The Quest for Speed - Stride v Cadence
As the season progresses, most of us are seeking more speed.
The basic mathematics of running speed is pretty simple.
Speed = Stride length x Strides per minute
So more speed requires either longer paces or more of them per minute (called cadence) or a combination of both.
Higher Cadence or Longer Strides
So which should you go for? Studies show that as most recreational athletes trying to increase their speed during a race, increase their stride length.
Interestingly most recreational athletes have a cadence of around 160 to 170 paces per minute while top endurance athletes have a cadence of 180 to over 200. On the other hand, studies of top athletes have shown that there is no absolute correlation between cadence and speed.
Does this mean that the jury’s out on the subject? Not really; we just have to look at the basic physics.
Increasing stride length
One of the reasons us mere amateurs increase stride length to gain extra speed is that it’s easier than increasing cadence. The problem is that there are only two ways to increase stride length, push off harder with the back leg or reach further forward with the front leg. Doing the former is difficult while the latter is comparatively easy.
When you reach forward with the front foot, it will hit the ground in front of you. The basic mechanics mean that the impact is slowing you down; when you think about it, you will realise that to stop yourself quickly, you actually put your foot out in front of you. Having slowed yourself down, you then have to pivot over the front foot, which involves raising the weight of your body over that pivot point.
In addition, your foot cannot give you forward propulsion until it is behind your centre of gravity; it can push but it cannot pull!
Obviously, this is a huge waste of energy, but it’s worse than that. Inevitably with the foot forward, you increase the impact on the heel which sends a shock wave up the leg, through the ankle, knee, hip and back joints. This is exacerbated further by attempting to extend the leg you straighten it and lose the impact dampening effect of the slightly bent knee. This increases the tendency to injury and is particularly fatiguing.
So what about increasing stride length by a harder push-off. To do that requires delivering more power in the glutes, hamstrings and the calf muscles. Curiously, however, the first thing to do is relax and stretch the quads. To produce more power, your back leg has to extend further behind you and tight quads restrict that. Actually, you will probably find that lengthening the quads immediately results in a longer stride.
Obviously, if you maintain the same stride length and increase the cadence, you will move faster; increase from 160 to 180 and you’ll be going 12.5% faster which is 7.5 minutes saved in every hour.
Regrettably, it’s not as simple as that since increasing your cadence will inevitably tend to shorten your stride – but not by the same % so you will see significant gains even if you do nothing else.
However, one of the reasons that recreational athletes have a lower cadence and a tendency to heel strike naturally is their underlying body posture. Watch amateurs at the local running track and you will see a most of them running with at least a slight bend at the waist a downward-looking head. And as a training session progresses, this becomes more pronounced.
Now watch the top-flight athletes. Head looking forward not down, hips thrust slightly forward, body largely straight but leaning forward. They are actually angled at the point at which, were they standing still, they would overbalance.
This slightly out of balance posture naturally encourages you to increase the cadence
Now consider the geometry of the run. The front leg naturally strikes the ground under the body’s centre of gravity. The knee is slightly bent and you are landing on the mid-foot
Compare this with the lengthened stride:
- As the foot strikes, it is not slowing you down
- It is in a position to start giving forward propulsion immediately
- You don’t have to lift your weight over the front foot
- Your trailing leg now naturally extends further behind you
- There is no shock wave going up your leg
In fact, you are now using the tendons in your legs to do the job for which they are intended; absorb the impact and return the energy as you move forward.
All of which means that the reduction in stride length is likely to be minimal and the gains in speed are potentially huge.
That’s it then – for more speed increase the cadence
Oh, were it that simple? Unfortunately, it really will take a little work.
Next month we will take a look at the long term process of increasing cadence but in the short term you can just work at it. First, get the posture right, then increase the cadence.
You will find two effects have an impact:
Increasing the cadence will increase the heart rate and you will tire more quickly. This will take you a month or so to adapt to so don’t expect to go out tomorrow and do complete training sessions at the higher cadence. However, when you are racing you can use the higher cadence approach for that sprint finish – lengthening the stride is like pressing the accelerator and the break at the same time.
You will be asking your calf muscles to do considerably more work than they have in the past and putting more strain on them as the Achilles starts doing its proper job of absorbing the impacts as a spring should.
Work ou what your current cadence is (if your watch counts it for you use it if not use a stopwatch and count) Initially set your self a target of an increase of about 10%. Then plan to increase your cadence in small steps – raise it by no more than 5 steps at a time. Even then do not attempt to do an entire session straight off at the higher rate, try a minute of fast before dropping to your original and gradually change the proportions.
You would benefit from some strength and conditioning work on those muscle but that can probably wait till the winter.