Oxygen Transport, Cardiovascular Responses, and Training Principles

Components of the oxygen transport system

Circulation and respiration. It involves the body's ability to get air into the lungs, bind oxygen to hemoglobin, and transport and deliver oxygen to the muscles.

Oxygen Cascade

The process of oxygen moving from the atmosphere all the way throughout the body, involving unidirectional blood flow.

a-VO2 difference

The arterial mixed venous oxygen difference. It represents the oxygen difference between artery and vein, indicating oxygen extraction by muscles. It is used to determine oxygen consumption (VO2).

Change of a-VO2 difference during exercise

It progressively increases.

Venous oxygen content decrease during exercise

Because oxygen is used in the muscles to make ATP.

VO2 max

The maximum ability of the body to transport and use oxygen in the muscles. A higher VO2 max means an athlete can sustain exercise for longer. It represents the capacity of the oxygen transport system.

Three things needed to be a good endurance athlete

High VO2 max, high anaerobic threshold, and high efficiency.

Hematocrit

The total concentration of red blood cells (RBCs) in the blood. RBCs are responsible for transporting oxygen. Hematocrit indicates the oxygen-carrying capacity of an individual.

Increase of hematocrit

Going to high altitudes, using EPO (which increases RBC creation), and blood doping.

Oxyhemoglobin Dissociation Curve (ODC)

A curve that tells us the percentage saturation of oxygen for a given partial pressure of oxygen (PO2).

ODC shift during exercise

The curve shifts to the right, which means there is greater unloading of oxygen at the tissue. This shift is key to improving oxygen delivery to the working muscles.

Bohr effect

Describes the oxygen binding affinity of hemoglobin.

Haldane effect

Describes how the oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin.

Primary way carbon dioxide (CO2) is transported in the blood

Primarily as bicarbonate ions (65%), but also dissolved in plasma (5%) and bound to hemoglobin (30%) as a carbamino compound.

Cardiac Output (CO or Q)

The amount of blood pumped by the heart per minute.

Formula for Cardiac Output (CO or Q)

CO (or Q) = Heart Rate (HR) x Stroke Volume (SV), expressed in Liters per minute (L/min).

Normal resting Cardiac Output (Q)

5 L/min.

Change of Cardiac Output with exercise intensity

It increases linearly with increased work, potentially reaching 30-35 L/min at maximal exercise. Untrained individuals typically reach around 20 L/min.

Stroke Volume (SV)

The amount of blood pumped out of the heart per beat.

Normal resting Stroke Volume (SV)

Approximately 70 mL/beat.

Change of Stroke Volume during exercise

It increases between rest and submaximal exercise, leveling off around 50-60% of maximum intensity. It does not significantly increase from submaximal to maximal exercise.

Why Stroke Volume levels off during exercise

Due to the limited capacity of the Left Ventricle.

Stroke Volume in endurance-trained vs untrained individuals

It is higher in endurance-trained individuals, meaning more blood is pumped per beat.

Heart Rate (HR)

Beats per minute (bpm).

Normal resting Heart Rate (HR)

60-80 bpm.

Maximal HR formula

Approximately 220 - Age (or 180-200 bpm).

Effect of exercise training on Maximal HR

Maximal HR is generally unaffected by exercise training.

Heart Rate (HR) response to increased work

It increases linearly with increased work and is an indicator of exercise intensity.

Heart Rate difference in trained vs. untrained individuals

It is lower in trained individuals because their higher stroke volume requires fewer beats to pump the same amount of blood.

Cardiac Output increase from rest to 50-60% of max exercise intensity

Both Heart Rate (HR) and Stroke Volume (SV) increase.

Cardiac Output increase from 50% to max exercise intensity

Only Heart Rate (HR) increases, because Stroke Volume (SV) has already leveled off.

Systolic Blood Pressure

The pressure in the vessels during ventricular contraction. Normal is 120 mmHg.

Diastolic Blood Pressure

The pressure in the vessels during ventricular relaxation. Normal is 80 mmHg.

