H-reflex Methods and Significance

1
H-reflex Methods and Significance

• Chetan Phadke, P.T., Ph.D.
• Post-doctoral Fellow, Mentor Carolynn Patten
• Neural Control Movement Lab
• VA, BRRC

2
Monosynaptic reflex pathway
3
H-reflex

• Paul Hoffmann first described it in 1910
• Electrical analog of stretch reflex
• By-passes muscle spindle and Gamma
• Direct sensory fiber (Ia) electrical stimulation

4
The H-reflex
Muscle Spindle
Ia
a
H-reflex
Muscle
M-wave
Stimulus Artifact
Courtesy University of Louisville (Dept. of
Neurosurgery) and Frazier Rehab.
5
Window into Spinal Cord

• Enables study of spinal excitability
• Excitability is regulated by inhibition from
  supraspinal and sensory flow
• The level of inhibition on the H-reflex
  determines the amplitude
• Easily evoked in most muscles
• Soleus widely studied

Palmieri (2004), Zehr (2001)
6
Functional Significance

• Greater in Sitting than Standing
• Greater in stance phase than swing
• Pedaling modulation similar to walking
• Arm swing and arm cycling alter soleus H-reflex
• Walking on a narrow beam
• Gymnasts

Capaday (1987), Trimble (2001), Phadke (2007),
Boorman (1992), Zehr (2001), Llewellyn (1990),
7
Phase dependent Hreflex modulation
8
H-reflex post-SCI
Non-injured
SCI
5V
31.25 ms
9
Functional Correlation

• Greater amplitude post-SCI and slower ground
  walking speed
• Single LT and bicycling session Smaller reflexes
  in walking and semi-reclined and increased ground
  walking speed
• Long-term LT resulted in smaller reflexes in
  walking and faster ground walking speed

Trimble (2001), Phadke (2009), Behrman (2008 -
unpublished)