Sports Wearable Technology

 

Running cadence, like many stride parameters, is partially based on educated guesses and myths handed down over generations.

After a year of experimentation and careful documentation, I am confident that I have a strong argument to support the use of the RunScribe sensor system. Most coaches will gravitate to its cadence feature, but wearable devices are far more enriching than just measuring strides per minute. The array of metrics—such as contact time, pronation velocity, and even the symmetry feature—offers a lot of information that is enormously actionable.

This summary of my findings is perfect for any running athlete, not just an endurance sport participant. The reader will learn why most of the cadence hype is often just cheap, impractical advice. Instead of leaving the reader more confused or frustrated, this article will break new ground on the nuances that explain how to apply better development solutions to running technique.

The Problem With Defining Running Cadence

If you asked two coaches on the same track team, you could get two similar but different definitions of running cadence. Any sprint coach worth their salt will use the term “stride frequency” (a rate per second) in reference to their sprinters, while a middle distance or distance coach will likely refer to “steps per minute” (SPM). The pace, or speed of the race, usually determines how we label or measure the rate of steps or strides. This is the reason the mythical number of 180 SPM from Jack Daniels has confused and even injured athletes in the sport of running for years.

 

Now that foot sensors and other wearable devices are flooding the market, we are seeing a rise in injury rather than a rise in performance because of the poor application of step rate modulation. Like the barefoot phenomena that once hit the fitness market, the wrong person applying good intentions can cause injury and obstruct growth or improvement.

As a race becomes shorter, the pace becomes faster, thus increasing the rate of strides per second or steps per minute. Training, a process that accounts for different speeds and velocities below and above the race distance, will have a range of stride rates. The inconvenient reality of pacing in races and in training tosses the 180 SPM number out, creating a need to think about crude and sometimes inaccurate summaries of running. Cadence is a very rough guideline, as steps or stride patterns are more complicated than the number of footfalls there are in a specific amount of time.

Dictionary.com defines the word cadence as: “A rhythmic flow of a sequence of sounds or words.”

While a little bit heavy on the prose, I like this definition because it uses the words “rhythmic” and “flow.” I wrote about rhythm in the past because a few of my mentors found the concept and practice instrumental to athletic development. When referring to cadence for running, we can replace “sounds or words” with “strides” in the definition above to come up with a wonderful working definition for performance, and sometimes rehabilitation.

 

Being a sprint coach myself, I always favor using the shortest or smallest unit of measurement to aggressively visualize and communicate speed. You can think of a single lap race as a quarter-mile or “the 400-meter dash.” I always pick the faster definition because it tends to foster a commitment to speed rather than to conditioning. For the sake of this article, I will focus on stride frequency as a rate in seconds, but will switch on and off to steps per minute because some of my conditioning workouts for other sports last longer than a minute.

Who Can Benefit From Running Cadence Awareness?

It is my experience that any athlete can benefit from an awareness of their running cadence. Some athletes, like sprinters and those in team sports, need to address running mechanics. Cadence can help athletes by getting them out of lazy foot strikes and helping them land with favorable ground contact. Some writers have warned and educated readers on the hazards of “overstriding,” but to me, the term is a misnomer.

Any athlete can benefit from an awareness of their running cadence. Click To Tweet

Overstriding is more accurately articulated as excessive reaching out or opening up too far in front, as a longer stride could be an improvement in mechanical efficiency and performance. A good stride lands and propels the body in a way that transmits forces effectively through the ground without risk of injury. Slower rates tend to create excessive braking actions, so any method that reduces the foot from casting out makes a favorable change.

 

Running used as punishment or for volume-driven programs can, unfortunately, lead to a stride that encourages a lumbering recovery swing phase or a crashing slap to the ground from a survival jogging pattern. It doesn’t matter if the stride is long or short; poor landings to the surface will decrease cadence with an increase of ground contact time.

I will cover contact times in more detail and what happens during ground contact time later, as those measures reveal why cadence can be compromised. A clean stride has the benefit of providing both the power needs for performance and the mechanical efficiency that reduces the incidence of injury. Some athletes are born with beautiful technique and some can muster an effective stride, while others, unfortunately, have their running form ruined by overzealous coaches.

Exposing an athlete to different cadences is part of teaching them awareness of their rhythm and body. Cadence awareness is more than speed awareness or pacing: An athlete can do drills at walking speed with a fast rate or race with an reducing SPM, so it’s vital to know and learn the difference hands-on.

