1. The Scientific Principles of Strength Training Muscular Strength: The amount of force a muscle can produce with a single maximal effort Muscular Strength: The amount of force a muscle can produce with a single maximal effort Mechanical Strength: the maximum torque that can be generated about a joint Mechanical Strength: the maximum torque that can be generated about a joint

2. Torque about the elbow joint Strength determined by: Absolute force developed by muscle Distance from joint center to tendon insertion Angle of tendon insertion

3. Shoulder joint torque as a function of arm position

5. Structural organization of skeletal muscle From Principles of Human Anatomy (7 th edition), 1995 by Gerard J. Tortora, Fig 9.5, p 213

6. 6-6 From Basic Biomechanics by Susan Hall (3 rd edition), Fig 6.6, page 153

7. From Skeletal Muscle: Form and Function (2 nd ed) by MacIntosh, Gardiner, and McComas. Fig 1.4, p. 8.

8. 6-5 From Basic Biomechanics by Susan Hall (3rd edition), Fig 6.5, page 152

9. 6-3 From Basic Biomechanics by Susan Hall (3rd edition), Fig 6.3, page 150

10. From Exercise Physiology: Theory and Application to Fitness and Performance (6 th Edition) by Scott K. Powers and Edward T. Howley. Fig 8.6 P. 147

11. A motor unit: single motor neuron and all the muscle fibers it innervates From Basic Biomechanics Instructors manual by Susan Hall (2nd edition, 1995), Fig TM 31

12. 6-7 From Basic Biomechanics by Susan Hall (3rd edition), Fig 6.7, page 154

13. 6-8 From Basic Biomechanics by Susan Hall (3rd edition), Fig 6.8, page 154

14. Types of muscle fiber: Fast twitch vs Slow Twitch Types of muscle fiber: Fast twitch vs Slow Twitch Type I Type IIa Type IIb Type I Type IIa Type IIb ST Oxidative FT Oxidative - FT Glycolytic ST Oxidative FT Oxidative - FT Glycolytic (S0) Glycolytic (FOG) (FG) (S0) Glycolytic (FOG) (FG) Contraction speed slow fast (2xI) fast (4xI) Contraction speed slow fast (2xI) fast (4xI) Time to peak force slow fast fast Time to peak force slow fast fast Fatigue rate slow inter. fast Fatigue rate slow inter. fast Fiber diam. small inter. large Fiber diam. small inter. large Aerobic capacity high inter. low Aerobic capacity high inter. low Mitochondrial conc. high inter. low Mitochondrial conc. high inter. low Anaerobic capacity low inter. High Anaerobic capacity low inter. High Sedentary people – 50% slow/50% fast, whereas elite athletes may differ e.g., cross country skiers – 75% slow 25% fast sprinters - 40% slow 60% fast sprinters - 40% slow 60% fast

15. Factors affecting force Production 1. Cross-sectional area Hypertrophy: increase in the # of myofibrils and myofilaments Hypertrophy: increase in the # of myofibrils and myofilaments Hyperplasia: increase in the number of fibers??? Hyperplasia: increase in the number of fibers???

16. 2. Rate Coding – frequency of stimulation From Basic Biomechanics by Susan Hall (3rd edition), Fig 6.9, page 155

17. 3. Spatial recruitment Increase # of active motor units (MUs) Increase # of active motor units (MUs) Order of recruitment Order of recruitment I ---> IIa -----> IIb Henneman's size principle: MUs are recruited in order of their size, from small to large Henneman's size principle: MUs are recruited in order of their size, from small to large Relative contributions of rate coding and spatial recruitment. Relative contributions of rate coding and spatial recruitment. Small muscles - all MUs recruited at approximately 50% max. force; thereafter, rate coding is responsible for force increase up to maxSmall muscles - all MUs recruited at approximately 50% max. force; thereafter, rate coding is responsible for force increase up to max Large muscles - all MUs recruited at approximately 80% max. force.Large muscles - all MUs recruited at approximately 80% max. force.

