Regaining Muscular Strength, Endurance, & Power

1. Regaining Muscular Strength, Endurance, & Power Chapter 9

2. 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 • 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

3. 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 • 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

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

5. 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

6. 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 • 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

7. 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

8. 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

9. 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 • **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

10. 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

11. 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

12. 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”

13. 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

14. 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 • 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

15. 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

16. 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

17. 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 Resistance Training Techniques Used in Rehabilitation

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. Resistance Training in Older AdultsKisner & Colby, p. 125

29. 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

30. 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)

31. 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

32. 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

33. 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

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