The XPO Trainer- Push Sled and Mobility

Crossfit legend Kelly Starrett uses the XPO push sled for rehab after total knee replacement

If you remember, back in November, we honored Crossfit legend Kelly Starrett and shared how instrumental he was in getting the XPO rolling from a prototype to a piece of equipment being pushed all over the U.S. Recently, Kelly mentioned to us how instrumental the XPO Trainer has been during his rehab for his total knee replacement! We were intrigued and wanted to hear more. And after visiting with Kelly, we knew we'd been given a mobility 101 lesson - it's too much good info not to share it with you! Kelly is a wealth of knowledge about mobility, and we learned so much more than just how he's pushing his way back to 100 percent with his brand new knee!

When he's not busy rehabbing his knee, Dr. Starrett is the co-founder, head coach, physical therapist, chief tinkerer, and movement optimist at The Ready State. The Ready State began as MobilityWOD in 2008. And for over a decade, they have pioneered new methods to help athletes with their movement, mobility, and recovery by offering a mobility training program. 

But The Ready State and mobility are not just for Olympic or pro sports athletes. Kelly and his team specialize in showing people how they can take care of their bodies themselves - whether that's improving power and wattage or working on positioning, or just getting out of pain. They believe that every human being should know how to move and be able to perform basic maintenance on themselves. 

The Basics of Mobility

First, the basics. What is mobility? 

We define "mobility" based on two components.

1 - You should be able to put your body into any pose or shape that is normal for a human being. You need to have the raw and full range of motion to do what your body needs to do. But having access is not enough. 

2 - You need to actually be able to achieve those positions in real life. In other words, you need to have the motor control skills to actualize your complete range of motion.

Historically what we saw when people talked about range of motion or flexibility (2 words we tend to steer away from) was lots of static stretching and/or low-level foam rolling. But that wasn't moving the ball. Many athletes didn't understand the components of movement and the positioning and shapes the body should be able to get into.

Even at the highest levels of sports performance, the best practice standard was that we'd work really hard, we'd break and get injured, back off, and then hope we got a little further next time.


We decided to look at the bookends of your position and talk through the physiology and way the human body works. We agreed on a normative range of motion and realized that if you don't spend time in those positions loading those tissues, you won't have access to that.

Mobility and the XPO Trainer - how do those work together? 

We've been doing this for over a decade, and in that process, we've come across and are exposed to a lot of tools that we can use to load the body. Load the tissues. Load positions.

And then I discovered the XPO Trainer. I actually still have the original prototype of the XPO. I feel like the huge advantage of the XPO (and what I like most about it) is that it scales across any age and any cohort. The fact that my daughter, my wife and I can all use the same load and same machine is pretty amazing.

The XPO Trainer is a sled that allow me to do things and put the body in positions to load tissues specifically for strengthening, which might be hard to do otherwise. It's one way I can get moms and dads and kids and athletes to spend more time loading the hip in a hip extension. It's a loaded, slower version of sprinting mechanics, which we could all use more of. 

Other bonuses - it's so quiet. It's so easy to use.

I really feel like if every family owned an XPO sled, we could reduce things like foot problems, plantar fasciitis problems, and even back pain!

For recovery and rebuilding mobility after your total knee replacement, how did you utilize the XPO Trainer?

When we're talking about restoration of position and tissue, the body works this way. You have to load tissues in order for those tissues to express themselves at a cellular level. So your tendon to be a tendon, you have to load it eccentricallyisometrically, and concentrically. You have to load it all three ways; otherwise, it's not a really tendon; it's a pseudo tendon.

When we're looking at essential movement patterns, walking and being able to drive off a single leg like you were in a big lunge or hopping across a creek on one leg is a pretty foundational position if you want to be able to run or walk or sprint.

All of this comes into play after a total knee replacement!

What's amazing about the XPO Trainer is that we can basically use it to modulate this fundamental position – this position that is a requisite to be a human. I can use the XPO as a pseudo crutch to offer some support, and I can begin to appropriately load those tissues on that leg with the hip in extension like in a walking pattern, all at the appropriate speed.