Simple rhythm is essential; athletes who run/do cyclical sports should invest in cadence training. Click To Tweet

Beyond video reviews, athletes have very poor options for biofeedback. Cadence awareness isn’t just for pure running; drills and other locomotive activities are an opportunity to build a foundation for athletes with the temporal coordination needs of controlling their cadence. Simple rhythm is so essential that all athletes who run or do cyclical sports should invest in cadence training.

Why Being a Great Runner Can Make You an Even Greater Sprinter

Many fast athletes can sprint, but to be a great sprinter an athlete needs to be able to run well. That’s why tempo running programs still succeed today. One of the greatest sprint coaches, the legendary Tom Tellez, was adamant that if fast athletes couldn’t run well, it would catch up with them down the road. I had recently phased out much of the running volumes and became a more purist type of sprint coach, but my personal meeting with Tellez in Houston changed my mind back.

One of my biggest mistakes was letting the masses convince me that talent was the reason running programs succeed in the U.S. and Caribbean. The athletes there are not just running off of talent; they have a sound training program.

Coordination adaptations at submaximal velocities have value beyond gross fitness and possible tendon adaptations. Being a solid running athlete at all speeds improves efficiency and increases global neuromuscular coordination, only if implemented carefully. High-velocity speed work is specific, but running slightly slower isn’t the doom and gloom many coaches worry about. Many people in the performance community share a fear of the conversion of fast fiber types slowing down and the resulting loss of power. The issue is not that running causes negative adaptations, but that too much running without high intensity work, or just too much running period, can break down anyone.

A good rule of thumb is that sprinters may not have to do quite the massive volumes that a Tellez program did in the ’80s and ’90s to be successful. Even if it’s just a few strides during warm down, a quality technique session done consistently is a game changer when all parties care.

 

Sprinting is natural, but running is more normal to the human species. Running programs that just hope athletes “turn it on” are not the best models for development, but they have enough athletes succeeding to influence others to repeat the process. The amount of running that is necessary is individual, but the athlete developing a sense for rhythm via cadence work is an effective way to cultivate sprinters with great genetics but less-skilled running.

Is Running Cadence Important for Stride Development?

When athletes, coaches, and sports therapists talk cadence, the assumption is that a simple change in frequency will improve running performance and perhaps reduce injury rates. Reinforcing what was stated earlier, a quick cadence will usually reduce the reaching (overstriding) that some athletes do when their strides are not compact. The assumption is that stride length is cut off, but many athletes who keep the stride mechanics efficient will have longer strides but keep their foot closer to the body.

One reason why this seems paradoxical is that contact length and stride length are not interchangeable:

• Stride length is the distance between each right and left foot contact during any period of running or sprinting.
• Contact length is the distance travelled by the center of mass during the entire foot contact period.

An easier way of visualizing this is to refer to stride length as the ground between contacts and contact length as the distance the pelvis travels during each step. Athletes who are taller are likely to have longer contact lengths, since it’s harder to generate rate of force with mechanically less advantageous levers. However, the trade-off for limb length usually offsets this, especially in the case of Usain Bolt. Higher frequencies, or an increase of cadence, are only valuable if performance increases over time. The promise of cadence is that a faster stride rate, due to higher turnover, improves the mechanical efficiency, increases the speed of the runner, and loads the body safer.

Many talented and fast runners have higher rates of stride frequency, but it’s about knowing which rates are ideal for each athlete and each velocity. The biggest problem with the 180 SPM number proposed by Daniels is that it’s not for everyone or for every speed. Still, a casual awareness and the starting point with norms are logical first steps, as some benefit from simple fine-tuning of stride frequency can help the average runner get better.

What Does the Science Tell Us About Running Cadence?

Research on stride cadence ranges from poorly designed summaries of recreational athletes to very sophisticated investigations of elite runners. Much of it is on injury patterns based on running cadence with general population runners. While the perfect study will likely never happen, when looking at the cadence studies it is important to look for two important elements: the level of athlete and population of the subjects. Look for clues in the author’s summary paragraph on how cadence correlates with their findings. The difference between causation and correlation is the reason many researchers, and then coaches, jump to conclusions later when the story behind the story is unclear.

