How to see heart rate and power from a GPX file

A GPX file looks like a list of coordinates, and for a planned route that is all it is. A file exported from a watch or a bike computer is more: on every point it can carry heart rate, cadence, power, speed and temperature, tucked into an <extensions> element that the GPX standard leaves open and Garmin’s schema filled in. Strava, Garmin Connect, Wahoo, Coros, Suunto and our own WorkoutGPX all write them. Most viewers draw the line and throw the rest away.

See them

Open the file in GPX Explore. The chart under the map has a picker listing whatever the file carries: elevation, heart rate, power, cadence, speed, temperature. Pick one and scrub; the marker follows on the map, so you can see where on the climb your heart rate peaked or where the power dropped.

A run exported from GPX Explore with the heart-rate chart under the map

The route card sums the sensors up next to the workout numbers: average and maximum heart rate, average and maximum power, cadence, the temperature range.

What the numbers mean

Heart rate is beats per minute at each point. The average is over the points that have a reading, the maximum is the highest single reading.
Power is watts. Running power from an Apple Watch or a Stryd, cycling power from a meter. Average includes zeros (coasting counts against you, as Garmin counts it).
Cadence is revolutions or steps per minute; the average leaves out the zeros, because a stopped pedal is not a slow one.
Speed is either recorded by the device or derived from the timestamps, over a window of a few seconds so GPS jitter does not invent a sprint.
Moving time leaves out the stops: any stretch slower than half a metre a second over a five-second window. Pace and average speed use that, which is why they match what the watch said and the elapsed time does not.

If the chart is empty

The file has no sensor data. That is the case for anything exported from a route planner, for Strava’s “export GPX” of an activity you did not record yourself, and for older exporters that strip extensions. Export from the device’s own service (Garmin Connect, Apple Health via WorkoutGPX) to keep the sensors.