CHAPTER 18:PART 2 LOCOMOTION: SOLID SURFACE KINESIOLOGY Scientific Basis of Human Motion, 12th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University Revised by Hamilton & Weimar KINESIOLOGY Scientific Basis of Human Motion, 12th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University Revised by Hamilton & Weimar Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin

18B-2 RUNNING Description  Difference from walking is that there is no double support phase.  Running has a flight phase.  Speed is the product of stride duration and stride length. Fig 18.7 (click above to see figure (click above to see figure)

18B-3 RUNNING Description  Two major types of running  Races: concerns are time and distance.  Games and sports: also concerned with change of direction, pace, and stability.  Two major types of running  Races: concerns are time and distance.  Games and sports: also concerned with change of direction, pace, and stability.

18B-4 RUNNING Anatomical Analysis  The difference in joint actions between walking and running are a matter of degree and coordination.  Essentially the same action, but the ROM is generally larger in running.  The difference in joint actions between walking and running are a matter of degree and coordination.  Essentially the same action, but the ROM is generally larger in running.

18B-5 RUNNING Anatomical Analysis:Swing Phase  More muscular than pendular and is longer than support phase.  Initial foot contact:  Fast running - ball of foot.  Slow running - heel or mid-foot.  The flexed leg brings the mass of the leg close to the hip, reducing the moment of inertia and increasing angular velocity.  More muscular than pendular and is longer than support phase.  Initial foot contact:  Fast running - ball of foot.  Slow running - heel or mid-foot.  The flexed leg brings the mass of the leg close to the hip, reducing the moment of inertia and increasing angular velocity.

18B-6 RUNNING Anatomical Analysis:Support Phase  The knee and ankle “give” in flexion, then extend as the body passes over the foot.  Support time decreases as speed increases.  Movements and muscles in spine and pelvis are the same as walking, but more vigorous in reaction to leg movements.  The knee and ankle “give” in flexion, then extend as the body passes over the foot.  Support time decreases as speed increases.  Movements and muscles in spine and pelvis are the same as walking, but more vigorous in reaction to leg movements.

18B-7 RUNNING Mechanical Analysis  Speed is governed by length and frequency of stride.  Stride length: determined by length of leg, ROM of hip, and power of leg extensors.  Stride rate: determined by speed of contraction and skill of performer.  Body becomes a projectile and depends on:  Angle of take off.  Speed of projection.  Height of center of gravity at takeoff & landing.  Speed is governed by length and frequency of stride.  Stride length: determined by length of leg, ROM of hip, and power of leg extensors.  Stride rate: determined by speed of contraction and skill of performer.  Body becomes a projectile and depends on:  Angle of take off.  Speed of projection.  Height of center of gravity at takeoff & landing.

18B-8 Mechanical Principles in Running 1.Inertia must be overcome. The problem of inertia decreases as speed increases. 2.Acceleration is directly proportional to power in the leg drive. 3.The smaller the vertical component of ground reaction force the greater the horizontal (driving) component. 4. The more horizontal force directed straight backward, the greater the contribution to forward motion of the body. 1.Inertia must be overcome. The problem of inertia decreases as speed increases. 2.Acceleration is directly proportional to power in the leg drive. 3.The smaller the vertical component of ground reaction force the greater the horizontal (driving) component. 4. The more horizontal force directed straight backward, the greater the contribution to forward motion of the body.

18B-9 Mechanical Principles in Running 5.The length of leg in the driving phase should be as great as possible when speed is a consideration. 6.By flexing the free leg at the knee and carrying the heel high up under the hip, the leg is moved more rapidly & economically. 7.The force of air resistance can be altered by shifting the center of gravity. 5.The length of leg in the driving phase should be as great as possible when speed is a consideration. 6.By flexing the free leg at the knee and carrying the heel high up under the hip, the leg is moved more rapidly & economically. 7.The force of air resistance can be altered by shifting the center of gravity.

18B-10 The Sprint Start  The sprint start enables the runner to exert maximum horizontal force at take off, providing maximum acceleration against inertia. Fig 18.8

18B-11 JUMPING, HOPPING, AND LEAPING  Goal is to propel the body into the air with sufficient force to overcome gravity & in the direction to accomplish the desired height or horizontal distance.  Path of the body is determined by the conditions at the instant of projection.  Differences between jumps related to the take off and landing.  Goal is to propel the body into the air with sufficient force to overcome gravity & in the direction to accomplish the desired height or horizontal distance.  Path of the body is determined by the conditions at the instant of projection.  Differences between jumps related to the take off and landing.

18B-12 Hop, Leap, and Jump  Hop: the same foot is used for the take off and landing.  Leap: take off is from one foot and landing is on the other foot.  Jump: take off from one or both feet and land on both feet.  Each may be initiated from a stationary position or preceded by some locomotor pattern.  Hop: the same foot is used for the take off and landing.  Leap: take off is from one foot and landing is on the other foot.  Jump: take off from one or both feet and land on both feet.  Each may be initiated from a stationary position or preceded by some locomotor pattern.

18B-13 Total Horizontal Distance  Sum of three distances: 1.Horizontal distance between take off foot and the line of gravity of performer. 2.Horizontal distance the center of gravity travels in the air. 3.Horizontal distance of center of gravity behind body part that lands closest to the take off point.  Sum of three distances: 1.Horizontal distance between take off foot and the line of gravity of performer. 2.Horizontal distance the center of gravity travels in the air. 3.Horizontal distance of center of gravity behind body part that lands closest to the take off point.

18B-14 Total Height  May be considered to be divided into:  Distance between the ground and the center of gravity at the moment of take off.  Maximum distance the center of gravity is projected vertically.  May be considered to be divided into:  Distance between the ground and the center of gravity at the moment of take off.  Maximum distance the center of gravity is projected vertically.

