Neck muscle strain when wearing helmet and NVG during acceleration on a trampoline.
BACKGROUND
The helmet-mounted equipment worn by military pilots increases the weight of the helmet system and shifts its center of gravity, increasing the loads on neck structures, especially during acceleration. The aim of this study was to determine neck muscle strain with different head-loads during trampoline-induced G loads (0 to +4 G).


METHODS
Under three conditions [no helmet, helmet, helmet with night vision goggles (NVG)], 14 subjects performed trampoline exercises including basic, hand-and-knee, and back bouncing. EMG activity was measured for the sternocleidomastoid (SCM), cervical erector spinae (CES), trapezoid (TRA), and thoracic erector spinae (TES) muscles. Muscle strain was determined as a percentage of maximal voluntary contraction (%MVC).


RESULTS
For the three exercises combined, the following significant changes were found: compared to control, the helmet increased muscle strain by 18%, 28%, and 18% in the SCM, CES, and TRA, respectively; NVG produced a further increase of 11% in the SCM and 6% in the CES. During back bouncing, the helmet increased muscle strain by 14% in the SCM and 19% in the CES, and NVG further increased this strain by 14% in the SCM. Hand-and-knee bouncing loaded extensors: the helmet caused increases of 46% in the CES and 29% in the TES, while NVG produced a further 13% increase in CES activation.


CONCLUSIONS
Helmet weight alone had a large effect on muscular workload. The additional frontal weight of the NVG caused a further increase in the activity of cervical muscles that were already subjected to high strain.
Sovelius
Roope
R
Training Air Wing, Kauhava, Finland. roope.sovelius@mil.fi
Oksa
Juha
J
Rintala
Harri
H
Huhtala
Heini
H
Siitonen
Simo
S
D000054:Acceleration; D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005135:Eye Protective Devices / Q000009:adverse effects*; D006112:Gravitation; D006260:Head Protective Devices / Q000009:adverse effects*; D006801:Humans; D019838:Neck Injuries / Q000503:physiopathology*; D009334:Neck Muscles / Q000293:injuries / Q000503:physiopathology