Stretching
what is a big imfluence of compliance, and why
# of crossbridges more you have, less compliant -look at when in action -active crossbridges more important
what is strain
% change in length
what is stress
(N/m2) tension per unit of cross sectional area
whats involved in autogenic inhibition, location, what does it respond to
-GTO -tension receptor located primarily in the musculotendinous junction -responds to increased active and passive tension -inhibits own muscle
what did stretching have an impact on
-ROM of leg (kick) -foot speed at impact (kick) -balance -reaction time -movement time
how does warm ups prepare teh body for exercise
-accelerating metabolism -decreasing intramuscluar resistance -increasing mechanical efficiency -increasing ROM/flexibility -increasing speed and F of muscle contraction
what besides injury does stiffness and flexibility have to do with
-age -CNS(need to retrain)
how can it cause injury
-as comp increases, decreased energy able to be absorbed -different sarcomere lengths can injure muscle during ECC even if not over stretched -mild stretches even cause cytoskeleton damage -stretch tolerance masks pain
what does warm up increase
-body and muscle temp -blood flow to muscles -muscle compliance -speed of nerve impulses -O and energy substrate delivery to working muscle and removing waste products -O release from hemoglobin and myoglobin
what do ice and heat do for stretching
-can cause to go farther which can help tolerance but damage muscle
how does the nervous system affect output
-changes in it can change musculotendinous units which can be detrimental
what is reciprocal inhibition
-contracting tricept inhibits the bicep -agonist contraction helps inhibit antagonist and stretchies it
what can stretching do to joints
-decreased stability makes joint motion less efficient
what are adverse effects of stretching
-decreased strength up to 1 hour -increased arterial blood pressure -some evidence shows decreased running economy with increased flex
what happens to an injured muscle
-dont have same elastic properties so longer stretches required -can neurologically inhibit
what is the strongest predictor of injury risk
-fitness level -across all soft tissue and bone injuries (except ankle sprains) -least fit 14x more likely to get lower limb injury -modifiable risk factor for injury
how does increased ROM/flex check out
-has been demonstrated to increase joint flex -most likely stretch tolerance*** -some support PNF stretching as most effective
why is stiffness/stretching good sometimes
-if less complient, F transmitted against muscle unit quicker (for when need speed and F) -so dont want complient unit bc more elastic energy stored and cant transmit as quickly -with too much stretching, firing GTO which impedes contraction of that muscle
what are the goals of stretching
-increase ROM/flex -improve performance -decrease soreness -decrease risk of injury
wat is increased flex mostly from and why
-increased stretch tolerance -some reflex inhibitions -change in viscoelasticity -lower crossbridging -some say PNF
how does increased ROM/flex indirectly decrease it as well
-indirect decrease due to reflex inhibition and therefore changes in viscoelasticity from decreased crossbridging
what are factors in how frequent one should stretch
-joint irritability -some require longer duration, reps, and freq
what activities is static stretching bad
-leg strength -jump height -peak jump force
how does improved performance check out -what is advantageous vs disadvantagous
-less stiffness is advantageous for stretch-shortening cycle activity -less stiffness is a disadvantage for isometric and concentric performatnce
viscous, def
-like liquid, means can have a permanent change or plastic deformation (silly putty)
how can stretch duration be bad?
-may be detrimental on performance -1 min stretch has less jumping impairment than 2-4 min -strong ev of impairment when static stretch > 90 sec (3rep of 30 sec)
what are the physiologic basis for passive stretching
-mechanical stretch of soft tissue -autogenic inhibition: GTO
what is optimal flex
-med flex -most and least flexible subjects at increased risk of injury
what grades are for passive stretching
-mobilization for grades 3 and 4 (more tissues around joint than muscle)
whats involved in mechanical stretch of soft tissue
-muscle -parallel and series elastic components -articular structure -tintin(stiffness component)
what resistance is there to stretching
-neurophysiological constraints (contractile activity should be minimized) -biomechanical constraints (stiffness)
does stretching decrease risk of injury
-no evidence, more likely to cause actually
look at study on slides 34-35 results on flip side
-no impairments in rx time or balance when 6 sec static with warm up -6 6sec static streth with/without 5-10 min aerobic activity improved height, muscle T, and balance -all conditions improved
what does sarcomere length have to do with injury
-no way of knowing the different lengths -can damage easily -can damage cytoskeleton bc more F more likely to damage(especially with eccentrics)
how frequent should one stretch
-one stretch per day per muscle group -4 stretches 4xday can be beneficial after injury
muscle spindle (1A) do?
