For beginners who have just started to run, whether it is on a treadmill or outside, going up an incline can be an intimidating progression. But the fitness world is obsessed with inclines. Run up a parking ramp, they say. Increasing the incline by 1% on the treadmill is another common progression. So it’s natural to wonder about the science behind these theories.
I had a minor knee injury a couple weeks ago. An experienced sports official advised me to run on an incline when I eventually start getting up to speed again. Why was he asking me to do something that seemed tougher? But as I found out, the science of the incline is rather interesting when it comes to injuries.
Multiple research papers, including one titled The Use Of Incline Treadmill Walking In The Rehabilitation Of ACL Reconstructed Individuals, published by the Steadman Philippon Research Institute, suggest that a 3 percent increase in treadmill incline reduces the impact that the legs must absorb by about 24 percent. That is a really large number in the context of returning from injury. Or even minimising it.
An incline angle increases knee flexion and adds more to the quadricep and hamstring functional activity. “The increased knee flexion allows the hamstrings a better mechanical advantage to restrict anterior tibial displacement and protect the integrity of the joint capsule and ACL graft,” the paper says.
But let’s say you’re not injured, especially that seriously. Running on an incline will engage the muscles differently. And probably also engage more muscles. That means trimming training time and increasing calorific output. It also means the body is relying on the posterior chain muscles, which can often feel left out without an incline.
“When you shift to incline mode, you’ll feel the posterior chain muscles working with each step. That’s why it’s common to hear people say their glutes and hamstrings are ‘on fire’ after walking up a hill. Strong posterior chain muscles can prevent injuries, improve posture, boost athletic performance, and help counteract sudden forces,” states a Healthline article on the benefits of incline walking. In this, it cites research published in the American College of Sports Medicine titled, Posterior Chain Exercises For Prevention and Treatment Of Low Back Pain.
How does all this happen though? It’s because your foot strikes the surface at a more gradual angle when you are on an incline. Walking enthusiasts, who are unable to run, or simply don’t want to, can particularly benefit from walking up inclines. A highly educational paper titled The Paradigm Of Uphill Running goes deep into the metabolic output an incline surface will put on the body. These are the parameters they tested during experiments: heart rate, heart rate variability, oxygen intake and blood lactate, metabolic cost, kinematics, ground reaction force and muscular activity. One of the findings was that a 2 to 7 percent incline increased heart rate by almost 10 percent when compared with running on a flat surface. It is simply a more wholesome workout and that hike will feel easier.
However, the claim of increasing the incline by 1 percent on the treadmill to mimic outdoor running might not be as scientifically valid as the other benefits. The Runners World website, which usually has an answer to most questions on running, puts it into the context of speed, so that seasoned and new runners can figure out whether they want to use the 1 percent calculation.
“At paces slower than 8 mph [12.87 kmph], no adjustment is necessary. Between 8 mph and 11.2 mph [18 kmph], a 1 percent treadmill grade provides the right adjustment. At higher speeds you will need at least a 2 percent grade to offset the lack of wind resistance. Don't worry if you choose to ignore your well-meaning friend's advice. You'll simply run at a slightly faster pace than you could outside with less effort. Consider it a confidence boost,” says the article, titled The 1% Incline Treadmill Debate.
The best way to approach this would be to switch between level and incline surfaces whether you are using treadmills, or running outdoors. There is a popular saying in the running world which makes it the most overthought and overtrained physical activity. Simplify it, enjoy it, and see how the body responds.
Pulasta Dhar is a football commentator, podcaster and writer.