18. 4. Velocity of shortening: Force inversely related to shortening velocity The force-velocity relationship for muscle tissue: When resistance (force) is negligible, muscle contracts with maximal velocity. Velocity Force (Low resistance, high contraction velocity)

19. The force-velocity relationship for muscle tissue: As the load increases, concentric contraction velocity slows to zero at isometric maximum. Velocity Force isometric maximum

20. Force-Velocity Relationship in different muscle fiber types Type II fiber Type I fiber

21. Effect of Temperature on Force-Velocity relationship (22 o C, 25 o C, 31C o, and 37 o C)

22. Force -Velocity Relationship (Effect of strength-Training)

23. Force-velocity Relationship During Eccentric Muscular Contractions

24. Force/Velocity/Power Relationship Force Velocity Power 30% Force/velocity curve Power/velocity curve From Basic Biomechanics by Susan Hall (3rd edition), Fig 6.25, page 175

25. Effect of Muscle Fiber Types on Power-Velocity Relationship

26. Consequences of the force-velocity relationship for sports practice When training for sports that require power, train with the appropriate % of 1 RM that will elicit the most power. When training for sports that require power, train with the appropriate % of 1 RM that will elicit the most power. 24 weeks of: a). heavy weight-training b. Explosive strength training a). heavy weight-training b. Explosive strength training From Science and Practice of Strength Training (2 nd edition) V.M. Zatsiorsky and W.J. Kraemer (2006) Fig 2.19 P. 39)

27. Why do elite weight lifters start a barbell lift from the floor slowly? Why do elite weight lifters start a barbell lift from the floor slowly? They try to accelerate maximally when the bar is at knee height. Two reasons: 1. At this position, the highest forces can be generated as a result of body posture

28. 2. Because force decreases when velocity increases, barbell must approach the most favored position at a relatively low velocity to impart maximal force to the bar. From Science and Practice of Strength Training (2nd edition) V.M. Zatsiorsky and W.J. Kraemer (2006) Fig 2.20 P. 40)

29. Adaptations associated with strength training 1. Activates protein catabolism. This creates conditions for enhanced synthesis of contractile proteins during the rest period (break down, build up theory) From R.L. Leiber (1992). Skeletal Muscle Structure and Function. Fig 6.1, p. 262.

30. 2. Neural adaptations occur to improve intra-muscular and inter-muscular coordination. Intra-muscular coordination – affects the ability to voluntarily activate individual fibers in a specific muscleIntra-muscular coordination – affects the ability to voluntarily activate individual fibers in a specific muscle Inter-muscular coordination – affects the ability to activate many different muscles at the appropriate timeInter-muscular coordination – affects the ability to activate many different muscles at the appropriate time

31. Intra-muscular coordination changes with training Untrained individuals find it difficult to recruit all their fast-twitch MUs. With training, an increase in MU activation occurs Untrained individuals find it difficult to recruit all their fast-twitch MUs. With training, an increase in MU activation occurs Strength training also trains the MUs to fire at the optimal firing rate to achieve tetany Strength training also trains the MUs to fire at the optimal firing rate to achieve tetany MUs might also become activated more synchronously during all out maximum effort MUs might also become activated more synchronously during all out maximum effort

32. Consequently, maximal muscular force is achieved when: 1. A maximal # of both FT and ST motor units are recruited 2. Rate coding is optimal to produce a fused state of tetany 3. The MUs work synchronously over the short period of maximal effort.

