Transcript ch01_lecture

Introduction to Nutrition for
Health, Fitness, and Sports
Performance
Williams, 8th edition,
Chapter 1
Starting Points
• Review effects of regular exercise on
risk for disease (Table 1.1)
• Review health problems associated
with poor dietary habits (Figure 1.5)
• Define “moderate amounts” of physical
activity (Table 1.2)
• What is “Sedentary Death Syndrome?”
Surgeon General’s Report on Physical
Activity and Fitness: weekly caloric
expenditure from exercise should meet
or exceed 1000 per week.
General guidelines for exercise
(See pyramid - Figure 1.3)
• Level I: 30 minutes daily: low-intensity
• Level II: 3-6 days/week, > 20 minutes
at 50-85% increase in heart rate
• Level III: 3-7 days/week stretching
to fitness
• Level IV: 2-3 days/week resistance
activities
• Level V: physical inactivity (e.g. TV
watching
Can too much exercise be
harmful?
• A few health risks of “over exercising” 
impaired immune function, increased risk of
injury, and menstrual irregularities for
women
• See “Revised Dietary Guidelines for
Americans”
http://www.health.gov/dietaryguidelines/
Key recommendations:
– http://www.health.gov/dietaryguidelines/
dga2005/recommendations.htm
What is fitness?
Health related fitness
– Body weight and body composition within
normal range
– Cardio-respiratory fitness
– Adequate flexibility, strength, and
endurance
– Appropriate body composition
Sports-related fitness: ability to
maximize genetic potential with
appropriate physical and mental
training
• General definition of physical activity
is any movement caused by muscle
contraction that results in caloric
expenditure.
• Components of Fitness:
– Flexibility
– Strength
– Endurance (muscular and cardiorespiratory)
• Flexibility: range of motion of a joint:
(e.g. lower back, hamstrings, shoulder
rotation)
• The structure of the joint itself, and
the muscles and connective tissue
(ligaments and tendons) that surround
it restrict flexibility.
• Using a variety of stretches will
increase flexibility. Static stretches
are most common, and involve putting
the intended muscle to be stretched
into a lengthened position and holding
that stretch for at least 12 - 15
seconds
Muscular strength and endurance:
Strength: ability of muscles to move against force
• Static or “isometric” strength: muscle action with no
noticeable change in muscle length (e.g. pushing
against resistance)
• Dynamic constant external resistance (DCER)
training: resistance training where external
resistance of weight does no change; joint flexion or
extension occurs with each repetition (formerly
known as “isotonic” exercise)
• Dynamic strength measures are done using the “one
repetition maximum (1-RM) technique; device used is
a dynamometer.
 Isometric: force, no joint
movement
 Concentric: force, while muscle is
shortening
 Eccentric: force, while muscle is
lengthening
For strength training, apply:

