Chapters 18 & 22 Flashcards
energy balance equation
change in macronutrient energy stores = energy intake - EE
- energy intake = food consumption
- EE = REE + PA/E + TEF
REE
resting energy expenditure
PA/E
physical activity/exercise EE
TEF
thermic effect of food
DRI
dietary reference intakes
quantity of nutrients needed for proper function and health
is the basis for RDA and AI
RDA
recommended daily allowances
quantity of each nutrient to meet the needs of nearly all (97-98%) healthy persons within a specific life stage
AI
if one can’t use RDA then use AI
recommended daily intake based on apparently healthy people
BMI
weight (kg)/height (m2)
EER
estimated energy requirement
average dietary energy intake predicted to maintain energy balance considering age, sex, weight, height, and level of physical activity
classes of nutrients
carbs
fats
proteins
water
mineral
vitamins
carbohydrates
sugar and starches that can be digested and metabolized for energy
blood glucose is maintained with narrow limits by
the endocrine system
1 gram of CHO yields how many kcal energy
4
dietary fiber is a
CHO
characteristics of dietary fiber
cannot be digested or metabolized
provides a sense of fullness during a meal
reduces transit time in intestine
who needs more fiber : men or women
men need more
as exercise intensity increases what happens to fuel selection
increase in fat use and decrease in CHO due to a limited number of glycogen stores
as exercise duration increases what happens to fuel selection
contribution of fats is much greater than contribution of CHO
time to exhaustion is related to
initial muscle glycogen stores
increased muscle glycogen stores = increased duration
*increased storage capacity for glycogen = more likely you will be able to extend that duration at LT (~70% VO2 max)
muscle glycogen level is dependent on
1) CHO content of diet
2) prior exercise
3) muscle glycogen “supercompensation”
effect of high CHO diet on endurance performance
performance is increased by a diet high in CHO
- increases muscle glycogen and performance time
- most important in events at high intensity lasting more than one hour because we usually have enough glycogen stores on board to sustain 40-60 min of exercise
how does prior exercise effect muscle glycogen level
glycogen depletion leads to greater synthesis following exercise
*regardless if you have a high or low starting CHO diet, we all have same starting muscle glycogen point
* those with high CHO diets are able to recover their glycogen levels almost back to normal vs those who do not consume as high CHO in their diets (they can’t even get to half the original amount)
muscle glycogen sypercompensation
the effects of exhausting exercise and diet on quadriceps muscle glycogen content
only exercise one leg:
- exhausting exercise depletes glycogen content in active, exercised leg
- rest and high CHO diet results in glycogen overshoot (supercompensation) in the exercised leg ONLY
- unexercised leg remains at baseline glycogen levels
two methods for supercompensation
classical
modified
classical method
prolonged (high intensity) exercise to deplete glycogen stores
then eat a high fat/protein diet for three days while continuing to train (avoid CHO to deplete glycogen)
then eat a 90% CHO diet for three days with inactivity to lead to supercompensation
modified plan
tapering workouts (90 to 40 minutes) over several days while eating 50% CHO diet
two days of 20 minute workouts while eating 70% CHO diet
day of rest eating 70% CHO diet before event
leads to supercompensation
CHO intake before exercise 30-40 minutes prior to exercise may cause
not optimal
faster rate of muscle glycogen utilization
fall in blood glucose during exercise (not dependent on amount CHO consumed)
- any meal in general = spike in insulin = decrease blood glucose levels
recommendations for CHO intake before exercise
eat either 2-4 hours before or consume CHO in the last 5 min before exercise or during warm up to minimize risk of hypoglycemia
avoid high glycemic index CHO
the form of CHO does not matter
CHO intake during exercise
CHO ingestion can maintain plasma glucose even as glycogen is depleted which delays fatigue and improves performance
* can be ingested throughout exercise or prior to fatigue
how many g/CHO is required during exercise to improve performance
30-60 g/CHO
CHO intake after exercise
glycogen synthesis is enhanced after exercise due to increased glycogen synthase activity which is why CHO should be consumed IMMEDIATELY after exercise (within 30 minutes)
- high glycemic index foods are better (such a s sports drink which is easily digested) and addition of protein is also helpful
how many CHO should be consumed immediately after exercise
1-1.5 g/kg within 30 minutes
and then at 2 hour intervals for 6 hours
which is the addition of protein with CHO helpful immediately after exercise
reduces CHO need to resynthesizes glycogen and enhances muscle protein synthesis
fats
fuel for energy involved in :
hormone synthesis
absorption of fat-soluble vitamins
cell membrane structure
insulation
protection of vital organs
are proteins a major source of energy
no
only during starvation or really high intensity workouts
high quality proteins contain
the 9 essential AA that cannot be synthesized by the body (i.e. must be consumed)
do most americans meet protein intake requirements?
