Regaining Muscular Strength, Endurance and Power
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Transcript Regaining Muscular Strength, Endurance and Power
Regaining Muscular
Strength, Endurance, &
Power
Chapter 9
Regaining Strength, Endurance & Power
Critical to maintain and improve in each area in order to
achieve competitive fitness levels and return athlete to
functional level following injury
Muscular Strength
Muscular Endurance
Ability to generate force against some resistance
Important to maintain normal levels for normal healthy living
Imbalance or weakness can impair normal function
Ability to perform repetitive muscular contractions against some
resistance
Power
Ability to generate force quickly
Combination of strength & speed
Performance is limited without power
Types of Skeletal Muscle Contraction
Isometric Contraction
Concentric Contraction
Resistance is greater than the muscular force being produced &
muscle lengthens while producing tension
Econcentric contraction
Contraction that causes m. shortening while tension increases to
overcome some resistance
Eccentric Contraction
Contraction that produces m. tension but no change in m. length
Controlled concentric & eccentric contraction of same muscle over 2
separate joints
Hamstring and rectus femoris of quadriceps
Strength training must focus on functioning of muscle
Multi-planar
Various contractions - functionally
Factors That Determine Levels of
Strength, Endurance & Power
Size of Muscle
Proportional to cross-sectional diameter of muscle
fibers
Increased cross-sectional area = increased strength
and force production
Hypertrophy
Atrophy
Increase in muscle size
Decrease in muscle size
Number of Muscle Fibers
Strength is a function of the number and diameter of
muscle fibers
Number of fibers is inherited characteristic
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
Efficiency enhanced strength in 3 ways
Increase # of motor unit recruitment
Increase in firing rate of each motor unit
Enhance synchronization of motor unit firing
Age
Men & women increase strength throughout puberty
& adolescence
Peaks at age 20-25
After age 25, max strength declines 1% annually
Decline is related to physical activity
Able to retard decline in performance through activity
Biomechanical Considerations
Position of tendon attachment
Relative position of tendon attachment to fulcrum of the joint
Change in attachment will alter force generating capabilities
Length-Tension Relationship
The closer the tendon is to resistance, the greater the force
produced
Length of muscle determines tension that can be created
Varying lengths will produce varying tensions
Determined by overlap of actin-myosin filaments
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
Fast-Twitch vs. Slow Twitch
Slow Twitch Fibers
Type I or slow oxidative (SO)
More resistant to fatigue
Time required to generate force is greater in slow twitch
fibers
Primarily associated with long duration, AEROBIC activities
Fast Twitch Fibers
Type IIa (fast oxidative glycolytic- FOG)
Type IIb (fast glycolytic - FG)
Moderately resistant to fatigue
Fatigues rapidly – true fast twitch
Type IIx – fatigue resistant with force capacity (a<x<b)
Produce quick, forceful contractions
Short-term, high intensity activities, ANAEROBIC activities
Ratio in Muscle
Both fiber types exist in individual muscles
Ratio varies by muscle and by individual
Postural muscles = % primarily type I fibers
Power, explosive strength muscles = % type II
fibers
Genetically determined
Large role in determining ability for a given sport activity
Fiber changes due to training
Enhanced metabolic capabilities through specific training
Physiology of Strength Development
Muscle Hypertrophy – 3 theories
Hyperplasia – in number of muscle fibers
Hypothesized increased number of capillaries – partially
correct
No new capillaries
Increase in dormant capillary activity to meet needs of muscle
**Increased size and number of myofilaments
Genetically determined & does not seem to increase with training
Evidence exists of fibers splitting – conducted in animals
Actin (thin) and Myosin (thick)
When muscle is stimulated to contract, cross-bridges pull
myofilaments closer which shortens the muscle, & produces
movement at joint that muscle crosses
Reversibility – adaptations of muscle due to training can
begin to reverse within 48 hours of removing training
Other Physiological Adaptations to
Resistance Exercise
Strength of non-contractile structures
Improved oxygen uptake
Tendons and ligament increase
Increased bone-mineral content
If resistance training is high enough to elicit a
cardiovascular response/adaptation
Increased metabolic enzymes
Techniques of Resistance Training
Overload Principle
