Several studies have attributed the prevalence of low back pain (LBP) in he
licopter pilots mainly to poor posture in-flight and whole-body vibration.
with the latter hypothesis particularly related to a cyclic response of the
erector spine (ES) muscle to vibration. This work aims to determine if hel
icopter vibration and the pilot's normal posture during flight have signifi
cant effects on the electromyogram (EMG) of the ES muscle. The bilateral su
rface EMG of the ES muscle at the L3 level was collected in 10 young pilots
before and during a short flight in UH-50 helicopters. The vibration was m
onitored by a triaxial accelerometer fixed to the pilots' seat. Prior to th
e flight, the EMG was recorded for relaxed seated and standing postures wit
h 0 degrees (PO) and 35 degrees (P35) of trunk flexion. The effect of the p
osture during the flight was tested by comparing left and right EMG (normal
ized with respect to P35). The in-flight muscle stress was evaluated by his
tograms of EMG activity, and compared to PO values. Only one pilot in ten s
howed significant (p <0.05) correlation between the vibration and the EMG o
ver cycles of vibration, and no consistent causal effect was found. The pil
ots' posture did not show significant asymmetric muscular activity, and low
EMG levels were observed during most of the duration of the flight. The re
sults do not provide evidence that LBP in helicopter pilots is caused by ES
muscle stress in the conditions studied. (C) 2001 Elsevier Science Ltd. Al
l rights reserved.