Running Economy and Power
When you are running at a constant speed, energy production and energy loss
are in balance, i.e. your muscles produce energy at the same rate as it is lost
due to mechanical friction, heat radiation, and air resistance.
Two people running at the same speed might have very different
energy consumption rates, even if they weigh the same.
An athlete who just started running might use 400 Watt
at the speed where an experienced runner uses just 200 Watt.
Peter and Eddie
Imagine the following two athletes:
-
Peter Power:
- weight: 75 kg
- maximum aerobic power: 1000 Watt
- inexperienced runner (prefers swimming and cycling)
- bad running economy (uses 1000 Watt at 7-minute/mile pace)
-
Eddie Economy:
- weight: 75 kg (like Peter)
- maximum aerobic power: 500 Watt
- very experienced runner (running is the only sport he likes)
- very good running economy (uses 500 Watt at 7-minute/mile pace)
When Peter and Eddie run together, they are equal training partners.
Because of his bad running economy, Peter uses twices as much energy,
but this is no problem for him, since he can produce twice as much energy.
For both runners, 7-minute/mile pace is the fastest sustainable pace.
In a race, both would finish in the same time.
Uphill and downhill
Peter and Eddie go running together. When they run at 80% of their maximum
aerobic power, they use 800 Watt and 400 Watt, respectively.
Now they encounter a hill. To maintain their pace, an additional effort
of say 150 Watt is required. This is precisely the problem with hills:
regardless of running economy, the same amount of extra energy is required
from all runners!
So what happens next?
Peter increases his effort to 950 Watt (95%) which is still within his limits,
and maintains his pace.
Eddie increases his effort to 550 Watt (110%) and fails after a while.
He has to slow down by 10% to bring his effort down to 500 Watt (100%),
while Peter runs on and wonders what's the matter with Eddie.
But it's not over yet. The next mile is downhill and both runners can
decrease their effort by 150 Watt while maintaining their standard pace.
Now Peter runs at 650 Watt (65%) and Eddie runs at 250 Watt (50%).
To get his revenge, Eddie now suggests to double the speed and starts
sprinting downhill at 500 Watt (100%). Peter tries to follow, but soon
realizes that he cannot sustainably run at 1300 Watt (130%), and falls behind,
wondering again what's happening here: Eddie just seems to be flying downhill.
Headwind and tailwind
A similar situation occurs when Peter and Eddie run into a headwind
or are supported by a tailwind. Assuming Peter and Eddie are approximately
of the same size and shape, wind increases or decreases the required effort
to maintain the pace by a constant, just like a hill.
Therefore, headwind is an advantage for Peter,
and tailwind is an advantage for Eddie.
Treadmills
Running on a treadmill is equivalent to running with a tailwind
where the wind speed equals your running speed. (This is quite a
strong tailwind!) Therefore, on the treadmill, Eddie will be better.
A common myth is that running on a treadmill is easier because
you are actually running in place and don't propel yourself forward.
This is not true! Anyone who says that has not understood Einstein's
theory of relativity! When you run on a treadmill, you do propel
yourself forward - relative to the treadmill belt. And this is
what matters.
Running economy and power
Runners with little power and good running economy are more sensitive
to hills and wind. Runners with powerful muscles and bad running economy
are affected much less, so relative to others, they are best
when conditions are tough (incline, headwind) and worst when
conditions are easy (decline, tailwind).
Now ask yourself, whether you are more like Peter or more like Eddie,
and you will know whether you should work on your power
or on your running economy.
Training Methods
To improve your running economy or your power, you have to train
in a way that emphasizes the variable you want to improve.
This means that in order to improve your power, you should
add resistance, and in order to improve running economy,
you should add support.
Additional resistance can most effectively be overcome by additional power,
so your body will adapt by increasing your ability to generate it.
At the other end of the spectrum, when resistance is lowered
as far as possible, the remaining resistance can be overcome
most effectively by improved running economy, so your body
will adapt by adjusting your running form.
Eddie's Training Program - Improving Power
- Run uphill. Be careful: this is tough for your achilles tendons.
- Run into a headwind.
- Wear a weight vest.
Peter's Training Program - Improving Running Economy
- Run downhill. Be careful and use a very slight decline, since
the risk of injury is high. Also, you can easily develop shin splints from downhill running, so do not overdo it.
- Run on a treadmill or with a tailwind.
- Run on a treadmill strapped in a harness that supports say 25%
of your bodyweight.
Select the right program
Eddie's training program improves power, but slightly deteriorates your running economy. Peter's program improves your running economy, but your power will decline a little.
Overall, the improvement in the one variable will outweigh the decline of the other variable, unless you select precisely the wrong program for you.
This is what once happened to me: I did daily incline running workouts for four weeks. My running economy was bad when I started, but after the four weeks were over, my running economy was a mess. When I was running on the track, it looked like I was trying to run up a stairway and was always falling back down to earth with every stride, because the stairway wasn't there.
To select the right program for you, find out first what kind of runner you are. How do you do on inclines and declines compared to others? Your hill performance is a good indicator whether you are lacking power or running economy.
© 2005 Mark Dettinger
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