The latest heart screenings by Craig's Heartstrong Foundation were blighted by no-shows.
Organisers are frustrated by what happened at the weekend, as there were others who could have filled those slots.
Paula Lunt of the foundation told John Moss how many had failed to show up on the Saturday:
TT organisers announce revised Saturday race schedule
Senior race to be restarted over four-lap distance tomorrow (6 June)
TT campers in 'high spirits' despite rain affecting race week
'Costa del Ballaugh' one week, mud the next
Rider taken to Noble's Hospital after Senior TT red flag
Competitor 'conscious and talking' after incident at 11th Milestone
Red flag stops Senior TT race
Race halted during second lap