RunScribe Metrics

Pace

Running speed is a function of both Stride Rate (SR) and Stride Length (SL) and is calculated by the equation: Speed = SR X SL. The system will estimate a default stride length for you. This can be made more accurate by adjusting the estimated distance of the run. These adjustments will be used when determining the stride length of subsequent runs.

Stride Length

The distance between two successive placements of the same foot, consisting of 2 step lengths. The system will estimate a default stride length for you. This can be made more accurate by adjusting the estimated distance of the run. These adjustments will be used when determining the stride length of subsequent runs.

What We Know
  • Runners with shorter stride lengths and higher step rates tend to have lower impact forces and Impact Gs at footstrike which, in turn, may help prevent injuries.
  • Running speed is a function of both stride length and step rate but there is no “one size fits all” when it comes to how runners increase or decrease speed. Some are step rate dominant and others are stride length dominant.
What to Look For: In a Run
  • Does your overall strategy change as you go from a slow to a medium speed compared to going from medium speed to a sprint?
  • As you increase in pace, does your stride length or your step rate increase more?
  • As you get tired during a run, how do you maintain pace? Do you notice an increase in stride length or step rate?
What to Look For: Over Time
  • As you get faster, look to see whether you’re increasing your Step Rate, Stride Length, or a combination of both.
 

Efficiency

Efficiency metrics are an indicator of running performance. Shorter contact time, longer flight time and a higher step rate are three variables linked to higher running efficiency. It is a complex combination of these metrics, which vary with pace, that give an indication of running form quality.

Efficiency metrics are a powerful way to:

  • Evaluate the quality of your stride mechanics
  • Quantify the impact of training on performance
  • Assess the impact of pace on stride efficiency

In addition to providing average and per-footstrike efficiency metrics, the Run Detail view provides a comparison of your run efficiency against the RunScribe community databank. As the RunScribe databank grows, these comparisons may change.

Because efficiency metrics change dramatically with pace, the Community Comparison efficiency gauge compares the average efficiency metrics calculated during your run against the average of the RunScribe databank at that same pace.

Step Rate

Step Rate (SR) refers to the number of steps a runner takes per minute. Speed is a function of both SR and Stride Length (SL) and is calculated by the equation: Speed = SR x SL.

What We Know
  • It is well documented that more experienced runners tend to have higher SRs than novice runners at comparable speeds.
  • Runners with shorter SLs and higher SRs tend to have lower impact forces and Impact Gs at footstrike which, in turn, may help prevent injuries.
What to Look For: In a Run
  • Running speed is a function of both SR and SL but there is no “one size fits all” when it comes to how runners increase or decrease speed. Some are SR dominant and others are SL dominant. Which are you?
  • Does your overall strategy change as you go from a slow to a medium speed compared to going from medium speed to a sprint?
What to Look For: Over Time
  • Many coaches have recently begun advocating that 90 strides/min (180 steps/min) is the optimum cadence for distance running. There is some individual variation but how does your long term average compare to this?

Flight Ratio

This is the ratio of a runner’s “Flight” time in the air (non ground contact phase) and overall step time. Step time is defined as flight time plus ground contact time. Flight time and contact time have both correlated well with running economy and Flight Ratio combines these two into a single composite metric. Basically, it is the percentage of your stride spent in the air.

 

What We Know
  • Is a composite metric that combines the information from contact time and stride rate
  • More efficient runners tend to have a higher flight ratio
  • Values can range from 0 (walking) to approximately 50%
What to Look For: In a Run
  • Compare your flight ratio over a variety of terrains, at different paces, and with different shoes
  • Note how your flight ratio changes with fatigue
What to Look For: Over Time
  • As you train, watch to see if your flight ratio changes as fitness improves

Contact Time

Time in ms the foot is in contact with the ground. Contact time is measured from heel to toe off.

 

What We Know
  • Experienced runners tend to have shorter ground contact time
  • As speed increases, contact time decreases
  • Sprinters have contact times between 115ms to 150ms
  • Distance runners tend to range between 170ms to approximately 400ms
What to Look For: In a Run
  • Compare your Impact Gs to your Contact Time, see if there is an increase in Impact Gs as your Contact Time and Pace increases
  • Note how your Contact Time changes as fatigue hits during a run
What to Look For: Over Time
  • Pay attention if your Impact Gs increase as contact time shortens, which can increase the overall strain of your run
  • As you train, watch to see if your contact time decreases while your pace remains the same. This is a good indication that your efficiency is improving.
 

Shock

RunScribe’s Shock metrics include Impact and Braking Gs, as well as a composite score that combines Impact and Braking Gs into a single metric, representing the total amount of “shock” incurred per footstrike.

Shock values are provided per run (cumulative shock experienced during a run), per footstrike and the average over the duration of a run. Shock values are helpful in assessing injury or overtraining risk. Runners can use shock values:

  • As an indicator of overall stress during a run or over a training period – shock values can help manage the risk of overtraining
  • In assessing impacts of terrain and pace on their shock
  • To provide a view into potential risks that may result from changes in training or gear

To contextualize Shock values, the Run Detail page provides a comparison of average shock calculated during a run with the RunScribe Community Databank. As the RunScribe databank grows, these comparisons may change.

Because shock changes dramatically with pace, the Community Comparison shock gauge compares the average shock (per footstrike) calculated during your run against the average of the RunScribe databank at that same pace.

Shock

Shock is a RunScribe defined composite metric, which combines Impact Gs and Braking Gs into a single metric, representing the total amount of “Shock” incurred per footstep.

