Kettlebell Training For Aerobic Endurance Gains

Introduction

Endurance is a broad term. Different types of endurance (short -, medium - and long term) are fueled by different energy systems. The first one or two maximum muscle contractions are powered by the phosphates in the muscle cell. After that, short bursts of up to 12 seconds draw their energy from the creatine- phosphate reserves. These two modes of energy production are known as anaerobic (lacking oxygen) alactic (without significant production of lactic acid). Longer efforts, up to roughly 3 minutes, primarily make use of the anaerobic lactic system, also called anaerobic glykolysis, i.e., the utilization of sugar in the absence of sufficient oxygen. Finally, even longer work is primarily fueled by the aerobic system. Here, oxygen is available in sufficient amounts such that sugars and fats can be oxidized in the Krebs cycle. It is this system that will be in the scope of this article.

The aerobic system is, amongst other things, relevant for recovery after training sessions or in the case of combat athletes, the recovery between rounds [TOWE2001]. In the case of longer rounds, such as the five minute rounds frequently met in mixed martial arts competition, the aerobic system also contributes greatly to the total energy production. The more energy can be produced this way the less the anaerobic system, which can not be sustained for a long time, needs to be tapped into.

Adaptations to aerobic training include eccentric hypertrophy of the hearts left ventricle, reduction in blood pressure [KEL+2001, WHE+2002], resting heart rate, stroke volume and oxygen utilization. Hence, developing this aspect can be highly beneficial for long time health in non - athletic populations.

Amongst the most commonly used methods of endurance training are running, cycling and swimming. While each of those is effective, they present limitations that need to be considered when planning a training program.

Running results in high impact forces and may not be suitable for certain populations. Knee, hip, and lower back problems might prevent a person from talking up a concentrated running program. These issues are also common among combat athletes. An unstable mechanical axis, i.e. a valgus collapse ( knock knees) can lead to joint wear due to sub - optimal biomechanics.

Cycling places the trainee in a seated position and might therefore not offer big benefits regarding posture. The western lifestyle requires a large portion of the day to be spent in a sitting position. This may lead to weakened gluteal muscles and functionally shortened hip flexor muscles. Janda expands on muscle inhibition and shortening in detail.

Hulsey et al. [HUL+2012] present kettlebell training as an alternative to treadmill running. Although the authors state that

subjects are likely to have higher oxygen consumption, work at a higher MET level, and burn more kilocalories per minute during TM running than during KB swings

they also conclude that

according to the American College of Sports Medicine standards, this KB drill could provide sufficient exercise stress to produce gains in aerobic capacity. 

Given the fact that combat athletes tend to experience high amounts of joint stress during specific practice, kettlebell training may offer a feasible means of implementing low - impact endurance training protocols. This article aims at investigating different training protocols and giving advice on actual implementation.

Related Work

Joel Jamison [JAMI2009] presents eight different methods of aerobic training. For his cardiac output protocol, he proposes a heartrate (HR) zone between 130 and 150 beats per minute (bpm) in order to maximize the hypertrophic effect on the left heart ventricle. While this heart rate zone might seem overly generic, research [ROLA2002] has shown that the commonly used formula of 220 - age is also highly inaccurate and "has no scientific merit for use in exercise physiology and related fields".

Tanaka et al. [TAN+2001] suggest a regression model that estimates HRmax as 209 - 0.7 * age. The authors point out that a large portion of variability with regards to HRmax was explained by age alone, rather than other attributes such as gender and physical activity status. On the other hand, Verschuren et al. [VER+1022] suggest that HRmax does not vary with age and propose using a fixed max HR of 194 bpm when precise exercise testing is not available.

Considering the current apparent lack of a scientific consensus on the one hand and the existence of empirical evidence [HAGE2009] that the HR zone defined by Jamieson leads to the desired results, it seems safe to plan the CO sessions as written. Training can be structured in multiple ways.

Continuous training methods call for the uninterrupted performance of an activity. Usually, heart rate is kept to a narrow, pre - defined range. Traditional steady state training (SS), Fartlwk training, Low Intensity Steady State (LISS) and High Intensity Continuous Work (HICT) are amongst the variations of this training method.

Interval training, in contrast to continuous training, alternates work intervals and rest intervals. The choice of a specific work to rest ratio (WTR) is dependent on the desired training adaptation. In extensive interval sessions, rest periods are equal to or shorter than the respective work intervals. Conversely, in intensive intervals, rest is longer than the associated work.