33. Psychological factors are also of importance Psychological factors are also of importance CNS either increases the flow of excitatory stimuli, decreases inhibitory stimuli, or both CNS either increases the flow of excitatory stimuli, decreases inhibitory stimuli, or both Consequently, an expansion of the recruitable motor neuron pool occurs and an increase in strength results Consequently, an expansion of the recruitable motor neuron pool occurs and an increase in strength results Hidden strength potential of human muscle can also be demonstrated by electrostimulation Hidden strength potential of human muscle can also be demonstrated by electrostimulation Muscle strength deficit (MSD) = Muscle strength deficit (MSD) = (Force during electrostimulation-Maximal voluntary force) x 100 Maximal voluntary force Maximal voluntary force Typically falls between 5-35% Typically falls between 5-35%

34. Electrostimulation Electrostimulation Possibility exists to induce hypertrophy through electrostimulationPossibility exists to induce hypertrophy through electrostimulation However, does not train the nervous system to recruit motor unitsHowever, does not train the nervous system to recruit motor units Bilateral Deficit Bilateral Deficit During maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically larger than the sum of forces exerted by the same muscles bilaterallyDuring maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically larger than the sum of forces exerted by the same muscles bilaterally Bilateral training can eliminate this deficit, or even allow bilateral facilitationBilateral training can eliminate this deficit, or even allow bilateral facilitation

35. Other benefits of strength training Increase in resting metabolic rate Increase in resting metabolic rate Each additional pound of muscle tissue increasesEach additional pound of muscle tissue increases resting metabolism by 30 to 50 calories per day = 10,950 to 18,250 calories a year = 3-5 lb of fat resting metabolism by 30 to 50 calories per day = 10,950 to 18,250 calories a year = 3-5 lb of fat Increase in bone mineral content and, therefore, bone density Increase in bone mineral content and, therefore, bone density Increases the thickness and strength of the connective tissue structures crossing joints such as tendons and ligaments – helps prevent injury Increases the thickness and strength of the connective tissue structures crossing joints such as tendons and ligaments – helps prevent injury Increased stores of ATP, Creatine Phosphate (CP), and glycogen Increased stores of ATP, Creatine Phosphate (CP), and glycogen Aids rehabilitation from injury Aids rehabilitation from injury Aging gracefully! Less falls in latter years Aging gracefully! Less falls in latter years Looking better, feeling better. Greater self-esteem Looking better, feeling better. Greater self-esteem

36. Metabolic stress of resistance training Classed as only light to moderate in terms of energy expenditure per workout Classed as only light to moderate in terms of energy expenditure per workout Standard weight-training does not improve endurance or produce significant cardiovascular benefits like aerobic type activity does Standard weight-training does not improve endurance or produce significant cardiovascular benefits like aerobic type activity does Circuit-training increases metabolic stress Circuit-training increases metabolic stress

37. Delayed onset of muscle soreness (DOMS) The intensity and the novelty of a workout influence how sore you become The intensity and the novelty of a workout influence how sore you become Lactate does not cause muscle soreness due to: Lactate does not cause muscle soreness due to: 1. Lactate returns to baseline within an hour of exercise1. Lactate returns to baseline within an hour of exercise 2. After exercise, lactate is in equal amounts within the muscle and the blood2. After exercise, lactate is in equal amounts within the muscle and the blood 3. DOMS is specific, not generalized3. DOMS is specific, not generalized Muscle soreness is due to the physiological response to muscle fiber and connective tissue damage (microtears) Muscle soreness is due to the physiological response to muscle fiber and connective tissue damage (microtears) White blood cells enter the muscle tissue, clean up the debris of broken proteins, and then initiate the regeneration phase White blood cells enter the muscle tissue, clean up the debris of broken proteins, and then initiate the regeneration phase

38. Muscle Soreness (continued) Edema (increase in fluid) to the area accompanies the above response Edema (increase in fluid) to the area accompanies the above response The pressure from edema is thought to produce the sensation of soreness The pressure from edema is thought to produce the sensation of soreness Also, metabolic by-products released from the macrophages may sensitize pain receptors Also, metabolic by-products released from the macrophages may sensitize pain receptors Next stage is the proliferation of satellite cells - help form new myofibrils Next stage is the proliferation of satellite cells - help form new myofibrils Eccentric contractions cause the greatest amount of soreness Eccentric contractions cause the greatest amount of soreness