Chapter 18/22: Nutriton for Health and Performance Flashcards
what is RDA (Recommended Daily Allowances)?
quantity of each nutrient to meet the needs of nearly all healthy persons within a specific life stage
what is AI (Adequate Intakes)? when is it used?
recommended daily intake based on apparently healthy people, used when RDA cannot be determined
underweight BMI
<18.5 kg/m2
normal BMI
18.5- 24.9 kg/m2
overweight BMI
25-29.9 kg/m2
obesity - class I BMI
30-34.9 kg/m2
obesity class II BMI
35-39.9 kg/m2
extreme obesity - class III
> 40 kg/m2
what is the EER (Estimated Energy Requirement)?
average dietary energy intake predicted to maintain energy balance considering age, sex, weight, height, and level of physical activity
examples of carbs than can be digested and metabolized for energy
sugars and starches; BG is maintained within narrow limits by endocrine system
example of carbs than cannot be digested or metabolized. purpose?
dietary fiber, provides a sense of fullness during a meal and reduces transit time in intestine
who needs more fiber, men or women?
men
how does fuel selection change with increasing exercise intensity?
increased carb utilization
how does fuel selection change with increasing exercise duration?
increased fat utilization
time to exhaustion is related to..
initial muscle glycogen stores
3 factors affecting muscle glycogen levels
1) carbohydrate content of diet
2) prior exercise
3) muscle glycogen “supercompensation”
how does a high carb diet affect performance? when is it most important?
endurance performance if improved by a diet high in carbs, most important in events at high intensity lasting over an hour
mechanism by which a high carb diet increases endurance performance
increase muscle glycogen and performance time
how does prior exercise affect muscle glycogen level?
glycogen depletion leads to greater synthesis following exercise
describe the concept of muscle glycogen “supercompensation”
exhausting exercise depletes glycogen content in active muscles, then rest and high-carb diet results in glycogen overshoot in those muscles
classical method of muscle glycogen supercompensation
1) prolonged strenuous exercise to deplete glycogen stores
2) a high-fat/protein diet for three days while containing to train
3) 90% carb diet for three days with inactivity
why is the classical method of muscle glycogen hard for athletes to maintain?
both diets are incredibly hard to do & asking athletes not to train before their event makes them feel unprepared
modified plan of muscle glycogen supercompensation
1) tapering workouts (90 to 40 minutes) over several days while eating 50% CHO diet
2) two days of 20 minute workouts while eating 70% CHO diet
3) day of rest eating 70% CHO diet before event
major purpose of glycogen loading prior to prolonged exercise?
improve performance
what does consuming CHO 30-45 minutes prior to exercise cause? why?
faster rate of muscle glycogen utilization & fall in blood glucose during exercise (not dependent on amount of CHO consumed); because of spike in insulin
best time to eat CHO before exercise
2-3 hours before or 5-10 mins before
3 recommendations on CHO intake before exercise
1) avoid high glycemic index carbs (broken down too quickly)
2) consume carbs in last 5 mins or during warmup to minimize risk of hypoglycemia (no insulin spike)
3) the form of CHO (gel or liquid) does not matter
advantage of consuming carbs during exercise?
carb ingestion can maintain plasma glucose even as glycogen is depleted, which delays fatigue and improves performance
recommendations for carb intake during exercise
throughout exercise or prior to fatigue (30-60 g CHO/ hour)
advantage of consuming CHO after exercise
glycogen synthesis is enhanced after exercise due to increased glycogen synthase activity
3 recommendations for CHO consumption after exercise
1) CHO should be consumed immediately after exercise (1-1.5 g/kg within 30 minutes, then at 2 hour intervals for 6 hours)
2) high glycemic index foods are better
3) addition of protein is beneficial because it reduced CHO need to resynthesize glycogen and it enhances muscle protein synthesis
purposes of dietary fats
fuel for energy, hormone synthesis, absorption of fat-soluble vitamins, cell membrane structure, insulation, and protection of vital organs
what do high-quality proteins contain?
nine essential amino acids that cannot be synthesized in the body
protein RDA? do most Americans reach it?