Jay [JAY2009] proposes different training protocols for increasing VO2Max by means of KB snatches. Specific guidelines for testing the cadence that elicits a VO2Max response are presented. Due to the mobility demands the snatch places on the glenohumeral joint and the thoracic spine, it might not be a feasible option for trainees with limitations in these areas. Simpler exercises such as the kettlebell swing may be an option that is accessible to a larger population.

In later work, Jay [JAY2011] investigates the effect of ballistic kettlebell training on aerobic fitness and finds that 10 - 15 minutes of training, performed on average twice per week, does not produce significant improvements in aerobic fitness. The author points out that the short training duration may explain this lack of results. Also, it must be noted that trainees also performed unweighted and non - ballistic exercise regressions. Those placed low cardiovascular demands on the trainees and hence were unlikely to elicit an aerobic training effect in the fist place.

Conversely, investigating the effect of kettlebell snatches on aerobic condition, Falatic et al. [FAL+2015] found that

the 4-week 15:15 MVO2 kettlebell protocol, using high-intensity kettlebell snatches, significantly improved aerobic capacity in female intercollegiate soccer players and could be used as an alternative mode to maintain or improve cardiovascular conditioning.

Implementation

Different forms of endurance training can be implemented with a kettlebell. In the following sections, different training methods are discussed.

Continuous Training

True continuous methods are likely unfeasible when discussing kettlebell training. However, with regards to HR, sessions can be designed in a manner similar to Fartlek training. Figure 1 illustrates the HR recorded during a session that consisted of KB swings and the Bench Press (BP). The workout was organized as a modified Version of Dan John's 10,000 swing challenge [JOHN2012]. Swings were organised in ladders of four rungs each. The first rung consisted of 5 swings, the second of 10, then 15 and finally, 20. In between rungs, the BP was performed for 1,2,3, and 4, repetitions, respectively.

During the KB swing rungs, HR starts to climb. This increase continues for a certain time even after the swinging has stopped. During the time it takes to properly set up for the BP, HR starts to recover and is only slightly impacted by the actual pressing.

Also, High Intensity Continuous Training (HICT) protocols can be implemented easily with little more equipment than a kettlebell. Jamison [JAMI2010] explains the method as

different from other forms of aerobic training in that it is both high intensity, and relatively high volume.

Figure 1: Heart rate response to a combination of kettlebell swings and the bench press. Relatively long setup times for the bench press allow heart rate to drop in between sets. HR is kept to the range [130;150] for the vast majority of time.

Interval Training

Interval training is easier to implement by means of kettlebell training than continuous training. Periods of higher intensity are alternated with periods of lower intensity or rest. The choice of appropriate intervals and ratios determines the training outcome. Different configurations are possible. The following Sections briefly outline the basic ways interval training sessions can be set up.

Fixed Work, Fixed Recovery

In the most basic type of interval, both rest and recovery are fixed. Work can be given as a time frame, distance, amount of work or similar measure. Examples for time - based, fixed work, fixed recovery intervals are the infamous Tabata protocol or working the heavy bag for ten, two minute rounds with one minute of rest in between rounds. This type of interval is popular among group fitness instructors because it can be implemented with as little equipment as a stopwatch. On the downside, depending on the length of the work interval and the ratio between work and rest, certain factors may lead to suboptimal performance of this method. 

For one, a fixed work interval will inevitably lead to different heart rate responses from different athletes. When doing cardiac output training, the goal is to keep the heart rate in a certain range, such that the heart can fully extend and contract on each stroke and hence, optimally adapt in terms of left ventricular hypertrophy. A fixed interval, in a group setting, where the same exercise is usually performed by all participants, may lead some athletes to go far above the prescribed heart rate and therefore, inhibit optimal adaptation. In the case of very heterogeneous groups, well conditioned athletes may not reach the minimal required heartrate. Although protocols like Tabata call for supra-maximal efforts, personality differences must be considered, i.e., some athletes may not be willing or able to actually perform at a certain intensity in the absence of real-time feedback.

Despite this methods shortcomings, it is very easy to implement. In real life, practicality trumps optimality. Also, there are ways to attenuate the mentioned weaknesses and somewhat individualize this approach.

