When individuals bend forward to lift, their back muscles actually become totally inactive, and the
ligaments of the spine have to bear the entire load of
the upper body. This may decrease the ability of
ligaments to appropriately support the spine and lead to
decreased muscular functions. In addition, laboratory
studies show different pressures within the 3-4 disc
space under various conditions of load. The lowest
pressure occurs when lying down, the highest pressure
occurs when bending forward. Moreover, overloaded
manual lifting, prolonged sitting and standing on a
tractor result in LBP. They cause an increase in pressure
on the disk leading to disk rupture and muscle fatigue.4
Regarding lack of BME, the term muscle
endurance is the ability of a muscle group to execute
repeated contractions over a period of time of sufficient
duration to cause muscle fatigue. Transversus abdominis
(TrA) and multifidus muscles are the main muscles
for preventing LBP. TrA maintains the balance of
abdominal pressure while multifidus muscle shold the
vertebrae in a direct line. Muscle endurance has proved
to be a more significant predictor of new episode and
recurrence LBP than back muscle strength and
flexibility.Lack of SBE caused LBP. Regarding
back muscle capacity among Thai farmers with LBP,
a previous study showed they lacked static BME.11
Moreover, about 90% of farmers lacked regular exercise
and knowledge about SBE.3 Back muscle consists of
two muscle fibers – fast-twitch fibers and slowtwitch
fibers. The fast-twitch fibers are the superficial
muscle layer with large and long sizes to fix and
support upper back structure whereas the latter is the
deep muscle layer with small and short size to fix
inner vertebrae, control rotation of vertebrae, and
respond to changes of postures and extrinsic loads.
Additionally, slow-twitch fibers is a part of TrA and
multifidusmuscles,19 and usually atrophies in people
with chronic LBP.20 Thus, a knowledge of both
proper working and SBE for preventing LBP should
be improved among Thai farmers. However, the main factors associated
with LBP among Thai farmers are physical stresses
and lack of BME. These stresses include heavy
manual labor, whole body vibration, static working
posture and improper working posture, especially
bending forward lifting objects. Moreover, 50% of
Thai farmers lack knowledge of the proper posture for work. Over 80% of farmers habitually bend forward
to lift the objects putting them at risk for ligament
damage, leading to back muscles’ strain and LBP.,