Strength and the muscular system


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A lecture I gave for HPE 345, Strength Programming for sport at Wilmington College of Ohio

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Strength and the muscular system

  1. 1. Strength and the MuscularSystemSupertraining, Chapter 1
  2. 2. A Model of the Muscle ComplexIt is relatively meaningless todiscuss muscle action withoutconsidering the role played bythe connective tissuesassociated with muscle.Connective tissues occur inthe sheaths of muscle and itssub-units at all levels.
  3. 3. The Muscle ModelSeries Elastic Component (SEC)Tendon, Myofilaments, Z-Discs, TitinBasically, the tendons and actual muscle fibersParallel Elastic Component (PEC)Muscle Sheaths and sarcolemma
  4. 4. A Better Picture
  5. 5. Muscle Model ForcesPEC is responsible for force exerted by arelaxed muscle when it is stretchedbeyond its resting lengthSEC is put under tension by the forcedeveloped in an actively contractedmuscle
  6. 6. Who Cares?You should care for 2 reasons….well 3.1. So you can sound smart when talking toexercise physiologists.2. So you know that more than just the muscleis involved in human movement, elastic partsare very important too!3. So you know that static stretching influencesthe PEC more than the SEC and that staticROM is different than dynamic ROM.
  7. 7. Muscle Actions:Basic TerminologyAgonist: Prime movers in an actionAntagonist: Muscles acting in opposition toagonistStabilizers: Muscles that stabilize a bodysegment while other muscles carry out amovement
  8. 8. Muscle Action Examples:Agonist: In a leg extension exercise, thequadriceps are going to be agonists of theexercise.
  9. 9. Muscle Action Examples:Antagonist: In a leg extension on amachine, the hamstrings would be theantagonists to the movement. If thehamstrings were firing during the upwardportion of the movement, the action wouldbe severely affected, or could not happen.
  10. 10. Types of Muscle ContractionIsometricConcentricEccentric
  11. 11. Types of Muscle ContractionIsometric ContractionThere is ALWAYS an isometric phase of anylift, jump, throw, etc.The isometric phase of a slow movement, suchas a barbell squat will take much longer thanthe isometric phase of a vertical jump.The brief isometric contraction betweeneccentric and concentric phases in plyometricsis of great importance!
  12. 12. Types of Muscle ContractionConcentric contractionThis is the part of contraction where positivework is done. The power of this contraction isoften influenced by the previous two phases ofmuscle contraction (eccentric/concentric)Eccentric (yielding) contractionCan produce 30-40% greater muscle tensionthan other two contractionsDOMS (delayed onset muscle soreness)producer
  13. 13. Eccentric ContractionsThe eccentric phase can store moreenergy than the other two phases.Because of the elastic properties of themuscle-tendon complex, the more energystored during the eccentric phase, themore energy is released in the concentricphase.We will get to this more later when we talkabout the Stretch-Shortening Cycle indetail.
  14. 14. A Dynamic example
  15. 15. An Example:
  16. 16. An Example:
  17. 17. The Fundamental Principle of StrengthTrainingThe production and increase of strengthboth depend on neuromuscular processes.Strength is not primarily a function ofmuscle size, but one of the appropriatemuscles powerfully contracted by effectivenervous stimulation.Example: Tara Nott, Olympic Weightlifter
  18. 18. The Fundamental Principle of StrengthTrainingBasically the nervous system ultimatelycontrols the outcome of a trainingprogram.
  19. 19. Nervous SystemThe central nervous system (CNS) is thepart of the nervous system that functionsto coordinate the activity of all parts of thebodies of multicellular organisms(Wikipedia)CNS is a term you should be familiar with!
  20. 20. The Neuromuscular System and Strength Stimulation (training) of the nervous systemproduces two basic effects on the body:Functional muscle actionMuscle hypertrophy(hypertrophy=increase in size of the muscle) With this in mind there are two basic types ofstrength training:Functional strength trainingStructural strength training
  21. 21. Functional vs. StructuralStructural strength training would aimspecifically at producing musclehypertrophy (increase in muscle size).Functional strength training is associatedwith improving static strength, speed-strength, muscle endurance, and reactiveability.
