Let’s take a pace of 4.5 mph, and then ask yourself if jogging this will yield more fitness benefits than walking this speed (which would be a very fast walk).
For most people, walking very fast feels like more work than jogging the same speed.
This is especially true when an incline is involved (hill outside, or treadmill without holding on).
Why does fast walking seem harder than slow jogging at the same speed?
There’s a very logical explanation for this: the gastrocnemius muscle in the lower leg. This is the main calve muscle.
At around 4.5 mph, jogging makes more efficient use of the gastrocnemius, better use of it than while walking.
This was shown by Dr. Gregory Sawicki and Dr. Dominic Farris, biomedical engineers at North Carolina State University.
The researchers used ultrasound imaging, high-speed motion-capture methods and a force-measuring treadmill to investigate the “gastroc” muscle’s behavior during jogging/running and walking.
This powerful muscle makes adjustments based on whether a person walks or runs.
The gastroc “speeds up,” i.e., alters its length more and more rapidly as a person walks faster and faster.
However, this correlates to decreasing power as a person walks faster: less efficiency.
Now, when people start jogging at around 4.5 mph, the gastroc “slows down,” that is, the length changes more slowly.
This yields more power while working less: higher efficiency. This explains why it’s easier to run at 4.5 mph for 10 minutes than it is to walk at this same speed, unless a person is a trained “race walker.”
This phenomenon can be applied to slow incline walking vs. same-speed jogging.
“The muscle can’t catch up to the speed of the gait as you walk faster and faster,” says Dr. Sawicki.
“But when you shift the gait and transition from a walk to a run, that same muscle becomes almost static and doesn’t seem to change its behavior very much as you run faster and faster, although we didn’t test the muscle at sprinting rates.”
A fitness walking program should include fast walking, and a jogging program should include it as well.
Lorra Garrick is a former personal trainer certified through the American Council on Exercise. At Bally Total Fitness she trained women and men of all ages for fat loss, muscle building, fitness and improved health.