Transcript Presentation Package - Information Technology at La Trobe

chapter
15
Ergogenic Aids
and Sport
Learning Objectives
• Review various substances that have been proposed to
be ergogenic aids—substances or phenomena that
enhance performance
• Learn the importance of including control groups and
placebos when studying the ergogenic properties of a
substance
(continued)
Learning Objectives (continued)
• Find out the proposed ergogenic benefits, proven
effects, and risks of several pharmacological, hormonal,
physiological, and nutritional agents
• Discover which substances that have been considered
ergogenic are actually ergolytic—that is, they impair
performance
Ergogenic vs. Ergolytic
Ergogenic aid: any substance or phenomenon that
enhances performance
Ergolytic agent: any substance or phenomenon that
has detrimental effects on performance
Researching Ergogenic Aids
Placebo effect: An effect produced by the subject’s
expectations after administration of an inactive
substance (placebo)
The Placebo Effect
on Muscular Strength Gains
Data from G. Ariel and W. Saville, 1972, "Anabolic steroids: The physiological effects of placebos," Medicine and
Science in Sports and Exercise 4: 124-126.
Pharmacological Agents
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Sympathomimetic amines
Beta-blockers
Caffeine
Diuretics
Recreationally used drugs
Sympathomimetic Amines:
Amphetamines
• Central nervous system stimulants
• Examples: ephedrine and pseudoephedrine
• Proposed benefits:
– Increased concentration and mental alertness (state
of euphoria)
– Decreased sense of mental fatigue
– Enhanced athletic performance (speed, strength,
fatigue resistance)
Proven Effects and Risks
of Sympathomimetic Amines
Proven effects
Risks
• Weight loss
• Reaction time, acceleration,
and speed
• Strength, power, and
muscular endurance
• Possibly aerobic endurance
• Higher maximum heart rates
and peak lactate
concentrations at exhaustion
• Better focus
• Fine motor coordination
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Death
Cardiac arrhythmias
Delay the sensation of fatigue
Extreme nervousness
Aggressive behavior
Insomnia
Beta-Blockers
• Prevent the binding of norepinephrine and decrease
the effects of the sympathetic nervous system
• Proposed benefits: may improve accuracy (for shooting
sports), decreased anxiety
• Proven effects: decrease maximum and submaximal
heart rate and improve scores in shooting sports
• Risks: bradycardia, heart block, hypotension,
bronchospasm, hypoglycemia, fatigue, and decreased
motivation
Caffeine
• CNS stimulant; effects are similar to amphetamines
• Proposed benefits:
– Increased mental alertness, concentration, reaction
time, and energy level
– Reduced fatigue
– Increased mobilization and use of FFA
Proven Effects and Risks of Caffeine
Proven effects
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↑ Mental alertness
↑ Concentration
Elevated mood
↓ Fatigue and delayed
onset
↓ Reaction time
↑ Catecholamine release
↑ FFA mobilization
↑ Use of muscle
triglycerides
Risks
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Nervousness
Restlessness
Insomnia
Headache
Gastrointestinal problems
Tremors
Dehydration
Diuretics
• Increase urine production and excretion
• Used for weight reduction and to mask other drugs
during drug testing
Proven Effects and Risks of Diuretics
Proven effects
• Significant temporary
weight loss
• ↓ Aerobic capacity
Risks
• ↓ Thermoregulation
• Electrolyte
imbalances
• Fatigue
• Muscle cramping
• Exhaustion
• Cardiac arrhythmias
• Cardiac arrest
Hormonal Agents
• Anabolic steroids
• Human growth hormone
Anabolic Steroids
• Are nearly identical to male sex hormones; synthetic
form maximizes building effects
• Proposed ergogenic benefits
– ↑ Fat-free mass and strength
– ↑ Recovery from exhaustive training bouts
Proven Effects and Risks
of Anabolic Steroids
Proven effects
Risks
• ↑ Body mass and fat-free
mass
• ↑ Total body potassium and
nitrogen
• ↑ Muscle size
• ↑ Strength
• Testicular atrophy
• Reduced sperm count
• Prostate and breast
enlargement in men
• Breast regression,
masculinization, and
menstrual cycle disruption in
women
• Personality changes
• Liver damage
• Cardiovascular disease
Percent Changes in Body Size, Body
Composition, and Strength When Athletes
Used Anabolic Steroids and a Placebo
Adapted from G.R. Hervey et al., 1981, “Effects of methandienone on the performance and body composition of men
undergoing athletic training,” Clinical Science 60: 457-461.
Relationship Between Total Dose
of Steroid and Change in Fat-Free Mass
(in kg)
From an article published in Metabolism, vol. 34, G.B. Forbes, "The effect of anabolic steroids on lean body mass:
The dose response curve," pp. 271-573, Copyright 1985.
Changes in Fat-Free Mass and Quadriceps
and Triceps Muscle Areas From MRI, and
Changes in Strength
Reprinted, by permission, from S. Bhasin et al., 1996,
“The effects of supraphysiologic doses of testosterone
on muscle size and strength in normal men,” New
England Journal of Medicine 335: 1-7. Copyright © 1996
Massachusetts Medical Society. All rights reserved.
