We have all had those days where it seemed every task required continual mental effort to the point you just feel drained. Now you think, let's go and get that afternoon workout, run or bike in... that should clear your head. Then there you are, drained, mentally tired and you start your 3-mile run or perhaps 10-mile bike ride. After a few minutes you feel like your body is carrying an extra 50 pounds and you just cannot get into the workout. I know this has happened to me and I would think "hey a little exercise is suppose to snap me out of it."

Well, a recent study out of Bangor University's School of Sport, Health and Exercise Sciences seems to indicate that people become exhausted sooner while exercising if they have performed intense or difficult cognitive tasks prior to physical activity. The study showed that mental fatigue can have a negative effect on physical performance. The test subjects who performed an intense 90-minute set of cognitive task experienced a significant drop in stamina. As I looked into this, I wanted to know more about why it occurred beyond the mental aspect. Does mental fatigue affect cardio or muscle performance?

In a different study, researchers found again that mental fatigue did show reduced athletic performance and loss of stamina. They performed tests where cardio-respiratory and musculoenergetic measurements where taken. There was no significant change in either cardio or muscle performance in any of the test athletes. The test athletes still indicated that they perceived a higher level of exhaustion when mentally tired than they do mentally rested doing the same exercises at the same intensity.

This all sounds pretty straight forward: if you are mentally fatigued, it negatively affects how you perceive your ability to perform exercise. Not so fast... As I was researching this, I found another potential culprit, Tryptophan.

What is Tryptophan or sometimes called L-Tryptophan? Tryptophan is an essential amino acid which is in your bloodstream attached to your blood plasma protein, albumin. As you perform endurance types of exercise like running, it causes your blood fat levels to increase, as fat levels increase in your bloodstream, the tryptophan releases from the albumin. Once these increased levels of tryptophan enters your brain, they are converted into serotonin. We have all heard of serotonin which plays an important role in the regulation of learning, mood and sleep. Research has shown that serotonin may induce fatigue, which in turn reduces your athletic performance levels.

How can we better manage our energy and performance levels during exercise when faced with mental fatigue and other factors like tryptophan? There are a few basics we all need to consider that starts with good nutrition and proper amounts of sleep.

First, let's start with eating a balanced diet with healthy whole foods, meaning foods in their natural state which are high in vitamins and minerals. Non-whole foods are high in sugar and highly processed leaving you with a spiked insulin response, plus increased cortisol levels which affects concentration and can add to mental fatigue.

The second area is proper sleep requirements, which differ from person to person and depend on many factors, including age. For example, teenagers need to average about nine hours a day. Most healthy adults need to average seven to eight hours a day, but some people can live with as little as five hours or as much as 10 hours of sleep each day. The one thing that most of the current sleep research has shown is most of us are not getting enough sleep which is impacting our health in many adverse ways. If you ever feel drowsy during the day, it is likely you haven't had enough sleep. This, of course, can lead to mental fatigue.

What should you do to minimize the effect of tryptophan release during exercise? The answer to this is not as straightforward as proper nutrition and proper rest. Some studies indicate taking a supplement of Branched Chain Amino Acids or BCAA can minimize the levels of tryptophan entering the brain. Perhaps a better approach would be to ensure you have properly fueled up on good complex carbohydrate before exercise. Studies have also shown good complex carbohydrate have a noticeable effect in reducing mental fatigue. Eating good complex carbohydrate prior to exercise can reduce the amount of fat circulating in the blood. Less fat in the blood would then decrease the amount of tryptophan that would be released from the albumin, so less would enter your brain.

Here are a few things to consider if you find that mental fatigue is having an adverse effect on you when you exercise or compete:

1. Keep your diet and nutrition with whole, preferably organic foods.

2. Avoid simple carbohydrates and highly refined sugary foods at least 8 hours before training sessions or competitions.

3. If you fast, only do it on days you do not work out or compete. Fasting can be counterproductive on many levels if done while exercising.

4. Maintain appropriate levels of protien, good fats and complex carbohydrates prior to training sessions or competitions.

5. Stay hydrated. Drinking plenty of water is key to all good health.

6. Get plenty of sleep. Figure out what your body needs and be sure that you get those hours of sleep every day. Remember, lost sleep does catch up with you and your body will need to make up for the rest it has lost.

These are just a few things that could help your training sessions or competitions. Maintaining these practices will have a positive effect to your overall health and fitness.

You should always try to do your best in training or competitions while mentally rested, but if you're like me, there are times you need to get your exercise done after work and you should continue doing so, even if mentally fatigued. A training session done with moderate intensity, even if mentally fatigued, is still better than no exercise and you will always get benefits, including lower stress levels and it will help clear your head which could lead to improved mental performance after a long day.

Judd Jones is a director for the Hagadone Corporation.