Fixed Work, Variable Recovery

In a given recovery period, different athletes will recover at different paces. Also, it might take the athlete longer to recover from the same amount of work in subsequent intervals. Over the course of a session, fatigue accumulates and restoring homeostasis becomes more challenging for the body. This is where variable recovery time offers a solution. Rather than resting for a prescribed time, rest intervals are as long as it takes the athlete to recover to a certain heartrate. Usually, a recovery target of 60%-65% max HR is prescribed.  To keep things simple, in a cardiac output session, a HR of 130 bpm can be used as a recovery target. As soon as that threshold is reached, another set is started.

Figure 2 illustrates the heart rate response to the following protocol: Kettlebell swings and push-ups were alternated, as described in the Section on continuous training.  After each ladder, heart rate was allowed to recover back to 130 bpm. As can be seen from the chart, heart rate rose higher with subsequent sets. While the heart rate after the first ladder was around 150bpm, it went above 170bpm after the tenth ladder.

Conversely, Figure 3 illustrates the heart rate response to a slightly different protocol. Recovery was again variable to a HR of 130bpm. Work intervals were shorter than in the previous example, though. Each set consisted of a set of 20 kettlebell swings and 5 pull-ups. Due to the shortened work intervals, heart rate was inside the designated target heart rate of 130-150bpm for most of the time.

While this method alleviates some of the shortcomings of a fixed work, fixed recovery protocol, it still fails to address some issues. As pointed out, left ventricular heart hypertrophy is optimized when the heart rate is kept to a specific range where the heart can maximally increase volume on each stroke. The same work interval (e.g., 10 kettlebell swings) may elicit very different HR responses in different athletes. What takes the HR from 130bpm to 150bpm in one athlete might push it to 170bpm in another. While training at a near max HR can have its place, e.g., in cardiac power intervals, it may be counterindicated in other scenarios, such as cardiac output work.

Figure 2: Heart rate response to a fixed work, variable rest protocol that consisted of kettlebell swings and push-ups. After each ladder (i.e., a series of four sets of variable repetitions for both exercises), heart rate was allowed to recover back to 130bpm. As can be seen, in later intervals, heart rate well exceeded 150bpm and went as high as 170bpm. Hence, the target heart rate of 130-150bpm was only met for a fraction of the total time.

Figure 3: Heart rate response to a fixed work, variable rest protocol that consisted of kettlebell swings and pull-ups. After each set, heart rate was allowed to recover back to 130bpm. The target heart rate of 130-150bpm was met for the majority of time.

Variable Work, Variable Recovery

The most sophisticated form of interval training monitors the HR during both work and recovery. For example, a prescription might call for 20 sets of work to 90% max HR and inter set recovery back to 65% max HR. While this method of performing intervals has the highest organisational cost associated with it, it also offers the athlete and trainer the highest form of control over the training outcome.

Hybrid Models

While the variable work, variable recovery protocol may look superior to the other formats, it bears repeating that practicality trumps optimality. In a group setting, some participants might not have a heart rate monitor. Linked monitoring systems that offer the trainer an overview over all athletes on the team are rather expensive. Self - monitoring by the athletes might take attention away from the actual training and instead divert it to the associated technology. Since many monitors work wirelessly and broadcast to a mobile app, taking the cell phone to practice becomes acceptable, which might again lead to attention issues down the road. 

Certain methods can be employed to alleviate these issues. A model can be built on an athletes heart rate response and further used without real time monitoring. An athlete is monitored and taken through a variable work, variable rest session once. The average interval durations are then prescribed for future sessions. For the work interval, this can be a specific number of kettlebell swings. Assuming the execution of a repetition takes a constant time, this is one of the easiest ways of timing work intervals. The rest interval can then be prescribed as a specific number of breaths. Again, this is simpler than setting a timer for each athlete. When building the initial model, it is important to remember that heart rate response is slightly delayed. After cessation of the exercise, heart rate will continue to climb for a few moments. If the goal is not to exceed a certain threshold, the testing threshold for determining the number of swings per interval needs to be set at a lower number to account for this.

Challenges and Solutions

Certain challenges arise when implementing a high volume kettlebell training block. Fung and Shore [FUSH2010] point out that during their study in aerobic and anaerobic work during kettlebell exercises,

Subjects reported that grip strength was the limiting factor.

Grip issues can be even more challenging when a concentrated loading block is implemented, as called for in Dan John's original 10,000 swing challenge [JOHN2012], which calls for swings to be performed five days per week. To circumvent this issue, several steps can be taken. Handle size can affect grip endurance. Competition kettlebells are designed to be used with one hand. Employing a two-hand grip for swings may not allow for proper hand placement and lead to premature lower-arm fatigue. Switching between two-handed swings for odd sets (i.e., on five and 15 swings) and single arm swings for even sets (i.e., for 10 and 20 swings), switching hands after every five swings, somewhat alleviates the demands on grip strength endurance. Also, while this is certainly a matter of opinion and many coaches will disagree, lifting straps can be used for higher-repetition sets.

