may comprise a hip marker 10 h a second marker may comprise a knee marker 10 k and a third marker may comprise an ankle marker 10 a together these three markers 10 h 10 k 10 a may be so affixed onto the cyclist to indicate a knee extension angle 40 in 3 dimensional space in one embodiment it may be advantageous to calculate a maximum knee extension angle in order to properly fit a bicycle 2 to a cyclist 1 in order to calculate an accurate maximum knee extension angle 40 the maximum knee extension angle 40 is calculated for each stroke in a series of consecutive strokes wherein a single stroke u2014 or cycle of motion may be characterized as a complete revolution of a pedal crank 5 in determining one knee extension angle 40 the first marker 10 h may emit light for 3 5 ms at a first time the second marker 10 k may emit light for 3 5 ms at a second time wherein the second time follows the first time and the third marker 10 a may emit light for 3 5 ms at a third time the third time immediately following the second time longer or shorter light emitting periods.