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Comfortable Seating for Underwater Workouts

machinedesign_v01_logoSherri Carmody | Machine Design
April 1st, 2004

Think those spinning classes at the health club are tough? Try them at deep-ocean depths.

That’s how divers at the Experimental Diving Unit (EDU) Section of Defence Research and Development Canada (DRDC) simulate the stress of working far beneath the surface. Rebreather-trained divers in full gear must first pedal for 5 min on the bottom of a hyperbaric diving chamber, rest for 5 min, then repeat the sequence over varying spans.

Underwater Pod

A diver fully submerged and in full gear, rides the Spongy Wonder bike with corrosion-resistant, high-strength stainless bike seat at Defence Research and Development Canada’s Toronto test facility.

Key to a comfortable ride on the underwater exercise bikes is a dual-platform, closed-cell foam seat. Unlike conventional bike seats, it puts no pressure on the rider’s urological system. The seat, developed by Spongy Wonder Inc., Riverview, NB, Canada (, also eliminates damaging pressures to the tailbone and rectal area that have been linked to the development of prostate cancer.

Robert MacLean, diving-systems technician for EDU, says the original mild-steel seat frames worked well on land but didn’t stand up under water. The frames fell apart after two dive series and began to corrode. This threatened to contaminate the water and foul expensive equipment being tested in the chamber.

The solution was a frame made from Type 304 SH (strain-hardened) stainless. EDU’s McLean says seats made with the material have been in continuous service for eight months with no sign of corrosion or seat pad damage, to simulated depths of 81 msw (meters seawater).The strain-hardened 304 stainless steel comes from Carpenter Technology, Reading, Pa. ( It boosts ultimate tensile strength (UTS) 30%, to 135 kpsi, versus 104 to 108 kpsi for standard Type 304 stainless. Its polished finish doesn’t corrode and resists scratches, marring, chipping, and discoloring.

The frame fabrication starts with a pneumatic machine that cuts stainless-steel bar to length. Five bends later the ends are welded together and ground smooth. The frame then mounts in a jig for the final bend. Additional sanding and grinding take place before the frame undergoes a two-stage polishing process, using a tumbling buffer.

Seat inventor Jeff Dixon worked with Carpenter metallurgist Bob Mohr to find the right steel for the frame. Another Carpenter alloy called A-286 will probably be the alloy of choice once Spongy Wonder retools its equipment for the material’s higher UTS of 169 kpsi.

– Jean M. Hoffman

Even more happy thoughts from SW Bicycle Seat Riders

Seeing injuries from bicycle seats fairly often in my internal medicine practice, I was happy to discover the Spongy Wonder Bicycle Seat. I immediately bought one for my own bicycle, and was quite gratified to see how comfortable it was, while still able to maintain good control of my bike. I've had mine for a year now, and have yet to put on the replacement cushions! If you're a rider, old or young, male or female, you need one of these bicycle seats.

Dr. Philip Alexander, MD
College Station TX

The Spongy Wonder Bicycle Seat is great and the best of the noseless, perineal sparing Bicycle seats that I've tried. I'm going to the site to order another one for my other upright bike.

Seth Manoach MD
Assistant Professor of Emergency Medicine
CPR Committee/Rapid Response Program
Brooklyn, NY

I lecture nationally on patients with pain and want to show a picture of your bicycle seat in my lectures. Please give me permission.

Hope K. Haefner, M.D.
Director, The University of Michigan Center for Vulvar Diseases
Dept. Obstetrics and Gynecology

Spongy Wonder MK10 in a micro-adjustable seat post

Spongy Wonder MK10 in a micro-adjustable seat post

Riding a bicycle was a no-brainer for Albert Einstein

Riding a bicycle was a no-brainer for Albert Einstein

The Spongy Wonder Bike Seat is critical in  underwater testing

The Spongy Wonder Bike Seat is critical in underwater testing

Spongy Wonder Inc. is the manufacturer of the world's only modular hornless bike seats. These two ergonomically and anatomically correct noseless bike seats eliminate the urological and neurological damage caused by conventional and "modified" conventional bike seats and are "fully customizable" and adjustable.