When to Increase the Incline of a Treadmill (and When Not To)

I recently experienced a shocking change in my running preferences: I no longer dread the treadmill. What changed? First, the poor air quality left me with no other choice. Second, I stopped using the treadmill exclusively for speed training and started using it for hill running .

I admit, this change in my outlook was due to the trendy 12-3-30 “hot girl walk” workout. In fact, some of my favorite workouts are now done at walking pace on my Merach 450 treadmill at home. The key is the incline.

Whether you choose a higher incline or a higher speed exercise depends on your goals. I approach this decision from a marathon training perspective, but I know the motivation of many gym-goers: which option will help me lose weight?

The truth is, no single workout will guarantee weight loss. As my colleague Beth Skuerecki puts it , “You lose weight by consuming slightly less than you burn , measured as an average over a period of time. Exercise can help you burn more calories, but your body often compensates by burning fewer calories at rest , so you can’t just rely on walking on a treadmill to burn a certain amount of calories every time.”

However, if you’re looking at your treadmill display wondering whether to focus on speed or incline for a more effective workout, here’s what you need to understand to make your decision.

When to Take a Slope

By increasing the incline of your treadmill, you essentially simulate running or walking uphill. (And no, you don’t have to set the incline to 1% every time to simulate air resistance.) You might be tempted to hit “quick start” on your treadmill and run as fast as you can for 30 minutes, but here are reasons why you should focus on incline.

Creating an aerobic base

For marathon training, incline walking or easy jogging at 3-6% incline is invaluable for developing basic skills. The increased intensity strengthens the cardiovascular system while keeping the impact relatively low. For runners building an aerobic base, I would recommend 30-minute sessions at a conversational pace at a 4-5% incline.

Strength training without weights

Incline training is essentially weight training for your legs. Steep inclines work the glutes, hamstrings, and calves more intensely than running on flat ground. For marathon runners who have trouble fitting a gym session into their training schedule, 15-20 minutes of walking on a steep incline (8-15%) can provide an additional strength workout.

Active recovery sessions

On easy days between hard workouts, easy incline walking helps maintain the training stimulus while improving circulation and recovery. Variations of the 12-3-30 method work well here—challenging enough to feel productive, but easy enough not to interfere with your next quality workout.

Injury prevention

For minor injuries or after a break, incline walking is good for your cardiovascular system and reduces impact. The controlled environment of the treadmill also allows you to gradually increase intensity as you recover.

When to keep flat

It’s not all hills. I am a runner , after all. Having run thousands of miles training for 26.2 miles, I’ve learned that knowing when to run smoothly is just as important as knowing when to climb a steep hill.

Speed work and intervals

Sometimes adding incline to speed work can degrade your running form and make it harder to hit your goal pace. Runners doing real track-style speed work should generally stick to 0-1% incline. Unless you’re training for a hilly event (like Boston), your goal pace work should be done on minimal incline.

Focus Sessions Format

When working on running mechanics, cadence, or efficiency, running on a flat treadmill provides the most stable platform. Inclines can hide technique issues or even create compensatory movements that don’t translate well to running outdoors.

High Intensity Days

Incline training may be trending, but there’s still a time and place for focusing on VO2 max . Long runs and high-mileage weeks should prioritize time on your feet over intensity. Excessive incline can turn aerobic, core-building workouts into strength-focused workouts, which can lead to overtraining and poor recovery.

My personal tilt strategy

Having recently switched to the treadmill, I’ve finally started to approach incline work strategically rather than haphazardly. Here’s how I plan to integrate incline work into my training cycles:

• Base Phase: 2-3 weekly sessions at a moderate incline (4-6%) with conversational load, aimed at developing aerobic capacity and building strength.

• Preparation Phase: One weekly hill workout with steeper grades (6-12%) for shorter intervals, preparing the legs for the climbs on race day.

• Peak phase: Minimal hill work, except in preparation for a race. If your goal is a marathon with significant hills, work on those hills and inclines.

• Recovery Phase: Walking at a slight incline for active recovery using the 12-3-30 method to maintain fitness.

Bottom line

Luckily, incline and speed aren’t necessarily mutually exclusive. You can run uphill one day and train for speed the next. The key piece of advice for runners is that a slow but steep climb can be more beneficial than a fast one — and that applies to any of your training.

Remember: The best workout isn’t necessarily the hardest. Sometimes the most productive thing you can do is slow down, turn up the incline, and let time and consistency do the work. Other times, you’ll want to leave the incline button alone and focus on a real cardio workout that gets your heart pumping .

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