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 Muscular Endurance Ability to perform repetitive muscular contractions against some resistance As strength increases, endurance increases

Definitions Power Ability to generate force quickly Combination of strength and speed Performance is limited without power

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

Types of Contraction So what? Strength training must focus on functioning of muscle Multi-planar Various contractions - functionally

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 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

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?

So What? First 8-10 weeks is training to be efficient Technique Neurophysiological input Position of load Position of limb Target fiber type as well as contraction type

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

Overload To improve strength, muscle must be worked at a level higher than it is accustomed to Without overload, muscle will maintain strength as long as training is continued against a resistance that it is accustomed to Existence of current strength but no additional strength gain

Overload Cont’d (Prentice, 2004) In rehabilitation, progressive overload is limited to a degree by the healing process Rate of progression determined by injured athlete’s response to specific exercise Increased pain and/or swelling indicate overload too high

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

Progressive Resistive Exercise Techniques and Programs Terminology Repetitions Repetition maximum (RM) Set Intensity Recovery period Frequency Multiple potential routines Single set Tri-sets Multiple sets Superset Pyramid Split routine Circuit Training

Progressive Resistive Exercise Techniques and Programs Cont’d Must consider 4 areas Amount of weight to be used Number of repetitions Number of sets Frequency of training

Open and Closed Kinetic Chain Open Kinetic Chain Movements in other segments within the chain are not predictable Origin is fixed and contraction causes movement of the insertion Closed Kinetic Chain Foot/hand meets resistance, movement of more proximal segment occurs in predictable pattern Not necessarily weight bearing Insertion fixed and contraction causes movement in of origin Concurrent shift: two joint muscles must work concentrically and eccentrically at the same time

Open Kinetic Chain ) Characteristics Increased acceleration forces Decreased resistance forces Increased distraction and rotational forces Usually isolated to a single joint Increased deformation of joint and muscle mechanoreceptors Concentric acceleration and eccentric deceleration Promotion of functional activity

Open Kinetic Chain ) Advantages Isolation of exercise to a specific joint Isolation of specific muscle groups Usually single plane Allow deficits to specific structures t be addressed when athlete unable to weight bear or when closed kinetic chain would cause compensation

Closed Kinetic Chain ( Characteristics Increased joint compression Increased joint congruency, hence stability Decreased shear with muscle contraction Decreased acceleration Large resistance forces Stimulation of proprioceptors Enhanced dynamic stability

Closed Kinetic Chain ) Advantages Safer than open kinetic chain Less stress on healing structures More functional for lower extremity activities, except kicking

Progressive Resistive Exercise Techniques and Programs Cont’d Regardless of program…. Initially exercises are performed daily WHY? Weight, sets, repetitions, rest governed by injured person’s response to exercise When pain and swelling resolved, exercise intensity can increase Exercise consistently every other day 3-4x/week What phase of healing?

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. Contracted / relaxed ?? Assignment # 3