Running is a simple sport, right?
It certainly seems to be.
After all you just lace up your shoes and go for a run!
If you are like me, you are constantly trying to improve your performance. To do so you work very hard, putting in the required time and effort.
You include a wide variety of workouts including Long Runs, Tempo runs, Intervals, Hill and Track work. You may even periodize your training throughout the season and calendar year to optimize adaptations and “peak” at the right time.
The question I ask myself is
“Am I being efficient or am I employing the shotgun approach to training?”
I am trying to uncover the basic physical, physiological and mental characteristics that are most highly correlated with performance and will therefore help me the most in my quest for improved performance.
The complete list of these attributes is extensive. We may not yet even know or understand them all, but technology today is offering a deeper insight into running than we ever had in the past.
GPS watches, smart chest straps and running power meters have opened a whole new frontier by providing data to runners that was the exclusive realm of research labs just a decade ago.
One of the metrics I have been pondering is Ground Contact Time (GCT), the time your foot is in contact with the ground during every stride cycle.
I want to know if and how it’s related to other aspects of your running, its trainability and resulting effects on your running performance.
Running, in its simplest form, can be viewed as a series of one-legged forward jumps.
There are two main components that determine how fast we go: how fast we turn our legs over, also known as Cadence, and how hard we push off the ground or Push off Force.
Together, these combine to provide us with power which is defined as Force x Velocity. For the action of the run we can substitute Cadence with Velocity and Force is the force with which we push off the ground or Push off Force.
The availability of run power meters that provide a variety of data, including Ground Contact Time and Power, allow us to investigate relationships among factors related to running we could only speculate were correlated in the past.
Most runners and coaches have “known” intuitively that pushing off with more force, spending less time on the ground with each step and a higher cadence result in faster running, but they had no data to confirm it or investigate the most effective methods to improve it.
Now I can compile the data and show an athlete this relationship, track it over a training cycle and make more accurate predictions of race performances in the future.
Cadence is often self-selected, individual and speed dependent.
It seems to me that most non-elite runners tend to have a cadence that is lower than what may be optimal for speed and efficiency.
I am not sure what the root cause of this is, but it is far more common to see a cadence lower than the 90 steps per minute standard than higher.
As the chart below shows, working on improving your cadence will likely yield positive results in your running.
Push Off Force
Push off force is the second factor determining our power output and will determine how far you travel while in the air during each step.
We can estimate Push off Force as the Power you generate divided by the time your foot is on the ground.
The units would be Watts/millisecond.
Whether you generate more power in the same amount of time or the same amount of power in less time you must be generating more force for each unit of time you spend on the ground – your Rate of Force Production increases.
This means you are pushing harder off the ground and it turns out that it correlates highly with how far you travel in the air with each step or Stride Length.
It stands to reason that the farther you travel with each step, the faster you will be moving overall. As can be seen in the chart below the data supports it.
It also turns out that the higher your Cadence the higher your Push off Force, as seen below.
It is a wonderful thing that both Cadence and Push off Force can be improved through training!
It further stands to reason that if Cadence and Push off Force can individually improve your running speed, then improving BOTH should have an even more powerful effect.
Let us call Push off Force multiplied by Cadence the Rate of Force Production per Step.
You can improve this metric by either pushing off harder, turning your legs over faster or both. As expected, this metric correlates positively with Pace.
Ok, now we have empirical evidence supporting what most runners have instinctively known all their lives – if you move your legs faster while pushing harder you will run faster.
Why is this important?
Having proof through data that is easy to obtain and create allows you, or your coach, to isolate the factors that are holding you back. Further, it allows you to train and monitor your progress to confirm you are improving.
Ground Contact Time
Ground Contact Time tends to be shorter in faster runners than in slower runners, so we would expect to see positive correlations with all factors that relate to faster running.
It makes sense that if you can shorten the amount of time you spend on the ground with each step, you would increase the speed at which you move forward.
Compound this over thousands of steps and you really have something.
If you were to run a 3:30 marathon with an average cadence of 180 steps per minute (90 per foot), you would strike the ground 37,800 times during your race.
If you could reduce your Ground Contact Time by 20 milliseconds you would improve your marathon time by 12 minutes and 36 seconds.
This assumes you maintain both your Stride Length and push off Power constant.
To put this improvement into context, a typical Ground Contact time for a non-elite runner is about 240 milliseconds, so we are talking about just an 8% improvement.
In the charts below, you can see that Pace and Power are highly correlated with Ground Contact Time in a positive manner.
The shorter the GCT, the faster you are moving. When you run fast you are spending less time on the ground with each step.
The same is true when you generate more power – you run faster. You tend to push harder when you are sprinting than when you are jogging.
It is not surprising then that GCT is also highly positively correlated to Power as well as Cadence. In order to run faster while spending the same time on the ground, you must be pushing with more force and/or turning your legs over faster – remember that Power = Force x Velocity.
It should come as no surprise then that Rate of Force Production is positively correlated to Pace.
Of course, not all the power you generate gets channeled into moving you forward.
Since we exist in three dimensions we can move laterally, vertically and horizontally.
Only Horizontal Power propels us forward.
Vertical power causes us bounce.
A certain amount of elevation is necessary for forward motion to overcome friction with the ground, but too much is just wasted energy.
There is also a percentage of the power we generate that goes into maintaining our form and counteracting lateral or rotational movement.
Not surprisingly, when you look at the data, only Horizontal Power displays a positive correlation with Pace.
Vertical Oscillation and Vertical Power (the Power channeled into your bounce during each stride) display a negative correlation with running pace.
Not surprisingly, the more Power you “waste” maintaining your form either through poor running mechanics, or excessive bounce or fatigue, the slower you will run.
The chart below shows the relationship between the percentage of your power not being used to move forward and running pace.
Why is this important?
It is important because it addresses not just your fitness but your form, and by extension how efficient and effective you are at harnessing your mechanical effort and turning it into speed.
Elite runners have great form and technique - they have very little wasted movement, either vertical or lateral. Their Form Power as a percentage of total Power output is likely on the low end of the scale - most of the power they produce is channeled into moving forward.
You now have empirical evidence showing that if you waste less energy through good form while pushing harder off the ground in the direction you are intending to move, you will run faster.
With this knowledge, we can start looking at how effectively you use the power you produce in your running.
While Running Efficiency and Economy cannot be calculated solely from the data a Running Power Meter provides, as they can only be measured in a lab, we can calculate Running Effectiveness or RE.
RE is calculated by Dividing your Power by your Speed – how good are you at turning effort into forward motion?
It turns out that running is not such a simple sport after all.
While running consistently will no doubt improve your race times, utilizing the data and structuring your training to address any “weak link” you may have or simply to target metrics that will most benefit you as a runner, will amplify the effectiveness of each training hour you put in.
In todays’ world with our busy lifestyles, time is the most valuable commodity. Being as efficient as you can in utilizing it and maximizing the results should be every athlete’s goal.
Building on the evidence presented next we will delve into what are the factors that influence Running Effectiveness the most and how we can leverage training to improve them.
Stay tuned for part 2...