Physiological control based upon media content selection

1. A method for playing media content items based on a physiological measurement, the method comprising:

receiving at least one physiological measurement of a user, the physiological measurement associated with a level of exertion of the user during performance of a repetitive-motion activity;

identifying a current physiological measurement of the user;

estimating a future physiological measurement of the user from a workout plan that involves one or more changes in the physiological measurement of the user, the workout plan requiring the user to maintain a first heart rate for a first predetermined interval, and to change the first heart rate to a second heart rate for a second predetermined interval; and

transmitting a signal configured to cause a media-playback device to modify playback of media content items based on the estimated future physiological measurement.

2. The method of claim 1 , further comprising comparing the current physiological measurement to the future physiological measurement to modify playback of media content items based on the comparison.

3. The method of claim 2 , wherein the current physiological measurement is a current heart rate, and the future physiological measurement is a future heart rate.

4. The method of claim 1 , wherein the first and second predetermined intervals are durations of time.

5. The method of claim 1 , wherein the first and second predetermined intervals are distances.

6. The method of claim 1 , wherein the signal is configured to cause the media-playback device to adjust a tempo used to select media content items for playback based on the estimated future physiological measurement.

7. The method of claim 6 , wherein the signal is configured to cause the media-playback device to match transition beats between current media content and new media content to maintain a steady cadence transition.

8. The method of claim 1 , wherein the signal is configured to cause the media-playback device to adjust a tempo of the media content that is currently being played by the media-playback device to a new tempo.

9. A media delivery system comprising:

at least one processing device configured to control operation of the media delivery system; and

at least one memory device storing software instructions that, when executed by the at least one processing device, cause the media delivery system to:

receive at least one physiological measurement of a user, the physiological measurement associated with a level of exertion of the user during performance of a repetitive-motion activity;

identify a current physiological measurement of the user;

estimate a future physiological measurement of the user from a workout plan that involves one or more changes in the physiological measurement of the user, the workout plan requiring the user to maintain a first heart rate for a first predetermined interval, and to change the first heart rate to a second heart rate for a second predetermined interval; and

transmit a signal configured to cause a media-playback device to modify playback of media content items based on the estimated future physiological measurement.

10. The media delivery system of claim 9 , wherein the software instructions, when executed by the at least one processing device, cause the media delivery system to compare the current physiological measurement to the future physiological measurement, and modify playback of media content items based on the comparison.

11. The media delivery system of claim 9 , wherein the signal is configured to cause the media-playback device to adjust a tempo used to select media content items for playback based on the estimated future physiological measurement.

12. The media delivery system of claim 11 , wherein the signal is configured to cause the media-playback device to match transition beats between current media content and new media content to maintain a steady cadence transition.

13. The media delivery system of claim 9 , wherein the signal is configured to cause the media-playback device to adjust a tempo of the media content that is currently being played by the media-playback device to a new tempo.

14. A media-playback device comprising:

a content output device that plays media content items;

a physiological measurement device programmed to measure at least one physiological measurement of a user, the physiological measurement associated with a level of exertion of the user during performance of a repetitive-motion activity;

at least one processing device configured to control operation of the media-playback device; and

at least one memory device storing software instructions that, when executed by the at least one processing device, cause the media-playback device to:

transmit at least one physiological measurement of a user, the physiological measurement associated with a level of exertion of the user during performance of a repetitive-motion activity;

acquire a current physiological measurement of the user;

receive an estimated future physiological measurement of the user based on a workout plan involving one or more changes in the physiological measurement of the user, the workout plan requiring the user to maintain a first heart rate for a first predetermined interval, and to change the first heart rate to a second heart rate for a second predetermined interval; and

receive a signal to modify playback of the media content items based on the received estimated future physiological measurement.

15. The media-playback device of claim 14 , wherein the software instructions, when executed by the at least one processing device, cause the media-playback device to compare the current physiological measurement to the estimated future physiological measurement, and modify playback of media content items based on the comparison.

16. The media-playback device of claim 15 , wherein the software instructions, when executed by the at least one processing device, further cause the media-playback device to adjust a tempo used to select media content items for playback based on the estimated future physiological measurement.

17. The media-playback device of claim 14 , wherein the software instructions, when executed by the at least one processing device, further cause the media-playback device to match transition beats between current media content and new media content to maintain a steady cadence transition.

18. The media-playback device of claim 14 , wherein the software instructions, when executed by the at least one processing device, cause the media-playback device to adjust a tempo of the media content that is currently being played to a new tempo.