Effects of Physical Training

Effects of Physical Training

Introduction

• This lecture discusses the effects of physical training.

• The type of training dictates the adaptations that occur (specificity).

  • Heavy resistance training yields different results than endurance training.

• Training-related changes can be categorized into:

  • Metabolic adaptations

  • Cardiovascular adaptations

  • Muscular adaptations

• Many adaptations have crossover effects, influencing multiple categories.

  • For example, improvements in $VO_2$ max (peak aerobic capacity) result from metabolic, cardiovascular, and muscular adaptations.

Metabolic Adaptations to Sprint and Strength Training

• Sprint and strength training lead to several metabolic and structural adaptations.

• Increased Muscular Stores of ATP and Creatine Phosphate:

  • These are high-energy phosphates present in limited supply.

  • Increased stores allow maintenance of high energy turnover rates for longer durations.

• Increased Muscle Glycogen Stores:

  • Glycogen can be used aerobically or anaerobically (anaerobic glycolysis).

  • Larger glycogen stores delay the onset of fatigue.

• Increased Anaerobic Enzymes:

  • Enzymes catalyze reactions, speeding them up when stimulated and slowing them down when inhibited.

  • More anaerobic enzymes increase the peak capacity for anaerobic metabolism.

• Increased Lactate Buffering:

  • Anaerobic metabolism (e.g., during strength training) produces lactate and hydrogen ions, leading to acidity.

  • Increased buffering capacity improves the ability to sustain workloads that produce high levels of lactate and acidity, delaying fatigue.

• Increased Muscle Fiber Size:

  • Sprint and strength training leads to muscle hypertrophy.

Metabolic Adaptations to Endurance Training

• Endurance training leads to distinct metabolic adaptations.

• Increased $VO_2$ Max:

  • Represents maximum aerobic capacity, leading to a greater aerobic engine.

  • Results in improved endurance performance.

• Improved Muscle Glycogen Stores:

  • Important fuel source for sustaining high-intensity efforts over long periods.

  • Increased stores delay fatigue.

• Increased Mitochondrial Enzymes:

  • Improves aerobic function because these enzymes are critical in the Krebs cycle and electron transport during aerobic metabolism.

• Improved Fat Utilization:

  • Fat is an essentially inexhaustible fuel source during exercise.

  • Upregulating fat usage spares glycogen stores.

• Improved Lactate Removal, Lactate Oxidation, and Lactate Threshold:

• Improved Capillary Number and Myoglobin Content:

  • More capillaries enhance oxygen delivery and offloading to the muscle.

  • Myoglobin aids in oxygen transport within the muscle.

Blood Lactate Response

• Lactate production remains low at low exercise intensities (primarily aerobic metabolism).

• Above a certain threshold, lactate production increases disproportionately with exercise intensity.

• Lactate Threshold:

  • Exercising at or below the lactate threshold allows for sustained exercise.

  • Exceeding the lactate threshold leads to quicker fatigue.

• Training shifts the lactate threshold curve to the right.

  • Allows sustaining higher exercise intensities before significant lactate production.

  • Untrained individuals: lactate threshold around 50-55% of $VO_2$ max.

  • Trained individuals: lactate threshold up to 65-85% of $VO_2$ max.

• Combined improvements in $VO_2$ max and lactate threshold result in increased sustainable speeds during aerobic work.

Cardiorespiratory Adaptations to Endurance Training

• Increased $VO_2$ Max:

  • Caused by both metabolic and cardiorespiratory adaptations.

• Decreased Resting and Submaximal Heart Rate:

  • Primarily due to increased resting and exercise stroke volume.

  • More blood is pumped per beat, reducing the need for a high heart rate.

• Increased Maximal Cardiac Output:

  • Maximal stroke volume is elevated, while maximum heart rate remains about the same or slightly suppressed.

• Increased Total Blood Volume, Red Blood Cell Number, and Hemoglobin Content:

  • Results in better oxygen-carrying capacity of the blood.

• Decreased Blood Viscosity:

  • Increased plasma volume offsets the increase in red blood cell number and hemoglobin content, leading to thinner blood.

• Lower Ventilation at Given Exercise Intensity, Higher Peak Ventilation at $VO_2$ Max:

  • Increased ability to remove carbon dioxide and hydrogen ions.

Training Responses

• Cumulative effects of metabolic and cardiorespiratory adaptations are important for function.

• Benefits are substantial in older individuals (e.g., 60-70 year olds).

• Trained individuals have substantially higher maximal cardiac outputs than sedentary individuals.

• Cardiac Output (Q) = Stroke Volume (SV) × Heart Rate (HR)

  • Where SV = Stroke Volumne and HR = Heart Rate

• Increased stroke volume (25% increase) is the main driver of higher cardiac output.

• Maximum heart rate shows little change between sedentary and trained individuals.

• Trained individuals also have an improved ability to extract oxygen from the blood.

• Higher $VO_2$ max correlates with the ability to perform weight-bearing tasks of daily living.

• Trained older adults may have aerobic capacities comparable to sedentary college students.