TLDR:

🏃🏻‍♀️ Run hard, recover smart – Improving in running is about balancing stress + recovery + adaptation (easier said than done).

👀 Tracking mileage is only a small part of the picture – Not all miles are created equal! Mechanical load (the stress on your muscles, tendons and bones) is what matters.

🔬 Biomechanical load monitoring is an exciting frontier - Quantifying the physical stress your body experiences during running unlocks opportunities for improved injury risk mitigation and performance optimization.

📱 Technology makes it possible - With a small sensor in each shoe, we can monitor mechanical load continuously and on every step, providing a valuable decision support system for better, smarter training.

A Missing Link

On the surface, the formula for improving in running is simple: Stress. Recover. Adapt. Improve.

The best runners master the art of pushing their limits without pushing too far. They train hard, recover well, and stay consistent—year after year. Sounds simple, right?

For most, figuring this out is a frustrating game of trial and error. Push too much, and you break. Pull back too much, and progress stalls. And too often, that trial and error ends in a sidelining injury.

If you've been there, you know the feeling. You’re training hard, making sacrifices, feeling fitter and faster. It’s addicting.

Then, seemingly out of nowhere, you can’t run. Your fitness slips. That daily dose of mental clarity? Gone.

If this sounds familiar, you’re not alone. Studies show up to 79% of runners get injured, a number that hasn’t budged in decades. Why?

Well, injuries are complicated. Training volume and intensity, biomechanics, nutrition, hydration, sleep, injury history, and stress all play a role, and every human is unique.

But we know this: one of the main causes of setbacks and injuries is training your body isn’t prepared for, commonly referred to as “training error”.

The good news? Avoiding these errors isn’t about luck or genetics. Smart training is a skill - one every runner can learn. Unfortunately, most of us are forced to learn through trial and error. We break to find our limits.

No matter your experience or ability, (the right) stress + (the right) rest is the formula to continually improve. Finding this balance starts with properly measuring and managing what matters most: training load.

And until now, we’ve been missing a critical piece of the picture.

Training Load and Capacity

Training load is the total stress you put on your body through running. It accumulates with every step, every workout, every week of training. Your capacity is your body's ability to handle this load. It changes over time, increasing as you train.

Every workout, every step causes tissue damage, breaking your body down.

With enough recovery your body repairs itself, adapting and growing stronger. As a result you’re able to handle greater training - more volume and intensity.

When training load exceeds capacity, performance suffers and injury risk increases.

We can bucket training load into two main types:

1. Physiological: The body’s physiological response to training

2. Mechanical: The physical forces applied to our muscles, tendons, and bones

The last decade of innovation has brought good tools to monitor physiological load. Smartwatches and other wearables make it easy to monitor metrics such as heart rate and heart rate variability.

But until now, runners haven't had an effective way to measure mechanical load - the physical pounding our bodies take while running. This mechanical load provides a crucial stimulus for tissue adaptation and influences both performance gains and injury risk.

And you can’t manage what you don’t measure.

The result: a massive blind spot, making it extremely challenging to strike the right balance between training and recovery.

Training Load Is Not Just Mileage

For most, weekly mileage still rules the realm. Mileage has been the primary way runners monitor training load, and many follow guidelines such as “don’t increase weekly mileage by more than 10%.”

But while easy to measure and follow, research shows these methods are oversimplified and ineffective.

“It is increasingly evident that running distance should not be the sole training metric, as it can often misrepresent and significantly underestimate training stress and resulting adaptation.”
- Moving Beyond Weekly “Distance”: Optimizing Quantification of Training Load in Runners, Dr. Max Paquette et al.

Let's say that again: mileage alone is an oversimplified and incomplete measure of the stress your body is under.

Not all distance is created equal. An obvious example: racing a 5K leads to greater mechanical load than running 5K easy, in large part because faster running requires greater force production.

Some training load scores capture physiological load by taking into account heart rate or rating of perceived exertion (RPE), but still lack an adequate measure of mechanical load.

We believe there’s a better way.

A New Frontier

Every time your foot strikes the ground, you apply force. In response, the ground exerts an equal and opposite Ground Reaction Force (GRF), helping propel your body upward and forward. This force can reach peak magnitudes of up to 5x+ your body weight (with certain joints, bones, muscles, and tendons absorbing force upwards of 15x your body weight). Your body has to be capable of dealing with and recovering from these forces, which are influenced by factors such as speed, surface type, incline/decline, shoes, and biomechanics.

