nutrition final

the problem with hyponatremia

An electrolyte imbalance commonly called water intoxication, which results from hyponatremia caused by excessive water consumption, is occasionally reported in endurance athletes. This condition appears to be most common among slow runners in marathon and ultramarathon races probably arises because of the loss of sodium in sweat coupled with extremely high intakes (8-10 L) of water. The symptoms of hyponatremia are similar to those of dehydration and include mental confusion, weakness, and fainting, and so it can be misdiagnosed in athletes.

regulation of core body temperature

Body temperatures of 36 to 38 C (96.8-100.4 F) are considered to be the normal range at rest and may increase to 38 to 40 C (100.4-104 F) during exercise. When body temperature rises toward 39.5 C (103 F), central fatigue ensues. Fatigue protects against damage. Further increases are commonly associated with heat exhaustion and occasionally with life-threatening heatstroke, characterized by a lack of consciousness after exertion and clinical symptoms of organ damage.

caffeine

Caffeine has been proven to be an effective ergogenic aid for endurance performance in most individuals. There are mixed results on caffeine and sprint or power performance. Some studies have shown an ergogenic effect and some have not. Chronic caffeine intake is associated with increased rates of anxiety, poor sleep, glycogen synthesis and bone formation.

iron

Dietary iron has two main forms: heme and nonheme. Plants and iron-fortified foods (including dairy) contain nonheme iron only meat, seafood, and poultry contain both heme and nonheme iron Iron makes up many types of important cells, but most notably, iron is a building block for red blood cells and deficiency can greatly impair health.

recomendations for heat acclimation

Early adaptations are obtained within the first few days, but the main physiological adaptations are not complete until ~1 week. Ideally, the heat acclimatization period should pass 2 weeks to maximize all benefits. Follow hydration guidelines. Consider precooling strategies (e.g., application of iced garments, towels, water immersion, or fanning) and internal (e.g., ingestion of cold fluids or ice slurry) methods. Muscle temperature should remain optimal

effects of training on thermoreceptors

Exercise training improves temperature regulation during exercise at the same absolute work rate. To obtain thermoregulatory benefits from training, exercise at a sufficiently high intensity (70%-100% of VO2max) and increase body temperature above 39 °C (102.2 °F). Acclimation to warm environments requires exercising in a hot environment, not just resting in that environment

body water

Failure to drink water for a few days can result in death. water is essential for human body functions. body water accounts for 50- 72%of the body mass lean body tissue contains 75% of water while adipose tissue contains 5% of water

vitamin D

Fat soluble vitamin - this means that it is stored in adequate quantities in the body and mainly in fat cells (adipose) It is synthesized from the sunlight in the skin and also converted to vitamin D in the gut through the diet Vitamin D can enhance calcium absorption from the gut and also can enhance cell growth and other important functions.

fluid loss in sweat

High rates of sweat are necessary during hard exercise Some people may lose up to 2 to 3 L per hour (1 L/hr avg in adult males) of sweat during strenuous activity in a hot environment. Even at low ambient temperatures of about 10 C (50 F), sweat loss can exceed 1 L per hour. Heat to mechanical work production through ATP breakdown is 4:1 Without heat loss during strenuos exercise, the body temp could increase 1o C every 5-minutes of exercise

preexercise hyperhydration

Hyperhydration (greater than normal body-water content) can improve thermoregulation by expanding blood volume and reducing plasma osmolarity, thereby improving heat dissipation and exercise performance. One well-controlled study reported that expansion of blood volume by 450 to 500 ml improved cycling time-trial performance by 10% (81 vs. 90 minutes). Hyperhydration can be induced by drinking large volumes of water or water-electrolyte solutions for 1 to 3 hours before exercise. Much of the fluid overload is rapidly excreted so expansion of blood volume is only transient

creatine

Is an amino acid In skeletal muscle, it acts to increase rates of ATP production during exercise Long term supplementation can increase the creatine content in skeletal muscle. There is an upper limit to creatine level in the muscle. Some people are not effected by creatine supplementation because the levels in their muscles are already very high. When creatine enters the muscle from the blood, it pulls a water molecule into the muscle with it. As a result, muscles tend to swell more than usually when taking creatine supplementation. This along with high volume resistance training can enhance gains in muscle size.

