Micronutrients and H₂O

Micronutrients

• Definition – small quantities of vitamins and minerals that:

• Facilitate energy transfer

• Optimize normal growth and development

• Needed in recommended quantities but not too much

Vitamins

• 13 vitamins have been found and noted as important for dietary function

– Classified as:

• Fat-soluble – A, D, E, K

- stored in body’s fat tissue

• Water-soluble – C, B-complex (B1, B2, B6, B12, niacin, pantothenic acid, biotin, folic acid)

- play an important role in energy-generating reactions

Vitamin Role with Antioxidants

• Certain vitamins (A, C, E) and B-carotene help protect plasma membranes from “free radicals” (destructive molecules that can cause cellular deterioration)

• Free radicals are formed from oxygen left over from energy metabolism in the mitochondria

Exercise and Free Radicals

• Two considerations:

• Exercise results in greater free radical formation so there is a potential for greater tissue damage

• However, this does not suggest problems unless individual is vitamin deficient. Appears that most potent antioxident vitamin is Vitamin E.

• Exercise-trained individuals show greater free radical defense systems

• Research shows that greater exercise training is associated with lower incidences of cancer and heart disease

Vitamin Supplements – Do They Give an Edge in Competition?

• No

• Vitamin supplements may actually be more harmful than good in people who are getting adequate nutrition

Minerals

• Account for ~ 4% of the body’s mass

• Classifications:

• Trace minerals – requiring less than 100 mg/day; e.g. iron

• Major minerals – requiring greater than 100 mg/day; e.g. calcium, phosphorus

• Minerals and physical activity

• Weight-bearing activity helps maintain bone mass

– 3 days/week for 50-60 minutes per workout

• Resistance training also is beneficial since muscular force stresses long bones of body

The Female Athlete Triad

• A disruption of normal menstrual patterns in women is believed to occur.

• Characteristics:

– Stress fractures, low body mass, compulsive behavior, highly competitive, low self-esteem, perfectionist, self-critical, depression

Minerals and Performance

• Consuming mineral supplements above recommended levels has not been shown to improve exercise performance or enhance training responsiveness

• Sufficient water intake (with its normal mineral content) is most critical for long term exercise performance

Water in Body

• Water accounts for 40-70% of total body mass

– 72% of a muscle’s weight is water

• Average individual consumes 1.2 liters/day

– 3 sources of water include:

• Liquids

• Foods

• Metabolic processes (25% of daily water requirement)

– Fluid intake can increase 5-6 times above normal in response to exercise or thermal stress

Water Requirement in Exercise

• 3 factors determine water loss through sweating:

– Severity of physical activity

– Environmental temperature

– Humidity

• Major defense from overheating during exercise occurs through evaporation

– If sweat loss of 2-3% of body mass occurs, it can significantly decrease plasma volume. This puts a great strain on the circulatory system.

Heat Disorders

• Build-up of heat in the body can result in:

• Heat cramps – involuntary muscle spasms usually occurring in active muscles during intense exercise

• Heat exhaustion – general weakness with rapid pulse and low blood pressure due to blood pooling; occurs from hard workout early in summer

• Exertional heat stroke – sweating ceases due to prolonged exposure to hot environment during heavy exercise; this is a medical emergency that requires immediate cooling of the body.

Practical Recommendations for Fluid Replacement in Exercise

• In hot environment, person should consume 13-20 oz of cold water 10-20 minutes before exercising

• During exercise:

– 5-8 oz every 15 minute interval

– 5-8% CHO solution

– Up to 75% of exercise intensity, stomach’s ability is not significantly hampered

Rehydration after Exercise

• Each pound lost corresponds to 15 oz of water that needs to be replaced

Water Intoxication

• Although not a “regular” occurrence, drinking too much H₂O can be harmful

– Why?

• Dilutes level of sodium (hyponatremia) in the body

– Predisposing factors to hyponatremia

– Prolonged high-intensity exercise in hot weather

– High sweat loss in untrained individuals

– Low sodium diet along with exercise

– Use of diuretic medication for hypertension

– Large volume consumption of sodium-free fluids during prolonged exercise.

• Exercise training helps body conserve sodium so is not always recommended to take sodium tablets unless diet is low in sodium.