KAWAMURA, Y. 
RESULTS 
The Pattern of EMG Recordings During Shivering 
Preceding visible shivering a generalized increase in muscle 
tone was evident. This increase was reflected in the bipolar elec- 
trode recording of single unit discharges from one motor unit (NMU) 
(Fig. 1). Such NMU discharges from a single fiber motor unit 
ranged from 6-26/sec and 100-2 00 mV. They were detected from the 
mylohyoid, external oblique, flexor, limb, or tail muscles. There was 
no clear relationship of the discharge of any given motor unit with 
that of any other motor unit of the same or other muscles. At first 
these discharges had no close relationship to the respiratory cycle, 
but, as shown in Figure 2, as the number of unit discharges in- 
creased they tended to become grouped into the inspiratory phase. 
When shivering became visible, though still feeble, the EMG record 
illustrated grouped discharges consisting of fused NMU activity, 
together with separated NMU discharges. These grouped discharges 
were concomitant with lung inflation (Fig. 3). 
The intervals between both NMU and grouped discharges were 
longer at the beginning and end of lung inflation that at peak inflation. 
Similarly, the amplitudes of grouped discharges were spindle 
shaped, concomitant with one respiratory cycle and illustrated the 
fusing of additional NMU's into each grouped discharge at peak lung 
inflation (Fig. 4). 
As shivering became more intense, the NMU discharge had a 
frequency of 10-12 /sec (Fig. 5). One grouped discharge corresponded 
to one cycle of limb movement discharge and one given NMU oc- 
curred per given grouped discharge. At this stage there was no re- 
lationship between grouped discharges and they had an amplitude 
of 1 mV or more. During intense shivering these grouped discharges 
had a duration double that during feeble shivering. Vigorous 
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