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© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Presentation revised and updated by
Brian B. Parr, Ph.D.University of South Carolina Aiken
Chapter 25Ergogenic Aids
EXERCISE PHYSIOLOGYTheory and Application to Fitness and Performance, 6th edition
Scott K. Powers & Edward T. Howley
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Objectives
1. Define ergogenic aid.
2. Explain why a “placebo” treatment in a “double-blind design” is used in research studies involving ergogenic aids.
3. Describe, in general, the effectiveness of nutritional supplements on performance.
4. Describe the effect of additional oxygen on performance; distinguish between hyperbaric oxygenation and that accomplished by breathing oxygen-enriched gas mixtures.
5. Describe blood doping and its potential for improving endurance performance.
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Objectives
6. Explain the mechanism by which ingested buffers might improve anaerobic performances.
7. Explain how amphetamines might improve exercise performance.
8. Describe the various mechanisms by which caffeine might improve performance.
9. Identify the risks associated with using chewing tobacco to obtain a nicotine “high.”
10.Describe the risks of cocaine use and how it can cause death.
11.Describe the physiological and psychological effects of different types of warm-ups.
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Ergogenic Aid
Substances or phenomena that are work-producing and are believed to increase performance– Nutrients– Drugs– Warm-up exercises– Hypnosis– Stress management– Blood doping– Oxygen breathing– Music– Extrinsic biomechanical aids
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Research Design Concerns
Amount of substance– Too little or too much may show no effect
Subject– May be effective in “untrained” but not “trained”
subjects, and vice versa– The “value” as determined by the subject
Task– Endurance vs. short-term events– Large-motor vs. fine-motor activities
Use– May enhance short-term performance but
compromise long-term performance
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Research Design Concerns
Placebo– Look-alike substance containing nothing that will
improve performance– Athlete’s belief in a substance may influence
performance Double-blind studies
– Neither the investigators nor the subjects are aware of who is receiving the treatment
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Changes in Performance–the Placebo Effect
Figure 25.1
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Dietary Supplements
Little evidence that dietary supplements improve performance with the exception of creatine
Creatine monohydrate supplementation– Increase muscle phosphocreatine (PC)
• For short-term, explosive exercise
– Supplementation increases muscle creatine levels• 20–25 g/day loading dose, 2–5 d/day maintenance dose
– Improves ability to maintain force and power output
– Increase in muscle mass • Due more to water retention than protein synthesis
– Side effects• Some reported, but no long-term adverse effects
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Aerobic Performance
Oxygen breathing
– Increases PO2 of blood
• Hyperbaric chamber
- Breathing air under higher pressure
• Increased %O2 mixtures
- Breathing >21% O2 mixtures at atmospheric pressure
– Before or after exercise• No effect on performance
– During exercise • No real change in O2 delivery
• Improved performance
- 3–5% increase in VO2max
- Especially in athletes who experience desaturation• Not practical
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Effect of PO2 on Performance: O2
Enriched Gas vs. Hyperbaric Chamber
Figure 25.2
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Aerobic Performance
Blood doping– Infusion of RBCs to increase hemoglobin
concentration and oxygen carrying capacity of blood• Autologous vs. homologous transfusion
– Effective in improving VO2max and endurance performance
– Erythropoietin (EPO)• Hormone that stimulates RBC production• Part of therapy for chemotherapy or dialysis patients• More difficult to detect than traditional blood doping
– Artificial oxygen carriers
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Changes in Hemoglobin Levels Following Removal and Reinfusion
Figure 25.3
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Anaerobic Performance
Blood buffers (sodium bicarbonate)– Enhances ability to buffer H+ during exercise– Improves performances of 1-10 minutes duration
or repeated bouts of high-intensity exercise• No benefit for tasks of less than one minute
– Optimal dose• 0.3 g•kg body weight-1 (with 1 liter of water)
– Side effects• Diarrhea and vomiting
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Drugs
Amphetamines– Catecholamine-like effect– Cause increased arousal and perception of
increased energy and self-confidence– Improve performance in fatigued subjects only
• No improvement in alert, non-fatigued subjects
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Drugs
Caffeine– May improve performance at the muscle, nervous
system, or the delivery of fuel to muscle– Can elevate blood glucose and increase fat
utilization– Can decrease perception of fatigue and lower
RPE during prolonged exercise– Effect is variable and dose-related
• Effect may be diminished in regular users
– Potential side effects• Insomnia, diarrhea, anxiety, irritability• Diuretic effect?
– Caffeine-ephedrine mixtures
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Factors Influenced by Caffeine That Might Improve Performance
Figure 25.4
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Mechanisms by Which Caffeine May Increase FFA Mobilization
Figure 25.5
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Drugs
Cocaine– Powerful stimulator of cardiovascular and central
nervous systems– May cause sudden death
Nicotine– Smoking or chewing tobacco– Can stimulate both sympathetic and
parasympathetic nervous systems• Cardiovascular or GI effects
– Known to cause diseases of the mouth, including oral cancer
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Mechanisms by Which Cocaine Can Kill
Figure 25.6
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
The Relaxing and Stimulating Effects of Nicotine
Figure 25.7
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Physical Warm-Up
Causes both physiological and psychological changes that are beneficial to performance– Increased muscle temperature, arousal, focus on
event Warm-up activities
– Identical to performance– Directly related to performance– General warm-up
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Physical Warm-Up
Recommendations– Short-term performances (≤10 s max effort)
• ~40–60% VO2max for 5–10 min, followed by 5 min recovery
• May reduce high-energy phosphates
– Intermediate-term performances (>10 s, ≤5 min)• ~60–70% VO2max for 5–10 min, followed by ≤5 min
recovery• Goal to begin performance with slightly elevated VO2
– Long-term performances (≥5 min)• ~60–70% VO2max for 5–10 min• Too much may deplete muscle glycogen or increase
thermal strain
© 2007 McGraw-Hill Higher Education. All Rights Reserved.
Stretching
Increases joint flexibility Increases muscle-tendon compliance Reduces risk of injury
– Little support in the literature– Stretching outside periods of exercise may reduce
risk of injury– Stretching just prior to exercise does not