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Muscular Strength and

Endurance There are many types of strength that an in- dividual may need in order to improve perfor- mance and/or function. In order to understand the benefits of exercise, we must first define and describe the different types of strength.

net muscle

actions Definition: Shortening of a

muscle fiber against a load “Raises” the load

Neural Factors Influencing

Strength Gains

Exercise elicits a training stimulus. One effect is structural (e.g. hypertrophy of muscles and connective tissues) while the other is functional. Functional affects of training will be seen as both increased intramuscular coordination (within a muscle) and increased intermuscular (within a group of muscles). During any movement, cer- tain muscles will be activated as a primary, sec- ondary, stabilizer, and/or neutralizer, to coincide with facilitation (actual recruitment or disinhibi- tion) or inhibition (shut off). This sequence of events takes place during all movements, espe- cially during the initial stages of training (motor learning/motor ability stage).

concentric

eccentric

isometric

“Accelerates” the load

Ex: Upward phase of a

dumbbell biceps curl

Definition: Lengthening of a

musclefiberagainstaload§

-“Lowers” the load

§-Ex: Downward phase of a

dumbbell bicep curl

Definition: Where a muscle

neither lengthens nor short-

ens against a load (no net

joint movement). A co-

contraction of agonist and

antagonist muscles.

§-Ex: Holding the elbow still at

90˚ in a dumbbell bicep curl

isotonic

isokinetic

Definition: Exercise where a

concentric and/or eccentric

action is generated to move

a load through a range of mo-

tion where the force on the

muscle does not change

Definition: Exercise on a spe-

cialized piece of equipment

where the muscle action

speed is constant

adaptations to

strength training Increased strength due to increased motor unit

recruitment (i.e. able to contract a greater num-

ber of motor units simultaneously)

Increased strength due to muscle hypertrophy

(increase in muscle cell size)

Possible conversion of Type 1 to Type II fibers

Possible hyperplasia leading to hyper-

trophy (increase in muscle cell number - rare)

Increased ATP, CP and glycogen stores (energy

stores)

Increase in size of the left and right ventricles of

the heart (wall thickness and chamber diameter)

types of strength

absolute strength

The maximum amount of force an individual can produce in a one repeti-

tion maximum lift (one rep max or 1RM), irrespective of body weight and

time of force development. This type of strength is particularly important

for shot putters and football linemen where bodyweight has a high correla-

tion to an increase in sports performance.

relative strength

The maximum force that muscles can generate in relation to one’s body

weight. This type of strength is important for individuals who have to move

their entire body weight, such as a gymnast. This type of strength is also

important for individuals who want to get stronger, but don’t necessarily

want to gain mass, as well as an important strength stage to fulfill prior to

mass-building.

strength endurance

(muscular endurance)

The ability to sustain muscular contractions for a long duration of time.

This type of strength is important for mid-level endurance events such as

cycling or rowing.

power

The physics definition of power is Force x Distance Time. In other words,

power measures how quickly work is performed (Work = Force x Distance).

The different ways to increase power are to increase the Force (ex: weight),

increase the Resisted Distance (ex: up if force is due to gravity) or to de-

crease the Time (ex: move faster). The factor most influential in increasing

power is decreasing the time to perform a movement or exercise.

What are the various types of strength? Be able to

identify exercises which emphasize a particular type of

strength. What factors contribute to muscle soreness?

This has been a small sample of what you will learn when you enroll on the NESTA Personal Fitness Trainer Certification.

Hypertrophy Intermuscular Intramuscular