Following a suggestion by CHdot on another string which was about budget cuts [but had an aside about people hiding behind nicknames or whatever - mentchies being my favourite word for such heteronyms - as a further digression, I am writing as Martin not Gembo here, - the great Portuguese Poet Fernando Pessoa had at least 72 heteronyms which were basically other poets who lived inside him - Ricardo Reis being the most famous but also Alvaro do Campos and a much more minor poet Alexander Self who was Scottish. In the novel by Jose Saramago - A Year In the Death of Ricardo Reis - Pessoa himself has died and Reis comes back to Lisbon from Brazil where he has been working as a doctor to pay his respects. The little statue of Pessoa in the Barrio Alto in Lisbon is identical to the one of Joyce on O'Connell St in Dublin.
Having set this context I would set out my view of the difference between Martin and Gembo. Martin is a fairly smug cyclist, he thinks he has cracked keeping fit and commuting to work. When he gets home he is not looking to avoid parental reponsibilities too much by having to go to the gym. He is pissed off that his office has moved five miles nearer to home but glad he still has an office. Gembo, though, he is slightly more manic and is easily wound up when he detects smugness in cyclists. Gembo doesn't think cyclists have any greater take on the world than anyone else (Martin does). Martin benefits from info posted by 'experts' on this forum. Gembo is more of a wind up merchant.