No pain, no gain is an accepted philosophy – so, how painful should your workout be?

Katy Kennedy’s first attempt to develop a running habit was a flop. She signed up for a half-marathon, punished herself up and down the hills in her neighbourhood to prepare, then struggled through the race.

“I walked the last mile, and someone shouted ‘Run!’ at me, and I was like, ‘I can’t,’” recalled Dr Kennedy, now a lecturer at the University of Chichester in Britain. “It was horrific, actually. I thought I might die. Then I gave up running for 10 years.”

The next time around she decided to do things differently. “I wanted to have a more pleasant experience,” she said. “And I thought, how can I learn to like running?”

That question eventually drove her doctoral research on the experiences of beginner runners – how they feel and how that affects their ability to stick with their new habit. And according to her peers in the emerging field of exercise psychology, the answers are far more important to your long-term physical and mental health than the humdrum details of how long, how hard or how often you exercise. After all, no exercise regimen is effective if you don’t stick with it.

But the connection between how a workout routine makes you feel and whether you’re still doing it in six months isn’t as straightforward as it may seem. If it makes you miserable, like Dr Kennedy’s first experience with running, you’ll likely quit. If it’s too easy, on the other hand, you may find it boring – or, perhaps worse, pointless. The most committed exercisers often crave a certain amount of discomfort.

So if you’re trying to form an exercise habit, how do you figure when to avoid suffering and when to embrace it?

WHY PLEASURE IS USEFUL

By one estimate, 97 per cent of us agree that physical activity is important for health. And yet a