Nutrition for Physical Activity & Sport

Readings: Chapter 14

Omit “Muscles & Muscle Fibers”, p. 559

What is Physical Fitness?Definition• the ability to perform moderate to vigorous

levels of physical activity without undue fatigue and the capability of maintaining this level of activity throughout life (ACSM)

Components: Cardiorespiratory Fitness Muscular Strength Muscular Endurance Flexibility

Physical Activity vs. Exercise

Physical Activity– any body movement carried

out by skeletal muscles and requiring energy

Exercise– a subset of physical activity

that is planned, structured, repetitive movement of the body designed to improve or maintain physical fitness

Benefits of Regular Physical Activity

Exercise is one of the most important things you can do to improve your

wellness!

• sedentary individuals have 50% more health problems that active individuals including increased risk of:

• hypertension• diabetes• obesity• hyperlipidemia• osteoporosis

Benefits of Physical Fitness• improved sleep• nutritional health• healthy body composition• healthy bone mineral density• improved immune function• reduced risk of CVD, Type II diabetes, some cancers• reduced stress and anxiety• improved self-esteem and lowered risk of depression• improved cognitive functioning, alertness and memory• injury reduction and low back pain• greater longevity and quality of life

* Recommendations from the WHO & the Institute of Medicine

Becoming more active…How much is needed to reap health

benefits?• 60 minutes of moderately intense physical activity every

day*

Is Lifestyle Physical Activity enough?• increased lifestyle physical activity promotes improved

health and well-being but does not necessarily improve physical fitness

• exercise programs designed to improve physical fitness contribute to even greater improvements in quality of life and greater reductions in disease and mortality risk

Canada’s Guide for Healthy Active Living

http://www.phac-aspc.gc.ca/pau-uap/fitness/pdf/guideEng.pdf

Increase Strength Activities

Increase Flexibility Activities

Increase Endurance Activities

days a weekContinuous activities for your heart, lungs, and circulatory system.

days a weekGentle reaching, bending, and stretching activities to keep your muscles relaxed and joints mobile

days a weekActivities against resistance to strengthen muscles and bones and improve posture

Reduce sitting for

long periods

4 - 7

4 - 7

2 - 4

Sources of Energy for Physical Activity

• physical activity increases the energy needs of working tissues including the muscles and the heart…where does this energy come from?– ATP & CP– Carbohydrate: Glucose/Glycogen– Fat– Protein

1. ATP & CP

• very small pool of ATP available in cells

• CP (creatine phosphate) can release phosphate which combines with ADP to form ATP

• supplies are limited, fuels activity for 3 - 15 seconds of maximal effort

• anaerobiccreatine phosphate + ADP creatine + ATP

exercise

rest

ATP-CP Energy System

2. Carbohydrate: Glucose• derived from muscle & liver glycogen

stores• fuels activities of extreme intensity (20 s

to 3 minutes):– oxygen needs of muscle exceed the

ability of cardiovascular system to supply oxygen

– glucose is used anaerobically (without oxygen) to produce ATP

– by-product is lactate

Anaerobic Metabolism of Glucose

2. Carbohydrate: Glucose

• in activities of high intensity (3 to 20 minutes):– glucose is used AEROBICALLY (with

oxygen) to produce ATP• in activities of moderate intensity (> 20

minutes):– glucose oxidation is supplemented

with fatty acid oxidation

3. Fat Metabolism• initially during exercise blood [fatty acid]

decreases• after 20 minutes there is an increase in release

of fatty acids from stores– due to hormone epinephrine (adrenalin)

