Dangers of Intense Exercise in Sedentary Persons

What They are and How You can Blunt Their Ill Effects

May 3, 2009 Alicia Richardson

Exercise has been promoted as a vital part of a healthy lifestyle. However, studies show oxidative stress may offset benefits in untrained people.

All living organisms that require oxygen to survive, produce small amounts of free radicals at rest.These highly reactive compounds are effectively managed by robust antioxidant defense systems in healthy people.

However, increasing evidence show intense workouts, trigger increased oxidative stress - a pathological condition where oxidants and free radicals outnumber antioxidants. Reason: Working muscles demand more oxygen (about 10 fold more -- depending on duration and intensity of activity) and fuel. When muscle, blood, liver-stored glucose gets depleted, fat is used as alternate fuel. This process yields not only fuel but also, some very poisonous substances.

Harmful Products of Fat Oxidation

When free radicals attack cell membranes they form F2-isosprostanes - toxic products of fatty acid metabolism (Arachidonic Acid). A powerful vasoconstrictor, it can impede blood flow to the kidney and cause malfunction. In some trials, blood levels higher than 57% of F2-isosprostanes have been noted immediately after intense training. Free radicals disrupt muscle function resulting in weakness and fatigue. In sedentary persons, prolonged rigourous workouts increases red blood cell fragility and deformation followed by hemolysis (destruction of erythrocytes/ red blood cells). Other harmful products of fat oxidation, and reliable markers of oxidative stress include malonylaldehyde (MDA) and 4-hydroxynonal (4-HNE).

Reducing Adverse Effects

Engaging in regular physical activities have many health benefits, and the desire to participate in one is a commendable goal, particularly if one has been sedentary. Experts suggest the following recommendations.

• Select a low to moderate activity to begin your programme. Walking at a moderate pace, swimming, mild aerobic dance (no jumping or strenuous movements) are some of the low to moderate impact activities you can begin with.
• Exercise for short periods (30 minutes) 3-4 days a week at the beginning, gradually working up to 45-60 minutes per session, until you are comfortable training 4-5 days or more a week. See Health Canada's Physical Activity Guide
• If you are working out alone, exercise carefully to avoid injuries.
• Keep your body well hydrated before, during, and after exercise.
• Replace/restore antioxidants used up during the workout. Vitamin E, the major fat-soluble vitamin antioxidant responsible for protecting cells from oxidative damage is mobilized during intense training.In addition, vitamin C, the major water-soluble vitamin antioxidant could also be depleted during strenuous exercise nutrition.suite 101.com/article.cfm/vitamin_c_protects_blood_vessels. Vitamin C rejuvenates"spent" or "oxidized" vitamin E which speeds vitamin C utilization. An 8 ounce glass of unsweetened orange juice will provide about 86 mg. of vitamin C. Its ORAC -Oxygen Radical Absorbance Capacity- or antioxidant capacity is: 726 micromoles per 100 ml. A small handful of nuts (about 1/4 cup) of pecans will give .84 micromoles of alpha-tocopherol, the most active form of vitamin E. The ORAC value of 1/4 cup of pecans is 8,970 - the highest value among nuts.
• Incorporate fruits and vegetables into your next meal(s). This will ensure a steady supply of antioxidant vitamins, minerals, and plant chemicals needed by your body.

References

Kema S et al. "Exercise-induced oxidative stress leads hemolysis in sedentary but not trained humans" Journal of Applied Physiology, 2005; 99(4):1434-1441

Ross A & Johnson D "Exercise-induced oxidative stress: theory and practical implications for older adults"

Aging Health June 2007;3(3):343-348

Canada's Physical Activity Guide To Healthy Living Health Canada Website

The copyright of the article Dangers of Intense Exercise in Sedentary Persons in Health Field is owned by Alicia Richardson. Permission to republish Dangers of Intense Exercise in Sedentary Persons in print or online must be granted by the author in writing.

Oranges and Orange Juice

Fruits et vegetables