Why Do My Workout Shoes Have Grooves? The Everyday Benefits of Siping and Slicing

When it comes to running shoes, there’s more technology at play than meets the eye—or foot. While I’ve spent almost 4 decades as a runner, including my collegiate years where I ran in whatever brand was provided, I was surprised to learn about a fascinating technique called siping or slicing.

Why should your running or walking shoe be flexible? The human foot has 33 joints and is comprised of 26 bones and over 100 muscles, ligaments and tendons. I’m always telling clients that your feet and shoes are your base of support. Side note, sometimes you need to walk around barefoot to help the muscles in the feet remain strong and mobile but that’s a whole different blog post. When it comes to running or walking shoes, we often focus on the brand, cushioning, or overall fit. This post explores a different way to thinking about the function of your shoes.

The joints in your foot and ankle are designed to articulate, to absorb shock and to propel the body. When these joints are immobilized or restricted, their function is lessened and thus the foot does not absorb shock as well or propel the body as efficiently. In fact, rigid shoes tend to make one run or walk inefficiently and have more up and down movement in their gait cycle, therefore wasting considerable energy. The foot will proceed in the direction of least resistance, so if the individual has issues with pain due to excess motion medially (overpronation) or laterally (underpronation), it is sometimes beneficial to create medial or lateral resistance but this making the shoe stiffer does not fix the problem. Siping may help!

Have you ever wondered about those grooves, cuts, or slices on the outsole of your shoes? This seemingly minor feature, known as siping or slicing, is a deliberate design choice that can have a significant impact on your performance, comfort, and even injury prevention.

About five weeks ago, curiosity got the best of me when several clients and one of our trainers mentioned they’d had their shoes “siped.” I was embarrassed to admit I hadn’t heard of this technique before, despite my extensive background in running and fitness. I even reached out to my former high school coach, a veteran runner still actively coaching, and he was equally in the dark. It felt like I’d stumbled onto a hidden gem in the running world. Don’t worry I have video of a shoe expert talking about this below.

What Is Siping?

Siping involves making small, precise cuts or grooves on the sole of a shoe. This technique is often inspired by tire technology, where similar patterns are used to improve grip on wet or uneven surfaces. The grooves help your shoes flex more naturally, enhancing traction and responsiveness during movement.

In some cases, shoe owners can have siping added post-purchase to optimize the flexibility and performance of their footwear further.

Everyday Benefits of Siping

1. Improved Traction: The grooves provide extra grip on wet, slippery, or uneven terrain, making them especially beneficial for runners who train outdoors year-round.
2. Enhanced Flexibility: Siping allows the shoe to bend and flex with your foot, leading to a more natural gait cycle. This is crucial for avoiding stiffness or discomfort during long runs.
3. Shock Absorption: By allowing the shoe to distribute pressure more evenly, siping can help reduce impact forces on your feet, knees, and hips.
4. Durability: While siping increases flexibility, it also prevents premature wear in certain areas of the outsole, extending the life of your shoes.

Why Might You Consider Post-Purchase Siping?

For some runners or walkers, siping can be customized to address specific needs. For instance:

• If your current shoes feel too rigid, siping can improve flexibility.
• If you struggle with traction in certain environments, additional grooves may provide better grip.

The Science Behind Grooves and Movement

Research shows that footwear design directly influences gait mechanics and injury risks. By mimicking the natural movement of the foot, siping helps reduce strain on the plantar fascia, Achilles tendon, and other key areas. Additionally, siping can improve energy efficiency by allowing smoother transitions from heel to toe during a stride.

What to Watch Out For

While siping can be beneficial, it’s essential to approach it with care and if you need to wear arch supports in them like me then you must listen to your body:

• Shoes with excessive or improperly placed grooves might lose structural integrity or wear out faster.
• Adding siping post-purchase should be done by a professional who understands foot mechanics and shoe design.

This practical feature can make a world of difference in how your shoes perform, making it a worthwhile consideration for both seasoned runners and everyday walkers especially many of you whose hip or feet mobility is decreased and have adjusted their gait.

