chapter 19 factors affecting performance l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 19 Factors Affecting Performance PowerPoint Presentation
Download Presentation
Chapter 19 Factors Affecting Performance

Loading in 2 Seconds...

play fullscreen
1 / 21

Chapter 19 Factors Affecting Performance - PowerPoint PPT Presentation


  • 617 Views
  • Uploaded on

Chapter 19 Factors Affecting Performance. EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Howley. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken. Objectives.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Chapter 19 Factors Affecting Performance


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 19 factors affecting performance

Chapter 19Factors Affecting Performance

EXERCISE PHYSIOLOGY

Theory and Application to Fitness and Performance, 6th edition

Scott K. Powers & Edward T. Howley

Presentation revised and updated by

Brian B. Parr, Ph.D.

University of South Carolina Aiken

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

objectives
Objectives
  • Identify factors affecting maximal performance.
  • Provide evidence for and against the central nervous system being a site of fatigue.
  • Identify potential neural factors in the periphery that may be linked to fatigue.
  • Explain the role of cross-bridge cycling in fatigue.
  • Summarize the evidence on the order of recruitment of muscle fibers with increasing intensities of activity, and the type of metabolism upon which each is dependent.

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

objectives3
Objectives
  • Describe the factors limiting performance in all-out activities lasting less than ten seconds.
  • Describe the factors limiting performance in all-out activities lasting 10 to 180 seconds.
  • Discuss the subtle changes in the factors affecting optimal performance as the duration of maximal performance increase from three minutes to four hours.

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors affecting performance
Factors Affecting Performance

Figure 19.1

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

sites of fatigue
Sites of Fatigue
  • Fatigue
    • Inability to maintain power output or force during repeated muscle contractions
  • Central fatigue
    • Central nervous system
  • Peripheral fatigue
    • Neural factors
    • Mechanical factors
    • Energetics of contraction

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

possible sites of fatigue
Possible Sites of Fatigue

Figure 19.2

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

central fatigue
Central Fatigue
  • Reduction in motor units activated
  • Reduction in motor unit firing frequency
  • Central nervous system arousal can alter the state of fatigue
    • By facilitating motor unit recruitment
      • Increasing motivation
      • Physical or mental diversion
  • Excessive endurance training (overtraining)
    • Reduced performance, prolonged fatigue, etc.
    • Related to brain serotonin activity
  • Exercise begins and ends in the brain

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

peripheral fatigue neural factors
Peripheral Fatigue: Neural Factors
  • Neuromuscular junction
    • Not a site for fatigue
  • Sarcolemma and transverse tubules
    • Ability of muscle membrane to conduct an action potential
      • Inability of Na+/K+ pump to maintain action potential amplitude and frequency
        • Can be improved by training
    • An action potential block in the T-tubules
      • Reduction in Ca+2 release from sarcoplasmic reticulum

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

peripheral fatigue mechanical factors
Peripheral Fatigue: Mechanical Factors
  • Cross-bridge cycling and tension development depends on:
    • Arrangement of actin and myosin
    • Ca+2 binding to troponin
    • ATP availability
  • Fatigue may be due to:
    • H+ interference with Ca+2 binding to troponin
    • Inability of sarcoplasmic reticulum to take up Ca+2
    • Lack of ATP
    • Inhibition of Ca+2 release from SR
    • Damage to actin and myosin

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

peripheral fatigue energetics of contraction
Peripheral Fatigue: Energetics of Contraction
  • Mismatch between rate of ATP production and utilization
    • Fatigue results in slowing of ATP utilization to preserve homeostasis
    • Accumulation of Pi
  • Muscle fiber recruitment in increasing intensities of exercise
    • Type I  Type IIb  Type IIx
    • Progression from most to least oxidative fiber type
      • Exercise >75% VO2max requires IIx fibers
      • Results in increased lactate production

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

order of muscle fiber type recruitment
Order of Muscle Fiber Type Recruitment

Figure 19.3

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors limiting ultra short term performances
Factors Limiting Ultra Short-Term Performances
  • Events lasting <10 seconds
  • Dependent on recruitment of Type II muscle fibers
    • Generate great forces that are needed
  • Motivation, skill, and arousal are important
  • Primary energy source
    • Anaerobic
      • Phosphocreatine

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors affecting fatigue in ultra short term events
Factors Affecting Fatigue in Ultra Short-Term Events

Figure 19.4

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors limiting short term performances
Factors Limiting Short-Term Performances
  • Events lasting 10–180 seconds
  • Shift from anaerobic to aerobic metabolism
    • 70% energy supplied anaerobically at 10s
    • 60% supplied aerobically at 180s
  • Primary energy source
    • Anaerobic glycolysis
      • Results in elevated lactate levels

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors affecting fatigue in short term events
Factors Affecting Fatigue in Short-Term Events

Figure 19.5

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors limiting moderate length performances
Factors Limiting Moderate-Length Performances
  • Events lasting 3–20 minutes
  • Increasing reliance on aerobic energy production
    • 60% ATP generated aerobically at 3 min
    • 90% ATP supplied aerobically at 20 min
  • Requires energy expenditure near VO2max
    • Type II fibers recruited
    • High levels of lactate
  • Factors that interfere with O2 delivery are limiting
    • Altitude
    • Anemia

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors affecting fatigue in aerobic performances lasting 3 20 minutes
Factors Affecting Fatigue in Aerobic Performances Lasting 3–20 Minutes

Figure 19.6

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors limiting intermediate length performances
Factors Limiting Intermediate-Length Performances
  • Events lasting 21–60 minutes
  • Predominantly aerobic
  • Usually conducted at less than 90% VO2max
  • Environmental factors are important
    • Heat
    • Humidity
    • State of hydration

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors affecting fatigue in aerobic performances lasting 21 60 minutes
Factors Affecting Fatigue in Aerobic Performances Lasting 21–60 Minutes

Figure 19.7

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors limiting long term performances
Factors Limiting Long-Term Performances
  • Events lasting 1–4 hours
  • Environmental factors important
    • Ability to deal with heat and humidity
  • Maintain rate of carbohydrate utilization
    • Muscle and liver glycogen
    • Diet and fluid ingestion influence performance

© 2007 McGraw-Hill Higher Education. All Rights Reserved.

factors affecting fatigue in aerobic performances lasting 1 4 hours
Factors Affecting Fatigue in Aerobic Performances Lasting 1–4 Hours

Figure 19.8

© 2007 McGraw-Hill Higher Education. All Rights Reserved.