MUSCULAR STRENGTH, ENDURANCE AND POWER

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MUSCULAR STRENGTH, ENDURANCE AND POWER

• Returning the athlete to competitive and
  functional level following injury

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Definitions

• Muscular Strength
• Ability to generate force against some resistance
• Important to maintain normal levels of strength
  for normal healthy living
• Muscular Endurance
• Ability to perform repetitive muscular
  contractions against some resistance
• As strength increases, endurance increases

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Definitions

• Power
• Ability to generate force quickly
• Combination of strength and speed
• Performance is limited without power

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Types of Contraction

• Isometric contraction
• Contraction that produces muscle tension but no
  change in muscle length
• Concentric contraction
• Contraction that causes muscle shortening while
  tension increases to overcome some resistance
• Eccentric Contraction
• Resistance is greater than the muscular force
  being produced and muscle lengthens while
  producing tension

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Types of Contraction

• So what?
• Strength training must focus on functioning of
  muscle
• Multi-planar
• Various contractions - functionally

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Factors That Determine Levels of Strength,
Endurance and Power

• Size of Muscle
• Proportional to cross-sectional diameter of
  muscle fibers
• Hypertrophy
• Increase in muscle size
• Atrophy
• Decrease in muscle size
• Can occur in as little as 48 hours
• Consistent exercise essential to prevent

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Factors Continued

• Number of Muscle Fibers
• Strength is a function of the number and diameter
  of muscle fibers
• Number of fibers is inherited characteristic

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Factors Continued

• Neuromuscular Efficiency
• Strength is directly related to efficiency of the
  neuromuscular system
• Initial increases in strength during first 8-10
  weeks are attributed to neuromuscular efficiency
• Enhanced strength in 3 ways
• Increase motor unit recruitment
• Increase in firing rate
• Enhance synchronization of motor unit firing

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Fiber Types

• Slow Twitch Fibers
• Type I or slow oxidative
• Resistant to fatigue
• Primarily associated with long duration, aerobic
  type activities and postural muscles
• Fast Twitch Fibers
• Type IIa (fast oxidative glycolytic) IIb (fast
  glycolytic)
• Produce quick, forceful contractions by tendency
  to fatigue

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Fiber Types Contd

• Ratio in Muscle
• Both fiber types exist in individual muscles
• Ratio varies by muscle and by individual
• Genetically determined
• Fiber changes due to training
• Enhanced metabolic capabilities through specific
  training
• Can fiber type change?

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So What?

• First 8-10 weeks is training to be efficient
• Technique
• Neurophysiological input
• Position of load
• Position of limb
• Target fiber type as well as contraction type

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Physiological Adaptations Summary

• Improved neuromuscular efficiency
• Muscle hypertrophy
• Number of muscle fibers does not increase
• Increased size and number of myofilaments Actin
  and myosin
• Increased number of capillaries
• No new capillaries
• Increase in dormant capillary activity to meet
  needs of muscle

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• Strength of non-contractile structures
• Tendons and ligament increase
• Increased bone-mineral content
• Improved oxygen uptake
• If resistance training is high enough to elicit a
  cardiovascular response/adaptation
• Increased metabolic enzymes
• Increased ability to withstand metobolic wastes

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Overload

• To improve strength, muscle must be worked at a
  level higher than it is accustomed to
• Without overload, muscle will maintain strength
  as long as training is continued against a
  resistance that it is accustomed to
• Existence of current strength but no additional
  strength gain

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Overload Contd (Prentice, 2004)

• In rehabilitation, progressive overload is
  limited to a degree by the healing process
• Rate of progression determined by injured
  athletes response to specific exercise
• Increased pain and/or swelling indicate overload
  too high

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Overtraining

• Imbalance between exercise and recovery
• Training exceeds physiological and psychological
  capacity of individual
• Can have negative effect on strength training
• May result in psychological or physiological
  breakdown
• Injury, illness, and fatigue can be indicators

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Progressive Resistive Exercise Techniques and
Programs

• Terminology
• Repetitions
• Repetition maximum (RM)
• Set
• Intensity
• Recovery period
• Frequency

• Multiple potential routines
• Single set
• Tri-sets
• Multiple sets
• Superset
• Pyramid
• Split routine
• Circuit Training

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Progressive Resistive Exercise Techniques and
Programs Contd

• Must consider 4 areas
• Amount of weight to be used
• Number of repetitions
• Number of sets
• Frequency of training

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Open and Closed Kinetic Chain

• Open Kinetic Chain
• Movements in other segments within the chain are
  not predictable
• Origin is fixed and contraction causes movement
  of the insertion
• Closed Kinetic Chain
• Foot/hand meets resistance, movement of more
  proximal segment occurs in predictable pattern
• Not necessarily weight bearing
• Insertion fixed and contraction causes movement
  in of origin
• Concurrent shift two joint muscles must work
  concentrically and eccentrically at the same time

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Open Kinetic Chain )

• Characteristics
• Increased acceleration forces
• Decreased resistance forces
• Increased distraction and rotational forces
• Usually isolated to a single joint
• Increased deformation of joint and muscle
  mechanoreceptors
• Concentric acceleration and eccentric
  deceleration
• Promotion of functional activity

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Open Kinetic Chain )

• Advantages
• Isolation of exercise to a specific joint
• Isolation of specific muscle groups
• Usually single plane
• Allow deficits to specific structures t be
  addressed when athlete unable to weight bear or
  when closed kinetic chain would cause compensation

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Closed Kinetic Chain (

• Characteristics
• Increased joint compression
• Increased joint congruency, hence stability
• Decreased shear with muscle contraction
• Decreased acceleration
• Large resistance forces
• Stimulation of proprioceptors
• Enhanced dynamic stability

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Closed Kinetic Chain )

• Advantages
• Safer than open kinetic chain
• Less stress on healing structures
• More functional for lower extremity activities,
  except kicking

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Progressive Resistive Exercise Techniques and
Programs Contd

• Regardless of program.
• Initially exercises are performed daily
• WHY?
• Weight, sets, repetitions, rest governed by
  injured persons response to exercise
• When pain and swelling resolved, exercise
  intensity can increase
• Exercise consistently every other day
• 3-4x/week
• What phase of healing?

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Girth Measurments

• Often girth measurements are taken prior to the
  development of the rehab program to provide the
  therapist with a starting point.
• Measurements are repeated a intervals on the
  program to be used as a way to monitor progress
• Increases and decreases in girth size are thought
  to be related to muscle strength

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Girth measurements

• To ensure accurate and reliable measurements the
  therapist should use the same anatomical
  landmarks when performing the measurements.
• Contracted / relaxed ??
• Assignment 3