Extreme Sports:

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Extreme Sports

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

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• 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
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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
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1965
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.
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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.
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Road Rider comes out with the first precision
bearing wheel replacing loose ball bearings.
Boards start to increase in width which
increases stability.
1975
Late 70s
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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.
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• Alan Gelfand invents the ollie. This
  fundamental trick would become the basis for many
  other more complicated tricks

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The progression of Skateboarding
The Progression of skateboarding
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Skateboarding performance improvements through
equipment

• Skateboard
• Wheels
• Bearings
• Trucks

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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 32.25 inches long.
• Todays modern board usually measures at 8.5
  inches wide and 30 inches in length, with very
  distinct concaves.

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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.

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Improvements in bearing design

• Original ball bearing were exposed to elements
  and easily rusted causing a slow roll and limit
  skate performance.
• Todays 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.

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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.
  Todays 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.

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The biomechanics of the Ollie
Red arrow represents the skaters weight. The
black arrows represent gravity. The blue arrows
represent the ground forces.
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• -Pierre Andre Senizergues
• Jeremy Determan Scotty Cox

Brief History
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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.
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The force plate tells us how much force
skateboarders are hitting the ground with when
they bail out or land a trick.
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Kinematic cameras tell how the skateboarders
whole body reacts to these impacting forces.
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Nice Watch!!!
Pressure insoles inside the shoes tell us
where the force is being applied to their foot
when they land.
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These readings are then sent to the computers for
observation.
Pressure!
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How they recruit their riders.
STIs plans for the future.
Working
Working
On the phone?
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STIs plans for the future.
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Machines
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On the phone again!!!
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Its a shoe idiot. Its used for walking.
Oh wow! Whats this?
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Injuries

• Most are upper body trying to break fall
• Arm hyperextended, abducted, and ext. rotated
  anterior glenohumeral dislocation
• Posterior dislocation-opposite

• Head-concussion
• Wrist?Scaphiod 60-70(Whiting Zernicke 1998)
• Contusions

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• Vf2Vi22ad
• Vf20m/s (29.81m/s29m)
• Vf13m/s

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Protective Gear

• Helmet
• Knee Pads
• Elbow Pads
• Wrist guards
• Shin, Bum guards

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Some fun at others expense

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• References
• www.independenttrucks.com
• www.Powellclassic.com
• www.Drskateboard.com
• www.exploratorium.edu/skateboarding
• www.stilab.com
• www.ocregister.com
• www.skateboardcollector.com
• www.vintageskateboardappreciationsociety.com
• www.z-boys.com
• www.ollieair.com
• Injury Video Toy Machines Welcome to Hell
  (1995)
• History Video Dogtown Documentary (2002)