Measuring neuromuscular fatigue in cervical spinal musculature of military helicopter aircrew.
Neck pain and muscle function in aircrew have received considerable attention. We hypothesized normalized electromyography (EMG) frequency would provide insight into appropriate methods to assess muscle fatigue in helicopter aircrew.


METHODS
40 helicopter aircrew performed isometric testing that included maximal voluntary contractions (MVC) and 70% MVC endurance protocols of extension, flexion, and left and right lateral flexion for cervical muscles. Bilateral muscle activity in the splenius capitis, sternocleidomastoid, and upper trapezius was monitored with EMG. Normalized mean EMG frequency was calculated for each muscle at the start and end of the 70% MVC trials to determine which muscles fatigued and limited force maintenance during each isometric movement.


RESULTS
For extension, the left and right splenius capitis fatigued by approximately 21-22% (p < 0.01); for flexion, the left and right sternocleidomastoid fatigued by approximately 11-14% (p < 0.01); for right flexion, the right sternocleidomastoid fatigued by approximately 15% (p < 0.01); for left flexion, the left spenus capitis and left sternocleidomastoid fatigued by approximately 7.2% (p = 0.02) and approximately 11.2% (p = 0.03), respectively; in no trials did the trapezius muscles display fatigue as measured by EMG.


CONCLUSIONS
The smaller agonist muscles were the most susceptible to fatigue during submaximal isometric endurance movements in the cervical muscles of helicopter aircrew.
Harrison
Michael F
MF
Faculty of Kinesiology and Health Studies, 3737 Wascana Pkwy, University of Regina, Regina, SK, Canada S4S 0A2.
Neary
J Patrick
JP
Albert
Wayne J
WJ
Kuruganti
Usha
U
Croll
James C
JC
Chancey
V Carol
VC
Bumgardner
Bradley A
BA
D000328:Adult; D000401:Aircraft; D000704:Analysis of Variance; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008889:Military Personnel; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D009334:Neck Muscles / Q000503:physiopathology*; D019547:Neck Pain / Q000503:physiopathology*; D009784:Occupational Diseases / Q000503:physiopathology*