From what I have seen and read, all top level Girevoy (kettlebell) sport athletes perform some type of cross training – this is most likely in an effort to improve their aerobic conditioning. Cross training may benefit GS athletes as kettlebell exercises have been shown to elicit a lower oxygen cost for the same given heart rate that treadmill running can produce. This would suggest that kettlebell training may be less aerobic than running. That being said, we know that the aerobic system is very important for GS performance as it is a ten minute event. Additionally, it can build work capacity for training. We will compare the pros and cons of running and cycling as forms of cross training for GS, and we’ll look at the biomechanics and oxygen cost of each.
Biomechanics
Muscle and Tendon
When people think of specificity they often think of range of motion and speed of contraction. Muscle tendon interaction is another thing that is worth considering. Below we have a two graphs – one of muscle length, another of tendon length from vertical jumping (most specific to GS) and cycling.
Lf; Length of the muscle, Lt; Length of the tendon
From these figures you can see that cycling and jumping have a different muscle and tendon interaction. The size change in tendon length is much smaller in cycling than vertical jumping. If we consider a jerk to be like jumping then cycling is not a specific exercise from a musculo-tendon (MT) standpoint. Running would have a much more specific MT interaction as it has a stretch shorting cycle (SSC). Simply put, the SSC involves a lengthening action (eccentric), followed by a shortening action (concentric), as the name suggests. There is also an amortization phase which is the point between the shortening and lengthening phases.
Muscle Architecture
Eccentric muscle actions have been shown to increase muscle length (sarcomerogenesis). Running and sprinting involves an eccentric component, whereas cycling does not. Runners have longer muscles (fascicles) than cyclists. Sprinters have longer muscles than runners. All things being equal, two sarcomeres (contractile units of muscle) in a series shorten twice as quickly as two sarcomeres in parallel and two sarcomeres in parallel produce twice the tension of two sarcomeres in a series.
Running may be more specific to GS than cycling, however running is more stressful on the body. In endurance and strength based programs, running has been found to inhibit strength more than cycling. Possibly because it places additional stress on areas of your body which you have already stressed during your strength training, or in this case, GS training. While running, your lower body will be exposed to an eccentric and concentric muscle action, making running more specific than cycling for GS. Cycling may be used as a form of active recovery or for some conditioning without going through impact on the lower body. Many high level GS athletes run as a form of cross training, for myself and a number of my clients, cycling is still a useful form of training because it is easy to recover from and has a much lower risk of flaring up old injuries (particularly tendons). At the end of the day, you’re better off spending most of your time training GS and if running gives you issues you should avoid it and switch to a type of training which is better suited to your body (ie, cycling.)
Oxygen cost
As mentioned earlier, the oxygen cost of running is most likely higher than that of GS exercises, which makes cross training an attractive option. Running and cycling are two common forms of cross training. To get the most out of cycling you need some skill to recruit maximum muscle mass, whilst running is more intuitive in terms of oxygen cost. The main thing beginners tend to not do during cycling is pull up – which flexes the knee and hip, resulting in less muscle recruitment and a lower oxygen cost. In the average person cycling results in roughly 90% of the oxygen cost of running, however, in trained cyclists this can be reversed. So if you enjoy cycling and work on your skill (pull up during each rep) it will be a useful training tool. Additionally, adding arm motion to your cycling will increase your muscle recruitment and oxygen cost to a comparable level to that of running, making it a useful option for non cyclists with old lower body injuries. The take away here is that if you want to optimise your cross training you can work on your cycling skill and/or add arm motion to your cycling, or going running. At the end of the day it comes down to the individual’s needs, program and injury history.
Strength
Combining strength and endurance training has been found to inhibit optimal gains in strength and power long term. This is not an issue for GS and you need both, however running has been found to interference greater than cycling, possibility due to the increased muscle damage. For example, if you have tendon injuries or your weakness is strength, and endurance is your better quality, then cycling (or no cross training) may be the better choice. That being said, running is a great choice if you need to improve your endurance and if your body is up to it. I hope this helps you to make an informed decision regarding the form of cross training you use.
Extra reading:
Muscle and tendon interaction during human movements.
http://www.ncbi.nlm.nih.gov/pubmed/12150568
The Effects of Strength Training on Muscle Architecture in Humans
In vivo human triceps surae and quadriceps femoris muscle function in a squat jump and counter movement jump.
http://www.ncbi.nlm.nih.gov/pubmed/11138584
Architectural Changes of the Biceps Femoris Long Head after Concentric or Eccentric Training.
http://www.ncbi.nlm.nih.gov/pubmed/26460634
Concurrent Training: A Meta-Analysis Examining Interference of Aerobic and Resistance Exercises
http://journals.lww.com/nsca-jscr/Abstract/2012/08000/Concurrent_Training___A_Meta_Analysis_Examining.35.aspx
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