Described herein are methods for determining a target musculoskeletal activity cycle (MSKC) to cardiac cycle (CC) timing relationship. The method may include detecting a signal responsive to a cyclically-varying arterial blood flow at a location on a head of a user； providing a recurrent prompt at a frequency of the heart pump cycle using the signal, such that the signal correlates with a magnitude of blood flow adjacent to the location, and the recurrent prompt is provided to guide the user to time performance of a component of a rhythmic musculoskeletal activity with the recurrent prompt； and guiding the user to adjust a timing of the component of the rhythmic musculoskeletal activity to substantially maximize a magnitude of the signal. In some embodiments, the method further includes generating the recurrent prompt by amplifying the sound generated by the blood flow in or in proximity to an ear of the user.
