Download LEcture 8 Muscular Strength E&P 2016

MUSCULAR STRENGTH,
ENDURANCE AND
POWER
Returning the athlete to competitive and functional level following
injury
Definitions
Muscular Strength
Ability to generate force against
some resistance
Important to maintain normal levels of
strength for normal healthy living
Measure with 1 RM –
In rehab 1 Rm too difficult for weak or
injured muscles
Could use a 10 RM – weight not as
stressful
Definitions
Muscular Endurance
Ability to perform repetitive muscular
contractions against some resistance
( less than max load)
Depends on energy systems
As strength increases, endurance
increases
Definitions
 Power
 Strength applied over a distance for a specific amount of
time
 P=Fxd/T
 Ability to generate force quickly
 Combination of strength and speed
 Performance is limited without power
 Speed depends on coordination , efficiency of
movement and timing
 Power is developed after strength ( in rehab)
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
Fiber Types Cont’d
 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?
Muscle Strength and Muscle
Endurance
 High intensity and low reps at one end of continuum
– strength gains
 Low intensity and high reps at other end of continuum
– muscle endurance gains
 Strength gains can be achieved with high rep and as
can endurance gains with low reps but not as well –
good to remember for rehab ….
 General rule a thumb
 Strength – 10 reps
 Endurance 15- 20 reps
Muscle Strength and Muscle
Endurance
 Berger 1962 – sets – three sets beneficial for strength
training
 This study has not been replicated
 ACSM- one set of 8- 12 reps to fatigue to increase
strength
 Recovery times vary for type of exercise
 Isometric – 1 minute
 Isotonic – 30 sec to a minute
 Isokinetic – 2-4 minutes
Types of Contraction
 Isotonic contraction
 Dynamic involves a change in the muscle length
 Concentric contraction
 Muscle shortens
 Eccentric Contraction
 Muscle lengthens
 20-40 % more force can be produced
 More likely hood of DOMS
 Isometric contraction
 Contraction that produces muscle tension but no
change in muscle length
Types of Contraction
 Isokinetic
 Velocity is controlled ( speed is unchanged) where as
the resistance is changed
 Often called accommodating resistance
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
Factors Continued
 Number of Muscle Fibers
 Strength is a function of the number and diameter of
muscle fibers
 Number of fibers is inherited characteristic
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
Evaluating Muscle strength
 Isokinetic devices, cable tensiometers , isometric
strength
 Manual Muscle test
 The basis of this test is assessment of the muscles ability
to move a joint through a ROM
 Muscle strength is graded from 0-5
 Always remember ACTIVE ROM first
 Resistance testing – isometric , mid range provide
stabilization
Strength equipment
 Varies greatly due to availability and cost , size of
room
 Manual resistance – resistance force applied by
therapist or by patient
 Advantage – no equipment required, cost , hands on ,
immediate feedback , can easily modify resistance
applied , can modify speed and can be easily
incorporated in to a program
 Disadvantages- requires one on one work – time
consuming , manual resistance nor measurable , not a
consistent force
 Body weight – use of patient’s own weight
 Advantage- no equipment , performed anywhere , cost ,
functional activities , performed independently
 Disadvantage – no guarantee doing right when not
supervised ,can not tolerate weight bearing ex
Strength equipment
 Rubber tubing /bands – dynamic resistance – lots of
different weights
 Advantage – cost is low, ex at home , not bulky can be
taken on road trips ,can make progressions , can mimic
functional exercises
 Disadvantage – performed independently – unsure of
technique, resistance greater at end when stretched ,
easier to use for upper than lower body
 Free weights – cuffs , bar bells
 Advantage – variety of free wts available, measurable
changes ,can be used in functional activities
 Disadvantages – safety , training supervision using too
much weight, boring
Strength equipment
 Isotonic machines – constant load during exercise
 Advantage- safety , readily available in gyms , multi
station units , can work more unsupervised
 Disadvantage – weight restrictions due to muscle
strength , boring , cost
 Isokinetic machines – accommodating resistance
machines - biodex and cybex
 Advantage- constant speed and accommodating
resistance , max and sub max outputs, patterns ,
measurable results ( computer charts graphs )
 Disadvantage- cost $40,000, exercises are mostly OKC
Exercise Progression
 No Pain , during , after , next day ( DOMS)
 No inflammation
 Make attainable goals yet challenging
 Progressive overload – loads must increase
progressively – overload principle
 Cross training – training contralateral side – can be
used when limb movement is restricted
Strength
 Four principles SNAP
 Specific exercise
 No Pain
 Attainable goals
 Progressive overload
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
 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
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
Open and Closed Kinetic Chain
 Open Kinetic Chain
 Distal segment ( hand or foot ) moves freely in space
 Movements in other segments within the chain are not
predictable
 Kicking , throwing open kinetic chain
 Advantage – ex not delayed if can not weight bear
 Closed Kinetic Chain
 Distal segment is weight bearing
 Foot/hand meets resistance, movement of more
proximal segment occurs in predictable pattern
 Running , handstands
 Less shear force with CKC- safer to use especially in early
rehab program
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
Girth measurements
 To ensure accurate and reliable measurements the
therapist should use the same anatomical landmarks
when performing the measurements.