Sitting on a sloping seat does not reduce the strain sustained by the postural chain

Area of Science:

• Biomechanics
• Ergonomics
• Human Movement Science

Background:

• Understanding how seat design influences posture and muscle engagement is crucial for ergonomic interventions.
• Forward sloping seats are proposed to alter body positioning and muscular load during seated tasks.

Purpose of the Study:

• To investigate the impact of forward seat slope on the postural alignment and muscular activity of the trunk and lower limbs.
• To determine if forward sloping seats offer ergonomic benefits by improving posture or reducing muscular strain.

Main Methods:

• Twelve healthy participants were evaluated under varying seat slope (0°, 15° forward) and height conditions.
• Posture was measured using an inertial orientation system, and muscle activity was quantified via normalized electromyography (EMG) of 11 superficial muscles.

Main Results:

• Forward sloping seats significantly increased the activity of soleus, vastus lateralis, and vastus medialis muscles.
• A notable decrease in hip flexion was observed with forward sloping seats.
• No significant changes in the angular positions of the head, trunk, or pelvis were detected based on seat slope.

Conclusions:

• Forward sloping seats elevate the mechanical load on the lower limbs.
• The study did not find evidence that forward sloping seats systematically improve overall body posture.
• Findings suggest potential trade-offs between altered muscle activation and postural benefits in forward-sloping seat designs.