INTRODUCTION
• Following musculoskeletal injury there will be some
degree of impairment in muscular strength and
endurance
• Rehabilitation program must focus on regaining and
improving strength and endurance
• Through thorough evaluation; identify weak links and
address them during rehabilitation program
• Injured area and along kinetic chain
INTRODUCTION
• Muscle Strength: ability for muscle to generate force against
some resistance
• Weakness or imbalance can impair normal functional movement
• Muscle Endurance: ability to perform muscle contractions
against some resistance for an extended period of time
• As strength increases there is a corresponding increase in
endurance
• When Developing rehab. Plan, you must have an understanding
of what you are trying to accomplish
TYPES OF SKELETAL MUSCLE CONTRACTION
• Isometric: muscle contracts to produce tension, but there is no
change in muscle length
• Considerable force can be generated even though no
movement occurs
• Concentric: Muscle shortens in length, while tension increases to
overcome or move some resistance
• Eccentric: Muscle lengthens while producing tension
• Resistance is greater than the muscular force being
produced
TYPES OF SKELETAL MUSCLE CONTRACTION
• Recommended that strengthening programs include
exercises that strengthen muscles in a manner in
which they contract functionally
• All muscles function concentrically, eccentrically,
and isometrically in 3 planes of motion
• Rehab plan may begin with single joint, single plane
isolated contractions, but should progress to multiplane, multi-joint functional movement
FACTORS THAT DETERMINE LEVELS OF
MUSCULAR STRENGTH, ENDURANCE & POWER
• Size of muscle
• Number of muscle fibers
• Neuromuscular efficiency
FACTORS THAT DETERMINE LEVELS OF
MUSCULAR STRENGTH, ENDURANCE & POWER
• Size of muscle
• Muscular strength is proportional to the crosssectional diameter (CSD) of muscle fibers
• Greater the CSD, or bigger a particular muscle is,
the stronger it is, thus more force it is capable of
generating
• Size of muscle can increase with resistance training
• Hypertrophy: increase in muscle size
• Atrophy: Decrease is muscle size
FACTORS THAT DETERMINE LEVELS OF
MUSCULAR STRENGTH, ENDURANCE & POWER
• Number of muscle fibers
• Strength also determined by the number of muscle
fibers within a given muscle
• Inherited characteristic
• Person with a large # of muscle fibers has the
potential to hypertrophy to a much greater degree
than someone with relatively few fibers
• Through resistance training we can increase size of
muscle fibers, but NOT the number of muscle fibers
within a given muscle
FACTORS THAT DETERMINE LEVELS OF
MUSCULAR STRENGTH, ENDURANCE & POWER
• Neuromuscular Efficiency
• Strength is also directly related to the efficiency of the
neuromuscular system and the function of the motor unit in
producing muscular force
• Motor unit: motor nerve and group of muscle fibers it innervates
• Electrical impulse from CNS through motor nerve to muscle
fibers it innervates cause muscle contraction
• Initial increases in strength during 1st 8 to 10 weeks of a
resistance training program can be attributed primarily to
increased neuromuscular efficiency
• Increase in # of motor units being recruited
• Firing rate of each motor unit
• Synchronization of motor unit firing
MUSCLE FIBER AND MOTOR UNIT
Muscle Fiber and Motor Unit
FAST-TWITCH VS. SLOW-TWITCH
• All muscle fibers in a particular motor unit are either fast-twitch
or slow-twitch
• Each has distinctive metabolic and contractile capabilities
• Slow twitch
• Type I or slow oxidative fibers
• First on and last off
• Resistant to fatigue, however time required to generate force
is greater
• Associated primarily with long duration aerobic-type activities
FAST TWITCH VS. SLOW-TWITCH
• Fast –twitch
• Capable of producing quick, forceful contractions, but fatigue
more rapidly than Type I
• Useful in short term, high intensity activities which mainly involve
anaerobic system
• 2 types
• Type IIA or fast-oxidative-glycolytic
• Second on Second off
• Type IIB or fast-glycolytic
• Last on and first off
• Fatigue rapidly
• “true” fast twitch fibers
FAST-TWITCH VS. SLOW-TWITCH
• Ratio in muscle
• Within a particular muscle there are Type I and II
muscle fibers
• Ratio of types varies with each person
• Muscles whose primary function is posture against
gravity tend to have more slow twitch
• Muscles that produce powerful, rapid, explosive
strength movements tend to have a higher
percentage of fast-twitch
FAST-TWITCH VS. SLOW-TWITCH
• Ratio in muscle continued
• Genetically determined and may play a part in determining
ability for given sport activity
• Must recognize what muscle fibers you are targeting
during your rehabilitation plan and develop appropriate
exercises
• Can improve metabolic capabilities of each type through
specific strength and endurance training
• Can change Type IIB to Type IIA, but cannot change type
II to Type I or vice versa
PHYSIOLOGY OF STRENGTH DEVELOPMENT
• Muscle Hypertrophy
• Increase in size of muscle fiber
• Theorized that dormant capillaries might become
filled with blood to meet demands of increased blood
flow from resistance training
• Theorized that there is an increase in size and
number of actin and myosin (myofilaments) within
the muscle fiber
• Thus muscle fibers increase in CSD
• Hyperplasia: Increase in # of muscle fibers
• Seen only in animal studies and not generalized
for humans
PHYSIOLOGY OF STRENGTH DEVELOPMENT
• Reversibility
• If resistance training is discontinued or interrupted,
muscle will atrophy, decreasing strength and mass
• As little as 48 hours
• Consistent resistance training is essential to
maintain strength and size
TECHNIQUES OF RESISTANCE TRAINING
• Overload Principle
• For a muscle to improve strength it must be forced to work at a
higher level than it is accustomed to.
