The "wobble seat" of this stool by Canadian designer Darryl Agawin helps the user to exercise their core muscles and work off any extra Christmas weight while sat in the office (+ movie).

A half-sphere suspends the seat of Darryl Agawin's wooden Balance Stool above the concave surface of its base, meaning that the sitter has to constantly re-adjust their position to keep upright.

Reminiscent of a 1980s Pogo Ball, the unstable seat enables passive core muscle strengthening and balance exercises and can also be removed and used for balance exercises on any hard surface.

The stool is an extension of a furniture range Agawin designed to offer busy workers the chance to exercise in the office.

"The concept behind the original No, Sweat! Workspace Workout furniture collection is to help promote an active lifestyle in the work environment," Agawin told Dezeen.

"It's not only about finding the time for exercise, but about incorporating it in your daily routines, from taking the stairs, going for a walk and, with the Balance Stool, engaging and strengthening your core muscles in a passive activity. This activity becomes a part of your life, promoting a healthier lifestyle without you realising it."

The Balance Stool is made of wood reclaimed from ash trees destroyed by pests such as the emerald ash borer.

"This ash wood was originally headed for the landfill," said the designer. "Using it for my design utilises an untapped wood resource from Toronto, Ontario, where more than 200,000 trees are brought down annually."

Each element of the stool is made using computer numerically controlled (CNC) techniques and the legs are then friction fitted into holes in the underside of the seat.

"Features such as the negative hemisphere in which the balance board sits are best made through this technique," said Agawin. "I wanted to create a simple timeless design that utilises modern production techniques."

The wood is finished with a traditional Danish technique in which pure soap flakes are made into a paste with hot water and applied to the surface of the furniture.

"It lightens and evens the tone of the wood, provides a clean, durable and easy to maintain surface, and most importantly, provides a smooth connection between the seat and the base of the chair for the ball joint, enabling free movement of the seat," the designer told Dezeen.