1. Muscular Strength & Endurance Sports Medicine II

2. Muscular Strength & Endurance  Muscular Strength The maximum force that can be applied by a muscle during a single maximum contraction  Muscular Endurance The ability to perform repetitive muscular contractions against some resistance

3. Muscular Strength & Endurance  Slow Twitch Fibers (ST)  Type I/slow oxidative fibers  Dense with capillaries  Rich in mitochondria & myoglobin  Carry more oxygen  More resistant to fatigue  Associated primarily with long-duration, aerobic-type activities  Fast Twitch Fibers (FT)  Type II/fast oxidative glycolytic fibers  Produce quick forceful contractions  Fatigue more quickly  Useful in short-term, high-intensity activities  Subdivided into three groups

4. Fast Twitch Muscle Fibers Type IIa Fibers Moderately resistance to fatigue (like slow twitch fibers) Type IIx Less dense with mitochondria and myoglobin Fastest muscle type in humans Contract more quickly and with greater force Sustain short bursts of activity before contraction becomes painful Type Iib Less dense with mitochondria and myoglobin Fatigue rapidly White in color Considered true fast- twitch fibers

5. Skeletal Muscle Contractions  Isometric contraction:  Muscle contracts to increase tension but there is no change in the length of the muscle  Concentric contraction:  Muscle shortens in length during the contraction to overcome or move some resistance  Eccentric contraction:  Muscle lengthens while contracting due to the resistance being greater than the muscle force produced

6. Isometric Exercise  Length of the muscle remains constant  Tension develops toward a max force against an immovable resistance  10 seconds/5-10 x per day  Tendency to spike the systolic BP- potentially life-threatening (Valsalva effect)

7. Concentric Isotonic Contractions  Muscle shortens while contracting against resistance  Higher utilization of oxygen  Accelerate movement

8. Eccentric Isotonic Contractions  Muscle lengthens while contracting against resistance  Generates greater amounts of force  Oxygen utilization is much lower  More resistant to fatigue  Hamstrings/Rotator Cuff- great eccentric force- injury is quite common

9. Factors that Determine Levels of Muscular Strength  Size of Muscle  Strength is a function of the number and diameter of muscle fibers in a given muscle  Number of fibers is genetic  Muscle Hypertrophy  Increase in the number of muscle fibers?  Increase in the number of capillaries?  Increase in the size and number of myofilaments.

10. Factors that Determine Levels of Muscular Strength  Neuromuscular Efficiency  Muscle efficiency is achieved by getting more motor units to fire- causing a stronger contraction  It is not uncommon to see extremely rapid gains in strength at the first of a weight training program due to an improvement in neuromuscular function

11. Factors that Determine Levels of Muscular Strength Biomechanical Factors  Location of muscle attachment- longer lever means greater torque  Length of the muscle

12. Factors that Determine Levels of Muscular Strength  Overtraining:  “If you abuse it you will lose it”  Breakdown psychologically & physiologically  Minimize negative effects: proper & efficient training, proper diet, appropriate rest  Reversibility:  Muscle will atrophy if training if discontinued or interrupted  Begin in as little as 48 hours

13. Types of Resistance Exercise  Isotonic Exercise  Shortens and lengthens the muscle through a complete range of motion  Ratio of negative to positive should be 1:2  Free weights vs. machines  Repetitions: # of times a movement is repeated  Repetitions max (RM): max # of reps at a given weight  1 Rep Max: max weight that can be lifted one time  Set: number of repetitions  Intensity: amount of weight/resistance used  Recovery period: rest interval between sets  Frequency: number of times an exercise is done in 1 week

14. Types of Resistance Exercise  Isokinetic Exercise  Exercise at a fixed velocity of movement with accommodating resistance  Max resistance is provided throughout the range of motion  Only one isokinetic device is available commercially (Biodex)  Resists both concentric and eccentric contractions at a fixed speed to exercise the muscle

15. Types of Resistance Exercise  Circuit Training  Exercise stations that consist of various combinations of weight training, flexibility, calisthenics, and aerobic exercises  Can be designed to accomplish many different training goals  Specific time at each station  8-12 stations  Repeat 3 times

16. Types of Resistance Exercise  Calisthenics Strengthening Exercise:  Free exercise  Individual must support the body or move the total body against the force of gravity  Push-ups, sit-ups  10+ reps  Sets of 2 or 3

17. Types of Resistance Exercise  Plyometric Exercise  Type of exercise that takes advantage of the stretch- shortening cycle  Develop explosive movement over a short period of time  Jumping, bounds, med balls  Place a great deal of stress on the musculoskeletal system

18. Proper Spotting Techniques  Make sure the lifter understands how to get out of the way of missed attempts, particularly with overhead techniques  Check to see that the lifter is in a safe, stable position  Communicate with the lifter to know how many reps are to be done, whether a liftoff is needed, and how much help the lifter wants in completing a rep  Stand behind the lifter  When spotting dumbbell exercises, spot as close to the dumbbells as possible above the elbow joint

19. Proper Spotting Techniques  If heavy weights exceed the limits of your ability to control the weight, use a second spotter  Make sure the lifter uses the proper grip  Make sure the lifter inhales and exhales during the lift  Make sure the lifter moves through the complete range of motion at the appropriate speed  Always be in position to protect both the lifter and yourself from injury