• Must be overloaded
• Without overload, strength can be maintained with low to
moderate intensity resistance training, but will not increase
• Might be good training method for muscular endurance
• In rehabilitation, progression may be limited by tissue healing
and athletes pain, however most injuries will result in atrophy
or be caused by atrophy of one or multiple muscles, so
hypertrophy will lilely be goal of rehab. plan
TECHNIQUES OF RESISTANCE TRAINING
• SAID Principle
• Specific Adaptations to Imposed Demands
• When body is subjected to stress and overloads of
varying intensities, it will gradually adapt over time,
to overcome demands placed on it
• Must apply term to different phases of rehab.
• What are you trying to accomplish? BE SPECIFIC
• For example: When reconditioning a basketball
player would you want to have them run a mile?
TECHNIQUES OF RESISTANCE TRAINING
• Isometric Exercise
• Used in early phases of rehabilitation when full ROM exercises
exacerbate symptoms or could cause further injury
• 10 second hold for 10+ repetitions per hour recommended
• Can be useful in strength increases at specific point in ROM
• Submaximal to maximal intensities
• Must be careful with increase in intrathoracic pressure (Val
Salva) that occurs with maximal contractions
• Also used by weight lifters to help increase strength at “sticking
point” during a specific lift
TECHNIQUES OF RESISTANCE TRAINING
• Progressive Resistive Exercises(PRE)
• Exercises that strengthen muscles through a
contraction that overcomes some fixed resistance
• Dumbbells, machines, elastic tubing
• Uses isotonic contractions: contractions in which
force is generated while muscle is changing length
• Concentric and eccentric contractions
CONCENTRIC VS. ECCENTRIC
• Can generate more force against resistance with an
eccentric contraction
• Movement requires lower level of motor unit activity to achieve
certain force than a concentric contraction
• With fewer motor units firing to produce specific force
additional motor units can be recruited to generate increased
force
• Eccentric contractions are less resistant to fatigue because
requirement for Oxygen is less
CONCENTRIC VS. ECCENTRIC
• Eccentric contractions during rehabilitation have recently
received considerable emphasis in research
• Eccentric contractions critical in deceleration of limb motion,
especially during high velocity dynamic activities
• Strength deficits or inability to tolerate these forces may
predispose a person to injury
• Should focus on concentric and eccentric exercises during
rehabilitation
• Concentric movement: 1-2 seconds
• Eccentric contraction: 2-4 seconds
• Ratio of concentric to eccentric should be approximately 1:2
• Muscle will fatigue more rapidly concentrically than
eccentrically
• Eccentric loading can assist in increasing tensile strength of
healing tissue
PROGRESSIVE RESISTIVE EXERCISES(PRE)
• Repetitions: number of times a specific movement is repeated
• Repetition Maximum: Maximum # of repetitions at a given
weight
• Set: A group of repetitions and recovery intervals
• Intensity: Amount of weight or resistance lifted
• Recovery Period: rest interval between repetitions and sets
• Volume: Amount of work (reps x sets) in a given training session
• Frequency: # of training sessions in a week’s period
• Periodization: preplanned, systematic variations in training
specificity, intensity and volume organized in periods or cycles
• Used in strength and conditioning, but should also be used in
rehabilitative setting
PERIODIZATION MODEL FOR RESISTANCE
TRAINING
FREE WEIGHTS VS. EXERCISE MACHINES
• Exercise machines
• Can be safer and easier to use
• Design constraints often only allow single plane motions
• Not very functional
• Free weights
• Element of neuromuscular control to stabilize weight from
moving in different directions
• May decrease amount of weight lifted compared to machine
• Machines have restricted motion
• Can incorporate multi-joint, multi-plane functional movements
SURGICAL TUBING/THERABAND
• Widely used in rehabilitation
• Can perform isolated strengthening exercises or multi joint,
multi-plane exercises
• Easy for athlete to use at home
• Can purchase different resistance levels identified by colors
• Athlete can adjust resistance by increasing or decreasing
tension on the band
• Movement can occur in multi planes simultaneously
• Exercise against resistance in more functional movement planes
PLYOMETRIC EXERCISE
• Incorporated in later stages of rehabilitation
• Hops, bounds, depth jumps, weighted throws and rotations
• Specific exercises that require a rapid stretch of a muscle
eccentrically followed immediately by a rapid concentric
contraction
• Increase ability to use stored elastic energy
• Affected by time, magnitude of stretch and velocity of
stretch
• Facilitate and develop a forceful, explosive movement over a
short period of time
• Help in developing eccentric control in dynamic movements
OPEN VS. CLOSED KINETIC CHAIN EXERCISES
• Open chain: foot or hand is not in contact with ground or some
other surface
• Closed Chain: Foot or hand is weight bearing or fixed on ground
or surface
• Most functional activities involve some aspect of weight
bearing for the feet or hands
• May start with open chain exercises, but must progress to
closed chain exercises to optimize rehabilitation
• Closed chain exercises will transmit forces throughout kinetic
chain
• Strengthening and stabilization of multiple muscles and joints
CONCLUSION
• During rehabilitation must incorporate muscle strength and endurance
exercises
• Assist in tissue healing by realignment of scar tissue and increasing
tensile strength
• Identify weaknesses and address during rehab program
• Strength deficits or atrophy from the injury or that may have
predisposed athlete to the injury
• Use progressive resistance exercises following periodization, overload
and specificity principles when developing rehab program
• Communication with the athlete is essential to proper progression of
resistive exercises
• Pain and swelling can help guide your progression