Hand care also becomes an issue when training with kettlebells for high volumes. Pavel Tsatsouline [TSAT2016] offers solutions to this issue. Cutting the elastic part of sports socks and using it to protect the palm as presented in Figure 4 has proven invaluable in practice.

Figure 4: Cutting the elastic portion of a pair of sports socks and using it for palm protection can go a long way in preventing blisters and callouses.

While limiting endurance training to a single modality (e.g., kettlebell swings) may not be optimal, it may be feasible at times, especially when other forms of cardio (e.g., running) are counter-indicated due to already high joint stress during specific practice or simply not available (i.e., swimming requires a pool with free lanes and might be stressfull for athletes that are not skilled swimmers). In these situations, resorting to a swing protocol as outlined in this article might prove beneficial.

After going through a five week cycle, reudcing my bodyweight and bringing by resting HR down to the low fifties, I'm currently implementing such a protocol with my fighters as part of their aerobic block. At the end of the block, I will re-evaluate and draw further conclusions. If I find anything worth sharing, I'll certainly do it here.

So long,

don't get hurt

References

[FAL+2015] Falatic, J. A., Plato, P. A., Holder, C., Finch, D., Han, K., & Cisar, C. J. (2015). Effects of kettlebell training on aerobic capacity. The Journal of Strength & Conditioning Research, 29(7), 1943-1947.

[FUSH2010] Fung, B. J., & Shore, S. L. (2010). Aerobic and Anaerobic Work During Kettlebell Exercise: A Pilot Study: 3033. Medicine & Science in Sports & Exercise, 42(5), 834.

[HAGE2009] Hagenbuch, R. (2009). Echocardiography Evidence of Cardiac Output Training. www.elitefts.com. (www.elitefts.com/education/training/echocardiography-evidence-of-cardiac-output-training). Accessed: Dec 20th, 2017

[HUL+2012] Hulsey, C. R., Soto, D. T., Koch, A. J., & Mayhew, J. L. (2012). Comparison of kettlebell swings and treadmill running at equivalent rating of perceived exertion values. The Journal of Strength & Conditioning Research, 26(5), 1203-1207.

[JAMI2009] Jamieson, J. (200). Ultimate MMA Conditioning. Performance Sports Incorporated

[JAY2009] Jay, K. (2009). Viking warrior conditioning. Dragon Door.

[JAY2011] Jay, K., Frisch, D., Hansen, K., Zebis, M. K., Andersen, C. H., Mortensen, O. S., & Andersen, L. L. (2011). Kettlebell training for musculoskeletal and cardiovascular health: a randomized controlled trial. Scandinavian journal of work, environment & health, 196-203.

[JOHN2012] https://www.t-nation.com/workouts/10000-swing-kettlebell-workout

[KEL+2001] Kelley, G. A., Kelley, K. A., & Vu Tran, Z. (2001). Aerobic exercise and resting blood pressure: a meta‐analytic review of randomized, controlled trials. Preventive cardiology, 4(2), 73-80.

[ROLA2002] Robergs, R. A., & Landwehr, R. (2002). The surprising history of the" HRmax= 220-age" equation. Journal of Exercise Physiology Online, 5(2), 1-10.

[TAN+2001] Tanaka, H., Monahan, K. D., & Seals, D. R. (2001). Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology, 37(1), 153-156.

[TOWE2001] Tomlin, D. L., & Wenger, H. A. (2001). The relationship between aerobic fitness and recovery from high intensity intermittent exercise. Sports Medicine, 31(1), 1-11.

[WHE+2002] Whelton, S. P., Chin, A., Xin, X., & He, J. (2002). Effect of aerobic exercise on blood pressurea meta-analysis of randomized, controlled trials. Annals of internal medicine, 136(7), 493-503.

[TSAT2016] Tsatsouline, P. (2016). Kettlebell Simple & Sinister. Blue Vision, sro.

[VER+1022] Verschuren, O., Maltais, D. B., & Takken, T. (2011). The 220‐age equation does not predict maximum heart rate in children and adolescents. Developmental Medicine & Child Neurology, 53(9), 861-864.