Raising the incline on a treadmill simulates walking or running uphill, which increases how hard your muscles and cardiovascular system work without requiring you to move faster. At just a 5% incline, your body’s energy cost jumps roughly 52% compared to flat walking. At 10%, it more than doubles. That means you can burn significantly more calories, build more lower-body strength, and get a harder cardio workout all at a slower, more comfortable pace.
How Incline Affects Calorie Burn
The calorie increase from incline is steep and measurable. Research on walking mechanics found that the metabolic cost of walking rises about 52% at a 5% incline and about 113% at a 10% incline compared to walking on a flat surface. In practical terms, if flat walking at your pace burns roughly 300 calories per hour, that same pace at 10% incline pushes you closer to 640 calories per hour.
The reason is straightforward: your body has to fight gravity with every step. On flat ground, you mostly move yourself forward. On an incline, you’re also lifting your body weight upward. That extra vertical work demands more oxygen, more muscle engagement, and more fuel. The ACSM’s metabolic equation for treadmill walking accounts for this by multiplying your speed by the grade, meaning even a modest incline at moderate speed adds a meaningful bump to intensity.
One important caveat: those calorie estimates assume you’re walking without gripping the handrails. When researchers compared supported and unsupported incline walking at 10%, they found that holding the rails and leaning backward dropped energy expenditure so much that it was no different from walking unsupported at 5%. Simply resting your hands on the rails while staying upright didn’t cause the same problem. The takeaway is that if you’re going to use incline for calorie burn, avoid hanging onto the front bar and leaning back, because you’re essentially erasing the benefit of the incline.
Which Muscles Work Harder
Incline shifts the workload toward the muscles on the back side of your legs, collectively known as the posterior chain. Your glutes, hamstrings, and calves all have to work harder to propel you uphill, while your quadriceps handle a relatively smaller share of the effort compared to flat walking. This is one reason incline walking has become popular for people who want to build their glutes without heavy squatting.
Hamstring activation increases noticeably with grade. EMG studies on 10% incline treadmill running show hamstring activity reaching roughly 49% of maximum voluntary contraction at moderate speeds, which approaches the activation levels seen in dedicated hamstring-strengthening exercises. Your calves also take on extra load because your ankle has to push off more forcefully on each stride to drive you uphill. Over time, this can build endurance and strength in the lower leg that flat walking simply doesn’t demand.
Cardiovascular Effects
Incline is one of the most efficient ways to raise your heart rate without running. In one study comparing flat and inclined running on a treadmill, going from 0% to 7% incline increased heart rate by about 12 beats per minute and boosted oxygen consumption by roughly 15%. For walkers, the effect is even more pronounced relative to effort: brisk walking at a steep incline can push your heart rate into the same training zone as a flat jog, making it a viable alternative for people who find running uncomfortable or unsustainable.
This is partly why incline walking has gained traction as a cardio strategy. You get a high calorie burn and elevated heart rate while moving at a pace that’s easy to maintain for 30 to 45 minutes. Your breathing gets heavier, your heart works harder, and you accumulate training volume for cardiovascular fitness, all without the pounding that comes with faster speeds.
Impact on Your Joints
One of the biggest practical benefits of incline is that it increases workout intensity without increasing joint stress. Research on kneecap joint forces found no significant difference in peak stress between level running and incline running. That’s a meaningful finding: you’re doing substantially more work, but your knees aren’t absorbing more punishment per step.
This makes incline walking or running particularly useful if you’re recovering from a knee issue, carrying extra body weight, or simply trying to protect your joints over the long term. Instead of running faster on a flat belt to burn more calories, you can walk at an incline and get a comparable or even greater metabolic effect with less impact force per stride.
Effects on Your Achilles Tendon and Ankle
Walking on an incline stretches your Achilles tendon more than flat walking does. A study on treadmill walking at a 10-degree incline found that just 10 minutes of graded walking significantly lengthened the Achilles tendon and improved ankle flexibility (specifically, the ability to pull your toes toward your shin). Before walking, the tendon measured about 20.6 cm on average. After the incline session, it stretched to about 21.7 cm when measured on an inclined surface.
This is generally a positive effect, especially for people with tight calves or limited ankle mobility. The incline naturally puts the tendon through a greater range of motion on each step, essentially functioning as a dynamic stretch. That said, if you already have an irritated or inflamed Achilles tendon, jumping straight into steep inclines could aggravate it. Building up gradually, starting at 3% to 5% and increasing over weeks, gives the tendon time to adapt.
Fat Burning at Lower Intensities
Your body uses a mix of fat and carbohydrates for fuel during exercise, and the ratio depends on intensity. At moderate effort levels, treadmill walking produces a lower respiratory exchange ratio than higher-intensity cycling at the same perceived effort, meaning a greater proportion of calories come from fat. Walking at a moderate incline sits in a sweet spot: hard enough to burn a lot of total calories, but not so intense that your body shifts entirely to carbohydrate fuel.
For people whose primary goal is fat loss, incline walking at a pace where you can still hold a conversation tends to maximize the percentage of calories coming from fat while still keeping total calorie burn high. This doesn’t mean incline walking burns fat “better” than running in absolute terms, since higher-intensity exercise still burns more total calories per minute. But it does mean you can sustain incline walking for longer sessions with less fatigue, which often adds up to more total work over the course of a week.
How to Use Incline Effectively
If you’re new to incline training, starting at 3% to 5% at your normal walking speed is enough to feel a noticeable difference. Most people find that 8% to 12% at 3.0 to 3.5 mph is a challenging workout that’s sustainable for 20 to 30 minutes. Inclines above 12% are intense and tend to shorten your stride, which can feel awkward and lead to compensations like gripping the handrails.
Keep your torso upright and take natural strides. Shortening your steps is fine, but avoid hunching forward or locking your arms on the side rails. If you need the handrails for balance, a light touch with your fingertips is enough. Swinging your arms naturally adds to your calorie burn and helps maintain proper walking mechanics.
Mixing incline intervals into a treadmill session works well too. Alternating between two minutes at 10% incline and two minutes at 0% to 2% keeps your heart rate elevated while giving your calves and glutes periodic recovery. Over time, you can increase the incline, lengthen the work intervals, or add speed to keep progressing.