Exercise Physiology Week 5: Lactate and Fatigue

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the Respiratory Quotient (RQ) value for carbohydrates?

0.71

0.74

1 (correct)

0.8

Which energy source is primarily used during static resistance exercise?

Carbohydrate oxidation

Anaerobic metabolism (correct)

Fat oxidation

Aerobic metabolism

What happens to oxygen consumption immediately after static exercise is terminated?

It gradually decreases without any increase.

It decreases sharply and remains low.

It experiences a sudden increase. (correct)

It remains constant for a short duration.

How are dynamic resistance exercises described in terms of energy contribution?

They have both anaerobic and aerobic components. Signup and view all the answers

What is the Respiratory Exchange Ratio (RER) for fat oxidation?

0.71 Signup and view all the answers

What primary metabolic process contributes to muscle acidosis during exercise?

Production of carbon dioxide and carbonic acid Signup and view all the answers

Which reaction results from the breakdown of ATP during exercise?

ATP → ADP + H+ + energy Signup and view all the answers

What role do monocarboxylate transporters (MCTs) play in exercise physiology?

Transporting lactate out of cells into the blood Signup and view all the answers

Why is carbonic acid considered a weaker acid than lactic acid (LA)?

It has a higher pKa value than lactic acid Signup and view all the answers

What happens to lactate during exercise when it is converted back to pyruvate?

It allows for carbohydrate replenishment Signup and view all the answers

Delayed onset muscle soreness (DOMS) is primarily associated with which physiological factor?

Microtrauma within the muscle Signup and view all the answers

Alkalosis can result from which of the following?

Loss of acids or accumulation of bases Signup and view all the answers

Which compound is formed when the body combines excess pyruvate with hydrogen ions?

Lactic acid Signup and view all the answers

What physiological change is observed in older adults when performing anaerobic exercises compared to younger individuals?

Lower lactate concentrations at the same relative workload Signup and view all the answers

How does the average peak power on the Margaria-Kalamen Stair Climb test change from age 20 to 70?

Declines at approximately 10.3% per decade Signup and view all the answers

What factor is likely to increase the time required to achieve steady state during exercise?

Higher intensity of exercise Signup and view all the answers

Which measurement technique is primarily used to assess aerobic metabolism in exercise physiology?

Indirect open-circuit spirometry Signup and view all the answers

What is a key reason for measuring aerobic metabolism during physical activity?

To quantify energy requirements for activities Signup and view all the answers

What causes oxygen drift during submaximal activity?

Increased blood levels of catecholamines Signup and view all the answers

Which factor is NOT associated with decreased lactate production in older males during maximal static contraction?

Increased blood volume Signup and view all the answers

In which condition is oxygen drift most likely to occur?

During prolonged activities above 70% VO2Max Signup and view all the answers

What is the typical decline in maximal anaerobic power observed in males from ages 20 to 88?

Approximately 10.3% per decade Signup and view all the answers

What is typically the duration of a maximal aerobic exercise test?

8–12 minutes Signup and view all the answers

What is the primary purpose of calorimetry in physiological studies?

To measure heat energy in metabolic processes Signup and view all the answers

What does VO2 max represent?

The highest amount of oxygen utilized aerobically during heavy exercise Signup and view all the answers

How does ventilation (VE) change during incremental exercise?

It increases with energy demand Signup and view all the answers

What is the relationship between muscle mass and lactate diffusion in older adults?

Older adults have a smaller ratio of muscle mass to blood volume, affecting diffusion Signup and view all the answers

What is commonly observed in healthy individuals during a ramp protocol aerobic test?

Rectilinear increase in VO2 Signup and view all the answers

During incremental aerobic testing, what physiological response is typically noted?

Increase in both ventilation and oxygen consumption Signup and view all the answers

What was concluded by Meyerhoff and Hill about lactic acid in relation to muscle fatigue?

Anaerobic metabolism leads to lactic acid production, causing acidosis and muscle fatigue. Signup and view all the answers

What role does lactate play during exercise according to Dr. Brooks' research?

Lactate serves as fuel for muscles and the heart. Signup and view all the answers

What primarily causes acidosis during exercise according to the content?

