Transcript Sport Biomechanics - Academics | Kansas State University

Exercise Biomechanics Reading
Assignment
• Textbooks:
– Kreighbaum pp 233-241, Chapter 8 (spinal exercises and resistive
exercise equipment)
Hamill pp 202-207, 216-222 (conditioning, stresses, and injury
potential of lower extremity)
• Journal article summaries by students
– Nicholls et al (2002) Bat kinematics in baseball: Implications for
ball extit velocity and player safety. Journal of Applied
Biomechanics, 19:283-294.
– Hinterman and Nigg(1998) Pronation in runners: Implications for
injuries. Sports Medicine. 26:169-176.
– O’Conner and Hamill (2002) Does running on a cambered road
predispose a runner to injury? Journal of Applied Biomechanics,
18:3-14.
Biomechanical correlates of exercise –
areas of interest, endeavor, & contribution
• Design and analysis of fitness programs
• Design of fitness exercises
– Which exercises are most effective in meeting program ogjectives?
– Which exercises are potentially, or inherently unsafe and to be
either avoided or used with caution?
– movements, forces, injury potential
• Analysis of fitness exercises
– are exercises being executed properly?
• Design, selection, and analysis of fitness equipment
– resistive equipment (e.g., thesis on abdominal ex equip)
– aerobic equipment
• Relative merits of different exercise modes (e.g., stairclimber, bicycle,
treadmill, rowing machine, elliptical exerciser)
• Running shoes
Methods of Evaluation of Ex Equip
• Source: (Jung, A.P. The evaluation of home exercise equipment
claims. ACSM’s Health and Fitness Journal. 4(5): 14-16,30-31.
• Check physiological and biomechanical principles and ACSM
standards.
• Review research, if available
– Critically review research – Are appropriate methods used? Who sponsored it?
Where was research reported?
• Ask professors or other experts (Barstow, Harms, Gyurcsik,
Estabrooks, Ferguson)
• Review product reviews in fitness magazines (Club Industry, Athletic
Business, Fitness Management)
• Try it yourself.
• Interview professionals who have supervised its use.
• Design and conduct your own research.
• Note: guidelines for selection are on Federal Trade Commission
Website (http://www.ftc.gov)
Criteria for evaluating aerobic exercises
• Degree of overload on cardiorespiratory system
• Relevance to fundamental movements and activities of daily
living
• Proportion of total body musculature involved
• Degree of compressive stress on femoral head and lumbar
vertebral bodies (sites of most osteoporotic fractures)
• Compressive stress on patella and knee joint
• Range of motion and torque at hip, knee, and lumbar spine
• Motivational features (comfort, user friendly, feedback,
RPE)
• Likelihood of continued usage
• Cost
• Other?
Biomechanical and anthropometric
considerations in selecting and conducting
aerobic exercises
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Potential for injury increases with body weight
Airborne activities produce greater forces than non-airborne activities
Fast twisting movements of arm and upper trunk produce lower back reaction forces
Stress is inversely proportional to body surface area exposed
Joint shear stress is minimal if bones are aligned in a straight line
Knee joint stress is minimized it knee is alighted above the foot
Alignment of trunk above pelvis minimizes unbalanced stress of spine
Keep limbs close to trunk for maximum equilibrium
Longer limbs involve greater MOI, thus they are harder to move and accelerate
Joint reaction force increases with speed of angular movement
The taller person needs more time to perform an activity
Safety can be increased or decreased by modifying the intensity of the exercise
Biomechanics of Resistive exercises
• Factors affecting force
application
– Force-velocity relationship
– Strength-joint position
relationship (combination of
angle of pull and force/length
relationship)
• Should we provide the same
degree of overload
throughout the movement? If
so, how do we do it?
Use of Cams in Ex Equipment:
Pelvic Girdle Balance
Lumbar spinal shear force is directly
related to pelvic girdle position
Spinal Flexion
Exercises
• Effect of
– Anchoring feet?
– Bending knees?
– Placement of hands and
arms?
– Inclined board?
Back Extension Exercises to Avoid:
Good morning exercise:
Hyperextended back:
Recommended Extension Exercise
Effect of speed on effects of exercise:
Torque = Wd + MOI x ang acc
Effect of posture on
lumbar compression
force:
Lifting quidelines:
(1)bend knees
(2)keep weight close to hips
Knee Joint
Structure:
25% of Alpine skiing
injuries are ligament
injuries
Peripatellar pain
(runner’s knee)
caused by imbalance
of stress on patella
Lower Extremity
Misalignment:
Q angle is larger in females due to
Wider hip structure, increasing
potential for PFPS (Patellofemoral
pain syndrome)
Quadriceps Tendon
and Patella Force
Lines
Compressive force at PFJ is ½ body
wt during normal walking, and over
3 times bw during stair climbing
Comp force increases as knee flexion
Angle increases
Cruciate Ligaments
and Shear Stress
Loads on Knee
• Forces at tibiofemoral Joint
– Shear stress is greater during open kinetic chain exercises
such as knee extensions and knee flexions
– Compressive stress is greater during closed kinetic chain
exercises such as squats and weight bearing exercises.
• Forces at Patellofemoral Joint
– With a squat, reaction force is 7.6 times BW on this joint.
• Beneficial to rehab of cruciate ligament or patellofemoral
surgery
Movement of subtalar joint
Foot Pronation and Tibial Torsion:
Rearfoot Movement During
Running:
Types of running injuries
Example of Double Density
Midsole:
Effects of Rearfoot Double
Density Midsole
on rearfoot
position:
Effects of Rearfoot & Forefoot Double
Density Midsole on takeoff angle: