The short answer: walking uphill costs substantially more energy than walking on the flat at the same speed, and it increases the work done by the hip, knee and ankle muscles. Those two points are well supported. Several other claims on the earlier page were not: that regular incline walking "noticeably builds" glute strength, that it has "no impact," and the specific impact multiples compared with running.
The energy cost
The standard way to estimate the cost of treadmill walking at a given grade is the American College of Sports Medicine's walking equation. Oxygen use in millilitres per kilogram per minute equals 3.5 plus 0.1 times speed in metres per minute plus 1.8 times speed times the fractional grade. It applies to walking speeds of roughly 1.9 to 4 mph and can't be used for downhill walking, and it was derived from small samples, so it is only an estimate. Here is what it gives for 30 minutes at 3 mph (4.8 km/h) for a 75 kg person. The extra column subtracts what you'd burn sitting.
| Grade | METs (approx.) | Total calories in 30 min | Increase vs flat | Extra calories (above resting) |
|---|---|---|---|---|
| 0% | 3.3 | 124 | - | 86 |
| 3% | 4.5 | 170 | +38% | 133 |
| 5% | 5.4 | 201 | +63% | 164 |
| 8% | 6.6 | 248 | +100% | 210 |
| 10% | 7.4 | 279 | +125% | 241 |
| 12% | 8.3 | 310 | +150% | 272 |
| 15% | 9.5 | 356 | +188% | 319 |
The percentage increases are larger than the ones on the earlier page, which started from a higher flat-walking baseline; the steepest rows come out close to the old figures. The "12-3-30" routine popular online, which is 12% incline, 3 mph and 30 minutes, comes out at roughly 300 calories for 75 kg by this equation. We haven't found a trial of that routine, so we can't say more than that it is hard and the arithmetic is plausible. For the same method applied to flat walking, see how many calories walking burns. The earlier claim that a steep incline puts walking "in the same range as jogging" depends on the grade; we haven't compared them directly, so treat it as a rough comparison.
Which muscles work harder
An electromyography study (Franz and Kram, Gait & Posture, 2012) recorded leg muscle activity during level, uphill and downhill walking at different speeds. Compared with level walking, hip, knee and ankle extensor muscle activity increased to walk uphill, while only the knee extensors increased for downhill. That backs the idea that uphill walking recruits the glutes, quadriceps and calves more. What it doesn't show is a training effect. We couldn't find a trial showing that weeks of incline walking build glute or hamstring strength, so we've removed the claim that it does "noticeably," and the claim that incline walking improves your posture. If you want to build strength, see walking vs gym.
Joints and impact
The earlier page said running puts 2.5 to 3 times body weight through the knees while walking, even uphill, is 1 to 1.5 times, and called incline walking "zero impact" on the treadmill. We couldn't confirm those multiples from a primary source, so we've dropped the numbers. Walking involves vertical force peaks somewhat above body weight, and running's are higher, which is the real basis for calling walking lower-impact (walking vs running covers injury rates). But reviews of sloped walking report that it raises forces in the lower-limb joints compared with level walking, particularly at the knee, so "no impact" overstates it. If you have knee problems, ease in and check with your doctor or physiotherapist; walking and knee arthritis covers the evidence.
Downhill
Going down is not free. In the EMG study the knee extensors worked harder walking downhill, and the knees take eccentric load on the descent. The earlier advice to slow down, take shorter steps and consider trekking poles on steep descents is common practice. A treadmill avoids descents, which is a practical advantage if your knees object to them.
Using incline
This part is general advice, not trial findings. Start with a gentle grade, add steeper sections gradually, and build up over weeks, since calves and Achilles tendons work harder on a slope. The old page's schedule and its settings table, including the claim that 1 to 2% "compensates for the treadmill belt," had no walking studies behind them, so we have left them out. Holding the handrails is widely said to cut the effort, and the calorie estimates above assume you aren't leaning on them; if you need support, reduce the grade. Power walking is the other way to raise intensity, treadmill vs outdoor walking compares the two settings, and rucking adds load instead of slope.
Sources
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription: metabolic calculations for walking, as summarised here. engramkinetics.com
- Franz JR, Kram R. The effects of grade and speed on leg muscle activations during walking. Gait & Posture. 2012;35(1):143-147. sciencedirect.com
- Lower limb joint work and joint work contribution during downhill and uphill walking at different inclinations. Journal of Biomechanics. sciencedirect.com
- Effects of hiking-dependent walking speeds and slopes on spatiotemporal gait parameters and ground reaction forces: a treadmill-based analysis in healthy young adults. Applied Sciences. 2024. mdpi.com
Correction note: an earlier version of this page gave a calorie table for incline walking, said regular incline walking noticeably builds glute and hamstring strength, said running puts 2.5 to 3 times body weight through the knees against 1 to 1.5 for walking, called treadmill incline walking zero impact, said incline walking reinforces better posture, and gave a treadmill settings table including a 1 to 2% grade that compensates for the belt. We could not support the strength, posture, impact-multiple and settings claims, so they were removed, and the calorie table is now rebuilt from the ACSM walking equation. The equation is an estimate with known limits, and we did not read the Franz and Kram paper in full. This article is for informational purposes and does not replace medical advice. This is general information, not medical advice.