January is the traditional time for people to begin their fitness resolutions, but going too hard, too fast is guaranteed to undermine their best efforts.

Lachlan Chisholm, of Nowra Sports Physio and Rehab, says he understands the temptation to rip in to a new fitness regime.

"Middle-aged men like myself start to train like we did when we're 18 and not factor in that we're now in our 40s," he said.

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The former two-time national champion in the 1500 metres said a soft start is the best way to prevent injury and ensure a new fitness regime stays part of your life for the long haul.

A good rule of thumb is to choose a fitness goal, then halve it.

"If your goal is to run five days a week and you haven't run in a year, break it down," Mr Chisholm said.

"You can start with a mixture of walking and running, and make it three days to begin with.

"After a few weeks, add a bit extra."

Mr Chisholm said it is also important to set realistic fitness goals.

You don't need to be a marathon runner to improve your health with fitness.

"The World Health Organisation recommends half an hour of moderate-intensity exercise five days a wek," Mr Chisholm said.

"That could be a brisk walk, some laps in the pool, or a bike ride.

"More serious athletes will train five to six days a week, but even then you don't want to go flat-chat every session. You want to build a solid base."

If you're prone to boredom, there's nothing wrong with doing a different exercise each day, as long as you keep moving.

Adding in a yoga class or stretching routine can be a boon for tight muscles, and helps prevent little niggles from becoming full-blown injuries. Pilates or a bodyweight strength routine can help develop core muscles.

If you have overdone it, Mr Chisholm said the classic RICE - rest, ice, compression and elevation - is the best immediate fix, but try not to stop your routine completely.

"We like the term 'relative rest'," Mr Chisholm said.

"If running hurts, but walking doesnt, replace your run with a walk until you're able to run again.

"If you're not feeling better after a few days, or you have a constant niggle, get on top of it early.

"Go see your ostepath, physiotherapist or doctor as soon as possible."