# Validity of the Stryd Power Meter in Measuring Running Parameters at Submaximal Speeds

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Experimental Approach

#### 2.2. Participants

#### 2.3. Protocol

#### 2.4. Materials

#### 2.4.1. Power Meter

#### 2.4.2. Gas Exchange Measures

#### 2.4.3. Force Platforms

#### 2.4.4. Motion Analysis

#### 2.5. Calculations

#### 2.5.1. Ground Contact Time, Stride Time and Stride Frequency

#### 2.5.2. External Mechanical Power, Mechanical Cost of Running and Mechanical Efficiency

#### 2.5.3. Leg Stiffness

#### 2.5.4. Time Matching

#### 2.6. StatisticaL Analysis

#### 2.6.1. Reference Measures

#### 2.6.2. Mechanical Power

#### 2.6.3. Ground Contact Time

#### 2.6.4. Leg Stiffness

## 3. Results

#### 3.1. Reference Systems: Force Platforms, Portable Metabolic System and Motion Capture

#### 3.1.1. Mechanical Cost of Running

#### 3.1.2. Metabolic and External Mechanical Power Relationship

#### 3.1.3. Ground Contact Time and Leg Stiffness

#### 3.2. Stryd and Reference Measures Comparisons

#### 3.2.1. Consumed Metabolic Energy and Power Output

#### 3.2.2. Mechanical Power

#### 3.2.3. Ground Contact Time

#### 3.2.4. Leg Spring Stiffness

## 4. Discussion

#### 4.1. Reference Measures

#### 4.2. Power Meter and Reference Measurements Comparisons

#### 4.3. Other Measures

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Abbreviations

${A}_{x}$ | anterior-posterior acceleration of the centre of mass of the whole body |

C | foot impact given by optical sensors |

$Cm$ | mechanical cost |

${\overrightarrow{D}}_{i}$ | displacement at time i |

F | resultant of external forces |

$FIT$ | flexible and interoperable data transfer |

g | acceleration due to gravity |

$GCT$ | ground contact time |

$GPS$ | global positioning system |

$GRFs$ | ground reaction forces |

$ICC$ | Intraclass correlation coefficient |

$IMU$ | inertial measurement unit |

${K}_{leg}$ | leg stiffness |

L | initial leg length |

$LMM$ | linear mixed model |

$LSS$ | leg spring stiffness |

m | mass of a subject |

$MAS$ | maximal aerobic speed |

$ME$ | mechanical efficiency |

$PO$ | power output |

$RE$ | running economy |

${\overrightarrow{S}}_{i}$ | speed at time i |

${T}_{c}$ | contact time |

${T}_{s}$ | stride time |

$\dot{V}{O}_{2}$ | oxygen consumption |

$\dot{V}{O}_{2}max$ | maximal oxygen consumption |

${\dot{W}}_{ext}$ | external mechanical power |

${W}_{k}$ | kinetic work |

${\dot{W}}_{met}$ | metabolic power |

${W}_{p}$ | potential work |

${W}_{t}$ | total work |

$\omega $ | stride frequency |

## Appendix A. References Measures: Models

## References

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**Figure 1.**MAS test protocol on a 200 m indoor track. The symbol a represents the start line, b is a photoelectric cell to reset the force platform records, both c are the two motion analysis sensor modules, d is the control panel and e are the cones laid every 20 m and $FP$ is the force platform recording area.

**Figure 2.**Mechanical stride changes during the MAS test. The top plots (

**a**,

**b**) represent changes in GCT over speed and stride frequency respectively. The bottom plots (

**c**,

**d**) represent changes in leg stiffness (${k}_{leg}$) over speed and stride frequency according to McMahon and Cheng [22]. In each figures, dots represent the group mean values, error bars the standard deviation in both x, y axes. The solid line is the regression line from the Bayesian linear model, surrounded by the 95% credible intervals.

**Figure 3.**Consumed metabolic energy ($\dot{\mathrm{V}}{\mathrm{O}}_{2}$) – Stryd power output (PO) relationship during the incremental test. A strong and positive linear relationship was observed across participants. Lines represent each individual linear regression between $\dot{\mathrm{V}}{\mathrm{O}}_{2}$ and PO.

**Figure 4.**Comparison of PO estimated by the Stryd power meter and the force platform. The left plot (

**a**) represents the strong positive relationship between the Stryd and the reference measures. The right plot (

**b**) represents the averaged PO in response to speed, where the dotted line is the corrected Stryd PO (see text for details).

**Figure 5.**Bland–Altman plots for comparison of measurements between the force platforms (reference) and the power meter. Mean bias (middle dashed line), lower and upper limits of agreement (dashed lines) and their 95% confidence interval areas are represented.

