The celeb trainer says that while fitness should come first, there can also be too much of a good thing

Products in this story are independently selected and featured editorially. If you make a purchase using these links we may earn commission.
Harley Pasternak

Harley Pasternak is a celebrity trainer and nutrition expert who has worked with stars from Halle Berry and Lady Gaga to Robert Pattinson and Robert Downey Jr. He’s also aNew York Times best-selling author, with titles including The Body Reset Diet and The 5-Factor Diet. His new book 5 Pounds is out now. Tweet him @harleypasternak.

It’s no news that exercise is good for you. A combination of cardio and weight-bearing activities sculpt and tone your body, help maintain a healthy weight, strengthen your heart and lungs as well as your bones, improve your blood sugar control and reduce blood pressure.

It also helps you sleep better, enhances your mood and stimulates your brain. But like sunshine, caffeine and red wine, too much of a good thing can turn against you. Even the healthiest food can be problematic when you overindulge. And exercise is no different.

Too Much of a Good Thing
There are a number of ways you can get into trouble by over-exercising. Some problems are immediate; others are just counterproductive:

1. Muscle and joint pain. It’s fine to push yourself, but stop before you feel pain. You want to fatigue your muscles when you exercise, but working them (and yourself) beyond their limits can result in pulls or strains. Even worse, you could damage your ligaments or joints.

2. Risk of injury. The more tired you are the more apt you are to sustain an injury. Overdo exercise, and you increase that risk. Every time you do weight-bearing exercise, you slightly tear muscle fibers. That’s a good thing because it stimulates the fibers to grow stronger. But each muscle group needs at least a day to recover before it is stressed again. What good is a boot camp if you hurt yourself going too hard? And what good is marathon training if you destroy your knees in the process?

3. Dehydration and electrolyte imbalance. Both can be extremely serious. Muscle cramping, heart palpitations, nausea, vomiting and dizziness are all signs that you need to stop exercising and drink water.

4. Muscle depletion. Over-exercising can also force your body to turn to its own muscle tissue for energy once it has used up its primary fuel source (glycogen, which is a form of stored glucose). You want to build and strengthen muscle mass, not poach and weaken it.

5. Plain old boredom. I see this scenario all too often. Someone gets all gung ho about exercising, overdoes it and then gets burned out, returning to his or her former pattern of inactivity.

Making physical fitness an important part of your life is terrific, but moderation in all things is the way to go. As the research below makes clear, this advice applies even to endurance athletes.

Another Reason to Exercise Moderation
In addition to the five reasons above, a recent study published in the International Journal of Sports Medicine points out one more: Over-exertion can cause gut inflammation, which can lead to blood poisoning.

The subjects in this study were ultra-marathon runners. The researchers took blood samples from 17 athletes both before and after they ran up to 130 miles in a 24-hour (!) period. The physical trauma and lack of blood flow to the gut created a condition called leaky gut, in which the contents of the intestines (including bacteria and other toxins) can leak into the blood. The body’s natural and protective reaction to this incursion is an autoimmune response: releasing antibodies to fight and neutralize the toxins. However, some of the runners experienced blood poisoning from the toxins by the end of the run. In those cases, their immune system appeared to not have been strong enough to fight the toxins in their blood.

While you are unlikely to be contemplating a 24-hour run, the findings of this study are a dramatic example of the interconnection of all the body’s systems.

Lessons Learned
To get the most out of exercise, enjoy it more and minimize the risk of injury, follow these guidelines:

1. Listen to your body and know your limits. Gradually build your strength and endurance.

2. Exercise regularly, vary your routine and take a day off when you need a break.

3. Combine cardio and weight-bearing exercise, and always cool down after a workout.

4. Stay hydrated not just during exercise, but all day. I keep a bottle of smartwater with me at all times.

5. When doing weight-bearing exercise, work different muscle groups on alternate days.

RELATED: All of Harley’s Blogs and Training Advice

Celeb Trainer Harley Pasternak Shares a Go-To Move to Get Buns like Beyoncé