Accumulation of hydrogen ions (H+). Signup and view all the answers

What happens to the tissue pH after intense exercise?

The pH returns to normal within 30 to 60 minutes post-exercise. Signup and view all the answers

What misconception regarding lactic acid and fatigue is highlighted in the content?

The acid component of lactic acid is not the cause of fatigue. Signup and view all the answers

What effect do H+ ions have on muscle function during exercise?

They lower tissue pH, interfering with muscle function. Signup and view all the answers

How have perceptions of lactate changed since the 1970s?

Lactate has been recognized as a potential fuel rather than just a waste product. Signup and view all the answers

What are the primary contributors to acidosis during exercise as mentioned in the content?

Accumulation of acids and loss of bases. Signup and view all the answers

Which statement about the availability of ATP-PC in males and females is true?

Males generally have more total energy available from ATP-PC than females. Signup and view all the answers

What is true regarding lactate accumulation during exercise in males and females?

Both sexes show equal lactate concentrations at workloads above their lactate threshold. Signup and view all the answers

In examining mechanical power output during anaerobic exercise, which of the following is accurate?

The average peak power output for females is roughly 65% of that for males. Signup and view all the answers

How does age affect the availability and utilization of ATP-PC?

There is a reduction of about 32% in ATP-PC capacity from youth to old age. Signup and view all the answers

What can be said about lactate levels across different age groups?

Resting blood lactate levels remain consistent across age groups, varying only slightly. Signup and view all the answers

What differentiates the lactate thresholds of males and females?

Males tend to have a higher absolute workload for their lactate thresholds than females. Signup and view all the answers

Regarding the mechanical power output in anaerobic exercise, which statement is incorrect?

Females possess greater absolute power output than males on average. Signup and view all the answers

Study Notes

Course Information

Course name: Exercise Physiology
Course code: DPT-413
Instructor: Monira I. Aldhahi
Week: 5th

Class Objectives

Understand the lactate buffering system
Identify gender-related differences in anaerobic exercise characteristics
Explain laboratory and field assessment techniques for aerobic metabolism during exercise
Explain major variables used to describe aerobic metabolic response to exercise

The Lactic Acid Myth

The myth that lactic acid causes muscle fatigue originated with Otto Meyerhoff and Archibald V. Hill
Their theory is that anaerobic metabolism leads to lactic acid production, which causes acidosis and muscle fatigue
The 1970s saw a "lactate revolution" changing understanding
Dr. Brooks and others showed lactate as a muscle and heart fuel, not a cause of fatigue

Hydrogen Ion Production During Exercise

Acidosis arises from acid accumulation or base loss.
Alkalosis occurs from acid loss or base accumulation
Key contributors to exercise-induced muscle acidosis include:
- Carbon dioxide and carbonic acid production in working skeletal muscles
- Lactic acid production in working muscles
- ATP breakdown in working muscles

Pyruvate and H+ Ions

The body combines excess pyruvate with H+ ions to form lactic acid
This enables muscles to work longer than their normal capacity

Buffer System

Lactate and H+ lower blood pH.
The body uses buffer systems (like sodium bicarbonate) to maintain normal blood pH
Lactate is transported to the liver and non-exercising tissues for conversion back to pyruvate during exercise or recovery

Lactate Clearance

Lactate is transported via monocarboxylate transporters (MCTs)
Lactate is shuttled from the muscle to the heart and other tissues where it can be oxidized or used by the liver

Lactate as a Viable Fuel

Lactate can be converted back to pyruvate and then glucose
This process plays a crucial role in energy production and carbohydrate replenishment

Delayed Onset Muscle Soreness (DOMS)

DOMS is unrelated to lactate
DOMS is believed to be related to microtrauma within the muscles

Male vs. Female Anaerobic Exercise Characteristics

Females exhibit generally lower anaerobic characteristics than males in young and middle-aged adults
- ATP-PC availability and utilization do not differ between the sexes but males have more total energy available due to muscle mass difference
- Lactate thresholds occur at higher absolute workloads in males, but at a given relative workload above LT, lactate concentrations are the same.

