Matt Pullinger, Head of PE at Etonbury Academy in Arlesey, and Matt Guest, who works at Kempston Challenger Academy, will be tackling the week-long adventure in the autumn.
The first six days of 26.2-mile runs will take them from Bedford, where they both live, to Manchester – Mr Guest’s hometown.
They will then complete their challenge by running the Manchester Marathon on 10 October.
The friends will be raising money for the Motor Neurone Disease Association and Multiple Sclerosis Therapy Centre (NW) respectively.
Mr Pullinger said: “We wanted to do something for charity as both our dads have different conditions.
“We’d been running quite a bit in the first lockdown so we thought we’d try and do something a bit more out there. We contacted our charities and they threw this out – we thought ‘yea, why not, let’s give it a go.’
“Neither of us have run a marathon before but we’ve bitten the bullet and said if we’re going to do one, we might as well do seven!”
He added: “It seemed all right when we first signed up for it, but now we’ve started the training we’ve realised what a mammoth task it’s going to be.”
Mr Pullinger added the many miles of training logged so far had led to a newfound love of running.
He said: “I’ve always been sporty but before lockdown I had not really been a runner as such.
“I’ve never really been someone who thought ‘yea, long distance running is for me’ but I’ve been getting a real buzz from it actually – I’ve really enjoyed it, surprisingly so.”
Mr Guest, who is also Head of Year 9 at his school, said: “My dad was diagnosed with MS over 20 years ago, so I’ve always wanted to do something for him.
“I’m from Manchester, and the distance of the first six marathons straddles here and there – so it’s quite convenient in that way.
“Training’s been going really well and we’ve now got through the winter months, which makes it easier of an evening to get out and have a little bit more motivation, rather than getting home from work and it being pitch black and hammering it down!”
He added: “The challenge is going to be difficult, obviously, but I’m quite looking forward to it. It’s going to be fun… once it’s finished!”
The pair can be sponsored via the following fundraising links –
Matt Guest: www.justgiving.com/fundraising/matts7in7