ALPINE SKIING

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ALPINE SKIING

• BIO 555
• Alecia Pollard

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Changes in Skiing
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Changes in Skiing

• Shape of the ski
• Straight/Conventional vs. shaped/parabolic
• Length
• Bindings
• Who cares? What will it change?
• Biomechanics carving, easier turns
• Level and ability
• Speed
• Higher risk of injury possible

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Carving

• The new shape of the ski lets the skier steer or
  make turns along the ski edges
• Eliminates lateral skid or chatter in turns (if
  your good enough!)
• Shaped skis are marketed to be easier for a
  beginner and less work for an advanced skier
• Link

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Carving

• The more strongly waisted the ski and the greater
  the on-edge angle, the more strongly the ski must
  flex to maintain contact with the slope along the
  total length of the edge.

link
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Carving Study

• Journal of Sports Sciences -
• Skiers made 6 runs each with 8 turns per run
• Subjects performed the two types of turn with
  conventional and carving skis.
• GRF and presssure distribution in the ski boot
  were measured by 2 pressure measurement sole
  inserts
• EMG used to observe activities of the gluteus
  max., v. med, v. lat., RF, BF, Tib. Ant, and
  Peroneus longus muscles.

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• Comparison of the activity of the RF in both
  techniques.
• During the carving the inner leg is strongly
  co-loaded, whereas in the conventional turn the
  activity of the inner leg takes on a subordinate
  role.

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Conventional Phases

• Steering Phase
• setting up for next new turn
• Greatest load is on the outer ski
• Initiation Phase
• load change from outer to inner ski with and
  increase in load on the inner ski
• Coming out of this phase you go back into the
  steering phase, the skis edges are shifted and
  turned towards the direction of a new turn

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Carving Phases

• Steering Phase
• Setting up for new turn
• Outer ski is strongly loaded
• Goes into initiation phase quickly
• Initiation Phase
• Continuous increase in load on BOTH legs for a
  more equal distribution.

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Sound the Same?

• Carving
• Co-loading of both legs in the steering phase
• Short steering phase and a long initiation phase
• Turns demand better sagittal balance and improved
  edge steering ability to remain centrally
  positioned over the ski

• Conventional
• Predominant load is on the outer ski in the
  steering phase
• Initiation phase is similar

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• Going back to the ski waist and flexibility
• The more flexible the skis with the greater
  on-edge angles during the steering phase, make
  much smaller turning radii with the new carving
  technique
• So this could mean faster, smaller turns gets you
  down the mountain faster to wait in the long lift
  lines longer! Yippee.

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Energy/Fuel Utilization

• Anaerobic and Aerobic energy
• Elite racers can get up to 75-100 of their max
  aerobic power
• Max aerobic power (Vo2max) although important,
  is not a limiting factor determining success in
  skiing.
• More likely to be high as a result of
  conditioning
• Giant slalom calls for the largest reliance upon
  aerobic energy.

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Energy/Fuel Utilization

• Anaerobic power is important for skiing and both
  laboratory and field power tests correlate well
  with performance.
• Examples Wingate, vertical jump, 60- second
  repeated jump
• Used readily more in Slalom courses

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• Fiber Type
• Studies show that skiers do not have a distinct
  fiber type composition.
• Elite skiers have high knee extensor strength
• Rectus femoris, vastus lateralis, vastus medialis
• Darker Type I slow twitch, Lightest Type IIa
  fast oxidative, medium Type IIb fast oxidative

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EMG Studies

• Knee extensors (v. lat, v. med) were greater in
  eccentric then concentric phases.
• Reliance of slow and forceful eccentric muscle
  actions when performing turns in giant slalom or
  slalom.
• EMG intensity did exceed 100 of EMG attained
  during MVC (maximal voluntary contraction.

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• Muscle Activation reached near max levels during
  the course of almost every turn.
• To have maximal force output the skier relies
  on eccentric muscle actions.
• Why?
• Eccentric muscle actions have a larger force
  capacity , more rapid force development
• Less energy consuming
• Less fatigability

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• Muscles designed for force production
• Example hamstrings
• Uni-penniform fiber organization, so fibers run
  diagonally with respect to tendons

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Training/Conditioning

• Plyometrics
• provide more load and speed to exercises
• Increase muscle contraction
• Increase number of muscle cells that are
  recruited
• Trains neuromuscular pathways
• EX repeated broad jumps, box jumps, med ball for
  UE

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Training/Conditioning

• Core stability maintaining balance and control
  in all planes of movement.
• Very important in all levels of skiing.
• Ex Theraballs, medicine balls, BOSU ball, discs,
  uneven surfaces to challenge stretch-reflexes.

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• Agility
• Explosive power
• Upper body strength
• Aerobic conditioning
• On the mountain training and dry land training

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ACL Injuries

• Injuries to soft tissue structures at the knee
  joint account for more then 20 of all injuries.
• ACL injuries are very common
• Usually occur from high speed downhill skiing
  predominately during the landing phase following
  a jump.
• The landing can cause the skier to lean back and
  fall or a recovery attempt is made by a forceful
  contraction of the quad muscles putting the ACL
  at risk.

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• Other possible reasons for the increase in ACL
  injuries
• Internal/external rotation and abd/add of the
  tibia, is shown to influence ACL loading.
• Boot induced anterior drawer.
• Extended knee joint position when landing leaves
  the ACL vulnerable. Because the quad contraction
  translates the tibia anteriorly, loading the ACL.
• The opposite is when the knee joint is in a
  flexed position, the patellar tendon will pull
  the tibia backward with respect to the femur
  protecting the ACL.