3. When is the vastus lateralis most active (increased action potential firing r

Question

3. When is the vastus lateralis most active (increased action potential firing rate) during the squat? When is the vastus lateralis least active (decreased action potential firing rate) during the squat? 2 points We measured firing rate in the erector spinae during gait using wireless surface electrodes. Based on the figure below, when are the erector spinae muscles most active during walking gait? What normalization method was used for this muscle? 4 points 4. 10 9 2 Erector Spinae 0 5 10 15 20 25 30 35 40 4550 55 60 65 70 75 80 85 90 95 100 Gait Cycle (%)

Explanation / Answer

Question 3

First part

Vastus lateralis is most active during isometric back squat.

Explanation : Isometric muscle contraction is the type of muscular activity that strengthen the muscle but donot alter the muscle length and joint angle. In squat exercises the the hip extensors and knee extensors are getting strengthened. The knee extensors are rectus femoris, vastus medialis, vastus lateralis. Among these muscles the vastus lateralis is most active during isometric back squat. Different squat exercises activate different muscle of knee extensor group as squats are multijoint multidynamic work. Isometric back squats measures the strength and outputs at differnt joint angles and depending on the joint angles the muscle dynamic output varies.

Second part

Vastus lateralis is least active isometric hip abduction.

Explanation : Isometric exercises are included in the training schedule of athlet and non athlet pupulation to increase overall health. It sis also included in the rehabilitation programme of patients with hip or back or sholder injury so that the working muscle group can be strengthened without affecting the muscle length and joint angle as a characteristic of isometric exercise. Hip and knee muscle weakness is associared with knee pain and during hip adduction and abduction different muscle groups are active. In hip adduction the vastus lmedialis obliquus showed highest activity whereas in hip abduction the vastus lateralis obliquus showed maximum activity.

Question 4

First part

The erector spinae muscle is most active at the time of foot strike during walking gait.

Explanation : The erector spine muscle is not a single muscle but a group of muscle and tendon which lies in the groove of vertibral column and it runs along the lumber , thoracic and cervical region. The erector spine muscle activity varies with the kinetic nature of the work done by the trunk and and is reflected by the EMG signals. Erector spine muscle regulates the balance of body in different postures, during wallking , standing by regulating the pelvic joint movement. The EMG pattern of erector spine muscle activity is maximun during walking and it proves that tis muscle is active in repeative work pattern like walking and it reflects the central control of walking.

Second part

Electro myography can be used to measure this activity by placing electrodes under the skin and the given diagram showsthe erector spine muscle activity in walking gait as in different exercise conditions this muscle shows different EMG output. To assess the erector spine muscle activity static and dynamic both type of exercises are given to the subject.

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