"Your body adapts to everything," personal trainer Terry O'Hara said in her top tips for personal fitness training, featured in the Huffington Post.

"Ever noticed you start on new cardio equipment at the gym and it is hard to get through 20 minutes, but after a month you are hardly out of breath?"

According to Ms O'Hara, this means it is time to try something new. She recommends rowing as a high-cardio activity that will add interest to a regular exercise routine.

Your mental image of yourself defines what you will work toward, Ms O'Hara added.

She advises people to consider what they want to get out of exercise - to lose weight or get fit, or both - and keep a strong mental image of their goal to offer positive motivation.

Finally, Ms O'Hara advises that 'all or nothing' exercise gets you nowhere (or hurt).

It is not a good idea to overdo exercise without building up to it, she added.

Using low-impact fitness equipment, such as an indoor rowing machine, will help you to improve endurance without injury.