Wearable heart rate monitor

A wearable fitness monitoring device comprising:

• a motion sensor configured to provide output corresponding to motion by a user wearing the fitness monitoring device;
• a heartbeat waveform sensor;
• and
• control logic comprising instructions for:
• (a) collecting concurrent output data from the heartbeat waveform sensor and output data from the motion detecting sensor, wherein the output data from the heartbeat waveform sensor provides information about the user's heart rate and wherein the output data from the motion detecting sensor provides information about the user's periodic physical movements other than heartbeats;
• (b) determining a periodic component of the output data from the motion detecting sensor;
• (c) using the periodic component of the output data from the motion detecting sensor to remove a corresponding periodic component from the output data from the heartbeat waveform sensor;
• (d) determining the user's heart rate;
• and
• (e) presenting the user's heart rate.