Parameter | Estimate | Est.Error | ${\mathit{CI}}_{\mathit{lower}}$ | ${\mathit{CI}}_{\mathit{upper}}$ | Effects |
---|---|---|---|---|---|

Intercept | −8.530 | 8.842 | −27.898 | 7.197 | Population-level effects |

Mechanical power | 0.081 | 0.018 | 0.035 | 0.111 | Population-level effects |

sd(Intercept) | 15.234 | 7.535 | 3.123 | 32.769 | Group-level effects |

sd(mechanical power) | 0.029 | 0.019 | 0.004 | 0.078 | Group-level effects |

cor(Intercept,mechanical power) | −0.492 | 0.428 | −0.949 | 0.658 | Group-level effects |

sigma | 2.410 | 0.346 | 1.853 | 3.204 | Family specific parameters |

Parameter | Estimate | Est.Error | ${\mathit{CI}}_{\mathit{lower}}$ | ${\mathit{CI}}_{\mathit{upper}}$ | ${\mathit{BF}}_{10}$ | Effects | Measure |
---|---|---|---|---|---|---|---|

Intercept | 568.401 | 38.163 | 490.765 | 644.830 | Population-level effects | Mechanical power | |

Stryd | −304.952 | 9.817 | −324.304 | −285.993 | >100 | Population-level effects | Mechanical power |

Speed | 65.486 | 12.914 | 42.022 | 93.125 | 15.38 | Population-level effects | Mechanical power |

Stryd:speed interaction | −23.782 | 9.884 | −43.192 | −4.554 | >100 | Population-level effects | Mechanical power |

sd(Intercept) | 86.027 | 36.563 | 41.970 | 180.565 | Group-level effects | Mechanical power | |

sd(speed) | 17.260 | 18.408 | 0.438 | 66.867 | Group-level effects | Mechanical power | |

cor(Intercept,speed) | 0.349 | 0.516 | −0.819 | 0.978 | Group-level effects | Mechanical power | |

sigma | 52.325 | 3.651 | 45.751 | 59.970 | Family specific parameters | Mechanical power | |

Intercept | 0.241 | 0.008 | 0.226 | 0.255 | Population-level effects | Contact time | |

Stryd | −0.005 | 0.002 | −0.009 | −0.002 | 0.008 | Population-level effects | Contact time |

Speed | −0.034 | 0.012 | −0.058 | −0.011 | >100 | Population-level effects | Contact time |

Stryd:speed interaction | 0.000 | 0.002 | −0.003 | 0.004 | 0.72 | Population-level effects | Contact time |

sd(Intercept) | 0.016 | 0.009 | 0.007 | 0.039 | Group-level effects | Contact time | |

sd(speed) | 0.025 | 0.015 | 0.009 | 0.063 | Group-level effects | Contact time | |

cor(Intercept,speed) | −0.216 | 0.410 | −0.862 | 0.647 | Group-level effects | Contact time | |

sigma | 0.010 | 0.001 | 0.009 | 0.012 | Family specific parameters | Contact time | |

Intercept | 8.574 | 0.980 | 6.680 | 10.571 | Population-level effects | Leg stiffness | |

Stryd | −0.602 | 0.893 | −2.334 | 1.154 | 0.007 | Population-level effects | Leg stiffness |

Speed | 0.394 | 0.240 | −0.099 | 0.865 | 0.012 | Population-level effects | Leg stiffness |

Stryd:lap interaction | 0.063 | 0.244 | −0.418 | 0.534 | 0.020 | Population-level effects | Leg stiffness |

sd(Intercept) | 1.427 | 0.959 | 0.119 | 3.830 | Group-level effects | Leg stiffness | |

sd(speed) | 0.284 | 0.255 | 0.010 | 0.940 | Group-level effects | Leg stiffness | |

cor(Intercept,speed) | −0.105 | 0.572 | −0.953 | 0.927 | Group-level effects | Leg stiffness | |

sigma | 0.972 | 0.063 | 0.857 | 1.106 | Family specific parameters | Leg stiffness |

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## Share and Cite

**MDPI and ACS Style**

Imbach, F.; Candau, R.; Chailan, R.; Perrey, S.
Validity of the Stryd Power Meter in Measuring Running Parameters at Submaximal Speeds. *Sports* **2020**, *8*, 103.
https://doi.org/10.3390/sports8070103

**AMA Style**

Imbach F, Candau R, Chailan R, Perrey S.
Validity of the Stryd Power Meter in Measuring Running Parameters at Submaximal Speeds. *Sports*. 2020; 8(7):103.
https://doi.org/10.3390/sports8070103

**Chicago/Turabian Style**

Imbach, Frank, Robin Candau, Romain Chailan, and Stephane Perrey.
2020. "Validity of the Stryd Power Meter in Measuring Running Parameters at Submaximal Speeds" *Sports* 8, no. 7: 103.
https://doi.org/10.3390/sports8070103