When It Comes to Treadmill Intervals, Which Is Better, Speed or Incline?

HIIT Interval training produces amazing results. You may have tried Studio Three’s Torch, Shred 415, Barry’s Bootcamp or Orangetheory Fitness; all of these studios utilizes treadmills in their HIIT-style classes. The intense treadmill intervals promise to tone, build endurance as well as burn some serious calories. These classes switch between sprints and incline drills. Everyone has one they prefer over the other (mine is speed work) but I’ve always been curious, what is better for you, speed or incline?

Let’s take a step back. What exactly is HIIT? High intensity interval training (HIIT) alternates short periods of intense activity with less intense activity called recovery. Benefits range from increased endurance and metabolism to better heart health to major after-burn effects (the amount of calories you burn about two hours after your workout).


I know I can’t be the only one who dreads hearing my trainer say “Alright, let’s take it up to a 12%.” Inclines simulate running uphill – the higher the percentage, the tougher the “hill.” As it turns out, inclines are amazing for building muscles. Running at an incline activates the calves, hamstrings and glutes more than running on a “flat road” (0% incline). According to researchers at the University of Georgia, running uphill activates nine percent more muscles each stride compared to running at the same relative intensity on level ground. Just make sure you aren’t holding on to the sides, you lose out on a lot of the benefits, including stabilizing those abs.


Speed work training (also known as sprints) involves putting in maximum effort for a short period of time. Sprints are one of the most efficient exercises for fat loss. Sprints train your body to burn fat for energy, preserving muscle glycogen. Speed work is also one of the best ways to build endurance. Pushing it to your fastest speeds will amplify your oxygen uptake which helps increase the time it takes you to fatigue.

As always, make sure you are comfortable with your current treadmill use before adding hills and/or speed. Both inclines and speed work can be added to a walking treadmill workout, too. Even though they both have varying benefits, one thing is for sure – your mental toughness will grow stronger with ether one!


Endurance Move

About Rachel Mitz

The self-diagnosed work-out-a-holic, Rachel Mitz can be found all around Chicago, staying fit when she isn't crunching numbers as a director of corporate finance for a commercial real estate company. Chicago area bred and University of Illinois alum, Rachel works hard and plays hard so her daily workouts are her chance to connect with her mind and body. Rachel keeps it exciting by creating up a lineup of both fun and challenging morning workouts from personal training sessions, to boot camps, to spin classes or runs along the lake front (she just completed her first marathon in October). For fun, you can find Rachel trying new restaurants, traveling, volunteering with her favorite middle schoolers at San Miguel or enjoying a glass of red wine and fro-yo.