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Nutrition for Active Living and Athletes

Factors Governing the Selection of Fuels for Muscular Work

  At rest about ⅔ of the ATP production comes from fatty acids, the other ⅓ from glycogen and glucose.

  At 95% of VO2 max. and above carbohydrate is used almost exclusively.

  During prolonged endurance efforts (e.g. marathons) some of the energy will likely come from protein.

  Remember there are no protein reserves so you are often catabolising your body!

Glucose Metabolism vs. Exercise Intensity

Rest 10 20 30 40

4

3

2

1

0

leg glucose uptake

(mmol/min)

Exercise Time (min)

Severe exercise 75-95% max VO2

Mild exercise 25-30% max VO2

Moderate exercise 50-60% max VO2

2.5 hours 7 hours 12 hours

Muscle Gylcogen Content

30 km Run

Cross-country Skiing 86 km

100 km Run

Duration

Glucose Metabolism vs. Exercise Duration

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Glucose Metabolism vs. State of Physical training  For any given workload fitter person will

be at a lower % of their VO2 max. Hence more ATP from fatty acids than the less fit person.

 Secondly, the trained individual can get a greater % of energy production from fatty acids for any given % of their VO2 max.

Forms of Carbohydrate Fuels   Blood Glucose

 Usually between 90-140 mg/100 ml  Liver plays important role in BG levels  Muscle cannot supply blood with glucose  BG must be obtained from liver or food

  Muscle Glycogen  Once in the muscle cell, glucose cannot go

back out.  But lactate can be transported to liver and

processed back into glucose

Continuous Exercise vs. High Intensity Exercise

20 40 60 80 100 120 180

100

75

50

25

0

Muscle Glycogen (mM/kg)

Exercise Time (min)

31% max VO2

120% max VO2

150% max VO2

83% max VO2

64% max VO2

Level

Level

Level

Uphill

Uphill

Uphill

Vastus Lateralis

Soleus

Gastrocnemius

Glycogen Usage

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0 5 10 15 20 25 30

Fast-Twitch Fibres

Slow-Twitch Fibres

Distance Run (kilometers)

Vastus Lateralis

Muscle Gylcogen Content

0 1 2 3 4 5 6

Fast-Twitch Fibres

Slow-Twitch Fibres

Number of Sprint Bouts

Vastus Lateralis

Muscle Gylcogen Content

Carbohydrate Depletion

Pre Post Pre Post Pre Post 5th Day Day 1 Day 2 Day 3 Post

2.0

1.5

1.0

0.5

0

Muscle Glycogen

10 mile 10 mile 10 mile

(g/100g muscle)

Ergogenic Aids   We briefly discussed

Anabolic Steroids in the strength lecture.

  Many athletes take these illegal substances along with high protein diets.

  Athletes often take legal dietary supplements and engage in other nutritional strategies to improve performance.

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Carbohydrate & Work Time

0 10 20 30 40 50

200

150

100

50

0

Muscle Glycogen (grams/kg muscle)

Work Time (min) Low CHO Diet

Mixed Diet High CHO Diet

Carbo Loading from this study? Per-Olof Astrand

High CHO?   It is universally recommended that

endurance athletes have high daily CHO intake to enhance training load/effects.

 However, there is a failure of longitudinal studies to show consistent training adaptations and performance improvements when comparing high daily CHO intake with moderate-CHO intake. (BurkeLM,PracticalSportsNutr.pp.100,2007)

You have more fat!   From chapter 6 you should remember that

carbohydrate stores are limited so fat oxidation is needed.

  Low CHO availability will improve your ability to metabolize fat.

  Training with low CHO-availability is NOT chronically training on low CHO (or high protein and fat). Instead it is periodically altering CHO-availability acutely around specific training sessions.

Training for endurance (143 level)   This is what the Kenyans do!   Lots of volume   Twice a day runs (18-20km at 6:30am and

16-18km at 4:30pm). Fasted runs (up to 30km) in the morning.

  Training with low CHO availability improves fat metabolism.

  Fartlek (20/25 x 1 min fast, 1 min slow)   HIIT (12 x 1km… up to 3 x 10km)   Fartlek and Interval = 6-11% of load.