Systolic Blood Pressure change during exercise

It increases linearly with increased work, reaching up to 180-200 mmHg at maximum exercise.

Diastolic Blood Pressure change during exercise

It remains unchanged. If it were to increase, an individual might pass out.

Blood pressure difference in trained vs. untrained individuals

It is generally lower in trained individuals, who also tend to have more vascular compliance than untrained individuals.

Key cardiovascular adaptations to dynamic (aerobic) exercise

Resting heart rate decreases due to higher SV; endurance-type cardiac hypertrophy occurs; at any given intensity (except max), HR is lower than in untrained individuals; higher VO2 max; blood pressure remains normal.

Key cardiovascular adaptations to resistance exercise

Little evidence it lowers resting HR or BP compared to dynamic exercise; at any given resistance intensity, HR and BP are lower in resistance-trained individuals; ventricular walls become thicker; total peripheral resistance increases.

Alveoli importance

Gas exchange. A larger surface area in the alveoli allows for greater diffusion capacity.

Total Lung Capacity (TLC)

The maximum volume of air the lungs can hold, typically around 5 liters.

Vital Capacity

The maximum amount of air that can be exhaled after a maximal inhalation.

Tidal Volume (TV)

The normal volume of air inhaled or exhaled with each breath at rest.

Minute Ventilation (Ve)

The total volume of air moved in and out of the lungs per minute. Ve = Tidal Volume (TV) x breathing frequency (f).

Normal resting Minute Ventilation (Ve)

6 L/min, with a frequency of 12 breaths/min.

Minute Ventilation (Ve) during strenuous exercise

It can reach 140-200 L/min, with a breathing frequency of 35-45 breaths/min.

Ventilation as a limiting factor in exercise performance

Generally no, not for low to moderate intensity exercise or for healthy individuals at sea level during maximal exercise. It is potentially limiting only in elite endurance athletes at their absolute maximum capacity.

Ventilation during incremental exercise

It increases linearly up to 50-75% of VO2 max, then increases exponentially beyond this point.

Ventilatory Threshold

The point during progressive exercise where minute ventilation (Ve) increases exponentially while oxygen consumption (VO2) is maintained or declines. It is where hyperventilation occurs because acidosis is happening, requiring more oxygen to combat it.

Effect of training on ventilation at the same work rate

Ventilation is lower at the same work rate following training. This may be due to lower blood lactic acid leading to less feedback to stimulate breathing, and the respiratory muscles (diaphragm, intercostals) becoming more trained.

Alveolar Ventilation (Va)

The volume of air that actually reaches the alveoli for gas exchange, excluding dead space. Va = (Tidal Volume - Dead Space) x frequency.

"Second Wind"

A transition from feeling fatigued to experiencing comfortable exercise. It is attributed to ventilatory adjustments, metabolic adjustments, and psychological factors.

"Stitch in the side" during exercise

Pain in the side or rib cage, possibly due to hypoxia or anoxia of the respiratory muscles.

Anaerobic Threshold (AT)

The point during exercise where your body starts favoring anaerobic metabolism more.

Significance of a higher Anaerobic Threshold

It allows an athlete to maintain a higher exercise intensity for longer, using aerobic metabolism, which improves performance.

Effect of exercise training on Anaerobic Threshold (AT)

Exercise training will increase the AT point. For example, an untrained individual's AT might be ~60% of VO2 max, while a trained individual's can be >80%.

Endurance training and Anaerobic Threshold (AT)

Enhanced oxygen delivery to muscles, improved pyruvate oxidation (less pyruvate converted to lactate), decreased lactate formation and increased blood lactate removal, increased mitochondrial density (more aerobic metabolism), increased ability of cells to oxidize fats and free fatty acid uptake, and augmented pyruvate entry into mitochondria.

Efficiency in endurance athletes

The ability of an athlete to use the least amount of oxygen required to perform a given task or exercise intensity. Training results in greater efficiency.

