Abstract: The physical condition of a bicycle rider is tested by monitoring the heart beat of the rider and the distance traversed during testing. A portable electronic instrument housing includes a digital computer responsive to signals indicative of the heart beat and travel distance, numerical quantities associated with physiological parameters of the rider, and a clock source to derive signals indicative of different physical activities of the rider. The distance signal is derived by mounting a permanent magnet in a reflector carried by wheel spokes of the bicycle. A first reed switch responds to flux from the permanent magnet to derive a pulse for each wheel revolution. A pulse for each revolution of the bicycle sprocket assembly, derived by a second permanent magnet-reed switch combination, is coupled to the computer and combined with the clock source to derive a signal indicative of number of sprocket assembly turns per unit length of time.