-primary nerve ending afferent responding to quick stretch (1A) -1A doesnt inhibit but causes facilitation of contraction of own muscle -quick stretch, help cotract
why is location of weight important in passive stretching
-put weight closer/farther -farther has more impact -can control speed, control, and application of overpressure
what are cautions with ballistic stretching
-quick stretch stimulates muscle spindle stretch reflex -may cause microtrauma if too forceful -elastic changes greater than plastic so may not be lasting
what is viscousness dependent on
-rate and time dependednt -slow force over long time
what do warm ups do cellularly
-reboots waste -blood flow -more O -N system -lactate to liver -O released form hemo and myoglobin
whats the deal with warm ups, whats its downside
-some support for it being more important for preventions -amount of warm up is critical bc too much =fatigue which can increase injury risk
what should stretching duration be like for static, weights, and active
-static: 30 sec (60 if older) -weights: 15-30 min -hold at least 8 (Bohannan) -active: 6-10 sec contract 2-5 relax 15 sec stretch or contract 6-10 (antagonist or push down)
what are biochemical constraints to stretching
-stiffness of tissue -compliance -stretch tolerance
how do you maintain the range (easy to lose)
-strengthen agonist and antagonist in new range -home exercise programs -splints -serial casting
what is a compliant muscle to athletes
-temp imede performance for high intensity -more compliant sotres more elastic energy over long period of long distance
what happens with too much static stretching
-too much GTO firing which neurally impeeds its own muscle
what are various approaches to prevent injury/enhance performance
-warm up -stretching -strength training -plyometrics -proprioception training
which muscle type is most flexble and which more risk for injury
1/slow twitch- for flexibility 2- for injury
what percent can damage muscle
20% past resting
what duration is needed for increased flex
6-90 minutes -extensive programs for several weeks has produced increased flex that lasts for several weeks -hypermobility needed to stretch to maintain it
stretching Def
a maneuver used to lengthen shortened soft tissue structures as well as maintain range
what does warm up decrease
activation energy for cellular reactions and muscle viscosity
flexibility def
an intrinsic property of body tissues that determines the range of motion that can be achieved without injury at a joint or group of joints
what is the physiologic basis for active stretching
autogenic inhibition:GTO reciprocal inhibition
what should a person do to avoid injury from stretching
avoid prolonged static stretching prior to performance and minimize shorter duration stretching
is 1A good for stretching muscle good or bad
bad -dont want to contract -want to relax -makes contraction harder and need more F -can cause microtrauma
what is the stiffness of tissue
change in tension/unit change in length (how much stretch can be applied to a tissue/change in length) -stress and strain are factors -if stiffer needs more F to get change
what is stretch tolerance
feel less pain for the same force applied to the muscle -as stretch it improves -more important than decreasing stiffness
what is dynamic stretching
functional stretching exercise that uses sport-specific movements to prepare the body for activity -controlled movement thru ROM -better than static as a warm up -moving joints mimicking activity exactly
GTO
golgi tendon organ
what does elastic deformation need
high force, short duration ex: balistics
when do you see the biggest improvement in range, why
in first 4 reps of stretching -decrease in T and increase in length
viscoelastic deformation
increased muscle length can occur with sufficient duration and magnitude of stretch, but muscles elastic property limits magnitude and duration of the increased length
what does GTO do
inhibit own muscle for contraction
what happens with GTO as you lengthen a muscle
it feels tension, wakes up and fires -causes inhibition -protects from tearing
what do you want if you want plastic deformation
low force over long duraiton
what is the resistance in static stretching from
more vicoelastic properties than contractile components
what happens as you increase extensibility to the passive length tension curve
no change not maintaining extensibility
does stretching decrease soreness
no evidence -doesnt do reverse tho
what are stretching methods
passive static active isometric ballistic dynamic
elastic
permits recovery from deformation or elastic deformation (rubber band)
what is active stretching and how
proprioceptive neuromuscular facilitation (PNF) -contract/relax -hold relax -contract/relax/contract -contraction of antagonistic muscle
what is ballistic stretching
rapid lengthening of the muscle by use of jerking or bouncing movements -high force, fast, bouncy
what is compliance
reciprocal of stiffness (change in length per unit change in tension) -more F to get it to do something if less compliant
what is passive stretching and what forces does it have
slow, sustained muscle lengthening -weight of part plus gravity -weight of part plus gravity plus external load -manual overpressure
what is static stretching
slow, sustained muscle lengthening held by subject for 15-60 seconds -typically 30 is good -over 65 years old do longer
what is isometric stretching
static stretching against an immobile force -not contracting, but using resistance of something
what are types of flexibility
static: range measured with goniometer (holding) dynamic: resistive to active motion around joints
what do you want stretching intensity like
stretch to point of discomfort -pain tolerance -avoid reflex spasm (from pain)
what does improved flexibility have most to do with?
stretch tolerance
what is stress relaxation
stretching and T decreases and can go farther into range
what is different between short and long muscles in the T vs length graph
the shorter muscle has more T per unit length change longer muscles are more compliant and less stiff than shorter muscles
what are major factors in stretching
type intensity duration frequency force duration (elastic v plastic) temperature
what is flexibility depend on
viscoelasticity of muscles, ligaments and connective tissue
what are viscoelastic properties
viscous elastic deformation
what is more important than stretching
warm up
how does temp affect stretching
warmer has more extensibility and less stiffness increased ROM
who are more flexible
women and chldren
do you need full passive ROM to get full active ROM
yes
is it difficult to maintain increased flexion for long, and what is needed to maintain it
yes hypermobility