The sitting posture adopted by individuals when performing tasks can interfere with pressure area, since Makhsous
et al. (2003) measured this variable in 15 workers with and without support in the tuberosity of hamstring muscles
and found that there was difference in conditions with straight spine with and without support on the backrest in the
relaxed position and working with the trunk leaned forward using the table as arm rest. However, there was no
difference in peak pressure in the seat in the relaxed (p = 0.188) and working posture (p = 0.131). That is, when
individuals sat without support for hamstring muscles, variables were smaller in the seat in three conditions; but,
variables were higher in the backrest in two conditions in which this chair subsystem was used (upright and relaxed
with the use of the backrest). These results indicate that the forces applied to the chair supports vary according to the
posture adopted and the use of supports; therefore, the chair armrest can influence the distribution of the body mass
on the hamstring muscles, and posture less leaned laterally over the tablet arm can balance the pressure between
tuberosities of hamstring muscles.