 

Running cadence is simple and easy at first glance, so many coaches and athletes gravitate to it blindly. It will work for some athletes to simply be instructed to increase their frequency without preparing for the demands of the change or the root cause of their slower stride, but it will fail for the more advanced and faster runners. Cueing an active stride for higher rates of frequency works at slower speeds and sometimes faster speeds with less competitive runners, but elites need more physical and longer term solutions.

Research on cadence changes has been done on anatomical areas of the foot, ankle, knee, and even hip muscles, including muscle recruitment around those areas. Most of the research shows that small increases in step frequency help improve outcomes for both healthy and injured athletes, but most of the studies are with “participants,” meaning non-elites. Cadence isn’t magic, but just a small conscious boost to it can help load the body properly based on the current evidence.

What happens when the simple running cadence increase is not necessary or when injuries occur with a faster-than-normal cadence? The answer is not obvious, but running cadence has a limit to what it can do, and overtraining and other factors like surfaces and footwear all play a part in performance and injury patterns. Some athletes may have a good cadence, but they have other measures that need to be to changed or enhanced.

How Does RunScribe Measure Cadence and Other Stride Information?

The technology and sport science used to create the small RunScribe sensor kit is rather straightforward and elegant. Many systems are worn near the hip or wrist, and that choice is usually based on convenience, not data integrity. Direct measurement of foot strike by a wearable on the foot is not rocket science, but it’s hard to mount without some ingenuity.

The RunScribe can be placed behind the heel or on top of shoelaces, and the sensors inside the system collect the raw motions of the foot orientation in time and space. The data is filtered by algorithms, or calculations that detect specific milestones in running, such as ground contact and the small motions in the foot during stance. After collection and analysis of the information from the sensors, the patterns of the data are calculated again for summaries on the software side of the server, and displayed on the mobile or web app.

 

You need to know how the technology works, so that you are aware of what is just hype from companies and what is valid for coaches to use and trust. Data, be it a small snapshot in time or the accumulation of years of captured information, must be accurate and reliable or it’s a waste of time. The farther away the data source, the less true the information from the sensor is, sort of like that game of “Telephone” we all played as kids. Placing a sensor on the lower leg or thigh may get swing and some impact information, but it fails to get direct motion of the foot complex. Many systems can get an estimate of foot impact and some cadence scores are valid, but getting cadence alone tells us why the numbers are faster or slower.

RunScribe is not a pedometer; it’s a sensor collecting motion data to explain cadence patterns. Click To Tweet

As an athlete improves, the sophistication and precision of the product become more important. A direct measure from the foot ensures that the research values are actually being collected and improved on. When you need a 5% boost in frequency, being off by a few strides per minute matters. RunScribe is not a pedometer; it’s a sensor that collects real motion data that explains cadence patterns.

How the Other RunScribe Metrics Integrate With Running Mechanics

The takeaway with cadence is that it’s the end measure to several confounding variables, so it’s a resultant of other factors. Looking only at cadence without looking at the other RunScribe metrics is reductionist thinking, and you will miss out on the cause and effect of what happens when the foot hits the ground. One of the reasons running cadence is popular was because it could be seen by the naked eye with severely slow frequencies and on film when needed. More finite measures, like contact times or braking forces, require instrumentation.

 

RunScribe organizes gathered information into four categories of measurement type. The metric categories are efficiency, shock, motion, and symmetry. The most important part of this article is right here, describing the list of measurements and the way they are connected to cadence. Most readers gravitate to cadence because that measurement is familiar, but I argue that each measurement has similar value and all the measurements have relationships to one another. RunScribe founders did write an article for SimpliFaster, but the metrics were not fully fleshed out. Here are all of the measurements available from the device.

Efficiency – The stride rate or cadence score is what’s typically requested, but the steps per minute measurement is usually dependent on other metrics. The efficiency should be seen as the way mechanics interact with speed and, in order to get faster, the steps need to be more efficient at doing more with less time. As athletes get faster, they take more strides in a set amount of time, cover more distance, and spend more time in the air and less time on the ground.

• Stride Rate (steps/min): The number of steps taken per minute.
• Flight Ratio (%): The relationship between time on the ground and time in the air.
• Contact Time (ms): The absolute time on the ground in milliseconds.