0.8 g/kg*day
most americans meet this, may be higher for athletes
average athlete intake for protein
1.5 g/kg*day
what percent water loss affects performance
3-4% water loss
AI for water, women and men respectively
2.7 L/day for women, 3.7 L/day for men
what does water loss via sweat depend on?
exercise intensity and environmental conditions
fluid replacement goals before exercise
goal is to be euhydrated, foods and beverages consumed at meals should be sufficient
if additional fluids are needed: slowly drink beverage at least 4 hours prior, sodium in beverages or salted snacks help retain fluid
goal of fluid replacement during exercise
goal is to reduce risk of excessive dehydration, important for both prolonged and intermittent exercise
fluid replacement during exercise is associated with:
lower body temp, lower HR, and lower RPE
water replacement for events <1 hour (80-130% VO2 max)
500-1000 ml water
water replacement for events 1-3 hours (60-90%) VO2 max)
800-1600 ml of 6-8% CHO solution with 10-20 mEq Na
water replacement for events >3 hours
500-1000 ml of 6-8% CHO solution with 20-30 mEq Na
fluid replacement goal after exercise
goal is to replenish water, electrolytes, and muscle glycogen
recommended water intake after exercise
1.5 L fluid for every kg of weight loss
cold drinks more effective but carb-electrolyte beverages or skim milk equally effective
functions of calcium
provides bone and tooth strength, helps blood clotting, aids nerve impulse transmission, muscle contraction
calcium RDA
1000 mg/day
dietary sources of calcium
leafy greens, animals products
parathyroid hormone affect on blood calcium levels
increases blood calcium levels
purpose of bones in maintaining calcium homeostasis?
bones are a “store”, PTH causes bone breakdown to release calcium into blood when dietary intake is inadequate
how does intense and/or prolonged exercise affect PTH?
increases PTH
functions of iron
found in hemoglobin in RBCs, which is involved in oxygen transport to cells
iron RDA for men and women
8 mg/day for males
18 mg/day for females
dietary sources of iron
meat sources, leafy greens
what does an iron deficiency affect that is relevant to exercise?
VO2 max and endurance
who is iron deficiency more common in?
female athletes and distance runners
what might an iron deficiency be due to?
due to decreased calcium intake and decreased absorption (diets low in read meat, dieting for weight loss or vegetarian diets) or due to increased calcium loss (via sweat, feces, and urine)
affects of iron supplementation, rapid piece and slower piece?
rapid: restores hematocrit and VO2 max
slower: increase in mitochondrial activity and endurance
functions of sodium
major ion of extracellular fluid, directly involved in maintenance of resting membrane potential, generation of an action potential in nerves and muscles
AI for sodium
1500 mg/day
dietary sources of sodium
chips, pretzels, soup
average intake for sodium for Americans
3400 mg/day
what population requires more salt? why?
athletes because they must replace salt lost in sweat (1.9 g Na+ per L sweat)
best test of salt/water replacement
body weight, constant body weight indicates adequate salt and water intake
characteristics of fat soluble vitamins
A, D, E, K
can be stored in the body
excessive intake can be toxic
characteristics of water soluble vitamins
B vitamins, C
involved in energy metabolism
is supplementation with vitamins advised?
no, unless clear deficiency is known (some small athletes with low-energy diets may have deficiencies)
do vitamins improve performance?
not really
vitamins C & E may interfere with what?
muscle adaptations
purposes of precompetition meal
provide adequate hydration, provide CHO to top off liver glycogen stores, avoid sensation of hunger, minimize GI tract issues, allow the stomach to be relatively empty at the start of competition
nutrients in precomp meal
fluid: sufficient to maintain hydration
mostly complex carbs: limit simple sugars, especially fructose
low fat/fiber: to speed gastric emptying
low protein: contributes to acids in blood
food should be familiar
liquid meal replacements can also be used
