"My diary is pretty tight, but there's nothing like a bit of fresh air and some physical exertion to clear your head," he told the Herald.
Ardern said her most important strategy for coping with the campaign is a "reasonable night's sleep" - six or seven hours. Some nights she gets four hours.
Her other rule is not to read all of the media coverage: "I think probably you will get yourself tied in knots if you read everything that was written about you."
She's all but given up Twitter too. Her last tweet to her 85,000 followers was three weeks ago.
Ardern has previously spoken about being an anxious person, but she says it is never debilitating. It is natural to be anxious in her high-pressure role, she said: "I just think a lot about things - but who wouldn't in this scenario?"
English says stress is part and parcel of being an MP: "You don't survive in government if you can't deal with a bit of stress so I'm pretty used to it."
The rigours of the campaign sometimes lead politicians to forgo their usual vices. Former Prime Minister John Key used to stop drinking for the campaign, and NZ First leader Winston Peters says he has given up smoking.
Neither English nor Ardern are abstaining from anything, though Ardern says she's almost stopped drinking by default. "I'm not being strict about it, but you just don't really have time for that and it affects you too much."
They never turn their phones off. "I try, but it's not always possible," English says. "Prime Ministers don't get to turn their phones off, unless we're on a plane, which I enjoy. We've got military personnel deployed on peace-keeping operations and citizens scattered all over the world. You've got to be contactable 24 hours a day."
The two leaders rely heavily on a close group of friends and advisers.
Ardern has been using former Labour Party press secretary GJ Thompson - also a former spin doctor for SkyCity and Fonterra - to prepare her for debates.
There's been some special family support too. Her mother Laurell has returned to New Zealand from Niue and is living with her during the campaign.
"Every day when I am out on the road Mum has stuffed some lunch into my handbag. Which is lovely and has made a difference."
Finding time to eat is a particularly tricky thing for leaders. Ardern carries around a bag of almonds to stave off hunger. English's campaign schedule usually includes a stop-off at a cafe around lunchtime.
English's wife Mary has been at his side regularly on the campaign trail, and he has also called on some of his six children to accompany him from time to time. The two leaders' lives are also complicated by their security requirements. DPS staff have to be with them at all times.
"Actually it's a bit of a rigmarole", Ardern says. "I'm trying to get used to the DPS. Even if you got out for a walk, they like to know about it."
The Prime Minister's security requirements also make his commute trickier. It's understood that when he's travelling in a Crown limo, he is not allowed to be driven through tunnels.
That means avoiding the new Waterview Tunnel and going the long way to the airport when he's in Auckland. It also means he has to drive around the sea route in Wellington, rather than cut through the Mt Victoria tunnel.
