Lecture 16 - Reaction Forces & Muscle Forces

Question 1

What did the P value represent in Ashby and Heegaard’s study?

Answer 1

The probability that JFA and JRA are the same

Question 2

What is a significant P value?

Answer 2

A value less than 0.05

Question 3

What was the jumping distance defined as in Ashby and Heegaard’s study?

Answer 3

The horizontal displacement of the toe marker from initial position to touchdown location

Question 4

How much farther did subjects jump with arm movement?

Answer 4

21.2%

Question 5

How did arm movement contribute to displacement in Ashby and Heegaard’s study?

Answer 5

It allowed subjects to increase the horizontal displacement of the center of gravity before take off by 8 cm

Question 6

What happened to the take off velocity when arm movement was free?

Answer 6

The take off velocity increased by 12.7%

Question 7

How did jumping with free arms affect the distance at touch down?

Answer 7

It increased the distance between the toe and the center of gravity

Question 8

How did jumping with free arms versus restricted arms affect the vertical ground reaction forces?

Answer 8

It produced no difference

Question 9

How did jumping with free arms versus restricted arms affect the horizontal ground reaction forces?

Answer 9

There was a 15.4% increase in jumping with free arms

Question 10

What is a moment about the center of gravity?

Answer 10

A torque or rotational force

Question 11

How was the moment affected by jumping with free arms versus restricted arms?

Answer 11

The peak positive moment was greater for jumping with free arms

Question 12

How did arm motion improve displacement?

Answer 12

Increased center of gravity during the flight phase due to greater take off velocity, increase in horizontal displacement of center of gravity before take off, and increase in distance between toes and center of gravity at touch down

Question 13

How did Ashby and Heegard’s studies compare with past studies?

Answer 13

The jumping distance and take off velocity was less because other studies used trained athletes

Question 14

How did arm swing increase performance?

Answer 14

By helping with take off, flight phase, and touch down

Question 15

How may the arms help in increasing performance?

Answer 15

Added balance and control, alleviating excessive forward rotation of the center of gravity during flight phase

Question 16

Why does restricted arm jumping seem to produce smaller displacement?

Answer 16

Once the jumper is in the air, they are unable to change the body’s total linear or angular momentum

Question 17

Does arm motion increase performance in the standing long jump?

Answer 17

Yes