I love tools that scale across cohorts and athletes. In the first week after total knee replacement, I was walking around the block, and the XPO allowed me to lean in and challenge those positions. But because I had the two handles which acted as a stabilizing device, the XPO allowed me to work a little more on the physiology. 

The XPO sled has been part of my healing process all the way from week one to now month seven based on the simple ideas of progressive overload. All I've done is progressed from walking to waking a little faster, and now I'm able to add some dynamic load and speed and the XPO meets me right where I am. Don't worry; the faster you go, the harder it gets! But reversely, it's such a great machine because you don't have to be fit or need to be very strong, and it can be used to work on positions to load.

After you've completely rehabbed your knee and are now "Ready to Run," how does the XPO come in to play with your workouts?

I own the original XPO sled, and I have one of the new XPO sleds. They're in high rotation. As I heal and rehab, I'll just continue to up it more as the XPO allows me to have very different stimulus.

For me, one of my secrets is that I saw the truth and beauty of the XPO sled over a decade ago and immediately understood its power and impact on my life. I've been using it for a decade, and that's part of the reason I feel like I'm so functional as I approach 50 years old.

My benchmark workout on the XPO is an 800m hill that I push that is very steep. We do repeats on the hill. Getting back to doing that at my speed is one of my benchmarks for recovery. I have to be able to load that foot pushing the machine all the way up, connecting to something and the XPO is that thing. 

In this patterned position, there aren't a ton (besides running) of great ways to load up. You can do it in splits and lunges, but when we look at people's total movement language, loaded hip extension exercises (not extending the hip like standing up from a squat but having your knee and your foot behind your butt) aren't used or appreciated or loaded often enough. In the overall landscape of strength and conditioning fitness, that is probably the position in which we spend the least amount of time.

What sets the XPO apart from other sleds?

We know people like to grind, and we can certainly grind with the XPO. But one thing you can not do on other prowler-like devices is push at a high cadence because it's too heavy or light. The XPO is nice because it'll meet you at your mobility and strength, and capability, but we can also be running and introduce higher cadence, more impulse loading. 

So instead of just pushing and grinding, we use the XPO Trainer to do a lot of our running technique training. Because that individual is pushed up against a wall (in this case the wall is the 2 XPO handles), we can introduce to high cadence turnover – 90 contacts per minute on the right side or 180 on both sides (the minimum threshold for running). In this case, the XPO is a restorative device for runners and for people trying to normalize after injury or surgery because you can run with the XPO at 90 cadence, and you can't do that with any other device. It allows us to do very controlled running and introduce that impulse speed load. 

The XPO mile is an example of that training. We have a mile loop in our neighborhood (we call it the XPO mile), and you run it with a friend. As you run the mile pushing the XPO, you trade-off turns. You run, and the second your cadence comes down below 90, you're done, and your partner picks it up.

How often do you use the XPO Trainer personally or with clients?

Sometimes we're looking for high physiology, low skill cardiorespiratory demands (the assault bike, rowing machine, and skier are great examples). These are great monostructural pieces. But often, we want to use cardiorespiratory demand to challenge your positions. For example, if you run and do kettlebell swings, the kettlebell swings are harder after running because you have to manage your metabolic and cardiorespiratory demand load. 

So one of the tenants of our program is to challenge robustness of position with fatigue. Typically it's just challenged with load and volume (ie: do two more reps and heavier). But the options to have people appropriately loaded while also challenging their ability to manage the load by breathing hard are few. Running can do that, but usually, when people fatigue, you see poor running mechanics. 

With the XPO Trainer, I'm able to have a very unique stimulus when the hip comes into extension, and I'm in a running-like pattern. Yet because I'm holding on and pushing on something, I've reduced the skill load, but I can still maintain the significant and real cardiorespiratory demand stimulus that I'm after. 

This is why I use the XPO sled all the time – I still get the high physiology, less skill aspect of a workout, but clients are loaded, they're not sitting on a bike or rower, and they're getting the hip into extension, which is what more people need.

Wow! So much good information! To sum it up, we loved how Kelly wrapped up our "lesson."

I will have an XPO sled in my life for as long as they make them! It seems to last FOREVER!