ACUTE RESPONSES OF THE MUSCULAR SYSTEM

Question 1

acute responses of the muscular system

Answer 1

Acute muscular system responses to exercise are those that occur in the working muscles themselves. These responses vary according to the type, intensity and duration of the exercise.

Question 2

Muscular acute responses include:

Answer 2

• increased motor unit and muscle fibre recruitment
• increased arteriovenous oxygen difference
• increased muscle temperature
• increased muscle enzyme activity
• increased oxygen use
• decreased muscle substrate levels (ATP, creatine phosphate, glycogen and triglycerides).

Question 3

INCREASED MOTOR UNIT AND MUSCLE FIBRE RECUIRTMENT

Answer 3

When an individual engages in any physical activity, there is a need for muscular contractions to take place. When exercise begins, an increase in motor unit recruitment must occur so that more muscle fibres are activated to contract. The greater the force or effort required, the greater the number of motor units recruited, and the greater the number of muscle fibres activated.

Question 4

INCREASED ARTERIOVENOUS OXYGEN DIFFERENCE

Answer 4

During exercise, working muscles extract much more of the available oxygen from the blood, via myoglobin and mitochondria. As much as75 per centof the available oxygen is extracted and, as a result, the arteriovenous oxygen difference increase.

Question 5

INCREASED MUSCLE TEMPERATURE

Answer 5

Increased blood flow to the muscles, coupled with the heat generated as a by-product of the increased production of ATP during exercise, results in an increase in muscle temperature.

Question 6

INCREASED MUSCLE ENZYME ACTIVITY

Answer 6

Enzyme activity increases during exercise to produce the increased amount of ATP required by the muscles. This is because enzymes assist in the chemical reactions that resynthesise ATP. For example, the enzyme ATP synthase converts ADP and phosphate into ATP.
- Enzymes are involved in all of the chemical processes that produce energy via the three energy pathways.

Question 7

INCREASED OXYGEN USE

Answer 7

The cells within the muscle extract and use more oxygen from the blood during exercise because of the increased demand for ATP. This greater extraction and use of oxygen by the exercising muscle contributes to the increase in the arteriovenous oxygen difference that has been previously referred to.

Question 8

DECREASED MUSCLE SUBSTRATE LEVELS

Answer 8

Muscular stores of ATP, creatine phosphate, glycogen and triglycerides begin to deplete during exercise because they are sources of fuel for the production of ATP.
- The depletion of these energy stores, particularly creatine phosphate and glycogen, contributes to the fatigue experienced during exercise and physical activity.