3. Sports Physiology
Exercise Physiology
Improvements through training

4. Muscle Fiber Type Slow Twitch (Endurance) Fast Twitch a (Intermediate)
Fast Twitch b (Sprints)
Make-up of calf muscle…a comparison
Marathon runner - 90% Slow Twitch
Sprinter % Slow Twitch

5. Slow Twitch, Fast Twitcha, Fast Twitchb comparison
ST FT a FT b
Oxydative Capacity High Moderately High Low
Glycolytic Capacity Low High Highest
Contraction Speed Slow Fast Fast
Fatigue Resistance High Moderate Low
Muscle Fiber Low High High
Strength

6. Let’s Play the Muscle Fiber Game! Slow twitch or Fast twitch?

7. I – Slow-twitch II – Fast-Twitch

8. Energy Systems (source of ATP for cross bridge formation)
Phosphagen System (10 seconds)
Stored ATP – 3 secs 4 moles ATP/min
Phosphocreatine – 7 secs
Glycolytic System (1-2 minutes)
Glycolysis moles ATP/min
Inefficient but fast
Buildup of Lactic acid – must be buffered
Oxydative (aerobic) (indefinite)
Very efficient 1 mole ATP/min

9. Capacity of Energy System vs. Exercise Duration

10. Fiber Type Recruitment Order (As you increase the effort you recruit more numbers of fibers but what about fiber type?)
Low intensity (walk; slow jog)
slow twitch
Medium intensity (fast jog; run)
slow twitchfast twitch a
High intensity (run; sprint)
slow twitch & fast twitch a  fast twitch b

12. Oxygen and Fuel Oxygen Fuel Glucose Fat Protein From blood
Stored bound to myoglobin
Fuel
Glucose
From blood (liver make it from glycogen)
Stored in muscle (glycogen)
Fast delivery rate
Fat
Very abundant energy source!
Slow delivery rate
Protein
Abundant but not ideal source

13. Oxygen Debt

14. Tchotchke, Tchotcholate Tchallenge!

15. Assuming no change in physical activity, what would happen to the partial pressure of oxygen in veins of the systemic circulatory system if cardiac output were increased by a factor of 2?

16. Fatique Energy Depletion Buildup of Metabolic Byproducts
Phosphocreatine (short, hard efforts)
Glycogen Depletion (longer efforts)
Buildup of Metabolic Byproducts
Lactic acid
Inhibits glycolytic enzymes
Inhibits crossbridge formation (H+ interferes)
Nervous System
Mostly Psychological***

17. Can I Keep Going?

18. Endurance Training Increased Vascularization – more capillaries
Increased Myoglobin
More Mitochondria
More Oxydative Enzymes
Psychological factors
Become comfortable with/embrace pain & discomfort

19. Anaerobic Training (increase Anaerobic Threshold and increase Anaerobic Capacity)
More Glycolytic Enzymes
Increased Capacity for Lactic Acid
More blood
More bicarbonate
Increased ability of liver to metabolize lactic acid
Psychological Factors
Deal with Pain

21. A common nonsense polymorphism (R577X) in the ACTN3 gene results in complete deficiency of the fast skeletal muscle fiber protein a-actinin-3 in an estimated one billion humans worldwide. The XX null genotype is under-represented in elite sprint athletes, associated with reduced muscle strength and sprint performance in non-athletes, and is over-represented in endurance athletes, suggesting that a-actinin-3 deficiency increases muscle endurance at the cost of power generation. Here we report that muscle from Actn3 knockout mice displays reduced force generation, consistent with results from human association studies. Detailed analysis of knockout mouse muscle reveals reduced fast fiber diameter, increased activity of multiple enzymes in the aerobic metabolic pathway, altered contractile properties, and enhanced recovery from fatigue, suggesting a shift in the properties of fast fibers towards those characteristic of slow fibers. These findings provide the first mechanistic explanation for the reported associations between R577X and human athletic performance and muscle function.

22. A common nonsense polymorphism (R577X) in the ACTN3 gene results in complete deficiency of the fast skeletal muscle fiber protein a-actinin-3 in an estimated one billion humans worldwide. The XX null genotype is under-represented in elite sprint athletes, associated with reduced muscle strength and sprint performance in non-athletes, and is over-represented in endurance athletes, suggesting that a-actinin-3 deficiency increases muscle endurance at the cost of power generation. Here we report that muscle from Actn3 knockout mice displays reduced force generation, consistent with results from human association studies. Detailed analysis of knockout mouse muscle reveals reduced fast fiber diameter, increased activity of multiple enzymes in the aerobic metabolic pathway, altered contractile properties, and enhanced recovery from fatigue, suggesting a shift in the properties of fast fibers towards those characteristic of slow fibers. These findings provide the first mechanistic explanation for the reported associations between R577X and human athletic performance and muscle function.

23. Cost of Transport

25. 1 m/sec = 2.24 miles/hr

26. Endurance running and the evolution of Homo
Human
Nature 432, (18 November 2004) | doi: /nature03052; Received 25 July 2004; Accepted 23 September 2004
Endurance running and the evolution of Homo
Dennis M. Bramble1 and Daniel E. Lieberman2
H. erectus
Australopithecus afarensis [uh-fah-ren-sis]
Chimp
A.afarensis