Muscle Performance

the maximum force a muscle or group of muscles can generate at a specified speed or determined velocity
muscle tension generating capacity

process of initiating, directing, grading purposeful movement or abioity to regulate the mechanisms essential to movement

neural factors - motor unit recruitment
mechanical factors

size of motor units
number and size of muscle fibers in a cross section of the muscle
number of motor units firing
frequency of firing of motor units
sarcomere length
fiber arrangement
type of muscle contraction
velocuty

size of motor units
number of motor units firing
frequency of firing of motor units

return to sport: normative values of injured to non-injured that predict to play

max load through an arc of motion (weight)

max force produced at fixed speed

max force produced at a fixed angle

maximum fore a muscle or group of muscles can generate at a specified speed or determined velocity

one repetition maximum for a group of muscles
gold standard for strength

able to calculate peak torque and a torque curve

MMT - break test
Hand held Dynamometer - make test

how much tension can the muscle generat before the clinician can move the joint -graded MMT (0-5)
ordinal scale of measure

how much tension can a muscle generate against a fixed force
graded with hand held dynamometer
numeric value in newtons or pounds
speed to peak force value
time peak force sustained

end range

mid range

scores greater than 4 lose discrimination -> use dynamometry

scores less than 3 lose accuracy with HHD -> MMT

explain test to patient
position the patient in the gravity resisted position
stabilize the proximal joint segment
passively move the joint through the ROM, determine the end feel, and instruct patient in the motion
return the limb to the starting position
ask the patient to move through their available ROM actively while maintaining the stabilizaton of the proximal segment

can pt perform in an isolated fashion?
yes!
move non stabilizing hand to the appropriate position for resisting the muscle while maintaining proximal stabilization
instruct the patient to hold the current position while you apply resistance
apply resistance as indicated by gradually building up the resistance until the patient "breaks" or until maximal resistance has been applied
grade the muscle according to the 0-5 scale

no!
reposition the patient in the gravity minimized position
stabilize the proximal joint segment
instruct the patient in the specific motion while moving the joint passively through the ROM
return the limb to the starting point
palpate the muscle being tested while maintaining stabilization of the proximal segment
ask the patient to move actively through the avaiable ROM
if there is isolated movement - grade
if not - provide qualitative description

subtle weakness is difficult to detect

position muscle in shortest or longest position (active insufficiency)
induce fatigue (reduce motor unit recruitment)
- repeat multiple contractions
-resist through an arc of motion multiple times

2 joint muscles
stabilize proximal segment
passively move the distal segment to determine tissue stop
"stiffness" passive insufficiency