18. Biomechanical Applications

Question 1

What is anthropometry?

Answer 1

The science of measurement of body size

Question 2

Are Athletes Born or Made?

A study compared the foot shape in sprinters and non-runners
○ The heels were 25% shorter in sprinters than in non-athletes

What does this mean?

Answer 2

A shorter heal decreases the length of the lever (rigid body)

• This means that force is applied over a smaller area
• Sprinters are at a mechanical disadvantage

Stress = Force / Area

• As area decreases, stress increases
• A shorter heel puts more stress on the Achilles tendon

Question 3

How does the size of the achilles tendon help sprinters?

Answer 3

● Sprinting is all about developing force quickly

• Slack must be removed before a muscle can generate force
• The longer the tendon the faster you need to work to take up the slack
• As velocity of contraction increases, force decreases

Sprinters have a shorter Achilles tendon than non-athletes

• The calf muscles don’t have to work as fast to generate force
• As velocity of contraction decreases, force increases

Sprinters sacrifice leverage

• But the muscles force-generating capacity increases

Question 4

How does toe length help sprinters?

Answer 4

Sprinters have longer toes than non-runners

• Having longer toes generates a longer impulse
• The toes are in contact with the ground longer
• More time to apply the force against the ground

There is an energy cost to having longer toes though

• Greater muscle effort required to push the body

● Research has shown that toe length can change over time
○ Disease and activity can affect how bones and tendons length
○ Evolutionary research
○ Long distance runners have shorter toes

Question 5

Recording EMG during Submaximal Actions

Answer 5

Males were the same before and after

Females improved and outperformed men

only true for low level contraction
check ipad photos

Question 6

What is Active Insufficiency?

Answer 6

Failure to produce force when muscles are slack

e.g., Decreased ability to form a fist with the wrist in flexion

Question 7

What is Passive Insufficiency?

Answer 7

Restriction of joint range of motion when muscles are fully stretched

e.g., fingers cannot fully extend if the wrist is maximally flexed because the finger extensor muscles (which also cross the wrist) are stretched to their limit.

Question 8

Answer 8

Gastro primarily responsible (1st photo)

Mostly Soleus (2nd photo)

Question 9

What is Ergonomics?

Answer 9

● From the Greek words Ergo (Work) and Nomos (Laws)

● Ergonomics is about understanding the interactions between humans and other elements of a system (environment, tools, task, goal)

● Ergonomics is a profession that uses scientific investigation (tools) to optimize human well- being and overall system performance

● Ergonomists fit the job to the worker

Question 10

What is the goal of Ergonomics?

Answer 10

The goal is to reduce work-related musculoskeletal disorders
○ Soft tissue injuries that occur over time

Question 11

What are the causes of Causes of most overuse injuries include?

Answer 11

○ Heavy, Frequent, or Awkward Lifting
○ Pushing, Pulling or Carrying Loads
○ Working in Awkward Postures
○ Hand Intensive Work
○ Vibration
○ Contact Stress

● Risk of injury depends upon the duration, frequency, and intensity of exposure

Question 12

What is the benefit of Ergonomics?

Answer 12

An added benefit to increasing safety is that workers may have:

• More energy: increased productivity and efficiency
• Better focus: attention span
• Decreased fatigue: increased quality of life
• Reduced job turnover: improved morale and job satisfaction