Marathon data.zip

Data accompanying manuscript
Data of 7 runners during a Marathon is provided to accompany the manuscript “Quantifying and correcting for speed and stride frequency effects on running mechanics in fatiguing outdoor running”.

For each runner the following files are provided:

- Global Navigation Satellite System (GNSS) running speed

- Inertial Measurement unit (IMU) running speed

- Acceleration of foot sensor

- Acceleration of lower leg/tibia sensor

- Knee angles

GNSS running speed
GNSS running speed during the full marathon was based on different sports watches. Sampling frequencies between sports watches differed but was on average 0.7 (0.4) Hz. In line with the manuscript, missing latitude-longitude data was linearly interpolated before speed was computed as the distance between two latitude-longitude coordinates based on the Haversine formula. GNSS speeds above 20 km/h were deemed extremely unlikely and replaced with spline interpolation. GNSS speed was then resampled to 240 Hz to match the sampling frequency of the IMUs. Note that GNSS and IMU data are not yet time synchronized! 

- Filename: SubXX_gnss_speed.csv

- Size of matrix: [1xN] 

IMU running speed
IMU running speed was solely used for time synchronization of the GNSS running speed with IMU data. The scaled biomechanical model (as described in the manuscript) provided the velocity of the pelvis segment at 240 Hz. Pelvis IMU speed was then computed as the resultant pelvis IMU velocity. 

- Filename: SubXX_imu_speed.csv

- Size of matrix: [Nx1]

Acceleration of foot sensor
Accelerations of the right foot were used for initial contact detection in the manuscript. 3D accelerations of a sensor on the right foot are provided in a sensor-fixed coordinate system. The sensor was placed on the midfoot within the shoes, the sensor was aligned with the long axis of the foot. The positive axis of the first dimension points towards the center of the ankle joint. The positive axis of the second dimension points to the right. The positive axis of the third dimensions is directed approximately upwards. 

- Filename: SubXX_rfoot_acc.csv

- Size of matrix: [Nx3]

Acceleration of lower leg/tibia sensor
Accelerations of the lower leg were one of the quantities of interest in the manuscript. 1D acceleration of a sensor on the right lower leg at 240 Hz is provided in a sensor-fixed coordinate system. The sensor was aligned with the axial direction of the tibia. 

- Filename: SubXX_rtibia_acc.csv

- Size of matrix: [Nx1]

Knee angles
Knee flexion/extension angles were one of the quantities of interest in the manuscript. Knee flexion/extension angles of the right lower leg at 240 Hz are provided. Knee flexion angles were defined 0° when the leg was fully extended during neutral standing. Flexion resulted in positive knee flexion angles.

- Filename: SubXX_rknee_angle.csv

- Size of matrix: [Nx1]

随同行文稿附带的数据集
本数据集配套论文《量化并校正疲劳户外跑步中速度与步频对跑步力学的影响》"Quantifying and correcting for speed and stride frequency effects on running mechanics in fatiguing outdoor running"，包含7名马拉松跑者的跑步相关数据。
针对每名跑者，均提供以下数据文件：
- 全球导航卫星系统（Global Navigation Satellite System, GNSS）跑步速度
- 惯性测量单元（Inertial Measurement Unit, IMU）跑步速度
- 足部传感器加速度
- 小腿/胫骨传感器加速度
- 膝关节角度

## 全球导航卫星系统（GNSS）跑步速度
全程马拉松期间的GNSS跑步速度数据源自多款运动手表，不同设备的采样频率存在差异，平均采样频率为0.7(0.4) Hz。按照论文所述方法，在通过哈弗辛（Haversine）公式计算两点经纬度坐标间的距离以得到速度前，已对缺失的经纬度数据进行线性插值处理。对于速度超过20 km/h的GNSS数据，因其不符合常理，已采用样条插值进行替换。随后将GNSS速度数据重采样至240 Hz，以匹配IMU的采样频率。注意：GNSS与IMU数据尚未完成时间同步！
- 文件名：SubXX_gnss_speed.csv
- 矩阵维度：[1xN]

## 惯性测量单元（IMU）跑步速度
IMU跑步速度仅用于实现GNSS跑步速度与IMU数据的时间同步。论文中所述的缩放生物力学模型可输出240 Hz采样率的骨盆段速度，骨盆IMU速度即由该骨盆IMU速度矢量的合速度计算得到。
- 文件名：SubXX_imu_speed.csv
- 矩阵维度：[Nx1]

## 足部传感器加速度
论文中初始触地检测采用了右脚的加速度数据。本数据集提供了右脚足部传感器在传感器自身坐标系下的三维加速度数据。传感器安装于鞋内的中足位置，并与足部长轴对齐：第一轴正向指向踝关节中心，第二轴正向指向右侧，第三轴正向大致朝上。
- 文件名：SubXX_rfoot_acc.csv
- 矩阵维度：[Nx3]

## 小腿/胫骨传感器加速度
小腿加速度是论文关注的研究量之一。本数据集提供了240 Hz采样率的右小腿传感器在传感器自身坐标系下的一维加速度数据，传感器与胫骨轴向对齐。
- 文件名：SubXX_rtibia_acc.csv
- 矩阵维度：[Nx1]

## 膝关节角度
膝关节屈伸角度是论文关注的研究量之一。本数据集提供了240 Hz采样率的右小腿膝关节屈伸角度数据。定义中立站立状态下腿部完全伸直时膝关节屈曲角度为0°，屈膝动作对应正的膝关节屈曲角度。
- 文件名：SubXX_rknee_angle.csv
- 矩阵维度：[Nx1]