Monday, June 29, 2009

A Kinematic Comparison of Dive Fins

Ryan Lindsey is a master of kinetics and biomechanics.

In 1996, Ryan finished his Academic Masters at San Diego State University in this discipline. He has been working in the field ever since, but it is his work and the results of his Master’s Thesis Kinematic Comparison of Swimming With Two Different Dive Fin Designs
that I would like to share with the you today.

There are fin studies out there that use air consumption, thrust and distance as units of measure to determine how a particular fin compares with other fins. These studies have their limitation since it is difficult to get a large enough sample and control for the individual subjects’ predispositions, with respect to fin use and overall physical condition. Ryan Lindsey’s Thesis is different. It uses a tool of analysis that quantifies fin use and really gets to the guts of a fundamental reason as to why Force Fins are different and how those differences make Force Fins better.

The purpose of his study was to determine the difference, if any, in the mechanics of legs only swimming while utilizing two different designs of dive fins. The two designs were conventional fins and Force Fins.

Conventional fins utilize a flat blade shaped surface to provide propulsion, as well as an enclosed toe foot hold. Force Fin® incorporates a blade surface that is shaped like a whale tail, with a patented up-curved shape and open toe foot hold that rests across the instep of the foot. The toes are free to move independent of the Force Fin blade. It is these two differences that dictates the way the human leg responds as it moves the fin blade through the water.

Ryan told me, “The body is a perfect machine, but it has design limitations.” The leg can bend, lift and push in many different positions, but the joints are designed to lock when moving forward and bend when pulling back.

Ryan used a biomechanical analysis software program called Peak5® to digitize video footage of a swimmer moving past a viewing window in a pool kicking conventional fins and when kicking Force Fins. The software translated the range of motion, acceleration and velocity the hip, knee and ankle joints into data points that show the differences in that range of motion to reveal the strain put on those joints of the leg when kicking the fins.

Ryan was getting real information on the different effects of using different fin designs in the water, a comparison with no room for human interpretation. With the Peak5® software he could translate video footage of a diver’s leg in motion into percentages of range of motions on joints of the body, interpret forces acting on legs using known bio-mechanic norms and limitations of the human leg.

In 1971 I painted a picture of a leg “kicking motion”. This painting is the first thing I did, when I decided that I wanted to make a better pair of dive fins. The painting shows a human leg going through the range of kicking motion.

Ryan Lindsey points to a point where normal ankle range of motion stops in a kick cycle.

When Ryan was recently here at Force Fin Headquarters he explained to Blair that if a fin forces an ankle beyond its normal range of motion, it causes intense ballistic strain on the front of the lower leg. When you enclose the toes in a foot pocket and push a flat shape fin blade through the water the foot is forced into extreme plantar flexion. This over contraction on the muscles results in micro trauma, which causes muscle spasms that induce cramps over time. In his study the Peak5® software showed the ankle of the diver using conventional fins was forced beyond its normal 90 to 180 degree range of motion.

In contrast, when wearing Force Fins the toes are exposed. This is why when using Force Fins your ankle never goes past the normal range of motion and you will not experience the intense ballistic strain caused when wearing conventional fins. It is also one reason you do not feel the power of Force Fins.

Force Fins open out during the downward stroke to maximize the surface area pushing against the water. The shape of the Force Fin and its high quality material snaps back to its original shape on the up stroke allowing the diver to use less energy to create forward propulsion. This allows isolation of power output from the quadriceps, and limits strain on all other weaker muscles and the joints of the leg.

It was a true honor and very inspiring to work with Ryan Lindsay. He took the time to explain his work and I hope I have interpreted his study for you to have a better understanding of the kinetics and biomechanical differences of using two different types of fin designs. Ryan told me, “using fins underwater traditionally uses a lot of hip, knee and ankle and it hurts! ….. Why does it have to hurt?” Those who don’t like Force Fins might because they can not feel them. Hopefully, this will help some of them understand why, so that they too can free themselves from unnecessary strain!
It really is a Smart Fin!

Wednesday, June 24, 2009

The Earth is Round

Do you have a global perspective? Or, do you perceive life looking down at your feet?

Flat fins are designed by engineers who think linerally. They design their world against a 2-dimensional backdrop of points and grids. Connect the dots and you have terrestris fins. Its no coincidence that these other fins look like train tracks. Flat fins are made by those who have not evolved beyond moving across flat land.

Straight lines and linear angles stall your movement through water. They produce turbulence and drag. This drag may feel secure, like you're marching across land, but when in water secure footing defeats the 3-dimensional freedom you're set to enjoy by fancy foot free kicking with Force Fins.

Water gracefully flows over, under and around curved objects. Force Fins are curved. Their curves are sculpted by artist's hands to enhance the speed of water. They extend from, and power using the natural strength of your body. Kick forward. The tapered leading edges on every Force Fin model draw water over, under and across the arcing blade. A recoil is set, that rebounds and snaps water behind, catapulting you forward at a faster rate than you can kick any other fin. It is the unimpeded movement of water across Force Fins' curved foils that naturally propels.

If your in-water journey is to be stalled as if on land, then your flat fin selection is vast. If you choose to be free to fly through a 3-dimensional world as an aquatic being, then there is only one choice, one fin that frees you from land - Force Fin

Thursday, June 18, 2009

One bag at a time

Starting yesterday 6.17.09 we are shipping all Force Fin orders out with the invoice inserted into the shipping box, bag, or envelope.

We are concerned about the amount of plastic used for affixing the invoice on the outside of the box. We hope you support our efforts in contributing to slow down the amount of trash and wasted resources used in the USA. International orders will have to have external packing slips and invoices per shipping requirements, but we beleive we can still make a difference by cutting back with our domestic orders.

At Force Fin we are also big fans and supporters of "A Day without a bag"
and we have reusable bags in our backpacks or cars. Have a great Thursday and have a day without a bag.

Watch for announcements about other steps Force Fin is taking to join the world in Cleanin up our act!