  22. 22. A functional/structural scaleHere is a scale of exercises for a track andfield sprinter for the quadriceps muscle
  23. 23. A note about functional training Functional training is fairly simple, it involvesmotor movements that are close to that of theprimary sport. It can also be simply playing thegiven sport. Typically these movements will below or high amplitude jumping exercises,general calisthenics, sprints of varyingdistances, and other elastic exercises. In the early stages of training or duringstagnation at an advanced level, the functionalstages of training should precede „structural‟training work.
  24. 24. Don‟t get carried away when you hear“functional” Some trainers takefunctional training out ofcontext Trying to add too much„complexity‟ to anexercise or making itoverly sport specific canalter firing patterns. Also,too much element ofbalance in an exercisewill take away from forceproduction ability.Not “Functional” Training
  25. 25. A breakdown of „functional‟ training:4 Processes involvedIntermuscular coordinationIntramuscular coordinationFacilitory and inhibitory reflexive processesMotor learning
  26. 26. Intermuscular CoordinationCoordination between different musclegroups.This involves the synchronizing orsequencing of muscles in certainmovements.Some muscles might be inhibited fromcooperating, while some might bedisinhibited from cooperating in amovement.
  27. 27. Intramuscular Coordination This is the improvementof coordination of musclefibers in the samemuscle. Increase in number ofmuscle fibers activated ordeactivated Rate Coding: control oftension by modifying thefrequency that the fibersfire at Pattern Encoding: controlof tension by synchronizingthe firing of different typesof muscle (e.g. slow or fasttwitch fibers….sprintexample)
  28. 28. Motor Learning Motor learning is the process of programmingthe CNS to carry out specific movementtasks. Most gains found early in a resistanceprogram are due to motor learning! Motor learning will continue as the intensityand complexity of the exercise increases,because skill in demanding conditions ismuch different than skill in basic conditions.
  29. 29. CNS is important in training, so what?The way you train can affect the change ofthe CNS.Strength training on machines can modifythe circuitry and programming of the brainand thereby reduce the functionalcapability of the muscles used for aspecific movement.HIT trainees would disagree
  30. 30. CNS is important in training, so what?Because of the rapid changes produced inthe brain by repeated stimuli, even shortperiods of inappropriate patterns ofstrength training can be detrimental tosporting performanceExample: If I am a sprinter and train with a50lb vest for 3 weeks, and then competein a big meet, my motor patterns will bealtered, and I won‟t do very well.
  31. 31. CNS is important in training, so what?Over reliance on ergogenic devices likebelts, gloves, knee wraps and heelwedges can modify the neuromuscularsystem so that safe and effective trainingwithout them can become difficult
  32. 32. CNS is important in training, so what? The existence ofindividual style revealsthat each person willprogram the CNS insubtly different ways.This means that anattempt to place astereotypes, generalpattern of movementmight prevent an athletefrom reaching their fullpotentialAn Example of 2 Jumping Styles
  33. 33. Structural and FunctionalDeterminants of StrengthStructural FactorsCross-sectional area of muscleDensity of muscle fibers per unit cross-sectionalarea. (Muscle density)Efficiency of mechanical leverage across thejointMuscle insertionPennation angle of muscle
  34. 34. Functional Determinants of StrengthThe number of muscle fibers contractingsimultaneouslyThe rate of contraction of muscle fibersThe efficiency of synchronisation of thefiring of muscle fibersThe conduction velocity in the nerve fibers
  35. 35. Functional DeterminantsThe degree of inhibition of muscle fiberswhich do not contribute to the movementThe proportion of large diameter musclefibers activeThe efficiency of cooperation betweendifferent types of muscle fiber (fast andslow)
  36. 36. Functional DeterminantsThe efficiency of the stretch-shorteningcycleThe excitation threshold of the nerve fiberssupplying the musclesThe initial length of the muscles beforecontraction