18B-15 Mechanical Principles in Jumping, Hopping, and Leaping 1.For movement to occur, inertia must be overcome. 2.Use of the stretch-shortening cycle will enhance jump. 3.Jumpers project themselves into the air by exerting a force against the ground that is larger than the force supporting their weight. 1.For movement to occur, inertia must be overcome. 2.Use of the stretch-shortening cycle will enhance jump. 3.Jumpers project themselves into the air by exerting a force against the ground that is larger than the force supporting their weight.

18B-16 Mechanical Principles in Jumping, Hopping, and Leaping 4.The upward thrust of the arms in the jump accelerates the support leg downward, which causes a reaction from the ground.  Also raises the center of gravity immediately prior to take off, which may result in increased jump height or distance. 5.The magnitude of the impulse that the jumper exerts against the ground is a product of the applied forces and the time over which they act. 4.The upward thrust of the arms in the jump accelerates the support leg downward, which causes a reaction from the ground.  Also raises the center of gravity immediately prior to take off, which may result in increased jump height or distance. 5.The magnitude of the impulse that the jumper exerts against the ground is a product of the applied forces and the time over which they act.

18B-17 Mechanical Principles in Jumping, Hopping, and Leaping 6.The path of motion of the center of gravity is determined by the angle at which it is projected, speed of projection, height of the center of gravity at take off, and air resistance. 7.Angular momentum may be developed by the sudden checking of linear motion or by an eccentric thrust. 6.The path of motion of the center of gravity is determined by the angle at which it is projected, speed of projection, height of the center of gravity at take off, and air resistance. 7.Angular momentum may be developed by the sudden checking of linear motion or by an eccentric thrust.

18B-18 ADDITIONAL FORMS OF LOCOMOTION Wheels, Blades and Runners  Designed to allow humans to move farther faster for less effort, or to move quickly and easily over difficult surfaces.  Most common and efficient form is the bicycle. Wheels, Blades and Runners  Designed to allow humans to move farther faster for less effort, or to move quickly and easily over difficult surfaces.  Most common and efficient form is the bicycle. Fig 18.10

18B-19 Bicycle  Cycling motion has no braking or retarding phase.  Little kinetic energy is wasted.  Speed is determined by slope, gear ratio and pedal cadence.  Force producing pedal revolution is provided by a cyclic extension-flexion motion of the lower extremities.  Magnitude of force depends on gear ratio.  Cycling motion has no braking or retarding phase.  Little kinetic energy is wasted.  Speed is determined by slope, gear ratio and pedal cadence.  Force producing pedal revolution is provided by a cyclic extension-flexion motion of the lower extremities.  Magnitude of force depends on gear ratio.

18B-20 Roller (In-line) Skates  Movement is cyclic but not continuous.  Force is produced by each leg in turn, with a period of glide occurring between strokes.  During the glide there is a loss of velocity from friction.  Skateboards are similar but use only one leg.  Highly efficient during downhill motion.  Movement is cyclic but not continuous.  Force is produced by each leg in turn, with a period of glide occurring between strokes.  During the glide there is a loss of velocity from friction.  Skateboards are similar but use only one leg.  Highly efficient during downhill motion.

18B-21 Wheelchair  Similar to skating: cyclic but not continuous.  Propulsive arc of 50°- 100°.  Variability based on level of disability, chair type, surface, slope, etc.  Brief braking period at hand contact.  In racing, camber brings push rim closer to hands.  Similar to skating: cyclic but not continuous.  Propulsive arc of 50°- 100°.  Variability based on level of disability, chair type, surface, slope, etc.  Brief braking period at hand contact.  In racing, camber brings push rim closer to hands. Fig

18B-22 Ice Skating  Very little friction between blades and ice.  Friction further reduced by slight melting from pressure of the blade.  Blade sinks into ice and can be used to push off perpendicular to direction of travel.  Very little friction between blades and ice.  Friction further reduced by slight melting from pressure of the blade.  Blade sinks into ice and can be used to push off perpendicular to direction of travel. Figure 18.12

18B-23 Ice (Speed) Skating  Speed is based on stride length and stride rate.  Trunk is inclined forward to reduce drag from air resistance.  Speed is based on stride length and stride rate.  Trunk is inclined forward to reduce drag from air resistance. Fig 18.13

18B-24 Skiing: Cross-Country  Closely related to walking, running, and ice skating.  Diagonal stride vs. skate stride.  Closely related to walking, running, and ice skating.  Diagonal stride vs. skate stride. Fig 18.14

18B-25 Skiing: Alpine or Downhill  Relies primarily on gravity for a propulsive force.  At high speeds air resistance plays a role; drag must be reduced through compact body position.  Relies primarily on gravity for a propulsive force.  At high speeds air resistance plays a role; drag must be reduced through compact body position. Fig 18.15

18B-26 Rotary Locomotion  Factors responsible for rotary locomotion are magnitude, direction, and accurate timing of the forces contributing to the desired movement of the body, including advantageous use of the force of gravity whenever possible.

18B-27 Rotary Locomotion  Achieved by rotating about the body’s successive areas of contact with the supporting surface Fig 18.16

18B-28 Locomotion by Specialized Steps and Jumps  Acrobatic stunts and athletic events:  walking on hands, successive jumping, hurdling.  Activities of children’s play and forms of dance:  skipping, hopping, galloping, sliding, sidestepping, leaping, and standard dance steps.  Acrobatic stunts and athletic events:  walking on hands, successive jumping, hurdling.  Activities of children’s play and forms of dance:  skipping, hopping, galloping, sliding, sidestepping, leaping, and standard dance steps.