Exercise Physiology Lecture Quiz

Controlling Force Production

• Movement is a physiological process involving multiple interconnected systems.
• Various activities like cycling, running, weightlifting, and more demonstrate different forms of movement.
• The fundamental mechanisms of all these actions are the same.

Neural Drive

• Neural drive is the motor infrastructure controlling locomotion.
• The forebrain, brainstem, and spinal cord work together to initiate, select, and perform movement.
• Components of neural control include selection, initiation, and pattern generation.
• This system is further aided by feedback mechanisms and pharmacological activation.
• The cerebral cortex, cerebellum, and basal ganglia play crucial roles in coordination.

Muscle Contraction

• Muscle contraction occurs through the sliding filament model.
• In the relaxed state, actin and myosin filaments are separated.
• During contraction, myosin pulls on actin, shortening the muscle fiber.
• Cross-bridges form between myosin and actin.
• Energy needed comes from ATP molecules.

Energy Utilization

• ATP (adenosine triphosphate) is the primary energy source for muscle contractions.
• Energy sources for muscle include ATP, creatine phosphate, glycolysis, and aerobic respiration.
• Actin filaments and myosin filaments are the site of cross bridges.
• Calcium ions (Ca2+) are crucial for muscle contraction—they initiate the action.

Substrate Supply & Clearance

• The supply and removal (clearance) of substrates such as oxygen (O2), carbohydrates (CHO), lipids, and hormones are essential for movement and energy production.
• Key components for clearance are CO2, H2O, and bicarbonate (HCO3-).

Intensity

• Intensity is a variable influencing muscle action duration.
• Muscle fiber types (fast twitch, slow twitch, etc) vary in how they respond to intensity.
• The way muscles use energy differs depending on the intensity.
• ATP (Energy) use is related to the type of muscle fiber you use.

When are Fibres Active?

• Different types of muscle fibers (slow-twitch and fast-twitch) are engaged at different work loads.
• The 'size principle' dictates that motor unit recruitment starts with slow-twitch fibers and progresses to fast-twitch fibers as force demands increase.

Energy System Contribution

• The contribution of different energy systems varies based on exercise intensity and duration.
• During anaerobic activities, the phosphagen system is dominant, followed by the glycolytic system.
• During prolonged aerobic activities, the oxidative system is predominant.
• Phosphagen system, and glycolytic contribute most to the initial portion of the activity, whereas the oxidative system gradually assumes greater dominance over time.

Metabolic Contribution

• Different fuel sources contribute to energy production during exercise based on intensity and duration.
• Muscle glycogen is initially utilized for high-intensity exercises, followed by other sources like muscle triglycerides, and plasma FFA (free fatty acids) and plasma glucose, as the intensity and duration progress.

Time

• Duration of muscular action is reliant on both intensity level and energy source availability.
• High-intensity activities have a shorter duration, whereas low-intensity activities can be sustained for longer.
• Graph visually depicts the relationship between intensity and duration of muscular action.

Controlling Motion - Motor Unit Properties

• The motor unit is responsible for muscle activation and force production.
• Different types of motor units are involved depending on the demand of the task (e.g., FF for maximal force, S for sustained activities)
• The graphs portray fatigue curves and twitch responses.

Size Principle

• Gradual recruitment of motor units starts with slow-twitch (type I) fibers and progressively involves fast-twitch (type II) fibers as needed.
• This progression optimizes force production based on demand.
• Motor unit recruitment is a critical element of controlling motion.

Recruitment and Rate Coding

• Motor unit recruitment is the process of selecting and activating more motor units to increase force output.
• Rate coding is the rate at which motor units fire to produce greater force.
• Graphs illustrate recruitment (frequency of action potentials).

Muscular Variables Associated with Force

• Muscle variables like cross-sectional area, muscle morphology, architecture, and tendon structure influence force production.
• Muscle cross-sectional area directly impacts force.
• Fiber type distribution also factors in.

Neural Variables Associated with Force

• Motor unit recruitment, activation ratio, rate coding, and synchronization affect force production.
• The neural control plays a crucial role in generating coordinated muscle action.

Resistance Training - What Are We Trying To Accomplish? How?

• Resistance training aims to increase strength, power, muscular endurance, and/or hypertrophy.
• Techniques to accomplish goals include proper exercise selection, progressive overload, and adequate rest periods.

Metabolic Training - What Are We Trying To Accomplish? How?

• Metabolic training focuses on improving cardiovascular fitness, lactate threshold, and improving metabolic function.
• It will affect VO2 max and other related performance metrics.
• Methods include high-intensity intervals and prolonged, moderate-intensity exercise.

Weight Loss - What Are We Trying To Accomplish? How?

• Weight loss is the action of reducing total body mass and body fat.
• Methods include dietary modifications, increased physical activity, adequate sleep, and behavioral adjustments.
• Lifestyle changes are key to successful weight loss.

Exercise in Elderly - What Are We Trying To Accomplish? How?

• Exercise in elderly aims to maintain functional independence and reduce the risk of falls, maintain fitness and mobility, and reduce the risk of chronic disease.
• Programs focus on muscle strengthening, balance, flexibility, and aerobic capacity.

Does Getting Old Mean Becoming Deteriorated? Aging Process or Result of Sedentary Lifestyles?

• Aging is a complex biological process marked by various physical and physiological changes.
• A sedentary lifestyle can accelerate age-related decline and may result in reduced physical capacity as opposed to actually being a direct result of physiological aging.