Operation of an electric microswitch 14 for timing or other purposes during rowing is brought about by the rower moving the heels 8 of his/her shoes 3 in opposite sideways directions transitorily. A unit 10 containing the switch 14 involves two plates 19,20 that are tied by cords 11 to the two heels 8 respectively within the foot-well 6 of the boat, so as to slide relative to one another against a spring bias when the heels 8 move apart. The microswitch 14 operates in response to the sliding to energize an LED 16 for sending a light pulse via fibre-optic cable 23 to a timing unit 24. A modified unit 10 includes a wireless transmitter 25 in place of the LED 16, and an alternative modification involves two parallel fibre-optic cables 26,27 from the unit 24 and an optical block 32. The block 32 is moved in response to the heel-movement from where light transmitted by the unit 24 down the cable 26 is not reflected back via the cable 27, to where the light is reflected back up the cable 27 from reflective surfaces 36,37 of block 32. Light reflected back to the unit 24 via the cable 27.