Multitudinous. Many adjustments allow:
• Backrest up-down
• Backrest tilt/ angle forward or back
• Armrest up-down
• Armrest in-out
• Armrest pivot
• Seat height up-down
• Seat angle (including forward tilt on some models)
• Lumbar support depth (backrest forward/ back)
• Various seat height mechanisms
• Tilt lock, tilt tension
• Various recline mechanisms (knee tilt, column tilt, synchronous), etc.
• Each adjustment can have its own character: range, ease of adjustment, stiffness.
Basic Considerations- these are the minimum features an ergonomic chair should have
• Height- adjustable seat
• Height- adjustable back rest/ lumbar support
• Recline or rocking back rest mechanism
• Arm rests that adjust for support or remove for clearance
• Seat size that matches your leg-length, seat-width, and weight requirements
• Controls that are easily operated from a sitting position
• Stable 5-star base
• The chair should not feel uncomfortable to you
Some chairs offer more passive ergonomic features and controls where, for example, the individuals’ seat pressure (weight) modulates the back support pressure without requiring manual tension adjustments.