Impact Gs

Impact Gs are the vertical component of Peak Gs. It correlates with the ground impact force experienced at footstrike.

Braking Gs

Braking Gs are the horizontal component of Peak Gs. It correlates with the braking forces experienced at footstrike

What We Know
  • When the foot impacts the ground it goes through a very rapid change in velocity from around one meter per second to zero in a matter of milliseconds. The magnitude of the force impacted on your body with each running step is approximately 2.5 times your body weight. Each step causes a very small amount of damage to the musculoskeletal system, and if this micro-damage accumulates before the body is able to repair itself sufficiently, then there is an increased risk of injury. The way you run alters the way this impact force is distributed on the musculoskeletal system, and will influence the type of injury that is likely to occur.
  • Traditional laboratory studies use a force plate to measure ground reaction force during running. This requires expensive equipment and limits the number of steps that can be analyzed. RunScribe records the rapid change in velocity at footstrike, it is not a force, but recent studies have shown that this rate of initial deceleration may be a better indicator of injury risk than impact force peaks.
What to Look For: In a Run
  • How does Shock change with fatigue? Are you striking the ground harder as you get tired?
  • Is there a correlation between impact forces and contact time? Does increasing your pace increase shock for each step?
What to Look For: Over Time
  • As your shoes wear down with additional mileage, does that change your impact forces?
  • Do different shoes provide additional cushioning? How does a support shoe compare to a minimalist shoe?
  • How does terrain influence Shock? Is running on grass easier on your body than running on the road or a treadmill?
 

Motion

Motion metrics characterize what happens when your foot hits the ground — including Footstrike Type (Heel, Mid, Fore) to how you Pronate (the foot’s rolling motion at contact) and Pronation Velocity (how fast you’re pronating). To contextualize your motion metrics, the Run Detail page shows illustrations and designate pronation and velocity as Low, Average or High based on a comparison against the RunScribe community. As the RunScribe databank grows, these comparisons may change.

Runners naturally self-optimize their stride based on variables like shoes and different terrain. As a result, motion metrics can change dramatically under different conditions. Runners can use motion metrics to:

  • Evaluate how their motion breaks down with fatigue, and create a training program to target any weaknesses
  • Use real-world motion metrics to inform decisions on shoes and orthotics
  • Identify sudden or trending changes in motion, which can be an indicator of injury risk
  • Understand how motion changes with pace and terrain, which can inform shoe choices for specific workouts
  • Evaluate motion metrics for asymmetries, which can help runners assess injury risk or track progress in injury recovery

Footstrike Type

There are three general categories when describing Footstrike Type: heel, midfoot, and forefoot striker.

What We Know
  • Types of injuries tend to differ between the groups.
  • Heel strikers tend to have more knee and hip injuries
  • Forefoot strikers tend to have more Achilles and calf strains and metatarsal injuries
  • Midfoot strikers will have characteristics in common with the both, often moving between the heel and forefoot strike patterns.
What to Look For: In a Run
  • Many things can influence Foot Strike Type—speed, footwear, and terrain being the most common.Note the impact of these factors on your footstrike type.
What to Look For: Over Time
  • If Foot Strike Type changes over a period of time (weeks or months) and it is not due to a specific training program aimed at changing foot strike patterns, it is probably due to a change in footwear. Minimalist and low heel drop shoes tend to encourage mid and forefoot striking patterns. If you have more that one pair of shoes, tag each run with a particular pair of shoes and see if there is a relationship to your footstrike patterns.

Pronation Excursion

RunScribe measures Pronation Excursion, which is the total range of angular movement (in degrees) as the foot rolls inward between footstrike and the point of maximum pronation. It is estimated by measuring the rearfoot angle during ground contact while running and/or walking.

What We Know
  • Pronation has been labeled as a potential indicator for overuse injuries while running. However, it is a natural movement and is an effective means of shock absorption at footstrike.
What to Look For: In a Run
  • See how changes in running speed and terrain can influence Pronation Excursion.
What to Look For: Over Time
  • Different categories of shoes can have an influence on how much you pronate while running. Once you get a handful of runs on a couple of pairs of shoes, break the data out by shoes and see if there are any differences. If you have a specific pair that you race in, compare the data between those shoes and your typical training shoes.
  • Changing pronation values could indicate break down of shoe support, or be an indicator of injury risk

Max Pronation Velocity

The maximum angular rate at which the foot pronates between footstrike and the point of maximum pronation.

What We Know
  • Values range between 200 and more than 1000 deg/sec
  • Max pronation velocity is influenced by a number of factors including: running speed, terrain, Footstrike Type and footwear.
  • Research is not conclusive, but it is believed that max Pronation Velocity is related to increased injury risk.
What to Look For: In a Run
  • How does different terrain and running speed affect your pronation velocity?
  • Is there a relationship between Contact Time and Pronation Velocity?
  • If you wear orthotics try some short runs with and without them and compare the data. It is probably worth doing these types of comparisons on a track or treadmill and keep the runs pretty short.
What to Look For: Over Time
  • Shoes can have a big influence on pronation velocity. Over time compare the data between the different pairs of shoes you own. Any differences?
 

Symmetry

Runners can use symmetry to:

  • Identify areas of concern which could be addressed through physical therapy or corrected using orthotics
  • Assess the impact of injury on mechanics
  • Track progress in injury recovery

In addition to providing R v L metrics, the Run Detail page also includes a Symmetry snapshot.

The three rows represent average Efficiency, Shock and Motion, highlighting the severity of the asymmetries. Specifics on asymmetries can be found in the metrics details below.