EXERCISE PHYSIOLOGY

Department of Physiology

Faculty of Medicine

Universitas Sumatera utara

Systemic Responses to Exercise

NEUROMUSCULAR FUNCTIONS AND ADAPTATIONS TO EXERCISE

Exercise maintains neuronal health by improving blood flow to the brain and by increasing brain levels of growth factors that promote optimal function of neurons.

Recent study in humans has concluded that exercise improves brain function and reduces the risk of cognitive impairment associated with aging.

NEUROMUSCULAR FUNCTIONS AND ADAPTATIONS TO EXERCISE

Humans skeletal muscle can be divided into several different classes based on the histochemical or biochemical characteristics of the individual fibers.

Neural adaptations: ↑ maximal motor unit recruitment ↑ synchronous recruitment of motor units

SO motor units are recruited first during incremental exercise, followed by a progressive increase in FOG and FG motor unit recruitment as exercise intensity increases.

Both endurance and resistance exercise training have been shown to promote a fast-to-slow shift in skeletal muscle fiber types but does not result in complete transformation of all fast fibers.

Training adaptations: increases in muscle size from hypertrophy and hyperplasia.

METABOLIC RESPONSES TO EXERCISE: INFLUENCE OF DURATION AND INTENSITY

Short-term, Intense Exercise• During high-intensity, short-term exercise (i.e.,

two to twenty seconds), the muscles’ ATP production is dominated by the ATP-PS system.

• Intense exercise lasting more than twenty seconds relies more on anaerobic glycolysis to produce much of the needed ATP.

• High-intensity events lasting longer than forty-five seconds use a combination of the ATP-PC system, glycolysis, and the aerobic system to produce the needed ATP for muscular contraction.

METABOLIC RESPONSES TO EXERCISE: INFLUENCE OF DURATION AND INTENSITY

Prolonged Exercise The energy to perform prolonged exercise

(i.e., more than ten minutes) comes primarily from aerobic metabolism.

A steady-state O2 uptake can generally be maintained during prolonged, low-intensity exercise.

METABOLIC RESPONSES TO EXERCISE: INFLUENCE OF DURATION AND INTENSITY

Incremental Exercise• The maximal capacity to transport and utilize

O2 during exercise (maximal oxygen uptake, or VO2 max) is considered to be the most valid measurement of cardiovascular fitness.

• Indeed, incremental exercise test (also called graded exercise test) are often employed to determine a subject’s cardiovascular fitness.

• These tests are usually conducted on a treadmill or a cycle ergometer.

• Oxygen uptake increase in linear fashion during incremental exercise until VO2 max is reached.

• The physiological factors that influence VO2 max include:– The maximum ability of the cardiorespiratory

system to deliver oxygen to the contracting muscle.

– The muscle’s ability to take up the oxygen and produce ATP aerobically.

CARDIOVASCULAR FUNCTIONS AND ADAPTATIONS TO EXERCISE

With the start of exercise, cardiovascular function changes by: ↑ Heart rate ↑ Ejection fraction ↑ Stroke volume ↑ Cardiac output ↑ Redistribution of Q in favor of contracting

skeletal muscle ↓ Vascular resistance ↑ Muscle blood flow

Muscle Contraction

Venous Return

End Diastolic Volume

Contractility

Stroke Volume Heart Rate

Cardiac Output

Cellular Respiration

Sympathetic

Stimulation

Muscle Vascular Resistance

Muscle Blood Flow

a-vO2∆

Oxygen Extraction

Oxygen Consumption

Acute cardiovascular adaptations that combine to increase oxygen consumption during exercise

CARDIOVASCULAR FUNCTIONS AND ADAPTATIONS TO EXERCISE

Cardiovascular adaptations to training are extremely important for improving endurance exercise performance, and preventing cardiovascular disease

The more important of these adaptations are: ↑ Plasma volume ↑ Red cell mass ↑ Total blood volume ↓ Systolic and diastolic blood pressire ↑ End diastolic dimensions and ventricular

volumes ↑ Maximal stroke volume ↑ Maximal cardiac output

Training ForLong -Term Endurance

Plasma Volume

Red Cell Mass

Blood Volume

Venous Return

Ventricular Volume

End Diastolic Volume

Maximal Stroke Volume

Muscle Capillary Density

Maximal Muscle Blood Flow

Oxygen Delivery

VO2max

Exercise to Exercise to VOVO2max2max

Maximal Cardiac Output

Chronic adaptations of the CV system after exposure to training for long term endurance. Adaptations are related to their affect during both maximal & submaximal exercise

Training For Long-Term Endurance

Plasma Volume

Red Cell Mass

Blood Volume

Venous Return

Ventricular Volume

End Diastolic Volume

Stroke Volume

Sympathetic Stimulation

Heart Rate

Submaximal Steady State ExerciseChronic adaptations of the CV system after exposure to training for long term endurance. Adaptations are related to their affect during both maximal & submaximal exercise

PULMONARY ADAPTATIONS TO EXERCISE

After the onset of exercise there is: A rapid ↑ in ventilation A similar rapid ↑ in pulmonary blood flow An improved VE vs Q relationship in the lung ↑ Lung compliance Airway dilation and ↓ resistance to air flow

The lungs and pulmonary circulation do not express the degree of long-term adaptations to exercise. The improvement are more determined by muscular and cardiovascular function.

Endocrine Adaptations to Exercise