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 patent pending
How does the Power2Run application work?

The Power2Run application is measuring your Virtual Power, a real-time measure of your running performance.  Virtual Power combines your actual power output and your running economy into a single power performance metric.  Your Virtual Power measurement is determined by calculating the ideal power produced by an excellent runner of your weight running under similar conditions: incline, speed, acceleration, running surface and apparent wind.  Since Virtual Power is calculated from current running conditions, all runners of equal weight under the same conditions will generate the same Virtual Power.  With training, your ability to run at higher Virtual Power means you are either generating more power or getting more efficient, either way, you are becoming a faster runner!  

Can't you just measure my actual running power?
No, not with out laboratory equipment! Unlike cycling where economy of pedaling remains constant throughout a ride, direct measurements of running power are difficult because of changes in running economy.  In reality a significant portion of the energy of the runner is stored elastically in muscles and tendons during the impact phase of each stride. This stored energy is subsequently released to propel the runner forward and into the air.  Even if the ground reaction forces of the runner are measured precisely, it is not possible to tell the difference between forces generated by the release of elastically stored energy, and forces generated by contracting muscles.  For this reason, at Inspyridon, we are suspect of any product that claims to measure running power or running economy directly using force plate or accelerometer measurements.  Direct measurement of changes in a runner's economy can accurately be determined only by measuring an individual's rate of oxygen consumption.
What we do is even better
We use running conditions to accurately predict Virtual Power in real-time using the published running economy of excellent runners from verified laboratory data. Since the resulting Virtual Power directly reflects your running performance, we believe it is a superior training metric!  Virtual Power is directly comparable from runner to runner in the same way as the vDOT metric pioneered by legendary running coach Jack Daniels.  Practically this means if you produce more Virtual Power you are either fitter or more efficient. As Coach Daniels points out either is faster and running faster is what counts.
Virtual Power gives you an accurate measure of your running performance that can be
  • reliably compared from run to run
  • compared from runner to runner as Watts/kg
  • used to quantify training stress and training loads
  • used for accurate effort based pacing
  • compared over any terrain
  • used to track your caloric requirements
Try Power2Run for yourself, we believe you'll find it an indispensable training tool!
How is Virtual Power Calculated?
Virtual Power is calculated by accurately measuring running conditions, including the runner’s weight, incline, speed, acceleration, running surface, and apparent wind speed.  The runner’s weight and running surface (track, road or trail conditions) are entered by the runner prior to beginning a run, while incline, speed and acceleration are measured using the GPS and a barometric altimeter built into the iPhone or Watch.  Wind is accounted for by assuming an apparent head wind equal to the runner’s velocity and typically accounts for < 5% of running power.  Due to the lack of available input data, the Power2Run application does not currently account for power fluctuations due to wind related weather conditions, although we hope to address this in future product versions.
The running conditions are then used to calculate Virtual Power in real-time using a proprietary formula developed by fitting published academic data on VO2 consumption under all expected running conditions (see references below).  Prior to curve fitting, the VO2 data are converted to units of power (Watts) using metabolic efficiency.

Since a run may also include short periods of walking, we also tuned the Virtual Power calculation to accurately reflect performance at walking speeds.  Walking is a fundamentally different and significantly more efficient form of locomotion than running.
In the interests of transparency we provide the Virtual Power plot above to illustrate how measured running conditions such as pace and incline impact your power.  Please send us a message if you have further questions regarding the Virtual Power calculation.  You can reach us at or use the contact us message below.
  • Pereira, Mark A., Freedson, Patty S., Maliszewski, Ann F. (1994).  Intraindividual Variation During Inclined Steady-Rate Treadmill Running.  Research Quarterly for Exercise and Sport; June 1994; 65, 2 pg. 184

  • Teunissen, Lennart P. J., Grabowski, Alena, Kram, Rodger (2007). Effects of Independently Altering Body Weight and Body Mass on the Metabolic Cost of Running.  Journal of Experimental Biology 2007 210: 4418-4427

  • Barnes, Kyle R, Kilding, Andrew E. (2015).  Running Economy: Measurement, Norms, and Determining Factors.  Sports Medicine - Open (2015) 1:8

  • Chang, Young-Hui, Kram Rodger (1999). Metabolic Cost of Generating Horizontal Forces During Human Running.  The J. Appl. Physiol. 86, 1657-1662

  • Pugh, L. G. C. E. (1971) The Influence of Wind Resistance in Running and Walking and the Mechanical Efficiency of Work Against Horizontal or Vertical Forces. J. Physiol (1971), 213. pp. 255-276

  • Bobbert A. C. (1960) Energy Expenditure In Level and Grade Walking.  J. Appl. Physiol. 15(6): 1015-1021

  • Abe, Daijiro, Fukuoka, Yoshiyuki, Muraki, Satoshi, Yasukouchi, Akira, Sakaguchi, Yasushi, Niihata, Shigemitsu. (2011).  Effects of Load and Gradient on Energy Cost of Running.  J. Physiol Anthropol 30(4): 153-160, 2011

  • Al-Obaidi, Abdulkareem Sh. Mahdi, Koo, Mun Hon.  (2013).  Calculation of Aerodynamic Drag of Human Being in Various Positions.  EURECA 2013 pp. 99-100

  • Helgerud, Jan, Stoeren, Oeyvind, Hoff, Jan (2010).  Are There Differences In Running Economy At Different Velocities for Well-Trained Distance Runners? Eur J. Appl. Physiol. (2010) 108:1099-1105

  • Heise, Gary D., Martin, Philip E. (2001).  Are Variations In Running Economy In Humans Associated With Ground Reaction Force Characteristics?  Eur J. Appl. Physiol. (2001) 84: 438-442

  • Daniels, Jack.  Daniel's Running Formula.  Human Kinetics; 2 edition.  Oct. 2005

  • Hoogkamer Wouter, Taboga, Paolo, Kram, Rodger. (2014). Applying the Cost of Generating Force Hypothesis to   Uphill Running. PeerJ  2:e482

  • Minetti, Alberto E., Moia, Christian, Roi, Guilio S. Susta, Davide, Ferretti, Guido. (2002) Energy Cost of Walking and   Running at Extreme Uphill and Downhill Slopes.  J Appl Physiol 93: 1039-1046, 2002

  • Hubel, Tatjana Y., Usherwood, James R. (2013) Vaulting Mechanics Successfully Predict Decrease in Walk-Run Transition Speed with Incline.  Biology Letters 9: 20121121.

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