Muscular Strength &
Endurance
Sports 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)
 Fast Twitch Fibers (FT)
 Type I/slow oxidative
fibers
 Type II/fast oxidative
glycolytic fibers
 Dense with capillaries
 Produce quick forceful
contractions
 Rich in mitochondria &
myoglobin
 Carry more oxygen
 More resistant to fatigue
 Associated primarily
with long-duration,
aerobic-type activities
 Fatigue more quickly
 Useful in short-term,
high-intensity activities
 Subdivided into three
groups
Fast Twitch Muscle Fibers
Type IIa Fibers
Moderately
resistance to
fatigue (like
slow twitch
fibers)
Type IIx
Type Iib
Less dense
Less dense
with
with
mitochondria
mitochondria
and myoglobin
and myoglobin
Fastest
Fatigue
muscle type in
rapidly
humans
White in color
Contract more
Considered
quickly and
true fastwith greater
twitch fibers
force
Sustain short
bursts of
activity before
contraction
becomes
painful
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 Cuffgreat eccentric forceinjury 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 stretchshortening 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