• endurance training produces adaptations that enhance the ability to burn fat ’d size & number of mitochondria in muscles ’d number of capillaries to supply oxygen &

nutrients to muscles

4. Protein

• not a primary fuel for physical activity• contributes about 5 - 10% to energy

expenditure both during activity and at restFactors that influence protein use during

activity:– high dietary protein– increased duration of activity – increased intensity of activity – increased training (especially

strength training)

increase use of protein as a

fueldecrease use of protein as a

fuel

Effect of Intensity & Duration on Fuel Use

increased duration, decreased intensity

fatty acid oxidation

glucose utilization

decreased duration, increased intensity

fatty acid oxidation

glucose utilization

Effect of Intensity & Duration on Fuel Use

Summary…

Summary…

Duration Intensity Preferred Fuel Source

8 – 10 seconds EXTREME

20 sec – 3 min VERY HIGH

3 – 20 minutes HIGH

> 20 minutes MODERATE

ATP - CP

anaerobic glycolysis

aerobic glycolysis

fatty acid oxidation

Note: all energy sources are used to some extent at all times

Effect of Diet on Physical Endurance

Maximum Endurance Time

• fat and protein diet

• normal mixed diet

• high carbohydrate diet

57 min

114 min

167 min

Diet to Support Physical Activity

Water• nutrient required in largest amounts by the

body• needs increase during physical activityBody can lose water in four ways:

– urine– feces– sweat– respiration

**

* Loss increases during physical activity

Water & Temperature Regulation

• heat production increases 15-20x during exercise compared to rest

• body cools itself by sweating– 1 L of sweat dissipates about 600 kcal of heat– prevents an in body temperature of about 10°C

• EVAPORATION of sweat cools the body• blood is rerouted through capillary beds that lie just

beneath surface of skin to cool the blood• endurance athletes can lose 1.5 L of water or more

during each hour of activity

Lance Armstrong said blistering temperatures and not drinking enough fluids gave him a challenging day in the saddle during the 2003 Tour de France's 12th-stage time trial, won by German rival Jan Ullrich.

Water & Temperature Regulation

• in hot humid weather, need for water ’s even more

• dehydration not only decreases performance but can cause dizziness, cardiac arrhythmias, muscle spasms, delirium, and death

Hydration Schedule

2 hrs before 400 – 600 ml

15 min before 250 – 500 ml

every 15-20 min during 150 - 350 ml

after exercise 500 ml for each lb body weight lost, or 1.5x body weight lost

Water & Temperature Regulation

Too much water?• leads to a condition called HYPONATREMIA• symptoms include swelling, weight gain, nausea,

and dizziness• may occur in events where individuals replace more

water than they lose and do not replace electrolytes causing dilution of sodium in the blood

Electrolytes

• in addition to contributing to water loss, sweat also results in loss of electrolytes– electrically charged minerals– Na+, K+, Cl-, and Mg2+

• minerals are important for water balance• losses normally replaced through diet

– for exercises lasting longer than 1 hour, replacement of fluids with water & electrolytes may provide a performance advantage

– more important for athletes in competitions lasting 4+ hours with heavy sweating

Replenishing Energy DURING activity…

• during endurance activities lasting longer than one hour, glycogen supplies risk depletion

• maintaining blood glucose levels can prolong time to exhaustion

• glucose replacement (200 kcal) useful in activities lasting longer than 1 hour

• sports drinks with 6 - 10% carbohydrates (50 - 100 kcal per cup)

• depends on goal of exercise!

Replenishing Energy AFTER activity…

• a high carbohydrate meal eaten within 15 minutes accelerates rate of glycogen storage by 300%, called “glycogen window”

• Are energy bars or drinks necessary?

Glycogen Depletion and Fatigue Sensation

Protein in the Athlete’s Diet

• athletes have increased need for protein due to need to repair and build muscles after activity (max 2.0 g/kg body weight)

• see Table 13.4 for recommended intakes• protein intake after exercise helps replenish

glycogen storesToo much protein? Risks of Supplements:

– dehydration– displacement of carbohydrates from diet, insufficient

replenishment of glycogen stores– kidney problems

Fat Intake and the Athlete

• Fat intake should not be overly restricted. There is no performance benefit in consuming a diet with less than 15 percent of energy from fat. Extreme fat restriction limits food choices, especially sources of protein, iron, zinc, and essential fatty acids.

• Sports nutritionists recommend that any extra fat calories come from monounsaturated and polyunsaturated sources.

Vitamins and Minerals• many vitamins and minerals are important for energy

metabolism• deficiencies impair performance• extra from supplements DO NOT enhance physical

performanceIron• physically active young women prone to iron

deficiency• multiple contributing factors• supplementation should be based on blood tests, not

self-assessment