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it is suggested that ergonomic prevention have to be focused on the characterization of the worktechnique and especially on the interaction between motor patterns performance and the imposed
perturbations by the handling load, load’s weight and load’s spatiotemporal variables, rather to
focus only on the reduction of the biomechanical risk factors based on the recommended risk levels
(i.e, NIOSH) (Scholz, 1993a; Scholz and McMillan, 1995; Scholz, Millford, and McMillan, 1995).
For example, Oddsson et al., 1999, postulated that when the hip strategy of the postural control
mechanism get into action to correct exogenous postural perturbations during the lift of a load,
there is a a motor control conflict where different function of the same muscle is required (erector
spinae). Therefore, the erector spinae muscle is activated eccentrically after a silence period of
postural correction, and the concurrent risk to suffer an acute soft tissue injury is extremely high.
Thus, by the aforementioned it can be deduced that the execution of lifting and lowering tasks have
to be approximated as the “optimum” biomechanical solution to the motor problem encountered
during the task. In this sense, McGill (2007, pp.: 135) proposed that in order to reduced LBD it is
probably required to “change the worker to fit the task”, comparing workers’ technique during lifting
tasks with that of elite weightlifters. Similarly, Sedgwick and Gormley (1998) have underlined that
work-technique of lifting tasks should adapt the same principles that rule weightlifters’ technique.
Lavender (2006), in agreement with the latter, added that lifting tasks have to be thought and
taught as a complex motor skill, reinforced by the use of feedback performance tools and provide
peer-review means to maintain the desired motor behavior. Jarus and Ratzon (2005), proposed
a prevention model inspired by a behavioral psychology theory of motor learning (Schmidt and
Lee, 1998) in order to facilitate workers’ acquisition of correct motor patterns. A limitation is that
generalized motor programs cannot solve the question of how motor programs can be learned or
how a learned motor pattern can be applied to a variety of contexts or how a new motor skill can
be learned immediatelly. Moreover, biomechanical and environmental constraints played little
role (if not none) in the formation of that programs.
1.6.3.
Ergonomic Workplace Design
Prevention of WRLBD in MMH tasks refers to (re)design the workplace focused on the reduction
of the work-related risk factors. Several ergonomic assessment tools can be used to make useful
inferences about workers behaviour on a given job in order to identify potential precursors of
developing LBD before workers develop symptoms severe enough to require medical treatment
and to lead to work absenteeism and work disability. Nevertheless, if these tools cannot be used
proactively, when a workstation is designed, they have to be used reactively during work in order
to determine which specific workspace parameters or worker actions are most likely to be the cause
of LBD and therefore redesign ergonomically unacceptable workstations (Cohen et al., 1997).
The basic idea behind every ergonomic assessment tool is that work physical demands should
not exceed worker’s physical capacity, because any mismatch of human physical capacities and
human manual performance requirements in industry may produce or exacerbate LBD (Chaffin,
Andersson, and Martin, 2006). A drawback is that all these ergonomic assessment tools assumed
that a correct work technique is presented always, unconcernedly if lifting tasks are made under
ideal ergonomics conditions or not.
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