Higher GRF magnitude is associated with greater mechanical load*.

*Note: we are referring to “global” mechanical load, in other words the load experienced by your body as a whole. The amount of load each tissue absorbs varies depending on several variables. Measuring tissue-specific load (e.g. the load on the achilles tendon or the tibia, for example) is an exciting area of opportunity.

Research has also shown a non-linear relationship between load magnitude and the number of safe “loading cycles” (in running, a “loading cycle” = a step).

-Modeling Overuse Injuries in Sport as a Mechanical Fatigue Phenomenon, Dr. Brent Edwards

This is really important, something many runners miss. It means even small increases in load can quickly increase injury risk.

“Achilles tendon fatigue tests from Wren et al. illustrated that, on average, a tendon loaded at a strain of 6% will fail after approximately 1400 cycles, whereas a tendon loaded at half that (i.e., 3%) will fail after approximately 93,000 cycles. In other words, a 50% decrease in strain magnitude would correspond to a 6600% increase in fatigue life.”
- Cumulative Metrics of Tendon Load and Damage Vary Discordantly with Running Speed, Dr. Colin Firminger et al.

How often do you catch yourself running just a little faster than you should without really noticing? This can lead to a small increase in load magnitude, in turn adding up to a significant effect on injury risk.

Historically, getting GRF data required running in a lab on expensive equipment like force plates or instrumented treadmills. Technology makes it possible to calculate this outside of the lab on every step, by instrumenting footwear with sensors.

We can now arm runners with a complete picture of their training load. Runners who use it gain a clear advantage — enabling more personalized decisions about how much and hard to run, and how to balance recovery to maximize performance while minimizing injury risk.

The Avelo Methodology

Avelo shoes are each embedded with a sensor that calculates ground reaction force on every step. With its team of leading researchers and coaches at the forefront of running science, Avelo has developed two valuable metrics:

Impact Score: A measure of the cumulative mechanical load from all steps on each run.

Resiliency Score: Analyzes mechanical load over time to provide a daily score out of 100 that indicates if the athlete is adequately balancing training and recovery. There are four contributors:

• Acute Load: Identifies sudden spikes in load

• Chronic Load: Monitors training load trends over the prior weeks and identifies extended periods of heavy load without adequate recovery

• Training Variability: Looks for unusual patterns in day-to-day training load. Some variability is healthy. Too much can stress the body in ways it isn’t used to or prepared for

• Overall Load: Evaluates the accumulation of all the athlete’s historical training to determine whether their load is within a safe level given their training history

What makes the Resiliency Score unique from other recovery and readiness scores is that it includes a more precise measure of mechanical load.

Let’s go back to our hypothetical example of a 5K Easy run vs. a 5K Race and illustrate:

The 5K race results in an 80% increase in Impact Score despite distance being exactly the same.

With these metrics, runners are armed with valuable and objective insight about the true stress from training.

To make this actionable, Avelo provides daily and weekly mileage budgets to progress with the goal of minimizing the risk of training errors.

Conclusion and Our North Star

The last decade has brought tremendous advancements in wearable technology. We know so much about our bodies; our heart rate, heart rate variability, sleep, stress, recovery, and more.

Injury prevention is a challenging and elusive endeavor, and this article is not meant to suggest it is solved simply. We strongly believe that training load monitoring is the foundation of any system aimed at helping runners make smart training decisions, and continuously monitoring mechanical load outside of the lab provides a leap forward.

There are many variables that influence performance and injury and Avelo’s models will become more predictive and personalized over time, with a vision to incorporate additional data (heart rate, HRV, sleep, nutrition, hydration, etc) to provide athletes with a comprehensive picture.

Measuring every step from arguably the most crucial location of all - the place where our body meets the ground - unlocks opportunities for new discoveries.

One of the challenges running studies face is the inherent constraints of traditional research. Most studies are relatively small and conducted in a lab where runners are monitored on a treadmill for a few minutes.

While valuable, these snapshots miss the complete picture of what happens out in the world - on the roads and trails - making it challenging to draw strong conclusions.

We imagine a different approach. Our vision is to conduct the largest running study in history. Avelo runners will be able to opt in to participate in research. Working with our community and leading researchers, we aim to use this unprecedented dataset to discover new insights and help runners around the world run stronger, faster, and more resiliently.

Happy running.

