Factors affecting strength Flashcards
what is muscle strength in the MSK system?
- the ability of skeletal muscle** to develop force** for the purpose of providing stability and mobility within the MSK system, so functional movement can take place
why is muscle strength so important in sport, daily life activitiea and also throughout our life span?
- higher levels of muscular strength lead to better performance in sport
- we require an adequate level of muscle strength to **perform activities of daily living **
- higher muscular strength is associated with a **reduced risk of premature mortality **
define muscle tension
- force developed in a contracting muscle when the muscle acts on an object
- (internal force)
define load
the** force exerted on the muscle by an object** is called the load
compare active vs passive tension of muscle
- active tension - tension developed by the contractile elements of the muscle
- passive tension - tension developed by **stretching the non contractile elements **of the muscle - ie elasticity
what is the epimysium?
the membrane that surrounds the entire muscle, binding all of the muscle fibres together
what is the perimysium?
- a sheath of connective tissue which binds muscle fibres together into bundles called fasciculi
what is the endomysium?
- fibrous connective tissue that surrounds each individual muscle fibre
what is a torque?
- the capability of a force to **produce rotation **is known as a torque
what is a fulcrum in relation to muscle?
the joint around which the movement occurs
what 4 things is muscle force inhibited by?
- inflammation
- injury
- disease
- pain
of the connective tissue or the bone upon which the muscle acts
if muscle shortening (concentric contraction) is followed by an eccentric contraction, resulting concentric action is capable of generating greater force … why?
- because a stretch in a muscle increases its tension (force produced) by storing potential elastic energy in the elastic component of the muscle
- the shortening contraction must occur within a short time frame to use that stored elastic energy
how does muscle length affect muscle strength?
- as the muscle shortens -** the actin and myosin filaments start to overlap** and the** sarcomere** is then at an** optimal length** - where most force can be produced
- a sarcomere that is too short or that has been stretched will not be as efficient
Describe the length tension relationship in muscle
- **short length **- when a muscle has shortened to half its length, **the filaments have exceeded their overlapping capability **- fewer cross bridges forming
- long lengths - when the muscle is lengthened, cross bridges slip past one another and fewer cross bridges can be formed
3.** optimal length is slightly longer than resting length** because the contractile components are optimally producing tension and the** passive components are optimally storing elastic energy **
how does the velocity of a contraction affect the force in a concentric contraction?
*** as velocity increases, force decreases **
* as the velocity of muscle shortening increases, the cycling rate of cross bridges increases, leaving fewer cross bridges attached at one time
how does the velocity of a contraction affect the force of an eccentric contraction?
- force and velocity will increase together
- this is due to the external load causing the action
what is a motor unit?
a motor unit is a single motor neuron and all of the muscle fibres that it innervates
what is hennemann size principle?
- smaller motor units are recruited first, then larger ones
- slower twitch muscle fibres are recruited first, then faster twitch fibres
Describe the force-velocity relationship of skeletal muscle
- force and velocity have different relationships with e/o in skeletal muscle depending on whether the contraction is concentric or eccentric
- concentric - the higher the force, the lower the velocity of skeletal muscle contraction.. and the lower the force the faster - INVERSE relationship
- eccentric - as the force increases, the velocity of the contraction also increases
why is there an** inverse relationship** between force and velocity of skeletal muscle contraction for concentric action?
- velocity of muscle contraction increases, the cycling rate of cross bdirges increases, leaving fewer cross bridges attached at one time
why is there a linear relationship between force and velocity of contraction in eccentric contraction?
- force and velocity increase together
- this is due to the external load applied on the muscle
what 2 categories are skeletal muscle classified as?
- type 1 - slow oxidative fibres
- type IIa - fast twitch oxidative - glycolytic fibres
- type IIb - fast twitch glycolytic fibres
what effect does the cross sectional area of a muscle have on the force that can ne produced by the muscle?
- the greater the cross sectional area, the greater the force that can be produced
- due to the greater number of sarcomeres - more actin and myosin are forming cross bridges
- greater CSA- more contractile units
what affect does sex (gender) have on muscle strength?
- males have more muscle strength than women - due to testosterone
what effect does age have on muscle strength?
- as you age, muscle strength decreases
- peak strength is around the age of 25-30, and after that it starts to decline with every decade
- however - it is modifable with training
what are examples of psycholgical factors that might increase or decrease muscle force?
- confidence, motivation and encouragement from others can increase force
- fear, excessive stress can decrease force
how do neural factors affect muscle strength?
injury to the nervous system (CNS or PNS) will affect a muscles ability to contract and produce movement
