Physiologic Responses to Exercise (1)

The human body responds through a series of integrated changes involving physiologic systems to physical tasks.
Movement requires the musculoskeletal system's activation and control, while cardiovascular and respiratory systems sustain movement over time.
Regular exercise leads to specific adaptations in these physiologic systems increasing efficiency and capacity.
Effects of exercise depend on training intensity, duration, and the individual’s initial fitness level.

Involved Systems: Musculoskeletal, cardiovascular, respiratory, endocrine, and immune systems respond to exercise.

Key Functions:
- Provide oxygen and nutrients.
- Remove carbon dioxide and metabolic wastes.
- Maintain temperature and acid-base balance.
- Transport hormones from endocrine glands to target organs.
Response to Exercise:
- The cardiovascular system's effectiveness is dictated by muscular activity levels; demands increase with higher activity rates.
- Cardiovascular responses include increased cardiac output and blood flow, particularly oxygen extraction in exercising muscles.

Definition: Total blood pumped by left ventricle per minute = Heart Rate (HR) × Stroke Volume (SV).
Changes during Exercise:
- Cardiac Output increases linearly with exercise intensity until reaches maximum capacity (Qmax).

Blood pressure rises during exercise primarily due to increased systolic pressure, with diastolic pressure remaining constant.
Post-exercise Hypotension: Blood pressure can drop post-exercise below resting levels.

Increased A-vO2 difference indicates higher oxygen extraction from arterial blood as exercise intensity rises.

Coronary arteries supply the myocardium; blood flow and oxygen demand are closely related.
Adaptations:
- Endurance training increases capillary density, enhancing oxygen delivery.

Redistribution to active muscles during exercise (up to 80% of cardiac output) occurs, with skin receiving more blood for thermoregulation as well.

Pulmonary Ventilation: Increases immediately with exercise and varies based on intensity; can peak over 100 liters per minute in trained individuals.

Slow-Twitch Fibers: High in oxidative capacity, fatigue-resistant.
Fast-Twitch Fibers: Two subtypes (FTa and FTb), with FTb being less resistant to fatigue.
Performance Implications: Marathon runners tend to have more slow-twitch fibers, while sprinters have a higher proportion of fast-twitch fibers.

ATP Generation Systems:
1. ATP-PCr: Short, high-intensity activities.
2. Glycolytic System: Moderate to high-intensity, produces lactate.
3. Oxidative System: Long-duration activities using oxygen.

Skeletal Muscle: Increases in capillary numbers and cross-sectional area among slow-twitch fibers.
Resistance Training: Increases muscle size (hypertrophy) and strength through fiber recruitment.

Endurance training results in increased mitochondria and oxidative enzyme activity, enhancing aerobic capacity.

Increased stroke volume and efficiency during maximal exercise, with maintained resting rates.

Maintenance Training: Reduces the loss of fitness when exercise frequency is decreased.
Detraining: Significant losses in aerobic fitness occur within 2 weeks of cessation of training.
Effects of Prolonged Inactivity:
- Includes decreases in cardiorespiratory function, muscle mass, and strength.
- Regular activity is key in minimizing these effects.

Exercise responses in individuals with disabilities can be similar to those without disabilities depending on specific conditions.

Heat: Body temperature regulation during exercise; risks include heat cramps and heatstroke.
Cold: Can cause increased catecholamines and vasoconstriction, affecting overall performance.
Altitude: Reduces oxygen delivery; adaptations occur over time such as increased cardiac output.

Aging affects cardiovascular functions; age-related decline can be mitigated by training.
Gender differences manifest similarly in responses to exercise; however, women generally have lower maximal oxygen uptake (VO2 max), often due to smaller heart size.

Benefits of exercise extend beyond physical; enhancements include immune and metabolic functions.
Rapid reversibility of adaptations underscores the importance of consistent physical activity.