I have a set exercise schedule that I consider to be fairly heavy (I run 28 miles a week, devote one day a week to an hour-long cardio session, strength-train three times a week and take one rest day per week), and I was just wondering: Should those of us who do intense exercise every week have a “taper week” every so often, like those preparing for races? I don’t want to run my body into the ground, but I don’t want to deviate from my normal routine if it’s not necessary to do so.
Wow, you do have quite the intense routine going.
‘Taper week’ is a term that racers and marathoners use for the week where they lighten their training to make sure they have enough energy to perform well at their races.  It’s important to rest your body so that your muscles have a chance to heal stronger, and your body has a change to refuel and get its energy back.
When you consistently push it to the max with the same routine, you are setting yourself up for performance plateaus and doing damage to your body.
Many people think of plateaus only in regards to weight loss, but you can hit performance plateaus as well. When you make your body do something for a long period of time, it adapts.  Your body is lazy, so if it knows what to expect, it will find a way to produce the same result with less effort, which means less energy, calorie burn, cardiovascular and strength benefits.  You are doing a lot of work, and not getting as much out of it as you could if you switch up your routine or cut back.  You have to keep your body on its toes.
If your body thinks it’s in danger, it will slow itself down.  You still may be able to finish your workouts, and feel relatively fine, but inside your other systems have been slowed to put the energy toward your workout and have a little left over to, you know, live.
When your body systems slow, again, you will miss out on results-your runs won’t burn as many calories because your body slows your metabolism to protect itself from using all of its energy stores, if you do run through all of your energy stores by not eating enough for your activity level, your body will strip proteins from your muscles to use as energy. Exercise tears your muscle fibers, which when they are allowed to heal, they heal stronger and, thus, you gain strength.  It takes about 48 hours for the proteins to synthesize and heal your muscles, so if you tear them again before they have a chance to heal from the first workout, you will at the very least not see results, at the most tear your muscle.

Your body is like a machine, and if you push it too hard, it’s going to give out.  Repeated stress on the muscles, joints and bones can cause irreparable damage.  Marathon runners often suffer from stress fractures and hip and knee joint injuries.  The cartilage can wear away, nerves can be pinched and bone density can be compromised.

Take a break. Even Olympic athletes have rest days and varying workout/training schedules. Try and schedule in an extra rest day to your week to allow your body to heal itself, or try different forms of workouts to prevent injury and to make sure all your effort is worth it and your results keep coming.