To improve strength, muscle must be worked at a
level higher than it is accustomed to
Muscle will maintain strength if it is trained against a
consistent resistance that it is accustomed to
Existence of current strength & will result in increased
muscle endurance
Effective training requires a consistently increasing
effort against progressively more resistant loads
In rehabilitation, rate of progression is determined by
athlete’s response to specific exercise
Be mindful of pain when dealing with progression
Isometric Exercise
Capable of increasing muscle strength at specific joint
angles
May produce spikes in systolic blood pressure
Could cause life-threatening cardiovascular accident
To reduce this event to occur - REMIND the person to breath
Widely used in rehabilitation
Exercise with no change in muscle length
Attempt to use positional or functional exercise – work at
multiple angles throughout the range if possible
Contractions should be held for 10 seconds at
frequency of 10 or more per hour
Utilized to enhance lift or activity at “sticking point”
Progressive Resistive Exercise (PRE)
Exercises that work through a full range of motion
Isotonic or isodynamic contractions
Most popular & commonly used technique
Concentric vs. Eccentric
Greater force can be generated due to lower number of
motor units recruited allowing other motor units to be
recruited to generate increased force
Oxygen use is much lower with eccentrics
Efficiency of eccentric exercise is higher than concentric
exercise
Needs of the body – acceleration and deceleration
Must be able to control body movements – deceleration and
eccentrics allows for this control
Free Weights vs. Exercise Machines
Advantages & disadvantages for both
Machines –
Free weights –
Do not restrict motion
Incorporates certain level of neuromuscular control
Surgical Tubing (Theraband) or Exercise Band
Safety & easy to use
Constraints on motion & generally single plane of motion
Allow for motion in multiple planes
Ability to perform more functional movement
Can be utilized with PNF & plyometrics
Variable Resistance
Change in force required at different angles to move a
particular resistance
Greatest when joint is at 90 degrees
Accommodating resistance or variable resistance equipment
changes resistance at different points in range
Progressive Resistive Exercise Techniques (PRE)
Terminology
Repetitions
Repetition maximum (RM)
Set
Intensity
Recovery period
Frequency
Recommended Techniques of Resistance Training
Must consider 4 areas
Amount of weight to be used
Number of repetitions
Number of sets
Frequency of training
The healing process must dictate the program!
Intensity is key
Multiple potential routines
Single set – 1 set 8-12 reps at a slow speed
Tri-sets – 3 exercises for 1 muscle group, 2-4 sets with no rest
Multiple sets – 2-3 warm-up sets with progressively increasing
resistance followed by several sets at the same resistance
Superset – multiple exercises, 1 set of 8-10 repetitions or 1 or 2
exercises, with multiple sets of 8-10 repetitions
Pyramid – multiple sets decreasing repetitions and increasing
resistance
Split routine – Workouts exercise different groups of muscles on
different days
Circuit Training
Group of exercise (flexibility, callisthenic, strength, brief aerobic)
Used to increase strength or endurance
Move from one station to the next, performing exercise for a
given time period or number of repetitions
Resistance Training Techniques
Used in Rehabilitation
DeLorme’s method
Based on repetition
maximum of 10
Designed for early rehab
Designed for beginning
rehab
Introduced PRE –
“progressive loading”
Builds in warm-up period
MacQueen’s method
Utilizes varying sets for
beginning/intermediate &
advanced
Set of 10 RM
Oxford method
Used during early,
intermediate & advanced
levels of rehabilitation
Percentages of 10 RM-rep
max
Diminishes resistance as
muscle fatigues –
“regressive load”
Sander’s program
Utilized in advanced
stages of rehabilitation
Utilizes percentages of
body weight
Knight (DAPRE)
Daily Adjustable
Progressive Resistive
Exercise
Adjusted based on
individual’s progress
Based on 6 RM working
weight
Berger
Adjusts within individual’s
limitations
Should allow for 6-8 RM
repetitions on 60-90
seconds
Must be able to achieve 3
sets of at least 6 RM and
no more than 8 RM
Increases occur in 10%
increments
For rehabilitation
Base program on pain
and healing process
Should be performed
daily early on
Reduce workout to
every other day as
progress is made
Isokinetic Exercise
Involves muscle contractions where length
change of muscle is set at a constant velocity
Maximal resistance throughout the range of
motion
Variety of machines/manufacturers are available
Can be used with eccentrics & concentric exercise
