As we officially enter Spring (yes, it's dull and rainy today but longer, warmer days are coming!) this is a good time to look at adjusting your routine.
If you are thinking of doing your walks /runs outdoors instead of on the treadmill for example the advice is to make the transition gradually; running or walking outdoors engages more muscles and uses a longer stride so suddenly switching can cause fatigue or injury. Switch to one or two outdoor sessions a week at first and increase over a few weeks.
If you are increasing your level of activity or taking up a new sport, remember to do some conditioning work to prepare your body. A simple routine of weighted squats and lunges will help strengthen the legs and improve balance. Finally, never neglect your 10 minute warm up to prevent injury.
Have fun out there!