squat (231 N s). Hip-dominant kettle- Kettlebells range broadly in size, just greater in the bottoms-up position bell swings may therefore have appli- as dumbbells. In fact, several manu- carry than in the racked position carry cations in certain sporting movements facturers sell heavy kettlebells—one and in normal walking. that involve hip extension to create particular brand sells kettlebells of horizontal propulsion. For example, 80, 88, 97, 106, 124, 150, 176, and Lake and Lauder (11) investigated the it has been reported that horizontal 203 lb. Advanced strength and power ground reaction forces and power out- ground reaction forces display greater athletes of larger body weight puts during kettlebell swings with loads increases than vertical ground reac- can indeed progress to the 203-lb up to 32 kg and compared them with tion forces when accelerating to max- kettlebell for swings. Just as previous both heavy back squats and jump imal velocity during sprint running research has examined squats. In their description of the ket- (Randell et al. (18)). Hip-dominant and dumbbell training with a variety tlebell swing, they referred to the exer- kettlebell swings may therefore be of loads ranging from light to maxi- cise as a hip-hinge movement and useful for developing short-distance mal, future studies should examine noted that the subjects were instructed sprint running ability because such the kinematics, kinetics, and transfer to lead with the hips. This implies that sprints generally involve a large accel- of training of different loads of a hip-dominant swing was used. It was eration phase. Kettlebell swings may kettlebells. found that the ground reaction forces also produce other different training were greatest in the order: heavy back effects because of the greater impulses POWER AND GROUND REACTION squats . jump squats . kettlebell generated. FORCES swings. They therefore concluded that We still do not know the optimal load kettlebell swings using loads of 32 kg or SUMMARY OF CURRENT for maximizing system power produc- less may therefore not be optimal for KETTLEBELL RESEARCH tion, which takes into account the developing strength. This conclusion There is currently very little research subjects’ body mass and the mass of seems to be consistent with the equiv- investigating the effects of kettlebell the external resistance during kettle- ocal results of studies investigating the training on strength, power, and bell swings, cleans, and snatches. Since

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Table 1 Summary of research and recommendations in relation to kettlebell swings

Observation Recommendation Kettlebell swings seem to activate the medial hamstrings more Kettlebell swings may be suitable for sprinters because sprint than the lateral hamstrings in comparison with other running also involves the medial hamstrings more than the hamstrings exercises lateral hamstrings Kettlebell swings produce a higher ratio of horizontal-to-vertical Kettlebell swings may be useful for training for sporting actions ground reaction forces than jump squats or squats involving horizontal propulsion such as sprint running Kettlebell swings using a pronounced hip-dominant pattern Kettlebell swings may be useful for training for stretch- may be useful for strengthening the hamstrings at sports- shortening cycle sporting movements in sports as are found specific speeds and in a stretch-shortening cycle pattern in sports such as American football, baseball, basketball, and track and field Kettlebell swings produce greatest hamstring activity in high Kettlebell swings may be useful for injury prevention because degrees of hip flexion, which is different from other exercises coaches can use several exercises that target the hamstrings such as the Nordic hamstring curl, which produce the at different muscle lengths and therefore produce strength greatest hamstring activity in low degrees of hip flexion and size gains evenly along the whole muscle Kettlebell swings create peak gluteal activation at a point near Kettlebell swings may be useful for training the strength and full hip extension, the degree of hip flexion in which gluteal power of the gluteal muscles in full hip extension as activity is highest during maximum voluntary contractions a complement to exercises that train the gluteals predominantly in hip flexion such as squats and deadlifts Kettlebell swings using moderate loads produce a similar power Kettlebell swings may be useful for substituting into a power output to jump squats with conventional training loads phase of programming, particularly where horizontal propulsion is required

1RM loads are not always conducive knees, hips, and lumbar spine, along hip extensor hypertrophy as well. to kettlebell training, optimal loads with the muscle activation of the Finally, studies need to determine could be reported relative to body quadriceps, hamstrings, gluteals, and the nature of transfer between heavy weight. Vertical and horizontal forces core musculature, during kettlebell kettlebell training and must be taken into account when swings, cleans, and snatches of vary- and weightlifting performance, spe- calculating power measurements. ing loads. The hip extension torque cifically examining the effects on Moreover, we do not yet know the curve throughout the entire hip range squat, deadlift, clean, and snatch optimal load for maximizing individ- of motion should be graphed. Fur- performance. ual joint power during kettlebell thermore, the compressive and sheer swings, cleans, and snatches. In partic- loading with heavier swings should be ular, the optimal load for hip exten- studied. EFFECTS ON ENDURANCE sion power, determined by the PERFORMANCE product of the hip extension torque EFFECTS ON FUNCTIONAL AND Future research could investigate and the hip extension angular velocity, EXPLOSIVE PERFORMANCE the changes in aerobic fitness over should be examined. Finally, the Future research needs to examine the a period of several weeks as a result nature of vertical and horizontal training effects of kettlebell swing of more typical and challenging ground reaction force changes with training on functional performance. kettlebell routines such as the increasing loads should be For example, sit-to-stand, balance, 12-minute and 20-minute swing investigated. and gait performance in the elderly. and snatch workouts used in previ- Moreover, the effects of heavy kettle- ous acute studies (e.g., Schnettler JOINT MOTION, JOINT TORQUE, bell swing training on vertical and et al. (19), Farrar et al. (3), and Husley MUSCLE ACTIVATION, AND horizontal jumping, in addition to et al. (6)). Moreover, it would SPINAL LOADING acceleration and maximum speed be useful to compare the changes Studies should examine the inherent running, need to be examined in with the improvements that can joint motions of the ankles, knees, untrained, resistance-trained, and be obtained in a similar period with hips, and spine with progressively athlete populations. It would be ben- conventional continuous treadmill heavier swings. Research needs to eficial to know whether heavy ket- training or with interval training using determine the joint moments at the tlebell swings can induce significant other conventional gym equipment