Human Growth Hormone
• Secreted naturally by pituitary; synthetic form used by
some athletes
• Proposed ergogenic benefits:
– Stimulation of protein synthesis in skeletal muscle
– Stimulation of bone growth (if growth plates are not
yet fused)
– Increased insulin-like growth factor synthesis
– Increased lipolysis
– Increased blood glucose
– Enhancement of healing after musculoskeletal injury
Proven Effects and Risks
of Growth Hormone
Proven effects
Risks
(only in men > 60 years old)
• ↑ Fat-free mass
• ↓ Fat mass
• ↑ Bone density
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Acromegaly
Cardiomyopathy
Glucose intolerance
Diabetes
Hypertension
Physiological Agents
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Blood doping
Erythropoietin
Oxygen supplementation
Bicarbonate loading
Phosphate loading
Blood Doping
• Artificial increase in total volume of red blood cells
(often via transfusion)
• Proposed ergogenic benefits
– Improves endurance performance by increasing
blood’s O2-carrying capacity
.
– Increases VO2max, time to exhaustion, and
measurable performance
• Can cause blood clotting, heart failure, and transfusion
complications
Proven Effects and Risks
of Blood Doping
Proven effects
Risks
• ↑ Maximal oxygen
uptake
• ↑ Time to exhaustion
• ↑ Performance time in
endurance events
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↑ Blood viscosity
Blood clotting
Heart failure
Blood matching errors
Hepatitis
HIV
.
Changes in VO2max and Running Time to
Exhaustion After Reinfusion
of Red Blood Cells
Adapted, by permission, from F.J. Buick et al., 1980, "Effect of induced erythrocythemia on aerobic work capacity,"
Journal of Applied Physiology 48: 636-642.
Improvements in Running Times After
Reinfusion of Red Blood Cells
Adapted, by permission, from L.L. Spriet, 1991, Blood doping and oxygen transport. In Ergogenics—Enhancement of
performance in exercise and sport, edited by D.R. Lamb and M.H. Williams (Dubuque, IA: Brown & Benchmark),
213-242. Copyright 1991 Cooper Publishing Group, Carmel, IN.
Erythropoietin (EPO)
• Natural hormone produced by the kidneys to stimulate
red blood cell production
• Human EPO can be cloned and administered to
increase red blood cell volume
• Proposed ergogenic benefits
– Increases oxygen-carrying capacity of the blood
Proven Effects and Risks of EPO
Proven effects
Risks
• ↑ Hemoglobin
concentration
• ↑ Hematocrit
.
• ↑ VO2max
• ↑ Treadmill time
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↑ Blood viscosity
Thrombosis
Myocardial infarction
Congestive heart failure
Hypertension
Stroke
Pulmonary embolism
Oxygen Supplementation
• Breathed by athletes to increase oxygen content of
blood
• Proposed ergogenic benefits:
– Compete at higher intensities
– Fend off fatigue
– Speed recovery between exercise bouts
Proven Effects and Risks
of Oxygen Supplementation
Proven effects
Risks
• Breathing O2 during the
event enhances
performance
• ↓ Peak blood lactate
concentrations
• No known serious risks
• O2 is flammable
Bicarbonate
• Natural part of body’s buffering system to maintain
normal pH
• Proposed ergogenic benefits:
– ↑ Blood pH, allowing higher concentrations of lactate
in the blood
– Delays the onset of fatigue
Proven Effects and Risks
of Bicarbonate Loading
Proven effects
Risks
• Ingesting 300 mg per kg
body weight can
increase performance in
all-out exercise bouts
between 1 and 7 minutes
• Gastrointestinal
cramping
• Bloating
• Diarrhea
Concentrations of (a) Blood Bicarbonate
and (b) Blood Hydrogen Ion With and
Without Ingestion of Sodium Bicarbonate
Adapted, by permission, from D.L. Costill et al., 1984, "Acid–base balance during repeated bouts of exercise:
Influence of HCO3-," International Journal of Sports Medicine 5: 228-231.
Phosphate
• Loading is thought to increase phosphate levels
throughout the body, improving cardiovascular and
metabolic function
• Proposed ergogenic benefits:
– Increased potential for oxidative phosphorylation and
PCr synthesis
– Enhanced 2,3-diphosphoglycerate synthesis in red
blood cells
– Improved oxygen unloading from hemoglobin in the
active muscle
– Improved buffering capacity
– Improved endurance capacity
Proven Effects and Risks
of Phosphate Loading
Proven effects
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• Improvements in VO2max
• ↑ Time to exhaustion
• Results from studies are
divided
Risks
• No known risks
Nutritional Agents
• Amino acids
• L-carnitine
• Creatine
Amino Acids
• L-tryptophan and branched-chain amino acids
(BCAA) including leucine, isoleucine, and valine
• Proposed benefits include increasing endurance
performance by delaying fatigue
• Studies are inconclusive on effects on performance
Time to Exhaustion on .a Cycle
Ergometer at 70% of VO2max
Adapted, by permission, from G. van Hall et al., 1995, "Ingestion of branched-chain amino acids and tryptophan
during sustained exercise in man: Failure to affect performance," Journal of Physiology 486: 789-794.
Creatine: ACSM Position Stand
• Can increase muscle PCr content, but not in all
individuals
• The combination of creatine with large amounts of CHO
might increase muscle uptake of creatine
• Exercise performance in short periods of intense, high
power output activity can be enhanced, particularly with
repeated bouts
• Maximal isometric strength, rate of maximal force
production, and aerobic capacity are not enhanced by
creatine supplementation
(continued)
Creatine: ACSM Position Stand
(continued)
• Leads to weight gain within the first few days, likely
attributable to water accumulation with creatine uptake
in the muscle
• Combined with resistance training, creatine
supplementation is associated with greater gains in
strength and possibly associated with increased ability
to train at higher intensities
• The high expectations for performance enhancement
exceed the true ergogenic benefits