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Carbohydrate Loading Method A Carbohydrate Loading Method B 1st day Depletion exercise. 2ndday High carbohydrate diet (50%); regular exercise. 3rdday High carbohydrate diet (50%); regular exercise. 4thday High carbohydrate diet (50%); regular exercise. 5thday High carbohydrate diet (70%); little or no exercise. 6thday High carbohydrate diet (70%); little or no exercise. 7thday High carbohydrate diet (70%); little or no exercise. 8thday Competition. Regular exercise: begin tapering by reducing speed

(intensity) & distance

Carbohydrate Loading Method C Disadvantages of CHO Loading   An increase in muscle glycogen storage also

results in an increase in the water content of muscle. Each gram of glycogen that is stored binds 2.7 grams of water.

  The high fat, high protein dietary period used in Method C is often accompanied by irritability and other signs of hypoglycaemia if an athlete is not used to it.

  Changing diet can be disruptive to athletes. There may be an increased probability of injury or sickness during this period.

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Lance Armstrong In the months leading up to the Tour de France, Lance Armstrong will move from 3,000 calories to 6,000 calories per day and increase the percentage of carbohydrates in his diet (from 60% to 70%). Kristen Bieler, Runner’s World, July 2004

There is probably a danger of overdoing CHO if you are not doing grueling distance

Eating Prior to Athletic Events

 Avoid high glycemic index foods inside 2 hours prior to event

 Some suggest high GI is OK immediately before (??)

 Avoid foods high in fat and protein inside 4 hours prior to event

Ingestion of Glucose Before Endurance Competitions

-20 -10 0 10 20 30 40

5.5

5.0

4.5

4.0

3.5

3.0

2.5

Plasma Glucose

(mM)

Exercise Time (min)

Rebound Hypoglycemia

Ingestion of Glucose Polymer During Endurance Competitions

0 30 60 90 120 135 150 180 195 210 Time (min)

Plasma Glucose (mM)

5.5

5.0

4.5

4.0

3.5

3.0

2.5

Feeding

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Train Low CHO, Race High CHO   Although endurance athletes will train with low CHO

availability (on occasions – not all the time) they will definitely race with high CHO availability.

  They actually train to tolerate high levels of CHO – many athletes cannot tolerate too high a level.

  Marathon case study example:  150 mg caffeine 35 min prior  9 drinking stations (fluid x 7 and power-gel x 3)  Average 190 ml fluid and 20 gram CHO  Average per hour 78 g CHO and 696 ml fluid  CHO solution was 11.1%

Strength/Power Athletes

Endurance Athletes

Mixed (e.g. team sports)

Total Energy

Protein

Carbohydrate

Fat

Lyle McDonald, http://www.bodyrecomposition.com/

Don’t Forget Food Quality!

Supplements   Do you consume any of the

following:  Breakfast cereal  Orange juice  Sports drinks  Bread  Milk  Any packaged goods?

  If you answered yes then you take supplements!

Protein Supplementation   Good sources of protein (athletic view)

 Whey Protein  Eggs & Egg White  Casein

  Milk   Cottage Cheese

 Red Meat  White Meat  Legumes (beans)  Nuts

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Protein Supplementation   Literature suggests that Speed/Power athletes

may lack protein intake:   Typical is 1.0-1.5g/kg bodyweight   Aim for 2.0-4.0g/kg bodyweight

  100 kg athlete should eat 200-400g protein/day. Endurance athletes probably OK to be at low end, power athletes should be at high end.

  Team sport athletes Male 2.5-3.0 g/kg, Female 2.4-2.6 g/kg (McDonald 2009)

  Break protein uptake into 5-6 separate meals

Protein Supplementation

Breakfast Mid-Morning

Lunch Post-workout (30min)

Post-workout (90min)

Dinner

Combo Whey/Egg Whites/Milk Meat

Milk/ Cottage Cheese

Meat Whey Shake Whey/Milk/ Cottage Cheese

Meat

Fruit/cereal

Fruit Low GI carbs (Salad, veggies)

High GI Carbs (sugar, honey)

Low GI Carbs Low GI Carbs

Vitamin Supplements   Vitamin D (Calcitriol) – YES!

  Not just for disease prevention   Will help ensure strong bones   Can help gains in muscle mass   Linked to increased VO2 max!

  Iron (probably not needed for males, often required for females, prob. for all vegetarians)

  Calcium (yes if you eat no dairy)   Zinc/Magnesium (possibly for athletes)   Multivitamin (nutritional insurance?)

Creatine   Creatine is stored as free creatine or

bound to a phosphate molecule in skeletal muscle.

  Creatine supplementation can increase PCr and Cr stores by 10-40% (Kreider, 1998).

  These increased stores improve the ability of your muscles to re-synthesize ATP from ADP following high intensity, short duration exercise.

