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actors Affecting Performance

actors Affecting Performance. F. Chapter 19. How hard can it be? If world records were easy to set, then everybody would be doing it. Asafa Powell (100 m – 9.77s) ~48 kcal/min Michael Johnson (200 m – 19.32s) ~42 kcal/min Hicham El Guerrouj (1 mile – 3:43.13) ~34 kcal/min

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actors Affecting Performance

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  1. actors Affecting Performance F Chapter 19

  2. How hard can it be?If world records were easy to set, then everybody would be doing it. • Asafa Powell (100 m – 9.77s) ~48 kcal/min • Michael Johnson (200 m – 19.32s) ~42 kcal/min • Hicham El Guerrouj (1 mile – 3:43.13) ~34 kcal/min • Kenenisa Bekele (5K – 12:37.35) ~31 kcal/min • Paul Tergat (marathon – 2:04:55) ~28 kcal/min • Running at 10 mph (6 min/mile) ~19.6 kcal/min • Jumping rope ~10.2 kcal/min • Mowing the grass ~9.0 kcal/min • Walking at 4 mph (15 min/mile) ~6.9 kcal/min • Car washing ~5.7 kcal/min

  3. F atigue Inability to maintain a power output or force during repeated muscle contractions

  4. F atigue – confounding variables • Fiber type and training state of subject • Voluntary or electrical stimulation • Intensity/duration of training, continuous/discontinuous activity

  5. C entral Fatigue • Merton’s (1954) classical experiments • muscle fatigued with voluntary contractions, EMS could not restore tension • Ikai and Steinhaus (1961) • “Psyche” on strength • (1969) showed EMS  tension • Asmussen and Mazin (1978) • physical/mental diversion (i.e., contraction of non-fatigued muscle/math/opening eyes) improved strength (CNS arousal)

  6. C entral Fatigue • Mechanisms  exercise induced alterations in CNS neurotransmitters • Serotonin (5-hydroxytryptamine) • Dopamine • ACh along with the neuromodulators

  7. P eripheral Fatigue • Neural Factors • Neuromuscular Junction (Ø or ?) • Sarcolemma and T-Tubules • inability of NA++/K+ pump to maintain pace might lower action potential amplitude and the frequency • amplitude changes as observed do not appear to have an effect; shift in optimal frequency to preserve force • could be a blockage of the action potential in the t-tubule thus reducing Ca++ release

  8. P eripheral Fatigue • Mechanical Factors • functional arrangement of actin & myosin • Ca++ availability • ATP • disruption of sarcomere (eccentric) • H+ (reduce force, reduce force at [Ca++], inhibit SR Ca++ release)

  9. P eripheral Fatigue • Energetics of Contraction • high Pi levels reduce the cross-bridge binding to actin • inability to deliver oxygen (Type I & IIa) • inability to produce ATP (aerobic vs anaerobic) • production of lactate (recruitment of fibers)

  10. 2:15 time equates to 60 mL/kg/min submaximal VO2 VO2max LT80% = 75 mL/kg/min LT70% = 85 mL/kg/min LT60% = 100 mL/kg/min 3:00 time equates to 46 mL/kg/min submaximal VO2 VO2max LT80% = 58 mL/kg/min LT70% = 66 mL/kg/min LT60% = 77 mL/kg/min C omparative analysis (Marathon) • 4:00 time equates to 35 mL/kg/min submaximal VO2 VO2max • LT80% = 44 mL/kg/min • LT70% = 50 mL/kg/min • LT60% = 58 mL/kg/min

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