Abstract: Described herein are systems and methods for favorably coordinating a timing relationship between a musculoskeletal activity cycle and a cardiac cycle of a user. A method may include repetitively detecting a signal that correlates to a blood volume in the user; determining an actual value of the signal that varies with the timing relationship; computing a trend of the actual value of the signal; and adjusting the movement guidance based on the trend of the actual value. A system may include a prompt device configured to provide recurrently a movement guidance to the user for guiding performance of the rhythmic musculoskeletal activity; a sensor configured to provide a signal that correlates to a blood volume in the user; and a processor configured to determine an actual value of the signal that varies with the timing relationship and to adjust the movement guidance based on the trend of the actual value.