Muscular Strength & EnduranceSports Medicine II

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

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

Fast Twitch Muscle FibersType IIa Fibers

Moderately resistance to fatigue (like slow twitch fibers)

Type IIxLess dense with mitochondria and myoglobinFastest muscle type in humansContract more quickly and with greater forceSustain short bursts of activity before contraction becomes painful

Type IibLess dense with mitochondria and myoglobinFatigue rapidlyWhite in colorConsidered true fast-twitch fibers

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

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)

Concentric Isotonic Contractions

Muscle shortens while contracting against resistance

Higher utilization of oxygen

Accelerate movement

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

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.

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

Factors that Determine Levels of Muscular Strength

Biomechanical Factors

Location of muscle attachment- longer lever means greater torque

Length of the muscle

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

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

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

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

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

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

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

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