YOU know how it is with a love affair – that initial, heady rush of enthusiasm, then it all gets a bit more routine and sometimes it tails off to become a distant memory...

This may also describe your relationship with exercise.

Like any partnership, whether man and woman or your body and fitness, it's essential to put in effort and add interest to keep motivation and enthusiasm alive.

So if your fitness regime has flagged, it could be time to try running. It does not require expensive gym membership or any flashy kit.

There are plenty of nationwide charity events that you could take part in over the next few months to give yourself a goal.

While the 26-mile London marathon on April 13 is watched by millions and inspires many, one international marathon runner, Marielle Renssen recognises: "For some watching lengthy, punishing marathons is a real off-put and they immediately dismiss running and think 'I could never do that'.

"Well, you don't have to! The beauty of running is you can enjoy it and get fit by doing as little as a half-hour run three times a week.

"Many runners start out as non-exercising, overweight, stressed out smokers – self conscious and with low confidence.
"But by setting themselves small goals and keeping going they can be winners in their own terms, not just in terms of fitness but with raised confidence and self esteem."

Marielle, whose new book is the Complete Running Manual says: "Running – a cardiovascular exercise – makes the body produce its own endorphins, feel good chemicals which dull pain and put you on a 'high' for several hours afterwards."

How do I get started?
First have a thorough health check with a GP to ensure that there are no health issues you're unaware of. Tests should include blood pressure and a blood test.

Start walking for an amount of time that feels comfortable, anywhere from 10 to 30 minutes. Once you can walk for 30 minutes easily, sprinkle one-to-two-minute running intervals into your walking. As time goes on, make the running intervals longer, until you are running for 30 minutes straight. Stretch before and after a run.

Where do I run?
Marielle says: "When you start out try to avoid running on concrete pavements and tarmac roads. Those will impact more on vulnerable, untrained muscles and bones."

Choose safe well-lit routes in parks, around school or cycle tracks and keep them varied to avoid boredom. Never run alone in the dark or at night.

Breathing techniques
Learn to breathe properly. Breathe deeply into your diaphragm from the base of your lungs rather than from your upper chest, which results in shallow breathing. If you open up your chest you draw more oxygen into your lungs.

Running causes you to breathe harder than usual, so some amount of huffing and puffing is normal. Most of that out-of-breath feeling diminishes as you become fitter.

If you have to slow down or take walking breaks or if breathlessness persists, ask your doctor about the possibility you may have asthma.

When you want to give up
Marielle says: "Find an inspiring partner. The pressure of knowing someone is waiting for you is a great kick starter, and you can encourage each other.

"Force yourself out of bed by promising you'll give yourself 10 to 15 minutes at least – most times you'll keep going for longer."

Give yourself a mental image of a treat to lure you to the end of a run, maybe a "sinful downfall like chocolate or a glass of wine..."

What about the pain?
Some discomfort is normal as you add distance and intensity to your training. But real pain is not normal.

If something feels so bad that you have to run with a limp or otherwise alter your stride, you're probably injured. Stop running immediately, and take a few days off.

If you're not sure, try walking for a minute or two to see if the discomfort disappears. If it doesn't consult your GP.

• Cancer Research UK is inviting women from Calderdale to enter Race For Life 2008 from May 3 to the end of July. You can walk, run or jog 5k to raise money to help beat cancer. It's the UKs largest women-only fund-raising event. Call 0871 641 2282 or log on to www.raceforlife.org The nearest events are at Huddersfield, Bradford, Leeds and Manchester.