probiotics

Probiotics are organisms, mainly bacteria that claim to improve health through: improving the flora of the gut, and as a result, improve digestion and absorption on ingested foods

why dehydration impairs performance

Reduced blood volume and increased blood viscosity Reduced maximal cardiac output and VO2max Decreased skin blood flow, so less convective heat loss Decreased sweat rate, and so less evaporative heat loss Decreased heat dissipation Increased core temperature and central fatigue Increased rate of muscle glycogen use, and so more rapid glycogen depletion, which impairs endurance performance

fluid requirements of athletes

Relying on feeling thirsty as the signal to drink is unreliable because a considerable degree of dehydration (certainly sufficient to impair athletic performance) can occur before the desire for fluid intake is evident. Ideally, athletes should consume adequate fluids during activity so that body weight remains fairly constant before and after exercise or is prevented from falling by >2%. The composition of drinks to be taken during exercise should suit individual circumstances

fish and fish oil

Rich in omega-3's, which are an essential fatty acid The World Health Organization recommends eating 1-2 servings of fish a week. Or taking fish oil supplements. Studies have shown that people that eat a lot of fish have lower rates of heart disease. Fish and fish oil may increase HDL levels, but does not appear to decrease LDL levels

thermoreceptors

Sensory information about body temperature is input to the central controller by nerves emanating from deep-body peripheral (skin) thermoreceptors. Provides advanced warning of environmental heat input

falls in plasma volume with exercise

Sweat-loss rates during exercise depend on exercise intensity and duration and environmental conditions but vary considerably among individuals~1-3 L/hour). Plasma volume falls by ~10% to 15% during exercise, with further falls if fluid is not ingested. Falls in plasma volume reduce muscle blood flow and perfusion

post exercise rehydration

The main factors influencing the effectiveness of postexercise rehydration are: volume and composition of the fluid consumed. Plain water is not the ideal rehydration beverage when rapid and complete restoration of body fluid balance is necessary and all intake is in liquid form. Ingestion of water alone causes a rapid fall in plasma sodium concentration and in plasma osmolarity. These changes reduce the stimulation to drink (thirst) and increase urine output, both of which delay rehydration

benefits of adding sodium to drink

To increase palatability To maintain thirst (and therefore promote drinking) To prevent hyponatremia (low serum sodium concentration, which can occur when people ingest far more water than required) To increase the rate of water absorption Makes some contribution to offsetting sodium losses in sweat.

why drinks should not be hypertonic

Too much added carbohydrate in a sports drink, decreases the amount of water that can be absorbed. With hypertonic drinks, water is drawn out of the interstitial fluid and plasma into the lumen of the small intestine by osmosis. The ingestion of a concentrated hypertonic (16.5% carbohydrate) solution delays the restoration of plasma volume during exercise compared with the ingestion of a more dilute (3.6% carbohydrate) hypotonic drink

training adaptations

Training increases the size of existing sweat glands. Training induces an increase in total blood volume Increase in maximal cardiac output Training helps to maintain constant body temperature

vegetarian vegan flexitarian diets

Vegetarian diets may include dairy and/or eggs, but no meat products. Vegan diets include no meat, dairy or egg products. Flexitarian diets include some form of a vegetarian/vegan diet on most days of the week, with a cheat day or two that includes meat, dairy and eggs

what to drink during exercise

Where rehydration is the main priority (e.g., for prolonged exercise in the heat), the solution should contain some carbohydrate as glucose or glucose polymers (20-60 g/L) sodium (20-60 mmol/L) should not exceed isotonicity (290 mosmol/L). Fluid intake during prolonged exercise offers the opportunity to ingest some fuel as well. The addition of carbohydrate to some drinks consumed during exercise has an additional independent effect in improving exercise performance.

the importance of water intake

dehydration impairs exercise performance others over do it and may suffer from hyponatremia hydration status of the body is determined by water gain and loss