Resistance

Repetition

Overload
Result  hypertrophy
Isometric exercise
Source:
www.Bodylicious
Workout.com
Concentric exercise (biceps curl)
Source: www.netfit.co.uk/ assets/bicep8m.gif
Eccentric exercise
Overhead
squat
Source:
http://www.hhs.csu
s.edu/homepages/k
hs/Kilogram4/publi
c/KINS%20144/Kin
s144_OSQ.htm
Muscular endurance: ability of muscle to
sustain repeated contractions
– Measured by field tests (e.g. 60-second sit-up
test, or measuring number of sit-ups done
without rest.
– Another test: YMCA bench-press test; involves
performing standardized repetitions at a rate
of 30 per second.
• Cardio respiratory endurance:
Ability of heart, blood, and lungs to sustain
moderate to high intensity exercise for 20
minutes or more
Overall definition of nutrition: sum total
of processes involved in intake and
utilization of food substances by living
organisms, including ingestion, digestion,
absorption, transport, and metabolism of
nutrients in food
Sports-related fitness:
• Strength
• Power
• Speed
• Endurance
• Sport-specific neuromuscular motor
skills
• Ability to succeed in sports is largely
related to:
– Genetic endowment
– State of training
– Nutritional status
• Example: losing excess body fat will
enhance biomechanical efficiency
• Consuming carbohydrates during exercise
helps maintain normal blood sugar levels
and delays fatigue
• Adequate dietary iron prevents anemia
and ensures maximal oxygen delivery to
working muscles
• Sports nutrition: defined as the
“application of eating strategies to
promote good health and adaptation to
training, to recover quickly after each
exercise session, and to perform
optimally during competition” (Louise
Burke, in Williams, p. 14)
• Are athletes getting adequate nutrition?
• Groups that may be “at risk” due to
restrictive dieting: dancers, gymnasts,
body builders, distance runners are most
susceptible to inadequate diet
• Malnutrition: unbalanced nutrition
(either over or under needs).
• Basic purposes of food:
– To provide energy (calories)
– To regulate metabolic processes
– To support growth and development
• Certain diet modifications will influence
performance (e.g. high CHO
endurance)
• Diet for training:
Depending upon length and intensity of
exercise  may need extra 500-1000
extra calories a day.
What does a “sports nutritionist” do?
• Sports nutrition is a specialty that requires
traditional nutritional science studies
(minimum - BS in Nutrition)
• Involves investigation of interactions
between dietary manipulations and physical
performance
• Assessments and recommendations given
based on specific needs of athletes
• Ongoing research and review of professional
publications as well as attendance at annual
professional meetings is necessary
• See: http://www.scandpg.org/ (Sports, Cardiovascular,
and Wellness Nutritionists – Dietetic practice group)
Chronic training effect
• E.g. effect of “early” training for
long-distance running: increased
hemoglobin and myoglobin production
and cytochromes in muscle cells.
• These demand increased iron - often
a transient “sports anemia” may
develop.
• Excessive training may lead to
chronic fatigue
Role of dietary supplements:
• DSHEA definition: a food product that has at
least one of following: vitamin, mineral, herb, or
botanical, amino acid, metabolite, constituent,
extract, or combination of any of these
• (Note that most Americans do not suffer from
dietary deficiencies, yet over 40% regularly
take supplements)
• NOTE: Under DSHEA law (1994), any product
sold as a “nutritional product’ is free from FDA
approval, but this does not mean that all
products are safe. FDA must show in court
that there is an unreasonable risk posed by a
supplement to have it taken off market.
About supplements:
1. No scientific body regularly
recommends supplements
2. Food is more than the sum of its
nutrients  may be other beneficial
substances in food, making them a
better choice. Also, nutrients in
food and other food components
may be better absorbed in
combination than in isolation.
3. Dietary supplements vary WIDELY
in quality; some brands may contain
zero levels of the active ingredient
• Ergogenic aid: anything that increases work
performance
• Different classifications:
1.
Psychological
2.
Physiological
3.
Pharmacological
4.
Nutritional
• While most nutritional ergogenic aids are
legal, they may not all be safe.
• Note dangers of ephedra, DHEA,
androstenedione
Research and recommendations:
1. Epidemiological: studying large
populations to find relationships
between 2 or more variables;
researchers trace history and
patterns. (example higher fat diets
– greater incidence of heart disease)
2. Experimental: usually double-blind,
placebo controlled; lab-based
setting, variables are manipulated.
3. If study is done to determine
effects of a supplement, good to
have many variables tested.
• Example: a study on the effects of a
CHO drink and endurance exercise may
involve 2 groups: an experimental group
that would receive the high-CHO drink,
and a control group that would receive a
placebo drink. After administering the
drink to both groups, they would perform
an endurance activity (e.g. long distance
run or cycle). Observations might
include: blood sugar levels at various time
increments of the exercise, lactate
threshold, rating of perceived exertion,
and the length of time each participant
was able to exercise.
The independent variable (IV) or the
variable that could be manipulated
would be the sports drink:
(high CHO or placebo)
The dependent variables (DV) would be
blood sugar levels, lactate threshold,
rating of perceived exertion, and the
length of time of exercise.
Another example: A study is conducted to
examine the effects of pre-exercise
fluid–electrolyte solution intake on
rating of perceived exertion (RPE)
What is the IV? The DV?
Epidemiological research:
• Studying large populations to find
relationships between 2 or more
variables
• People (“subjects”) may be followed
for many years
• Example: Scientists may be looking at
relationships between diet and
exercise practices and health related
indicators (e.g. blood pressure, Body
Mass Index, blood glucose, heart
disease)
Characteristics of sound research:
• What type of design was used
(Experimental? Double blind?)
• Placebo controlled?
• Many variables?
• Were “extraneous” variables
controlled?
• Background or credentials of
researchers?
• Who financed the study (is there a
conflict of interest?)
What is a meta-analysis?
• Review process that involves statistical
analysis of previous studies.
• Many studies on a particular subject are
reviewed
• Patterns are examined
• (E.g. What are the findings from studies
done over the last 20 years on the effects
of caffeine ingestions on exercise
endurance?)
• May find meta analyses published in
professional journals
Next topic:
• Review dietary recommendations for athletes
• Must have good working knowledge of
exchange lists and proposed new food guide
pyramid
• Read: Rebuilding the Food Pyramid
• Walter C. Willett and Meir J. Stampfer /
Scientific American Jan03 at:
http://www.mindfully.org/Food/2003/FoodPyramidJan03.htm
• Be prepared to discuss in next class!!