Exercise Biomechanis

1. 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.

2. 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)

3. 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

4. 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?

5. Biomechanical and anthropometric
considerations in selecting and conducting
aerobic exercises
• 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

6. 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?

7. Use of Cams in Ex Equipment:

8. Pelvic Girdle Balance

9. Lumbar spinal shear force is directly
related to pelvic girdle position

10. Spinal Flexion
Exercises
• Effect of
– Anchoring feet?
– Bending knees?
– Placement of hands and
arms?
– Inclined board?

11. Back Extension Exercises to Avoid:
Good morning exercise:
Hyperextended back:

12. Recommended Extension Exercise
Effect of speed on effects of exercise:
Torque = Wd + MOI x ang acc

13. Effect of posture on
lumbar compression
force:

14. Lifting quidelines: (1)bend knees
(2)keep weight close to hips

15. Knee Joint
Structure:
25% of Alpine skiing
injuries are ligament
injuries
Peripatellar pain
(runner’s knee)
caused by imbalance
of stress on patella

16. Lower Extremity
Misalignment:
Q angle is larger in females due to
Wider hip structure, increasing
potential for PFPS (Patellofemoral
pain syndrome)

17. 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

18. Cruciate Ligaments
and Shear Stress

19. 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

20. Movement of subtalar joint

21. Foot Pronation and Tibial Torsion:

22. Rearfoot Movement During
Running:

23. Types of running injuries

24. Example of Double Density
Midsole:

25. Effects of Rear-
foot Double
Density Midsole
on rearfoot
position:

26. Effects of Rearfoot & Forefoot Double
Density Midsole on takeoff angle: