1. Wearing Incorrect Footwear. My husband was out taking his father for a walk recently and they were on a mulch path that had just been given a fresh layer of mulch. As a result the mulch was soft. His father is pretty tall, 6 foot three, and was wearing a pair of excellent New Balance running shoes. The great grey ones which are highly recommended for running. But running shoes are not great hiking shoes. About 30 yards into the walk on the path, the mulch gave way on the side and my father in law twisted his ankle and got a pretty bad sprain. If he had been wearing the appropriate shoe, the injury would not have happened.
2. Wearing Inappropriate Jewelry and Clothing. Incorrect clothing can lead to incorrect range of motion which is a very easy way to get hurt. Make sure you have very comfortable clothing. This can also provide a great way of motivating yourself to exercise more. If you have an "unstructured day" planned- like a weekend day with the kids or if you are single just doing errands- put on workout clothes in the morning. You will find yourself magically getting more exercise in.
3. Not Warming Up. I play tennis a lot, it is something I love and it is easy (and free!) to play outside on public courts nearby. But if I don't warm up for 15 minutes, I will hurt my shoulder. Warming up is also a great way to trick yourself into exercising if you don't feel like you want to workout. Just tell yourself you are going to 5 or 10 minutes of very light activity- walking and stretching. After 10 minutes you might feel that you are ready to get a little more active.
4. Poor Training And Form. I got my husband into tennis and we enjoy playing it a great deal. But when we started he developed a pretty severe case of tennis elbow which was a result of both improper grip and improper swing. Getting some tips from a good pro cured this pretty quickly. Always try and get advice from experts.
5. Overuse. If you do something a lot, the risk of injury from repetitive motion is huge. We work a lot in our coaching program on developing the mindset to exercise more. We want to get you out there and find something you love. But make sure to also mix things up and the minute you feel something funny, just stop.