FAQs
Who invented the S4? Long time and still active surfer Glenn Hening, well-known in the surfing world as the founder of the Surfrider Foundation and a co-founder of the Groundswell Society.
When? Why? Over 20 years ago Glenn needed a way to stay in shape for the powerful waves of Ventura County while being a husband, father, and full-time teacher. He discovered “granular resistance” one day at the beach and originally used boxes of sand. When he decided to go into business, he spent two years developing the S4 Trainer for the public.
What is “The Science of Granular Resistance”? The S4 utilizes resistance is based on the physics formulas derived from what happens when grains start flowing like a liquid around a moving object. In our case, the "grains" are recycled plastic pellets. The moving object is the hand/arm of a swimmer. We control the levels of resistance by changing the variables in the physics formulas, which in fact are quite complicated.
What are the grains? They are recycled plastic pellets produced from used milk and water containers. They are FDA compliant as being food safe. The pellets have no odor.
What other materials are used in the S4? Plantation-grown poplar, reinforced high strength joints, alloy-grade hardware, and specialized corrugated plastic sheeting, extra-strong plywood, and double-layered, padded yoga mat.
How do I use it? Simply extend your hands down into the granular resistance and exercise in your normal motion as if you were swimming or paddling a surfboard.
How long does a typical workout session last? 15 minutes a day, working up to full 45 min workouts.
Tell me more!!! You always start with stretching and range-of-motion warmups. You vary the levels of resistance by going deeper into the granular resistance. You can use music to set a specific cadence to match the desired intensity of your workouts.
Is it portable? The S4 weighs about 130 lbs and can be easily disassembled and stored in a space about 2’ x 5’.
What do I gain from using the S4? By varying the levels of resistance and the cadence of your stroke, you gain strength and stamina in the specific muscles you need for faster swimming and/or paddling a surfboard.
Can I use an S4 for physical therapy? We recommend you engage in physical therapy under the specific guidance of a PT professional. We have had S4 TrainerTM users augment their therapy program by carefully using granular resistance to increase levels of strength, range-of-motion, and joint flexibility. Again, any use for PT should be done under the guidance of a PT professional.