68 VOLUME 36 | NUMBER 3 | JUNE 2014 such as cycle ergometers or rowing or Olympic-style lift variations. How- Chris machines. ever, it may actually be more appropri- Beardsley is the ate to compare kettlebell strength and Director of DIFFERENT TYPES OF SWINGS power improvements with a hip- Strength and There are different ways to swing dominant exercise, such as an explosive, Conditioning a kettlebell. Swings can be per- submaximal deadlift, or a hex-bar dead- Research formed with more of a squatting lift jump, rather than a knee-dominant Limited. emphasis that places more stress on exercise, such as a squat or jump squat. thekneejointsorwithmoreof Finally, research should determine a hinging emphasis that places more whether kettlebell swing training is stress on the hip joints. Future safer or riskier and more or less effective research needs to clarify the differ- than traditional plyometric, heavy Bret Contreras ences in kinematics and kinetics, lower-body resistance training, or is currently pur- along with the transfer of training, Olympic-style lift training in developing suing his PhD at with the different types of swing var- lower-body speed and power. AUT University. iations. The CrossFit groups prefer what has been described as an “American” HOW KINEMATICS AND KINETICS swing (see Glassman (4)), whereas the CHANGE WITH EXPERIENCE Russian Kettlebell Certification use Finally, we need to learn how subjects what is termed a “Russian” swing. improve their performance over time The Russian Kettlebell Certification with kettlebell swing training. For was previously known as the Russian example, it would be important to Kettlebell Challenge (see Tsatsouline know how kinematics and kinetics (20)), and both have been abbreviated change with 2 years of consistent ket- as RKC. The “American” type of tlebell swing training. REFERENCES swing involves a greater range of ket- 1. Bloomquist K, Langberg H, Karlsen S, tlebell motion and a more quad- MadsgaardS,BoesenM,andRaastadT. dominant style of performance (see Effect of range of motion in heavy load CONCLUSION Glassman (4)). The “Russian” type squatting on muscle and tendon of swing involves a shorter range of Kettlebells can be used for all types of adaptations. Eur J Appl Physiol 1–10, 2013. kettlebell motion and a more hip- populations to develop physical fit- 2. Brumitt J, Gilpin HE, Brunette M, and dominant style of performance (see ness. They can be used in rehabilita- Meira EP. Incorporating kettlebells into Tsatsouline (20)). tion settings to develop mobility and a lower extremity sports rehabilitation stability, as Brumitt et al. (2) have program. N Am J Sports Phys Ther 5: OTHER KETTLEBELL EXERCISES noted. They can be used in the condi- 257–265, 2010. Future research should also study dif- tioning of endurance athletes and they 3. Farrar RE, Mayhew JL, and Koch AJ. Oxygen ferent kettlebell exercises. We have can be used to improve explosiveness cost of kettlebell swings. J Strength Cond a great deal to learn about Turkish in power athletes. Although there is Res 24: 1034–1036, 2010. Get Ups, goblet squats, and other clearly still a great deal to learn about 4. Glassman G. The kettlebell swing. CrossFit potentially effective kettlebell lifts, the properties of standard kettlebell J 25: 2004. Retrieved from http://www. insofar as no studies have ascertained training exercises and their effect on crossfit.com/journal/library/25_04_ kettlebell_swing.pdf the key joint moments and muscular strength, power, and aerobic fitness, activity in comparison with similar the research so far indicates that they 5. Higashihara A, Ono T, Kubota J, Okuwaki T, dumbbell or barbell exercises. could be a promising tool for strength and Fukubayashi T. Functional differences in the activity of the hamstring muscles with COMPARISON WITH OTHER and conditioning coaches, particularly increasing running speed. J Sports Sci 28: EXERCISES with respect to improving lumbo- 1085–1092, 2010. We need to learn how kettlebell train- pelvic-hip complex patterning and 6. Husley CR, Soto DT, Koch AJ, and ing compares with other training in posterior chain power during horizon- Mayhew JL. Comparison of kettlebell terms of power output, muscle activa- tal movements. However, the current swings and treadmill running at equivalent tion, and other measures. For example, body of literature is still very small, RPE Values. J Strength Cond Res 26: 1203–1207, 2012. it would be valuable to know the met- and there are many avenues to explore abolic effects of heavy kettlebell swings before it is clear how they can best be 7. Jay K, Frisch D, Hansen K, Zebis MK, Andersen CH, Mortensen OS, and versus maximal sprint running. It would implemented into training routines. Andersen LL. Kettlebell training for also be beneficial to know whether the Conflicts of Interest and Source of Funding: musculoskeletal and cardiovascular health: heavy kettlebell swing involved greater The authors report no conflicts of interest A randomized controlled trial. Scand J hip power production than jump squat and no source of funding. Work, Environ Health 37: 196–203, 2011.

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