—Royi Metser
Founder & CEO
Avelo Running

References

van Gent RN, Siem D, van Middelkoop M, van Os AG, Bierma-Zeinstra SM, Koes BW. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. Br J Sports Med. 2007 Aug;41(8):469-80; discussion 480. doi: 10.1136/bjsm.2006.033548. Epub 2007 May 1. PMID: 17473005; PMCID: PMC2465455.

Paquette MR, Napier C, Willy RW, Stellingwerff T. Moving Beyond Weekly "Distance": Optimizing Quantification of Training Load in Runners. J Orthop Sports Phys Ther. 2020 Oct;50(10):564-569. doi: 10.2519/jospt.2020.9533. Epub 2020 Aug 1. PMID: 32741325.

Edwards, W. Brent. Modeling Overuse Injuries in Sport as a Mechanical Fatigue Phenomenon. Exercise and Sport Sciences Reviews 46(4):p 224-231, October 2018. | DOI: 10.1249/JES.0000000000000163

Firminger CR, Asmussen MJ, Cigoja S, Fletcher JR, Nigg BM, Edwards WB. Cumulative Metrics of Tendon Load and Damage Vary Discordantly with Running Speed. Med Sci Sports Exerc. 2020 Jul;52(7):1549-1556. doi: 10.1249/MSS.0000000000002287. PMID: 31985576.

I’m Royi, Founder & CEO of Avelo. Here’s what I know—

Running is beautiful. It's pure and freeing. It rewards us with health, clarity, community, and a sense of accomplishment matched by few other activities.

Over 600 million people around the world run, and in recent years millions more have discovered the power of the sport. A second running boom.

I’m one of those people.

In 2021, a year into the Covid pandemic and for the first time in my life, I found myself unhealthy and overweight. I'd always considered myself young and fit, but the results of a blood test kicked me in the ass—my cholesterol was sky-high and my biological age was 10 years older than my actual age.

Three days later I was signed up for my first marathon. That’s the day I became obsessed with running.

6 months later I crossed the finish line. Turns out running really is great for you! My markers improved and my health was back on track.

About that marathon—I hit the wall at mile 21. Hard. But I had a blast and left energized for more. How do I conquer the distance? Can I run it faster?

So I ran another, but finished slower. Another wall. More fuel to figure it out.

It was through this mission to improve that I realized—

I had deep visibility into my physiology—my heart rate, HRV, sleep, stress, recovery, whether a training session is “productive” (thank you Garmin but I don’t believe you).

Incredible technological progress provided me with a profound understanding of my body.

And yet, I felt I had untapped potential. Opportunity to train even smarter. To reach my goals faster, with less trial and error.

And like so many, I fell into a frustrating cycle of injuries. Achilles tendinopathy. Stress reaction in my foot. Plantar fasciitis. One step forward, two steps back.

Something felt missing, and I had questions.

Despite running’s popularity, most of us aren't taught how to do it right. We just... lace up and go, left to figure it out along the way. Why?

Am I running too much? Not enough?

Running — in fact, all human movement — starts from the ground up. Why am I still flying blind about what’s happening down there?

My phone and watch are smart. Why are my shoes, my most important equipment, still dumb?

Simple questions. Frustratingly hard to answer.

I dove into the research, spoke with leading scientists and coaches, and saw an opportunity.

To measure what happens at the most crucial point of all — where our feet meet the ground. On every step. Every run. Continuously.

To unlock insight about force and form, and to use this insight to help runners run faster, stronger, and more resiliently.

And ultimately, to advance human health and performance.

I believe running well is a skill like any other — that can and should be coached.

That each of us is unique, and that data is the key which unlocks true personalization.

I believe a world where injuries are the exception, not the rule, is possible.

Where runners of every level have access to insights previously reserved for elites.

Where if you love to run, you can do it for the rest of your life.

So we’ve assembled a team to build the world’s smartest running shoe. A coach on your feet. It knows your running, and guides you to accomplish your running goals.

A few years ago this sounded like science fiction.

But here we are — with a team of ex-Nike executives, an Apple award-winning product designer, software and hardware engineers, data scientists, and 8 PhDs at the forefront of running science — inspired to have a positive impact on millions’ health and wellness through the sport.

It’s just the beginning of our journey. If this mission resonates with you, your support would mean the world to us. You can join our waitlist at www.avelorunning.com to follow along.

Let’s run.