  There is evidence that creatine works to increase fat free mass, muscle strength, and myofibrillar protein content for those engaged in resistance training

  Probably no more immoral than carbo-loading

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Caffeine  Caffeine is a central nervous system

stimulant. It reduces feelings of fatigue. It also increases:! O2 consumption! urinary output (diuretic)! metabolism! heart muscle contractions!

 Caffeine increases fat metabolism and has been shown to improve endurance performance in numerous studies.!

Other Supplements?   Percentage gains from supplementation?   Genetic potential, smart/hard training and

sensible nutrition are overwhelming factors.   Correct supplementation can give an already

elite athlete an important small % improvement.   Only true if that athlete has their daily nutrition,

and training optimized.   As that is seldom the case – worrying about

fringe supplements is a waste of time.

Nutrient Timing  When to eat certain

foods is important – it is not just about quantities.

Carbohydrate (post exercise)   100-200+ grams of carbohydrate within

two hours of endurance exercise is essential for storing adequate glycogen

  Waiting longer than two hours to eat results in 50% less muscle glycogen .

  Carbohydrate consumption stimulates insulin production that aids storage of muscle glycogen.

  Also consume some carbohydrate (sports drinks, fruit or juice) within 15 minutes post-exercise to help restore glycogen.

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Carbohydrate Plus Protein   Combining protein with carbohydrate in the two

hours after intense endurance exercise nearly doubles insulin response resulting in more stored glycogen.

  The optimal carbohydrate to protein ratio for this effect is 4:1 (four grams of carbohydrate for every one gram of protein).

  Insulin spikes post-exercise are good – remember it is chronically elevated insulin levels that are bad.

“Protein Timing”   Studied quite extensively, definite benefit of

immediate protein feeding post resistance training.

  Pre-workout protein can be beneficial.   Many athletes will consume a protein shake

within 30-minutes of a resistance training session.

  Lean body mass maintained better with 6 meals per day vs. same protein in 2 meals per day – probably protein was more available when needed in the 6 meals a day group.

Protein Timing (Eating Cycles)  Breakfast and 30-min Post workout meals

should be high in quickly absorbed protein   Whey   Egg White

 Evening and 90-min Post workout meals should be high in slowly absorbed protein   Lean red meats   White meats   Casein

Cyclic Diets   Some athletes eat macronutrients in varied

quantities in cycles – a nutrient timing strategy over weeks/months.

  Read section in Chapter 12. More detail than needed for exams except you should understand basic premise.

  High protein, high fat diet increases blood serum levels of anabolic hormones, testosterone, growth hormone (GH) and insulin-like growth factor (IGF-1).

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Cyclic Diets   Cyclic diets better regulate

natural production of testosterone, GH & insulin?

  Shift body from sugar burning to fat burning and decrease catabolic activity in body (i.e. reduce muscle protein breakdown).

  Can increase strength and endurance and decrease excessive body fat.

Cyclic Diets (example)  5 days

  Diet consists of   50% fat, 35% protein, 15% carbs   Fat & Protein from   “Good Oils”, meat, eggs and fish   Full fat cheeses, pepperoni, sausage,

nuts   Carbs down to approximately 100-150g/

day (sports team athletes need more)

Cyclic Diets (example cont.)

 Carbo Load days (1-2 days)   30% fat, 10% protein, 60% carbs

 Breads, rice, pasta, potatoes, pizza, etc.  Two purposes

  Psychological reprieve from low carbs   Intense Carbo load (uptake into muscle

cells) due to starvation during the week.   Similar to Method C carbo-load program

already discussed

Intermittent Fasting   I haven’t read a lot of research on this but I will

briefly mention it as it is “out there” in discussions on how to eat.

  The primary purpose appears to be that during fasting, insulin drops due to the lack of incoming calories from the gut.

  Along with that, blood glucose levels decrease to baseline. With no influx of glucose and fatty acids coming from the gut, there is no need for the storage hormone insulin.

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Intermittent Fasting   Also in the fasted state (around 12-14 hours

after your last meal) we start seeing increases in ACTH, cortisol, glucagon and epinephrine.

  These hormonal changes increase fat mobilization (lipolysis).

  The argument is that during regular fasts of 15-24 hours the body taps into stored fat but never gets too much time to breakdown lots of muscle tissue.

Insulin   Insulin is not the bad guy, it is an essential

hormone….it is just a chronic elevation of insulin that is a BIG problem.

  High carb spikes can be beneficial to release insulin-like growth factor….but…….

  On a constant high carb diets insulin levels are often chronically elevated. You therefore don’t get the edge of maximum release of testosterone, growth hormone and IGF-1.

