As we have already noted, in normal people
the extensor muscles go through a period of electrical
silence during forward flexion. 10 Loss of the normal flexion-relaxation
response. Muscle deficiency
and guarded movement may go together. 9. Also, these
hypotheses are not mutually exclusive.
Rapid forward bending causes reflex contraction
of the extensor muscles to decelerate the upper
There is evidence of other disturbed neuromuscular
function in patients with low back pain. This may start as a
mechanism to protect against painful movement. From Dr P Watson, with thanks. Position sense deteriorates with fatigue
I" ' t 7
They also questioned whether this dysfunction was
a cause or effect of pain.
Lund et a1 (1991) suggested a pain-adaptation
0 reduced maximum voluntary force
0 reduced velocity and amplitude of movement
0 increased antagonist activity
0 reduced agonist activity. 170 Their Planned to attend classes Damage REVOLUTION
Your guided Orbach.
However, the physiologic evidence suggests that
"muscle deficiency" is more important than muscle
tension (Lund et a1 1991, Cassisi et a1 1993). The
key may be that muscles work, and dynamic testing
is more relevant than any static findings. Adams et a1 (2002) reviewed
the limited evidence that loss or inhibition of such
reflexes might occur in back pain. Even
slight increases in muscle tension could be enough
to reduce resting muscle length. In patients
with back pain, this period of muscle relaxation is
reduced or even absent (Fig. 9. This
includes lower muscle strength, less total electrical
activity, faster fatigue, and lower endurance.
Patients with low back pain have poorer position
sense, possibly due to reduced paraspinal proprioception
(Brumagne et a1 2000, Newcomer et a1
2000). One of the best documented
muscle abnormalities in chronic low
-- E MG-T10 (left) EMG-T10 (right)
0 1 2 3
Figure 9. Once again, this seems to involve the multifidus
Asymmetric electromyogram activity during
back pain is loss of the normal flexion-relaxation
response (Ahern et a1 1988, 1990, Watson et a1
forward flexion in a patient with acute low back pain.
170 THE BACK PAIN REVOLUTION
This led Orbach & McCall(l996) to think about
possible indirect effects of muscle tension. Adams
et a1 (2002) showed that there can be large asymmetries
in EMG activity in the muscles of patients
with back pain (Fig.
From Adams et al (20021, with permission.
We now have much more EMG evidence. 10).
Attempts to move, and so stretch the muscle, could
lead to increased muscle proprioception, and muscle
contraction to guard against that movement. 9).