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 - switching to aerobic & depleted glycogen stores
time to exhaustion is related to..
initial muscle glycogen stores
the larger your storage capacity for glycogen the longer youll be able to put off exhaustion
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 (High-CHO diet = even greater synthesis)
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 (tapering?)
**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
* run risk of detraining with three days of inactivity
modified plan of muscle glycogen supercompensation
1) tapering workouts (90 down 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
with this plan we still see compensation within completely depleting glycogen stores
major purpose (ie what outcome we’re shooting for) of glycogen loading prior to prolonged exercise?
improve performance - running out of glycogen either mean exercise must stop or preformance is impaired
what does consuming CHO 30-45 minutes prior to exercise cause? why?
- faster rate of muscle glycogen utilization (faster decline)
- fall in blood glucose during exercise caused by spike in insulin (not dependent on amount of CHO consumed)
best time to eat CHO before exercise
- 2-3 hours before: allows time for digestion
- 5-10 mins before: quick energy - minimizes risk of hypoglycemia
3 recommendations on CHO intake before exercise (type, timing, form)
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)
* must ingest by the 2 hr mark or its too late to recover blood glucose
How many gels would a 30 year old female cyclist need to consume durin a 3 hour road race (1 gel = 21 g CHO)
30-60 g CHO/hr x 3 hrs = 90-180
90/21 = ~4
180/21 = ~8
4-8 gels
advantage of consuming CHO after exercise
We can enhance glycogen synthesis after exercise by feeding during the window of increased glycogen synthase activity