  Also on the high carb approach, you prevent your body from using body fat for fuel and actually encourage the laying down of new body fat.

SUMMARY (Faccioni)  Nutritional modification for one of the

following:

 Shock body into new growth phase  Reduce body fat stores  Nutritional variation to keep changing

stimulus-result continued adaptation  Similar to exercise?…… do not plateau,

add variety, periodization, etc.

Mechanisms of Heat Loss

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Mechanisms of Heat Loss Heat Gain  Basal Metabolic Rate - heat production of a

resting person is about 75 kcal/hr. If no heat was lost, core temperature would increase approximately 1.3oC per hour.

 Exercise - can increase heat production 10-20 times basal rate.

 Shivering - involuntary muscular activity can produce as much as 350 kcal/hr.

 Thermogenic effect of food - digestion of food raises the metabolic rate above fasting level .

Heat Flux Equation Temperature Regulation  The function of the thermoregulatory

system is to maintain a relatively constant internal body temperature. At rest the system strives to keep the temperature at 37oC. This is the reference temperature. In exercise, this reference temperature is increased

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A: Thermal Receptors  Central receptors - located in the

hypothalamus of the brain - sensitive to the temperature of the arterial blood perfusing them.

 Peripheral receptors - hot and cold receptors located in the skin. These sensors act as an early warning system that relays sensory information to the hypothalamus.

B: Effectors   Skeletal muscles - shivering, physical activity.   Smooth muscles encircling the arterioles that

supply blood to the skin.   Sweat glands.   Endocrine glands - thyroid, adrenal medulla.   Hot Environment - vasodilation and sweating.   Cold Environment - vasoconstriction,

shivering, increased heat production from metabolism.

C: Regulatory Centre

  Located in the hypothalamus - analogous to a thermostat in a house.

  In exercise, the setting of the body's thermostat is elevated. Heat dissipation mechanisms don't begin until the body core has warmed up to a level closely related to the relative exercise intensity (percent VO2 max).

Exercise in the Heat ê cardiac output & O2 transport to working muscle

Excessive Sweating ê plasma volume Interference with

temperature regulation

Result: Increased core temperature Decreased endurance capacity

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Heat Disorders in Athletics  Heat illness in order of increasing severity

are heat cramps, heat exhaustion and heat stroke.  Heat exposure  Loss of water and salt  Heat storage

 Athletes susceptible because:  they are competitive - ignore discomfort  clothing and equipment  coach may deny water.

Acclimatization   This involves the gradual increase in

duration and intensity of activities over a 10-15 day period.

  increased cutaneous blood flow, better distribution of cardiac output, lower resting body temperature, lower skin and core temperatures during exercise, decreased exercise heart rates and metabolism, and increase in onset and amount of sweating and cooling by evaporation of sweat (less salt in sweat).

Wet-Bulb Globe Temperature (WBGT) Apparent Temp

Danger Category

Injury Threat

Below 80o None Little or no danger under normal circumstances

80o to 90o Caution Fatigue possible if exposure is prolonged and physical activity

90o - 104o Extreme caution

Heat cramps/heat exhaustion possible if prolonged exposure

and physical activity 105o- 130o Danger Heat cramps or heat exhaustion

likely, heatstroke possible if prolonged exposure & phys activity

Above 130o Extreme Danger

Heatstroke highly likely

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Fluid Replacement Guidelines   Hydrate properly before prolonged exercises   Drink approx. 0.5 litres (16 fluid ounces) of a cool

beverage 2 hours before a workout.   Drink frequently. Approx. 6-8 fl. oz. every 15

min (NOW CONSIDERED POOR ADVICE)   Cool beverages around 10-20oC are ideal   Fluids should be readily available   Replenish fluids after exercise

  (around 0.5 Litres for every 0.45 kg of body weight lost)   Water is the ideal fluid replacement for short endurance

events (some salt can help)   Is dehydration or depletion of glycogen the issue?   Hypertonic beverages can be dangerous.

Dipsomania and Hyponatraemia

  More detail in the course text

Hyponatremia  Deficiency of sodium in the blood. It can

occur as a result of inadequate sodium intake, as in a sodium-restricted diet, excessive water ingestion or retention, or excessive sweating. Symptoms include muscular weakness and twitching, progressing to convulsions if unrelieved; alterations in level of consciousness; mental confusion; and anxiety.

Dipsomania  Definition:

“Uncontrollable desire for drink, especially alcohol.”

  In our context we are concerned with excessive water (or sports drinks) intake.