Electrophysiologic evaluation of muscle fatigue development and recovery in late polio.
OBJECTIVE
To study aspects of fatigue in late-polio patients and healthy controls. We hypothesized that late-polio subjects would develop more peripheral fatigue, assessed with surface electromyography (EMG), and that no major differences would exist between the two groups in neuromuscular junction transmission.


METHODS
Case-control study.


METHODS
University hospital laboratory.


METHODS
Ten patients with a history of polio (mean age, 54 yrs, SD = 5; mean time since polio onset, 49 yrs, SD = 7) and a matched control group (mean age, 52 yrs, SD = 8).


METHODS
A protocol with a stepwise force increase up to 80% of maximal voluntary contraction ending with an 8-minute recovery period was performed twice, first with surface EMG and then with electrical stimulation and surface-recorded evoked M-response.


METHODS
Surface EMG analysis of voluntary activity and evoked M-response.


RESULTS
No significant differences existed between groups in the relative decrease during the fatigue protocol. The recovery of force was slower in the late-polio subjects. A reduction in the root mean square (RMS) value during recovery was seen in the polio group, although a normalization of the mean power frequency (MPF) was seen in both groups.


CONCLUSIONS
The weakness during the fatigue procedure was not caused by neuromuscular blockade, because electrical nerve stimulation evoked a normal response. The weakness after exercise was the result of a slow recovery that may reflect both central and peripheral fatigue.
Sunnerhagen
K S
KS
Department of Rehabilitation Medicine, Göteborg University, Sweden.
Carlsson
U
U
Sandberg
A
A
Stålberg
E
E
Hedberg
M
M
Grimby
G
G
D016022:Case-Control Studies; D004558:Electric Stimulation; D004576:Electromyography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018763:Muscle Fatigue / Q000502:physiology*; D016262:Postpoliomyelitis Syndrome / Q000175:diagnosis / Q000503:physiopathology*