"I'm in pain"
Sometimes this really is a legitimate excuse not to exercise. Acute pain -- like if you stepped off a curb and twisted your ankle -- is certainly a reason to skip a turn on the treadmill until you can see a doctor for treatment. That said, if you keep skipping the gym because your back aches or your knee feels sore, it's time to pull your big-kid pants on and suck it up.
Alex VanHouten, Life Time Fitness master trainer & education specialist, puts it this way: "Unfortunately nearly 50% of the adult population experience chronic pain daily. I want to challenge you to make your pain a motivator rather than a buzzkill. All recent research suggests that being sedentary makes chronic pain worse over time, whereas exercise can diminish it."
Yes, exercise can actually help you manage your pain. It does this in several ways: by strengthening your muscles and soft tissue, correcting postural imbalances, and improving pain tolerance.
There are also lots of ways to exercise that won't exacerbate your pain. If you have an upper-body injury, focus on lower-body workouts like cycling or walking. If you have a lower-body injury, try a low-impact workout like water jogging. If you have back pain, opt for something like yoga or core work that helps strengthen the muscles surrounding your spine while enhancing flexibility. There's almost always a way to exercise that won't make your pain worse, so stop using your pain as an excuse. It's certainly not going to get better just sitting on the couch.