Anaerobic Exercise Characteristics of Older Adults

Local resting stores of ATP-PC are reduced
Anaerobic power decreases with age (ex: 32% decline from youth to old age)

Accumulation of Lactate in Older Adults

Resting blood lactate levels are consistent across different ages
Lactate accumulation is typically higher in older adults at a given absolute submaximal workload
Older males have an overall lower lactic acid production than younger males during a 60-second maximal static contraction

Mechanical Power and Capacity in Older Adults

Peak power in the Margaria-Kalamen Stair Climb test declines with age (20 to 70 years old)
Males show an approximate 10.3% decline in maximal anaerobic power per decade from age 20 to 88

Aerobic Metabolism During Exercise

The goal of measuring aerobic metabolism is to quantify energy needed for a given activity

Rationale for Fitness Assessment

Establish baseline
Design programs
Set realistic goals
Evaluate changes in fitness
Diagnose further
Describe pathology
Understand patient limitations

Measurement of Aerobic Metabolism

Methods include
- Direct calorimetry (measures heat)
- Indirect open-circuit spirometry (measures air; most common in exercise physiology)
  - Open circuit: subject breathes room air
  - Closed circuit: subject breathes in a sealed container containing oxygen

Calorimetry

Calorimetry measures heat energy released or absorbed in metabolic processes
Direct calorimetry measures heat production
It uses specially constructed chambers

Indirect Spirometry

Indirect calorimetry method for determining heat production by measuring and analyzing expired air
Measures O2 consumption and CO2 production
- In a closed system: subject breathes into a container with a designated composition that absorbs exhaled CO2 to measures O2 use
- In an open system:subject breathes room air, and exhaled air is collected and O2 and carbon dioxide levels measured

Open Circuit Indirect Spirometry

Most common lab method
Measurements take place at rest, during submaximal exercise, or at maximal exertion

Aerobic Exercise Responses

Oxygen consumption is the primary measure of interest, directly related to ATP
Measuring CO2 helps determine fuel utilization and caloric expenditure

VO2 and VCO2

VO2: Oxygen consumed (inspired - expired)
VCO2: Carbon dioxide produced during metabolism, primarily from aerobic cellular respiration

Short-Term, Light to Moderate Intensity Submaximal Exercise

VO2 levels plateau during short-term light to moderate submaximal exercise
Time to reach steady state VO2 is shorter in younger adults compared to older adults or at higher intensities
VO2 is highly correlated with exercise intensity

Long-Term Moderate to Heavy Submaximal Exercise

A situation where oxygen consumption increases (drifts upward) despite a constant exercise demand. This is likely due to an increase in lactate levels, rising catecholamines, changing energy substrate utilization, increased cost of ventilation, and increased body temperature.

Incremental Aerobic Exercise to Maximum

VO2 max is the highest oxygen intake an individual can reach
Max testing can last 8-12 minutes, but for healthy individuals, 7-26 minutes (cycle ergometer). Treadmill 5-26.
Shorter tests usually require a warm-up.
Ramp protocols show a linear increase in VO2

Ventilation During Max Tests

Ventilation (VE), VO2, and VCO2 all increase due to rising energy demands
For example, the person in Table 4.2 demonstrates reserve: VE rose from 25.21 to 139.04 L/min, meaning a significant reserve capacity

Respiratory Quotient (RER/RQ)

RER (respiratory exchange ratio) = ratio of CO2 produced to O2 consumed in entire body
RQ (respiratory quotient) = ratio of CO2 produced to O2 consumed by cells
Helps determine fuel source
- Carbohydrates= 1
- Fat = .71
- Protein= .80

Static and Dynamic Resistance Exercise

Physiological responses to static exercise are described relative to maximal voluntary contraction (MVC). Static contractions below 15-25% MVC.
Dynamic resistance activity has both an aerobic and an anaerobic component. The greater the work (repetitions/duration), the greater the aerobic contribution.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers key concepts related to the lactate buffering system, including gender differences in anaerobic performance and aerobic metabolism assessment techniques. It also addresses the historical myths surrounding lactic acid and its role in muscle fatigue during exercise. Test your knowledge on these essential physiological principles.