Shock – The sensor estimates Gs, or units of force from the accelerometer, and is not a direct measure. While a force plate is the gold standard, pressure mapping is a good proxy for forces because running in the wild is necessary and very good data can come from sensor technology. Shock is getting researched more and more now, especially for bone breaks and tibial strain, but it’s not a perfect indication of risk for injury. However, shock is excellent for estimating load and evaluating interventions like changes in shoe selection and training methods.

• Cumulative Shock (GS): The composite metric of vertical impact and braking forces.
• Impact (GS): The estimated vertical forces that correlate with peak Gs at foot strike.
• Braking (GS): The estimated horizontal forces that correlate with peak Gs at foot strike.

Motion – Some of the most controversial areas of sports biomechanics are pronation and foot strike types. The amount of motion (excursion) and with what foot landing (type), as well as the rate of that movement type (velocity), adds context to contact time. The use of the shock data as well also shows if this motion loads more, and it’s up to a team of people to really get the most out of the data. Sometimes simple changes to footwear, as well as training, can offload and manage forces if they are the cause of chronic injury or repeated acute injuries.

• Footstrike Type (heel, mid, fore): The primary part of the foot that hits the ground.
• Pronation Excursion (degrees): The range of motion during pronation.
• Pronation Velocity (degrees/second): The rate of motion.

Symmetry – Perhaps the most obvious metric category is symmetry, as the comparison between the right and left foot is commonly evaluated. While perfect symmetry is not realistic or even necessary, when things go wrong getting back to symmetry is useful.

• Shock (graphic chart): Right and left differences with regards to the loading parameters.
• Motion Profile (graphic chart): Right and left differences with regards to the summary of motion.
• Efficiency (graphic chart): Right and left differences with regards to efficiency metrics.

Don’t be overwhelmed by all of the measurements, as the goal with any technology is to solve problems, not create new ones. Receiving additional information beyond cadence may seem like an impossible undertaking, but the reality is a recreational runner can evaluate their own stride parameters on their own time. Even if the only interest is just seeing what an athlete’s cadence is, that’s a valuable enough reason to get the RunScribe. In time, users migrate to the other scores to see why things are fluctuating, speeding up, or slowing down. The RunScribe is extremely powerful and this data is useful to an array of professionals beyond running coaches. Sports medicine professionals, biomechanics researchers, podiatrists, and even body workers can all benefit from the data.

Just collecting data does have value later because baseline and historical data serves a purpose in the present and future. Many professionals claim that some data is not actionable, but if you know how to use it, all information is useful. The best way to learn is by doing and going at the pace you are comfortable with. It’s never a good idea to wait to get started, unless you expect too much from the data you are collecting. RunScribe collects relevant and useful information, and it’s up to those that prepare and rehabilitate athletes to be competent in applying the data.

Taking the Next Step in Building Your Own Stride Solution

RunScribe isn’t a quick-fix solution, but it does create immediate awareness after the training session review. Obviously, endurance runners benefit the most by using RunScribe, but any speed athlete that does tempo running as part of their conditioning program will benefit from adding RunScribe to their program. In my opinion, foot sensors like the RunScribe should have the same value as a heart rate monitor for coaches and athletes. Changes in fitness can be seen by repeating workouts of similar distances and velocities; improvements or negative trends can be seen in foot kinematics with the same sessions.

 

Based on my own experience, feedback from athletes, and other coach’s results with the sensors, I’ve determined that four progressions exist with RunScribe. Any of the progressions can be modified to fit the needs of your own running program, but the main point is that, without measuring the simple stuff consistently, time is lost in development. Here are the needs for getting started:

Calibrate – There are two simple things you need to do when first starting to use RunScribe: Calibrate the sensor to your running and calibrate your senses to the sensor. Calibration of the hardware needs to be done to put context from the device readings and add value beyond raw metrics. After using the device for a few sessions, the natural biofeedback you have when you are measuring occurs, and that is an opportunity to improve your own subjective indications of stride parameters. The most common error with technology is to use it as a replacement for human abilities, when most of the time it should be used to extend them.

Technology should be used as an extension of human abilities, not as a replacement for them. Click To Tweet

Awareness – Sometimes athletes are naturally able to self-gauge their running stride with amazing precision, but most athletes need direct measurement. The goal of calibration and data review is to merge both perception and actual information to enable athletes to feel the sensations accurately. Only when awareness is ingrained can effective change occur.

