© 2007 McGraw-Hill Higher Education. All Rights Reserved. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken Chapter.

© 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


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.


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.


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


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


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


Changes in Performance–the Placebo Effect

Figure 25.1


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


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


Effect of PO2 on Performance: O2

Enriched Gas vs. Hyperbaric Chamber

Figure 25.2


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


Changes in Hemoglobin Levels Following Removal and Reinfusion

Figure 25.3


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


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


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


Factors Influenced by Caffeine That Might Improve Performance

Figure 25.4


Mechanisms by Which Caffeine May Increase FFA Mobilization

Figure 25.5


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


Mechanisms by Which Cocaine Can Kill

Figure 25.6


The Relaxing and Stimulating Effects of Nicotine

Figure 25.7


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


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


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

© 2007 McGraw-Hill Higher Education. All Rights Reserved. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken Chapter.

Documents

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shortterm performance

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aerobic performance