Methods and apparatus for power expenditure and technique determination during bipedal motion
Training at the proper level of effort is important for athletes whose objective is to achieve the best results in the least time. In running, for example, pace is often monitored. However, pace alone does not reveal specific issues with regard to running form, efficiency, or technique, much less inform how training should be modified to improve performance or fitness. A sensing system and wearable sensor platform described herein provide real-time feedback to a user/wearer of his power expenditure during an activity. In one example, the system includes an inertial measurement unit (IMU) for acquiring multi-axis motion data at a first sampling rate, and an orientation sensor to acquire orientation data at a second sampling rate that is varied based on the multi-axis motion data.
1. A system for measuring motion of a user during physical activity, the system comprising:
a housing configured to be attachable to a shoe of a user, the housing including a sensor platform disposed therein, the sensor platform comprising:
an inertial measurement unit (IMU), disposed within the housing, to acquire multi-axis motion data, the multi-axis motion representing motion of the system; and
an orientation sensor, disposed within the housing, to acquire orientation data at a sampling rate, the orientation data representing an orientation of the sensor;
a barometer to acquire air pressure data while the user is engaging in the physical activity;
a processor, operably coupled to the IMU, the barometer, and the orientation sensor; and
at least one memory, operably coupled to the processor, to store the multi-axis motion data and the orientation data, the at least one memory storing instructions that when executed by the processor cause the system to perform operations comprising:
calculating at least one of a velocity or a change in velocity of the sensor platform based on at least the multi-axis motion data; and
generating, based on the acquired air pressure data, a body forward-facing surface area of the user and a drag coefficient, an estimate of wind resistance experienced by the user during the physical activity;
generating an estimate of power expended by the user, based on the estimate of wind resistance and at least one of the velocity of the sensor platform or the change in velocity of the sensor platform.
2. The system of claim 1 , wherein the housing is integrated into the shoe of the user.
3. The system of claim 1 , wherein the system is further configured to be worn or attached to the user during the physical activity.
4. The system of claim 1 , wherein the operations further comprise calculating an incline of a path based on the air pressure data.
5. The system of claim 1 , wherein the air pressure data includes an air pressure measurement at an anterior of the user and an air pressure measurement at a posterior of the user.
6. The system of claim 5 , wherein generating the estimate of wind resistance includes determining a difference between the air pressure measurement at the anterior of the user and the air pressure measurement at the posterior of the user.
7. The system of claim 1 , wherein the operations further comprise at least one of accessing or calculating at least one of:
a running economy coefficient;
a coefficient corresponding to a contribution of recycled power during human running;
a lactate threshold or anaerobic threshold of the user;
a maximal oxygen consumption (VO2 max) of the user;
a running efficiency of the user; or
an empirically determined performance-impacting physiological parameter derived from a pool of running data matching a profile of the user.
8. The system of claim 7 , wherein the empirically determined performance-impacting physiological parameter is accessed or calculated, and the estimate of power expended by the user is further based on the empirically determined performance-impacting physiological parameter.