Experimentation – Coaching is really educated guessing. The same can be said about athletes who are coaching themselves, as the science of sport has too many unknowns to make it a perfect process. Some experimentation in changing a stride comes from both instruction and adjusting the body physically with training, as well as shoe modification and, sometimes, medical attention. Coaching better mechanics that are individualized for the athlete is an article in itself, but for now the RunScribe is a tool that enhances the existing process of developing better running mechanics.

Reinforcement – Improvement without sustainability or cementing the stride changes is an exercise in futility and can really frustrate both the coach and athlete. Much of the problem with motor skill acquisition is the unrealistic expectation of assimilating and maintaining new mechanics. A good analogy for motor skill reinforcement is the similarity between weight loss and weight management. Many coaches spend much of their time trying to tinker and change things, but rarely focus the same energies on reinforcing what works and helping the athlete succeed. RunScribe is the perfect audit for seeing objective evidence that what we cue or train is sticking, rather than being just a flash of brilliance.

The above progression is not some holy scripture, but it does come with a cautionary tale that messing around with athletes without patience is a recipe for disaster. Gradual changes become more deeply rooted, but times do exist when everything falls into place almost too easily. The key lesson with any type of technique change is to know why the athlete is making an error, rather than just trying to modify the athlete because you see a problem visually. Much of what we see above the foot comes from very complicated joint actions below the ankle and addressing “symptoms” only makes the “disease” worse. No matter what approach is used, the universal suggestion of going slow is likely to be the best path to success.

Using RunScribe With Groups

Down the road, what is now just a few athletes using foot sensors for a few weeks is going to become everyone using the RunScribe for an entire season. At first glance, the support requirements may appear to be a major burden, but it’s really about making sure the entire team and staff is on board. I don’t have 60 athletes to worry about anymore, but I do remember the crowd management challenges of the past.

Likely, an anticipated fear is losing sensors or drowning in data, but the reality is that the same can be said for any wearable that collects information. Obviously, the sensors are small and the data can get big, but sport has experienced this already with heart rate data and even workout data. Now that we have GPS watches, fears of having too much information can be negated by software and better perspectives from education.

The priority with training groups of athletes is knowing who wants to be part of the solution and who just wants to receive the solution. Endurance sport differs from team sport, and a distance runner is more likely to have ownership of the data. Endurance athletes are more the former, because training is most of the equation for performance, so they are far more likely to be part of the process than team sport athletes. Team sport athletes sometimes just want to play, so that culture is harder to get cooperation from.

My approach with teams versus Olympic sport is fairly simple, as I manage track athletes with RunScribe or I use the system to investigate problems in individual team athletes. It’s possible to get some populations to buy in with team sport, but that won’t happen unless the staff is doing almost all the legwork for the athletes. The good news is that RunScribe is flexible, meaning you can get a lot out of it without feeling every session needs to be measured and analyzed.

RunScribe’s value is in its extraction of objective, deep data that is typically hard to get. Click To Tweet

Coaches need to appreciate progress, not perfection. Many technologies get put aside because they overwhelm a coaching program instead of assisting in the development process. Coaches can use RunScribe for specific and shorter phases with entire teams or similar smaller groups, or follow a few athletes for a long period of time. No rules really exist. RunScribe’s value is its extraction of objective and deep data that we could not collect by any other practical way.

How to Invest in RunScribe Wisely

I waited more than a year to write this article because I didn’t feel that most of the community was ready for the system. The RunScribe tool is fantastic, but as with anything that collects data, responsibility can be viewed more as a burden than a benefit. A good first step is to try it on yourself and then on an individual to see the difference between getting data yourself and the interplay of getting data from another person. After experiencing the workflow of one, scale it for a small group for a while before moving towards an entire team. Other options exist, but the process does work well for nearly any team or organization.

 

The real challenge of RunScribe lies beyond the cost and management of devices—it’s the analysis time. A healthy and realistic expectation is just being patient and knowing when interventions are appropriate, and this can range from a medical team helping an Achilles problem to an athlete on their own being cognizant of getting a little slow and sloppy in their stride rhythm. Whatever the case, just having the right data is enormous, since conjectures and speculation are not helpful when no actionable information is available.

When athletes are stagnating or hurt, objective measurement is the anchor to the problem. Having solid data eliminates casual shopping for a solution by the athlete or staff, and makes the solution internal rather than external. Empowerment from having every foot strike measured and summarized is the cornerstone to developing better running economy and the perfect running cadence.

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