yes
0.8 g/kg/day
* requirements may be higher for athletes
average athlete intake for proteins
1.5 g/kg/day
body loss of ___ affects performance
3-4%
water loss per day
under normal conditions without exercise, water loss ~ 2500 mL per day (most in urine)
water gain at rest due to
fluid intake (most)
food intake
metabolic water production (least)
water loss at rest due to
skin and respiration
sweat loss
urine (most)
fecal loss
water loss during exercise due to
sweating (almost all of it)
insensible water loss
water lost in sweat during exercise depends on
exercise intensity and environmental conditions
water losses during sweat during exercise may be as high as
2.8 L/hour
fluid replacement before exercise
goal is to be euhydrated before exercise to prevent dehydration (this is usually sufficiently met from food and bevs)
* if additional fluids are needed:
- slowly drink beverages at least 4 hours prior
-drink more fluid if urine is dark or none is produced two hours prior
- sodium in bevs or salted snacks help retain fluid
fluid replacement during exercise : goal
to reduce the risk of excessive dehydration
*important for both prolonged and intermittent exercise
fluid replacement during exercise is associated with
lower body temp
lower HR
lower RPE
*cardiac drift is lowered and can maintain steady state for longer
water replacement during exercise for events <1 hour
water is sufficient
water replacement during exercise for events >1 hour
CHO water solution with electrolytes
water replacement after exercise
goal is to replenish water, electrolytes, and muscle glycogen
~1.5 L fluid for every kg weight loss
* cold drinks more effective
* CHO-electrolyte bevs or skim milk equally effective
calcium function
provides bone and tooth strength
helps blood clotting
aids nerve impulse transmission to release ACh from synaptic bulb
required for muscle contraction
calcium dietary sources
animals and leafy greens
calcium homeostasis
the bones are a store of Ca2+ that helps to maintain the plasma [Ca2+] when dietary intake is inadequate
- if not getting enough Ca2+ from diet, body pulls Ca2+ from bones= not ideal = could lead to osteoporosis
falling blood Ca2+ level leads to
release of PTH from parathyroid gland which stimulates Ca2+ release from bones and Ca2+ uptake in kidneys which allows blood Ca2+ levels to rise back to set point
increased blood Ca2+ levels leads to
thyroid gland releases calcitonin which stimulates Ca2+ depoistion in bones and reduces Ca2+ uptake in kidneys which allows blood Ca2+ to return back to set point
iron
found in Hb in RBCs which is involved in O2 transport to cells
who needs more iron: males or females
females need more iron
dietary sources for iron
meat and non-meat sources
what is the #1 deficient nutrient in the world
iron
iron deficiency affects
VO2 max and endurance
*if I can’t bind RBCs it doesnt matter what stimulus tells us to produce RBCs, we need the materials (iron) to make them
iron deficiency in athletes
more common in female athletes and distance runners
due to decreased intake and decreased absorption (diets low in red meat, dieting for weight loss, and vegetarian diets)
due to increased loss of iron through sweat, feces, and urine
how do we transport/measure iron
using ferritin and transferrin
- without them we cannot release iron for erythryopoeisis
iron supplementation
increase iron intake through foods will rapidly restore hematocrit and VO2 max leading to a slower increase in mitochondrial activity and endurance
sodium function
major ion of EC fluid
directly involved in maintenence of resting membrane potential
responsible for generation of action potential in nerves and muscles - for hyperpolarization/depolarization
what kind of individuals may require more salt intake
athletes require more salt than sedentary individuals because they must replace the salt they lost in sweat but this is usually not a problem because most people consume more salt than is required
salt needs should be met at
meals and not via salt tablets
what is the best test of salt/water replacement
body weight (measuring before and after exercise)
- constant body weight indicates adequate salt and water intake
fat soluble vitamins
A
D
E
K
*stored in body in adipose tissue
excess intake of fat soluble vitamins leads to
toxicity
water soluble vitamins
$$ urine
involved in energy metabolism
B and C vitamins
Vitamin C involved in
maintenance of bone, cartilage, and connective tissue
supplementation of vitamins
not necessary on a well balanced diet unless clear deficiency is known
* some small atheletes who consume low energy diets may have deficiencies
would supplementation of vitamins improve performance
may not
* no evidence for vitamin D supplementation
* antioxidant (Vitamins C and E) may interfere with muscle adaptations
purposes of pre-competition meal
provide adequate hydration
provide CHO to top off liver glycogen stores
avoid hunger
minimize GI tract problems
allow stomach to be relatively empty at start of competition
nutrients in pre-competition meal
fluid
most complex carbs (for slower breakdown of food over time)
low in fat and fiber= speed gastric emptying
low in protein = contributes to acids in blood, lots of energy to break down
familiar well liked
liquid replacement means also can be used
