Running Mechanics Series: Cadence (Part 1)

Running Mechanics Series: Cadence (Part 1)

In my next series, I will be covering running mechanics and how to improve them. I’m also going to include a post about the difference in running mechanics between road and trail runners – something which I plan on doing my doctorate on. Lastly, I’ll be covering some content on how to improve your running mechanics to make sure you’re the best runner you can be.

 

Before we get into cadence or “stride frequency” (SF) – our first topic in the running mechanics series – it’s important to understand why it is a topic of importance in the first place. It is widely accepted that amongst athletes who exhibit similar maximal oxygen uptakes – it is their relative energetic cost (i.e. their running efficiency or economy) that will separate their performance (De Ruiter et al. 2014). Additionally, experienced or well trained runners tend to have lower or more efficient running costs/economies than their novice counterparts. SF is considered to be a contributing factor to the running economy of most athletes and is therefore very well researched. However not all research suggests that running economy is as affected by SF as we might think it is. Be that as it may, there are many articles out there showing scientific evidence for this relationship, and myself as a runner and coach strongly believes that SF has a determining factor in my running economy and in injury prevention.  

 

SF is a much more complex topic than one might think. Let’s start off with something relatively simple. Some researchers present SF as steps per minute (think mid to high 100s in the research discussed below), and some present it as strides (half as much as how many steps per minute, so think <100). It’s important to distinguish this as some research presented here uses steps per minute (spm) as their indicator of SF, while others use strides. This complexity is further apparent when observing stride frequency under fatigue. While it is expected that stride frequency will decrease with fatigue, there have been conflicting reports on this phenomenon as some researchers found stride frequency to decrease under fatigue, and others found stride frequency to increase (Hunter & Smith, 2007). There are many possible reasons for these conflicting results which include everything from the type of running one is doing (steady vs interval running), the distance of your run, and even inter-individual (between individual) differences, with some runners being more sensitive to fatigue than others (Hunter & Smith, 2007).

 

When thinking of the leg as a spring (mass-spring model), the stiffness of the leg (joints, muscles, and tendons) often has a determining factor in stride frequency with those with greater leg stiffness often having a greater stride frequency (Hunter & Smith, 2007). As such, leg stiffness decrements during exercise can have a negative effect on stride frequency and change one’s running gait as running continues. We also know that typically the metabolic cost of running increases as the run gets longer (which may have something to do with this change in running stride frequency and gait), and thus it is important to be able to maintain leg stiffness (and subsequent stride frequency and metabolic cost) throughout your run.

 

A study by Hunter and Smith (2007) required runners to perform a 60min steady-state run at 96-99% of their 10km race speed in order to fatigue these runners. The researchers found a clear relationship between stride frequency and leg stiffness throughout the 60min run. However, what they found was that only half of the runners demonstrated a significant decrement in stride frequency, while the others maintained their stride frequency throughout. They concluded that the self-optimization of stride frequency continues throughout the duration of a run as the metabolic cost of the run increases.

 

It is true that we all have a natural or preferred stride frequency (Hunter & Smith, 2007). This self-selected stride frequency (self-optimization) is likely dependent on a number of factors. These factors include, limb length, gait, height and weight, balance and coordination, foot strike pattern, shoe type and everything in between. Even gender has a role to play in stride frequency with women presenting with typically higher stride frequencies to men (even when normalized to standing height) which could be due to anthropometric differences, greater ground forces by men, or differences in muscle fiber type distribution (Chapman et al. 2012).

 

In a study by Kendell et al. (2017), the investigators sought to determine whether variability in stride frequency was minimized at this “preferred stride frequency”. The investigators got the runners to run on a treadmill at their relative preferred stride frequencies (PSF) and then at +-5% PSF, +-10PSF, and +-15PSF. What the investigators found was the stride variability continued to increase the further the athletes moved away from PSF – and significantly so for each 5% increment. It is therefore thought that one of the reasons we runners have our preferred stride frequency is to avoid having inconsistent or variable running patterns. This might be an inherent protective mechanism to avoid getting injured, and running more efficiently (think Born to Run and chasing the gazelle).

 

In a study by Cuevas et al. (2017), a similar test was performed on a treadmill where both well trained and recreational runners at +- 5% and +- 10% of their PSF. Interestingly, the well trained runners’ running economies all got worse when moving away from their PSFs, while the running economies of the recreational runners improved as their respective stride frequencies increased – although not significantly so. The authors speculated that recreational runners could benefit from increasing their stride frequencies by 5 – 10%.

 

Similar findings were demonstrated by De Ruiter et al. (2014) where experienced runners were found to have PSF closer to their optimal stride frequency (most economical) in comparison to their novice counterparts. In this study, novice runners were found to exhibit a PSF of 77.8 strides per minute with an optimal stride frequency of 84.9 strides per minute. Their experienced counterparts selected a PSF (84.4 strides per minute) much closer to their optimal stride frequency of 87.1 strides per minute. This suggests that not only do experienced runners have an absolute higher stride frequency, but that novice runners can benefit from increasing their PSF by up to 10% in order to reach their optimal stride frequency (OSF).