Determined to learn more, I visited Greenville Running Company on a Saturday morning. Jeff Milliman holds a U.S. Patent in running shoe design and has been involved in the running shoe industry for 42 years…He was awarded the “Golden Shoe Award” from Runner’s World magazine for helping thousands of runners to avoid injury and perform better. Additionally many years ago he was a nationally ranked runner. Armed with a pair of shoes and my phone, The above captured video of the owner explaining the siping process while demonstrating it on my newly purchased pair Watching the precise cuts being made to improve the shoe’s performance was fascinating.

For someone like me, who’s worn many brands and tested the evolution of shoe technology over the years, this opened my eyes to the customization possibilities beyond just selecting the “right shoe.”

My Experience with the Siped Shoes:

I was excited to test out my new running shoes with this innovative customization. I visualized myself running effortless like a gazelle. However, my first workout not even a running bout brought an unexpected lesson—and a stark reminder of how responsive my body is to even minor changes.

Let me back up for context. During my visit to Greenville Running Company, the staff had me go through a thorough evaluation process. I stood on a foot scanner with each foot individually, and Jeff, the owner, examined my feet while I stood barefoot. We discussed my long history of foot issues: flat feet, childhood corrective braces, bunion surgeries, and my reliance on custom arch supports. He did ask where I had tightness in my muscles in which I said calves and upper hamstring. He also asked about any injuries. I failed to mention that 15 years ago I had some SI joint issues but it had been so long ago and controlled with exercises and footwear I failed to mention.

Jeff asked if I’d ever tried going without the arch supports. I had, off and on, but always ended up needing them again. Still, I was open to trying this new approach. With my siped shoes, a new brand to me (Innovate), a composite fiberglass insert Jeff had patented, and no arch supports, I was ready to experiment. I also made it clear to him that my body tends to react strongly to even small adjustments.

Fast forward to my Monday workout. I followed my usual program, which I had been consistent with for four weeks, as I utilize the changing workout programs (8-12 strength training exercises and movements or each program twice a week) every 6 weeks or 12 workouts for muscle balance and avoid plateauing. I began with five minutes on the rowing machine, light stretches, a set on the leg curl machine for hamstrings, and then moved on to shoulder lateral raises with weights I’d lifted before.

But then, it happened. As I was stabilizing my body, specifically my pelvis to lift heavy dumbbells, I felt a sharp, searing pain in my sacroiliac (SI) joint, located in the pelvis. I immediately recognized what had happened—thanks to my background in Human Anatomy, which I’ve studied multiple times. The absence of my arch supports, coupled with the new shoes and fiberglass insert, had thrown off my body’s alignment. My low back went from a S curve to Flat instantly.

The pain was so intense I had to lower myself to the floor and remain hunched over for a few minutes. Determined to finish my workout, I pushed through with modifications and even attempted a 2-mile jog outside, hoping the motion would realign my pelvis. Unfortunately, it didn’t fix things.

For the next 2.5 weeks, I was in constant discomfort. Everyday activities—getting in and out of the car, putting on socks, sleeping—became excruciating. I relied on SI joint-specific exercises and therapy to recover.

In hindsight, while this experience was painful I prefer to take a positive spin on it. It forced me to make meaningful adjustments to my running form and put my arch supports back in the shoes. This limited the flexibility of the siped shoes past the arch to the heel but I need that stable. I then decided to record and analyze my stride on the treadmill from a side view and back view. I noticed that my motion had become more vertical, with a longer stride than I used in college likely from too stiff of shoes I had been training in. Shortening my stride and reducing up-and-down motion brought me closer to my collegiate running form, which minimizes pressure on the pelvis and reduces jarring impacts on the body and lowers risk of injuries.

The Lesson: If you’re considering siping or any significant change to your footwear or supports, proceed with caution and listen to your body. Make gradual adjustments, especially if you’re trying new inserts or ditching custom supports. And always remember: proper form is key, both in running, walking, lifting or any physical activity and in life.

Now that I’ve discovered it, I’ll definitely keep it in mind for myself and for our Energy Fitness clients who are always looking to improve their performance or comfort.

So, whether you’re a casual walker, a competitive runner, or someone just trying to stay active, exploring techniques like siping might just give your shoes—and your stride—the upgrade you didn’t know you needed.

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