Is Running On Incline Bad for Your Knees?
Recently I’ve had a slew of clients tell me that their orthopedic physician has told them to stop running on inclines because it’s bad for their knees. Without being present for the entire discussion I have to assume that the person has knee pain and upon a short conversation with their physician, the doc learns they run on a treadmill and recommends no hills. The situation has caused me to look into the impact of incline training more specifically and truly ask the question: Is incline training bad for my knees?
The answer is an overwhelming NO! It’s actually quite the contrary—incline training is rather beneficial to your knees; for many people, and it can be a welcome alternative to flat road treadmill running. Here’s why: Biomechanics.
First, when it comes to impact, running downhill — notably when you’re leaning back too far or improperly positioned—puts tremendous stress on your knees. That same downhill posture is something I see frequently on runners on the treadmill. The head is up, shoulders back, and their legs extended in front of them to reach out for the belt as it comes toward them. There’s not much you can do about that when running outdoors in hilly terrain, but treadmill training is different. Even in its neutral position a treadmill defaults slightly downhill which is why trainers will always start by raising the incline. By adjusting your treadmill an incline of one or two percent you reduce the strain on your knees and the rest of your legs. The slight incline also helps your body position match more closely to your natural biomechanics if you were running outdoor.
Next, one of the most common issues I see with treadmill running is foot strike; specifically heel striking. When you run and land with your heel first you’re extending your leg and jarring the body. The knee is less flexed and more extended at heel strike, which may also stretch-out the knee ligaments. One study found that runners who sustained a knee injury during an ultra-marathon, ran with a smaller knee flexion range (less knee bend) when running uphill vs running downhill, suggesting that the knee joint may have been more extended, and therefore, the muscles and tendons of the lower leg may have been eccentrically stretched too much. This kind of high impact heel strike running results in excessive loading on the leg, and combined with muscle fatigue can get you tendon inflammation. Additionally, another biomechanical factor of heel strike running is the repetition of forefoot lifting, or ankle dorsiflexion. Dorsiflexion is performed by the tendons in the ankle and shin to lift or extend the toes. Poor dorsiflexion is the number one contributor to heel strike, and is one of the most common causes of lower leg injury, including tendinitis of the foot, patellar tendon (knee), and Achilles tendon (ankle).
Finally, overuse. It’s not uncommon to see runners step on the treadmill, hit the “go” button and pound away for an hour without breaking stride. As the body fatigues from continued use the first thing to go is form. In the outdoors your body would naturally slow down, but on a treadmill you can just zero in on that 8mph pace the machine has set for you and power through. This especially applies to running on incline where runners will increase their incline, but not reduce the speed to compensate. Incline and speed are offsetting intensities when treadmill training. As one goes up, the other should go down. The most common overuse injuries are shin splints, IT band syndrome, Achilles tendonitis, and Plantar Fasciitis. All of which wind up putting strain on the joints and increased discomfort in the muscles.
So what works to reduce your chances of injury during incline running? First you have to slow down. I tell clients all the time that in order to get faster, sometimes you have to go slower. Most runners measure success based on how far they can go and how fast. It’s no secret that working out at higher speeds and inclines burns more calories. But what you might not know is that if you only train for speed, you don’t burn as much fat as if you train for resistance via incline training. Recent studies show that incline training at speeds of 2-3 mph burns 30 more calories per hour and burns more fat overall than does running on a flat surface at 6 mph. That alone should give you reason to slow it down and pick up the incline. Next focus on your mechanics. When you slow down you’ll be able to think about how you’re running and what your body is doing. Focus on a slight forward lean while running like you would do outdoors. Keep your knees bent at all times to help absorb the shock and focus on landing properly on your foot! This helps ease the tension in the tendons in the knees. Finally, watch your mileage. Several studies have linked increased mileage with the risk of sustaining an injury, suggesting a threshold between 25 and 50 miles per week.
In the end, running on inclines is a necessary tool to strengthen the entire body. It adds power and can improve running efficiency. That means that you’ll be better able to cope with hills and steps and even require less effort to run on flat ground. Furthermore, incline sprints can be protective of knee injuries because they improve the stability of your trunk, pelvis and feet. When you run hills, your body naturally stabilizes through the trunk, pelvis and feet in order to optimize the effect of power generated in the legs. Your foot becomes semi-rigid when it strikes the ground, and the pelvis becomes level. This allows the leg power to translate more effectively into trunk propulsion. Hill sprints are high intensity sessions, so you can get bigger benefits from shorter training (time and/or distance). And the benefit of shorter training distances is that you can minimise your exposure to mileage, therefore reducing the risk of sustaining a running injury.
Be mindful of your own body’s needs—and consult your trainer or your physician—since knee stress increases at higher inclines and faster speeds.