Isokinetics as a Conditioning Tool
Maximal effort for maximal strength gains
Dynamometer will move at a set speed whether
maximal or half of maximal effort is put forth
Athlete can cheat with machine and not put forth the effort
Not cost effective
Isokinetics in Rehabilitation
Gained popularity in rehabilitation during the 1980’s
Provide objective means of athlete/patient evaluation
Training at fast vs. slow speeds
Functional speeds
Plyometric Exercise
Encompass a rapid stretch of muscle eccentrically
followed by a rapid concentric contraction to
facilitate the development of explosive power
Greater stretch relative to resting length = greater
resistance muscle can overcome
Speed of stretch is emphasized over magnitude
Used to develop eccentric control of dynamic
movements
Exercises should be performed technically correct
Core Stabilization Strengthening
Fundamental component of rehabilitation
Strengthening of core (lumbo-pelvic complex)
Used to
Improve dynamic postural control
Ensure appropriate muscular balance & joint
movement about the core
Improve neuromuscular efficiency and expression of
dynamic functional movement
Provide optimal stabilization of kinetic chain and
balanced muscular functioning throughout the
chain
Open vs. Closed Kinetic Chain
Exercises
Anatomical & functional relationships that exist
in the upper and lower extremity
Open kinetic chain
May be needed when lower extremity is to be nonweight-bearing
Closed kinetic chain
Useful in rehabilitation
Most activities call for weight bearing of foot or hand in some
capacity
May be more functional than open chain activities in some
instances
Training for Muscular Strength vs.
Muscular Endurance
Strength and endurance are closely related
For strength development
As one improves, the tendency is for the other to do
the same
Heavier weight and low repetitions should be used
Endurance training
Lighter weight and high repetitions (10-15) are
suggested
Resistance Training Differences
Between Males & Females
Females tend not to develop significant muscle
bulk due to reduced levels of testosterone
While bulk generally does not increase muscle
tone will increase through training in females
Gains are primarily neuromuscularly related &
tend to plateau for females
Males tend to continue developing strength
through increased bulk following the
neuromuscular strength gains
Strength/Body Weight Ratio
Females tend to have a lower ratio due to higher
levels of body fat
Absolute strength differences
Reduced when body size & composition are compared
Leg strength can actually be stronger in females with
upper extremity strength greater in males
Resistance Training in Young
Athletes
Same principles can be applied to young athletes
Much debate sociologically & physiologically
If properly supervised, young athletes can make
improvements in all areas of fitness
Pre-pubescent child will experience gains in muscle
strength without muscle hypertrophy
Resistive exercise should be integrated into a
young athlete’s rehabilitation
Close instruction & supervision is necessary
Base on extent of maturation – critical to effectiveness
Resistance
Training in
Older
Adults
Kisner & Colby, p. 125
Specific Resistive Exercises Used
in Rehabilitation
Goal of program
To regain and possibly increase specific muscle
strength
Increase efficiency of movement
Variety of exercise modes can be utilized to
achieve goals
Isometric Exercise
Used during initial stages of rehabilitation
Useful when training through a full range of
motion is contraindicated
Serve to increase static strength, decrease
atrophy, create muscle pump to reducing
edema
Progressive Resistive Exercise (PRE)
Most commonly used strengthening technique
Incorporates free weights, machines and tubing
Utilizes isotonic contractions (concentric and
eccentric contractions)
Isokinetic Exercise
Incorporated in later
stages of rehabilitation
Uses fixed speeds with
accommodating
resistance
Provides maximal
resistance through full
range of motion
Commonly used as
criteria for return of
athlete to functional
activity
Plyometric Exercise
Generally incorporated in later stages of rehabilitation
Relies on a quick eccentric stretch to facilitate a
subsequent concentric contraction
Encourages dynamic movements associated with
power
Due to the need to generate power in athletic
activities, it is critical to incorporate it within a the
rehabilitation process
Core Stabilization
Essential for functional
strength
Core functions to
dynamically stabilize
the kinetic chain
Core strength enables
distal segments to
function optimally and
efficiently during force
and power generation
References
Kisner, C. & Colby, L. (2002). Therapeutic
Exercise: Foundations & Techniques, 4th
ed.