Question

A person is performing “Jumping Jacks” (from the anatomical position jumping off the ground and simultaneously abducting both upper and both lower extremities to land in this position, followed by a jump to return to the anatomical position). Answer the following questions about Situation 1….

What determines the length of time this person will remain in the air with every Jump?

a. the forcefulness of the shoulder abductions

b. the “net” vertical force acting on their body

c. their potential energy

d. none of the above

The force used to leap off the ground is a result of…

a. ground reaction force

b. muscle action

c. moment of inertia

d. angular acceleration

What is the role of the abdominal muscle group?

a. agonist for trunk elevation

b. antagonist of trunk elevation

c. neutralizer of trunk flexion

d. stabilizer of the trunk

The primary agonists for shoulder abduction are….

a. pectoralis major

b. deltoids

c. trapezius

d. gluteus medius

What is the role of the knee during the landing phase of the Jumping Jack?

a. concentric activation of quadriceps for knee extension

b. eccentric activation of quadriceps for knee flexion

c. isometric activation of quadriceps to transmit force to the ground

d. protection of the knee by the “screw-home” mechanism

Answer 1

What determines the length of time this person will remain in the air with every Jump?

The net vertical force acting on their body (b)

The force used to leap off the ground is a result of…

Muscle action (b)

What is the role of the abdominal muscle group?

   Stabilizer of trunk (d)

The primary agonists for shoulder abduction are….

  Deltoids (b)

What is the role of the knee during the landing phase of the Jumping Jack?

Eccentric activation of quadriceps for knee flexion (b)