1. Muscular Strength, Endurance and Power(Resistance Exercises)
Dr. Afaf A.M Shaheen
Lecture 8
RHS 322

2. Outlines Strength, Endurance & Power
Types of Skeletal Muscle Contraction
Factors That Determine Levels of Strength, Endurance & Power
Physiology of Strength Development
Overload Principle
Progressive Resistive Exercise (PRE)
Resistance Training Techniques Used in Rehabilitation

4. Critical to maintain and improve in each area in order to achieve competitive fitness levels and return athlete to functional level following injury

5. Strength, Endurance & Power
Muscular Strength
Ability to generate force against some resistance
Important to maintain normal levels for normal healthy living
Imbalance or weakness can impair normal function
Muscular Endurance
Ability to perform repetitive muscular contractions against some resistance
Power
Ability to generate force quickly
Combination of strength & speed
Performance is limited without power

6. Types of Skeletal Muscle Contraction
Isometric Contraction
Contraction that produces m. tension but no change in m. length
Concentric Contraction
Contraction that causes m. shortening while tension increases to overcome some resistance
Eccentric Contraction
Resistance is greater than the muscular force being produced & muscle lengthens while producing tension

7. Types of Muscle Contraction

8. Force and Types of Muscle Contractions

9. Types of Skeletal Muscle Contraction
Econcentric contraction
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

10. 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
Increase in muscle size
Atrophy
Decrease in muscle size

11. Factors That Determine Levels of Strength, Endurance & Power
Number of Muscle Fibers
Strength is a function of the number and diameter of muscle fibers
Number of fibers is inherited characteristic

12. Factors That Determine Levels of Strength, Endurance & Power
Neuromuscular Efficiency
Strength is directly related to efficiency of the neuromuscular system
Initial increases in strength during first weeks are attributed to neuromuscular efficiency
Efficiency enhanced strength in 3 ways
Increase number of motor unit recruitment
Increase in firing rate of each motor unit
Enhance synchronization of motor unit firing

13. Factors That Determine Levels of Strength, Endurance & Power
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

14. Biomechanical Considerations
Position of tendon attachment
Relative position of tendon attachment to fulcrum of the joint
The closer the tendon is to resistance, the greater the force produced
Change in attachment will alter force generating capabilities
Length-Tension Relationship
Length of muscle determines tension that can be created
Varying lengths will produce varying tensions
Determined by overlap of actin-myosin filaments

15. 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

16. 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)
Moderately resistant to fatigue
Type IIb (fast glycolytic - FG)
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

17. 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

18. Physiology of Strength Development
Muscle Hypertrophy – 3 theories
Hyperplasia –  in number of muscle fibers
Genetically determined & does not seem to increase with training
Evidence exists of fibers splitting – conducted in animals
Hypothesized increased number of capillaries – partially correct
No new capillaries
Increase in dormant capillary activity to meet needs of muscle

19. Physiology of Strength Development
**Increased size and number of myofilaments
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

20. Other Physiological Adaptations to Resistance Exercise
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

21. 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

22. Isometric Exercise
Capable of increasing muscle strength at specific joint angles
Exercise with no change in muscle length
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
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”

23. 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

24. Free Weights vs. Exercise Machines
Advantages & disadvantages for both
Machines –
Safety & easy to use
Constraints on motion & generally single plane of motion
Free weights –
Do not restrict motion
Incorporates certain level of neuromuscular control

25. Surgical Tubing (Theraband) or Exercise Band
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

26. 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

27. Multiple potential routines
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

28. 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

29. 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
50%, 75% and 100% of 10 RM
Oxford method
Used during early, intermediate & advanced levels of rehabilitation
Percentages of 10 RM
Diminishes resistance as muscle fatigues – “regressive load”
100%, 75%, 50% of 10 RM

32. Isokinetic Exercises
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

33. 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

34. 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

35. Plyometric Exercise

36. 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

37. 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 non- weight-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

38. Training for Muscular Strength vs. Muscular Endurance
Strength and endurance are closely related
As one improves, the tendency is for the other to do the same
For strength development
Heavier weight and low repetitions should be used
Endurance training
Lighter weight and high repetitions (10-15) are suggested

39. 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

40. Strength/Body Weight Ratio
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

41. 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

42. 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)

43. 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

44. 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

45. 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

46. Definitions of Some Terminology
Repetition: number of times you repeat specific movement.
Repetition Maximum (RM): maximum number of repetitions at a given weight.
Intensity: the amount of weight or resistance lifted.
Recovery Period: the rest interval between repetitions. 

47. References
Kisner, C. & Colby, L. (2002). Therapeutic Exercise: Foundations & Techniques, 4th ed.