lecture 6: Hot and Cold Flashcards
pain transmission
- pain receptors called nociceptors are sensitive to
- mechanical (squeeze, cut etc)
- thermal (hot, cold)
- chemical
- afferent never fibers carry information from nociceptors towards the spinal cord
two types of pain signals
1: A delta - myelinated fast pain (i.e. putting your hand on a hot stove and it tells you to move your hand quickly)
- large diameter
- touch, pressure, and temperature
- located in skin
2: C fiber- unmyelinated - slow pain
- small diameter
- pain and temperature
- located skin and deep tissue (muscle/ligament)
- the pain you have after injuring yourself
- this is the type of pain that we are trying to block.
gate control
1: without any stimulation, both A beta (large) and C nerve fibers (small) are quiet and the Substantia gelatinosa and inhibitory interneuron block the signal in the T cell that connects to the brain. the “gate is closed” and therefore, NO PAIN
2: With pain stimulation, C fibers become active. They BLOCK the inhibitory SG and activate the T cells. because activity of the inhibitory interneuron is blocked, it CANNOT block the output of the T-cell that connects with the brain. the “gate is open” , therefore, PAIN!
3: with non-painful stimulation, large nerve fibers (A beta) are activated primarily. this activates the SG, when then activates the inhibitory interneuron which then BLOCKS the signal in the T cell that connects to the brain. “Gate is closed” and therefore NO PAIN
types of A - beta input
1: pressure
- someone rubs head when you bump it
- you are blocking A beta nerves that blocks the C nerves because A beta are fast and large and they close the gate of the C fibers
- massage
2: vibration
- 4 hz taps on ankle x 10 min = released opiates and gate closed
3: position sense
- shaking finger
- When you do this, the beta is going off and blocking C pain because you are shortening and lengthening the muscle fibers
- AROM/PROM
accomodation
- accommodation = rise in the threshold
- if a nerve is submitted to passage of constant strength or current, the site of nerve under stimulation shows decrease of excitability
- constant input = no sensation to body
- A fibers will accommodate
- C fibers will NOT
cold and superficial heat
- two of the most commonly applied therapeutic modalities
- they conduct heat, to or away from the body
- traditionally they have been applied to speed up healing
- may cause injury if not used properly
- can get burned from a hot pack
- can do damage from chemical ice packs
Ice (Cryotherapy) the body’s response to cold depends upon:
- the cold media that is being applied
- (ice, cold water immersion, sprays, chemical packs.)
- conductivity of the area being cooled
- high water content in tissue means the better it is for cooling
- muscle cools faster than fat
- joints> muscle
- length of time of exposure
- longer not always better
- 10 on - 10 off - 10 on is superior to 20 mins on . less pain in first week
- put it on for 10 mins and get the blood flow down, then take off to avoid hunting syndrome and then repeat to keep it going
ice (cryotherapy) what is happening with acute injuries?
- tissue injury at primary and secondary sites
- cell death due to hypoxia
- increased bleeding into the area
- pain
- swelling/edema
primary site
mechanical damage that was done at the time of the event
secondary site
- stuff that occurs after the injury, such as reduced blood flow because all the cells around the injury are dying .
the case AGAINST using ice
- the inflammatory or “destruction” phase of healing is a necessary stage
- we need the athlete to go through the stages but not get stuck there
- there is evidence that ONE early ice treatment may slow down healing over the first 3-7 days.
- more necrosis in ice group at day 3 = at day 7
- less neutrophils day 1 and more day 3 on ice gorup
- less macrophages at day 1 and 3 with more at day 7 in ice group
the case FOR using ice
- good for pain
- C not myelinated!
- for every 1 degree drop in temperature, you cool a nerve , you decrease conduction velocity
- with a 4 degree cooling you knock out C fibers.
- when combined with exercise
- demonstrated better ability to decrease swelling vs. heat
- significant improvement in function vs functional training
- use of ice has been shown to maintain cell viability after injury
CBAND
cold, burning, aching, numbness
- the numbesness is freezing out the C fibers, this is typically what people feel when they go through the stages of applying ice
heat (thermotherapy)
- the bodys response to heat depends upon
1: type of heat applied
- moist heat (better for deeper tissues) dry heat (better tolerated), ultra-sound (mechanical)
2: intensity of heat energy
- some people are more sensitive
3: duration of the application
- blood flow until heat source is removed
- will peak after 6-8 minutes - body protects it from getting too hot
- only when heat source is removed will tissue temperature drop
physiological responses to cryotherapy
1: muscle gaurding
2: blood flow
3: capillary permeability
4: metabolic rate
5: collagen elasticity
6: joint stiffness
7: edema
8: pain perception
1: decrease breaks pain/ spasm cycle
2: decreases blood flow
3: decreases
4: reduced o2 required = less 2 degree injury
5: decreases
6: increases
7: controversial - will not reduce swelling that is present
8: decreases (C fiber conduction zone)