 

For those trail runners out there, it is interesting to note that OSF does not appear to change for individuals running up or downhill (Snyder & Farley, 2011). In general it is accepted that both a SF too far below or above the OSF will have a detrimental effect on running economy. This is because when the SF is too low, the muscles have to work too hard to produce power (metabolic cost of running increases), and when it is too high, the cost of force production and internal work increases (Snyder & Farley, 2011). Interestingly, it is found that cost of muscle work increases when running up hills or mountains, and that much higher forces must be produced by hip extensors when running uphill. Therefore because both the muscle work and force production required to run uphill increases when trail running, the cost of running increases as well, which subsequently maintains the OSF (a balance of muscle work/force production and cost) (Snyder & Farley, 2011). As such, trail runners should try to maintain a consistent SF regardless of present incline/decline.

 

Optimizing stride frequency may also have a positive effect on running related injuries (Morgan et al. 2016). In a study on recreational runners training for a half-marathon, 42.9% of the runners presented with a stride frequency of less than 163 steps per minute, while 32.1% of the runners had a stride frequency of greater than 168 steps per minute. The group of runners with the lower SF had injury rates of 66.7%, while the higher SF runners had an injury rate of 22.2%. This suggests that runners with a SF of >168 steps per minute are at less risk of getting a running related injury (Morgan et al. 2016).

 

There seem to be some misconceptions about what ones exact cadence should be. I think that some of these misconceptions stem from people not having full understanding of scientific evidence, but still proceeding to pass that message on. For example in all of the studies mentioned above, the researchers present an absolute optimal stride frequency – for example 84.9 and 87.1 for recreational and experienced runners respectively (De Ruiter et al. 2014) – which, to someone who doesn’t understand scientific research, seems that all runners should aim for somewhere between 85 and 87 strides per minute. However, this mis-perception drives the idea that simply because a small amount of runners should be running at this cadence – all runners should do so. It doesn’t take into account their unique running qualities such as; limb length, gait, height and weight, balance and coordination, foot strike pattern and shoe type etc. mentioned earlier.

 

Another example of this misconception of research can be seen when analyzing the Morgan et al. (2016) study. Some people may draw a conclusion that all runners should keep their SF at >168 spm to have a better chance of avoiding injury. However, it is not clear whether if these runners (regardless of what their absolute SF is), could all have benefited from an improved relative SF to avoid injury. In other words, regardless of whether your PSF is 160 or 180, if you improve that by 5 – 10%, are you at less risk of injury? This is why the researchers suggest that future research should investigate the effect of a pre-training intervention on stride frequency aimed at improving SF of runners with a SF of < 162 spm to see if that can be a protective factor against injuries.

 

The take home message from all of this research should rather be: if you are a recreational runner (trail or road alike), you most likely stand to benefit by increasing your running cadence by 5 – 10%. Trained runners have either learned to do this through self-optimization (Hunter & Smith, 2007), or because they have undergone deliberate cadence training at some point, and are therefore much more likely to have a preferred stride frequency closer to their optimal stride frequency. Any cadence changes should be treated with caution, and runners should attempt to change their cadence gradually over time, rather than all at once. For example, if your current cadence is 70 strides per minute, start off by increasing your cadence to 73 strides per minute (roughly 5%), and then try and maintain this for several consecutive runs and weeks before further increasing your cadence.

 

In my next post on running mechanics I’ll discuss some ways of improving your stride frequency safely and effectively to improve your running mechanics. Let me know your thoughts on the topic above and I’ll gladly write a post on them too. Happy running and keep striding forward!

 

References:

 

Chapman, R. F., Laymon, A. S., Wilhite, D. P., et al. (2012). Ground contact time as an indicator of metabolic cost in elite distance runners. Medicine and Science in Sports and Exercise. P. 917-925.

Cuevas, G. A., Reeder, M., Alumbaugh, B. (2017). The effect of stride frequency on running economy in collegiate and recreational runners. Medicine & Science in Sports & Exercise.49(5) p. 637-638.

De Ruiter, C. J., Verdijk, P. W., Zuidema, M. J. (2014). Stride frequency in relation to oxygen consumption in experienced and novice runners. European Journal of Sport Science. 14(5) p. 251-258.

Hunter, I., & Smith G. A. (2007). Preferred and optimal stride frequency, stiffness and changes with fatigue during 1-h high-intensity run. European Journal of Applied Physiology. 100 p. 653-661.

Kendell, S. G., Bailey, J., Joerger, J., et al. (2017). Is variability of stride frequency a factor that determines preferred stride frequency during running? Medicine & Science in Sports & Exercise. 49(5) p. 132-135.

Morgan, J., Franco, R. L., Harrison, K., et al. (2016). Stride frequency and injury rates in recreational runners training for a half-marathon.  

Snyder, K. L., & Farley, C. T. (2011). Energetically optimal stride frequency in running: the effects of incline and decline. The Journal of Experimental Biology. 214 p. 2089-2095.

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