732 Exercise Physiology Principles of Strength

muscle performance

the ability of a muscle to carry out its various roles in human movement

muscle strength

the amount of force an individual exerts in a single maximum muscle contraction. Can be measures through MMT or dynamometry

muscle power

the product of strength x speed. Power is an important component of many athletic activities that require both strength and speed

muscle endurance

the ability to perform low intensity activity over a sustained period without fatigue while maintaining proper alignment of the body’s segments. It relates to the muscle’s ability to generate and use ATP through aerobic respiration. It can be assessed by having patient perform many repetitions using low resistance or sustaining a muscle contraction for an extended period

fatigue

a loss in the capacity for developing force and/or velocity of a muscle, resulting from muscular activity under load which is reversible by rest

sarcopenia

age related decline in muscle mass

increased neural drive

refers to the magnitude of efferent neural output from the central nervous system to activate muscle fibers. Muscle force can be increased by recruiting more motor units and increasing the firing rate of motor units

increased motor unit synchronization

refers to the simultaneous recruitment of numerous motor units resulting in increased muscle force production

increased size of the neuromuscular junction

this adaptation is also accompanied by increase in the amount of ACh resealed. these adaptations improve the ability of the motor neuron to activate muscle

inhibition of antagonist muscle co-activation

the force generation by an agonist muscle is larger when the antagonist musle is not co-activated

hyperplasia

increasing the total number of fibers

hypertrophy

increasing the size of existing fibers

increasing size and strength of tendons and ligaments

one bout of resistance exercise rapidly increases the rate of collagen synthesis in human tendons; proportional increase with muscle strength

improved bone mineral content

increased bone mineral density

overtraining

lack of recovery

signs and symptoms of overtraining

• inability to recover from exercise

• lowered resistance to injury

• chronic fatigue or exhaustion

• loss of appetite

• inability to sleep

• lethargy

• muscle soreness

• altered metabolism

delayed onset muscle soreness (DOMS)

muscle soreness typically appearing between 24-56hours later

overload

for tissue to adapt, it must be loaded beyond the level to which it is accustomed

reversibility

fitness gains achieved by exercising at overload are quickly lost when training is ended, or the tissue is underloaded

specificity

the training effect is limited to the muscle fibers involved in the activity

isometric contraction

muscle is activating and generating force without any change in muscle length

isometric contraction advantages

• promotes ligament, bone, and muscular strength

• can be performed when the individual has a limited range of motion

• prevents atrophy

• often contributes to the stabilization of core muscles

isometric contraction disadvantages

• strength gains are not increased throughout the range

• does not activate all the muscle fibers

• no flexibility or cardiovascular benefits

concentric contraction

a shortening muscle contraction

concentric contraction advantages

• promotes ligament, bone, and muscular strength

• strengthens throughout the range

• effective for producing muscle mass and increased neural drive

concentric contraction disadvantages

• increased risk of injury to joints due to increased load at varying joint angles

• requires most skill to maintain safe form

• increased risk for muscle strain/injury

eccentric contraction

a lengthening muscle contraction

eccentric contraction advantages

• produces more force than concentric exercises

• uses less oxygen

• helpful when treating various conditions

eccentric contraction disadvantages

• increased risk of DOMS

• longer recovery time

flexibility

the capability of a single joint or series of joints to move through an unrestricted and pain free ROM