Lactate Threshold

The point during exercise at which lactate starts accumulating much more rapidly than it can be recycled, leading to a nonlinear increase in lactate production.

Effect of training on Lactate Threshold

Training at or above this point can increase the lactate threshold, allowing the individual to run faster before reaching this point of rapid lactate buildup.

Neuromuscular adaptations in sprinters vs. distance runners

Sprinters: Higher amount of anaerobic enzymes, more Type II (fast-twitch) muscle fibers. Distance Runners: More aerobic enzymes, more Type I (slow-twitch) muscle fibers.

Distance Runners

More aerobic enzymes, more Type I (slow-twitch) muscle fibers.

Muscle fiber adaptation to training

Muscle fiber number is fixed (hyperplasia, or fiber splitting, is mainly seen in animals, not humans). Muscle weight and size change primarily via hypertrophy (increase in the size of existing fibers) or atrophy.

Hypertrophy from resistance training

Due to an increase in the number and size of myofibrils, an increase in contractile protein, a decrease in capillary density (relative to muscle size), and an increase in the strength of connective tissue. The strength of a muscle is directly related to its cross-sectional area.

Fiber type that hypertrophies with resistance training

Fast-twitch (FT) fibers.

Biochemical adaptations to resistance training

Increased muscle concentration of ATP, phosphocreatine, creatine, and glycogen. There is generally no change in ATP-CP or glycolytic enzymes, a slight change in aerobic enzymes, and a decrease in the volume of mitochondria. No fiber type conversion typically occurs.

Body composition change with resistance training

Total body mass may not change, but lean mass (fat-free mass: muscle, bone, water, organs) increases, and fat mass decreases.

Main causes of muscle fatigue

Fast-twitch units fatigue more easily than slow-twitch. High-intensity exercise: accumulation of metabolites (H+, pH changes, ions). Endurance exercise: muscle glycogen depletion. Other factors: hypoglycemia, dehydration, loss of electrolytes.

Exercise definition

A subset of physical activity that is planned, structured, repetitive, and has a specific goal of improving or maintaining physical fitness.

Characteristics of an exercise 'dose'

Intensity, Frequency, Duration, and Type of activity.

Ways to measure exercise intensity

% VO2 max, % maximal HR, 1 Repetition Max (1RM), Rate of Perceived Exertion (RPE), or Onset of Blood Lactate Accumulation (lactate threshold).

Core Training Principles

Principle of Specificity: Training should directly relate to the demands of the activity or sport. Principle of Variation: Incorporating variety to prevent plateaus and boredom, while maintaining focus. Principle of Progression: Gradually increasing the workload to prevent injury, typically by no more than a 10% increase from the previous load.

Difference between strength and endurance in muscle training

Strength: The maximal resistance a muscle can overcome, focusing on tension placed on the muscle. Endurance: The ability of a muscle to repeatedly lift a load over a period of time, focusing on metabolic demand for ATP.

Phases of strength training

Adaptive/Endurance Phase: Focus on form and adaptation to the regimen (high repetitions, low load: >10 reps, 65-70% 1RM). Strength/Hypertrophy Phase: Increased intensity to build muscle size and strength (lower repetitions: 4-8 reps, 80-90% 1RM). Power Phase: For power athletes, focusing on speed and high force (very high loads: 90-100% 1RM, 1-2 repetitions).

Guidelines for anaerobic (sprint) training

Intensity: Heart Rate 5-15% higher than the anaerobic threshold point. Duration: 8-10 weeks overall; per session, repeated bouts of 25 seconds or less for ATP-PC system, or 3-4 minutes or less for anaerobic glycolysis. Frequency: 3-4 days per week.

Guidelines for aerobic (endurance) training

Intensity: 50-80% of maximal Heart Rate. Duration: 30-60 minutes or more per session. Frequency: 4-6 days per week.

Muscle fiber type more susceptible to exercise injury

Type I fibers, because they are smaller and are worked harder during low-intensity, long-duration exercise.