Extreme Sports: Ryan Koob Arthur Felix Mari Marquez Jennifer Seyler Johnny Bustamante KNES 461/Fall 2004 Dr. Noffal

Surfing is wildly popular. Skateboarding catches on as an after surf activity for Malibu teens. It soon explodes into a national phenomenon. These early boards were modified scooters, essentially consisting of a 2x4 with steel roller skate wheels attached to them. First commercial skateboard, the Roller Derby skateboard goes on the market 1950s: Late 50s:

Companies such as Makaha, Hobie, and Jack begin to mass produce skateboards. Over 50 million are sold within a 3 year period. Companies begin to form teams and hold competitions. Early boards featured clay wheels. Early 60s:

The skateboard industry collapsed due to safety concerns. Skateboarding became a largely underground sport and it became nearly impossible to find a commercially produced board. Skaters began to make their own boards from wood scraps or dresser drawers carved into a surfboard shape. They would screw on wheels usually stolen from roller skates. 1965:

Innovations of the 1970s Early 70s: Larry Stevenson invents the kicktail. Polyurethane wheels are invented. Frank Gainsworthy launches Cadillac wheels. Bennet & Tracker begin making trucks specifically for skateboarding. Many new skateboard companies spring up.

Late 70s: Road Rider comes out with the first precision bearing wheel replacing loose ball bearings. Boards start to increase in width which increases stability. 1975:

Z-Boys introduce a new low and aggressive style of skating. They are credited with the “birth of vertical”. They are the first to skate pools and pipes which leads to aerials.

Alan Gelfand invents the “ollie”. This fundamental trick would become the basis for many other more complicated tricks

The progression of Skateboarding The Progression of skateboarding

Skateboarding performance improvements through equipment Skateboard Wheels Bearings Trucks

Improvements in Skateboard design Skateboard decks have come a long way from their original intention of slalom and downhill speed skating. Skate decks begin as thin narrow boards made of scrape wood with a flat shape. The entire design of the skate deck changed as skating styles progressed. American hard rock maple wood become the standard material in deck making. Maple provided toughness and elasticity to give the best response. The maple wood consist of seven plies pressed and glued. The final product is sealed with an acrylic semi-gloss finish. The shape of skateboards begin to concave, giving the deck an arch. A distinct tail and nose were given to the deck to adapt to the progressing skate styles of street and pool which gave skaters more board control. The dimensions begin to change from the narrow down hill skateboards that resembled skis, to the thick, flat speed deck that measured at 10.5 inches wide and inches long. Today’s modern board usually measures at 8.5 inches wide and 30 inches in length, with very distinct concaves.

Improvement in wheel design Original clay wheels would easily stop on any rock and provide a bumpy ride. They measured at around 5-10mm, and weighed around 75 grams. The modern wheel is made of urethane, which provides much more traction and a smoother ride. They measures around 56-68mm, and weigh around 113 grams. Wheel size is dependent on the style of skateboarding intended. Street skaters (stairs, ledges, rails and flip tricks) use smaller wheels at around 51-57mm. Pool and vert. skaters (half-pipes, ramps, etc) use larger wheels that measure around 66mm.

Improvements in bearing design Original ball bearing were exposed to elements and easily rusted causing a slow roll and limit skate performance. Today’s bearings are sealed allowing longer life and faster rolling wheels. The faster the bearing, the higher the increase of wheel speed. The progression of bearings allowed skate designers to focus on wheel design.

Improvement in truck design The first skateboard truck made for skateboarders in 1978 was made of aluminum and measured at 77mm- 88mm wide. The truck has progressed by using lighter aluminum, and a wider base to increase stability. Today’s trucks measure at 126mm. The truck allows skateboarders to maneuver the skateboard to the left and right by shifting their weight. The kingpin located in the center of the truck can be altered. The tighter the kingpin, the more stable the board; but less maneuverable. The looser the kingpin, the more maneuverable the board.

The biomechanics of the “Ollie” Red arrow represents the skater’s weight. The black arrows represent gravity. The blue arrows represent the ground forces.

- Pierre Andre Senizergues -Jeremy Determan & Scotty Cox Brief History

STI is an onsite biomechanics lab (over 10,000 sq.ft.) that features everyday skateboard obstacles like the adjustable stairs. It is custom Built and by hydraulics can go from 8-12 feet.

The force plate tells us how much force skateboarders are hitting the ground with when they bail out or land a trick.

Kinematic cameras tell how the skateboarders whole body reacts to these impacting forces.

Pressure insoles inside the shoes tell us where the force is being applied to their foot when they land.

These readings are then sent to the computers for observation.

STI’s plans for the future. How they recruit their riders.

STI’s plans for the future.

Machines

Oh wow! What’s this? It’s a shoe idiot. It’s used for walking.

Injuries Head-concussion Wrist  Scaphiod 60-70%(Whiting & Zernicke 1998) Contusions Most are upper body trying to break fall Arm hyperextended, abducted, and ext. rotated = anterior glenohumeral dislocation Posterior dislocation- opposite

V f 2 =V i 2 +2ad V f 2 =0m/s + (2*9.81m/s 2 *9m) V f =13m/s

Protective Gear Helmet Knee Pads Elbow Pads Wrist guards Shin, Bum guards

Some fun at other’s expense

References: Injury Video: Toy Machines: Welcome to Hell (1995) 12.History Video: Dogtown Documentary (2002)