Rowing

1. A method comprising

providing to a first rower on a first rowing machine an audio, video, or audio-visual presentation of motion of another rower on a second rowing machine or in a shell on water,

the motion of the other rower including a series of rowing strokes,

the other rower being subjected to varying resistance by the second rowing machine or the shell on water during the series of rowing strokes,

the motion of the other rower corresponding to data representing parameters of the motion for the series of rowing strokes of the other rower, and

causing the first rowing machine to subject the first rower to a resistance for a series of rowing strokes of the first rower that varies over time to match the varying resistance to which the other rower is subjected in the series of rowing strokes of the other rower during the audio, video, or audio-visual presentation.

2. The method of claim 1 in which the audio, video, or audio-visual presentation is provided to the first rower in real-time with respect to the motion of the other rower on the second rowing machine or in the shell on water.

3. The method of claim 1 in which the audio, video, or audio-visual presentation is pre-recorded.

4. The method of claim 1 comprising providing to the first rower an interface by which the first rower can select the audio, video, or audio-visual presentation from among a library of available presentations.

5. The method of claim 1 in which the parameters represented by the data include one or more of the other rower's stroke rate, the other rower's stroke length, and a power measurement.

6. The method of claim 1 in which the other rower is in a shell on water and the parameters represented by the data comprise one or more of a speed of the shell and a distance traveled or remaining.

7. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the video or audio-visual presentation is from one or a combination of two or more of the following perspectives: a view seen by the other rower; a view directed from the back of the other rower; a bird's eye from a drone; a view from a shell traveling next to the other rower; a view from a front of a shell in which the other rower is rowing; and a view from a stern of the shell in which the other rower is rowing.

8. The method of claim 7 comprising providing to the first rower an interface by which the first rower can toggle among two or more of the perspectives while rowing on the first rowing machine.

9. The method of claim 8 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the video or audio-visual presentation shows a multi-person shell.

10. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the method comprises governing the resistance to which the first rower is subjected based on water conditions portrayed in the video or audio-visual presentation.

11. The method of claim 10 comprising presenting to the first rower information about a speed or stroke rate of the first rower and a speed or stroke rate of the other rower.

12. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the video or audio-visual presentation comprises a combination of a foreground and a background recombined from two different video clips.

13. The method of claim 12 in which the foreground comprises a shell, and in which the background comprises scenery.

14. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the video or audio-visual presentation comprises overlays.

15. The method of claim 14 in which the overlays comprise one or more of additional shells, additional rowers, or a coach.

16. The method of claim 1 in which the audio, video, or audio-visual presentation is provided in real time from a shell through a server.

17. The method of claim 1 in which the audio, video, or audio-visual presentation is received at the second rowing machine wirelessly.

18. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the video or audio-visual presentation includes a computer generated overlay presenting performance metrics of the first rower.

19. The method of claim 1 comprising receiving, at the first rowing machine, a stream of data representing the motion of the other rower.

20. The method of claim 19 in which the stream of data represents a timing of the series of rowing strokes of the other rower.

21. The method of claim 19 comprising governing the resistance to which the first rower is subjected based on the stream of data.

22. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the method comprises comprising adjusting a frame rate of the video or audio-visual presentation to cause a stroke rate in the video or audio-visual presentation to match a stroke rate of the first rower.

23. The method of claim 1 in which the audio, video, or audio-visual presentation comprises a video or audio-visual presentation, and in which the method comprises generating graphical simulations to fill in frame gaps in the video or audio-visual presentation to cause a stroke rate in the video or audio-visual presentation to match a stroke rate of the first rower.

24. The method of claim 1 , in which the audio, video, or audio-visual presentation is synchronized with a stroke rate of the first rower.

25. The method of claim 1 , in which the audio, video, or audio-visual presentation is synchronized with a rowing speed of the first rower.