lec 5

Vocabulary flashcards covering key concepts from the Week 5 lecture notes on aerobic endurance, AAT, LT, MLSS, CP, and related physiological adaptations.

Aerobic endurance

The body's ability to produce energy for sustained whole-body exercise using aerobic metabolism.

Aerobic-anaerobic transition (AAT)

The shift from predominantly aerobic energy production to greater anaerobic contribution, closely linked with lactate formation; identified by lactate or gas analysis.

Lactate threshold (LT)

The exercise intensity at which blood lactate begins to accumulate, marking a shift toward greater anaerobic metabolism.

VO2max

The maximal rate of oxygen consumption during exhaustive exercise; traditional gold standard measure of aerobic capacity.

Onset of Blood Lactate Accumulation (OBLA)

The exercise intensity at which blood lactate reaches about 4 mM.

Maximal lactate steady state (MLSS)

The highest intensity that can be sustained for 30 minutes with less than a 1 mM rise in lactate during the last 20 minutes.

Lactate threshold test

An incremental test used to identify LT, measuring blood lactate, heart rate, and sometimes RPE at the end of each stage.

D-max method

A mathematical approach to identify LT from lactate–intensity data by finding the maximum distance from a fitted curve.

Individual anaerobic threshold

An LT determination approach using a threshold tailored to the individual.

Steady-state exercise

A state where energy supply matches energy demand, typically reached after about 4 minutes of a constant workload.

Steady-state max

The maximal intensity that can be sustained with a steady-state energy supply; related to MLSS and CP.

EPOC (Excess Post-exercise Oxygen Consumption)

Post-exercise elevation in oxygen uptake as the body returns to homeostasis.

Oxygen deficit

Delay in the rise of aerobic metabolism at the start of exercise when energy demand exceeds immediate aerobic supply.

Exercise economy

The efficiency with which an athlete uses oxygen to perform a given load; better economy delays fatigue.

Capillary density

Number of capillaries surrounding muscle fibers; increases with endurance training (about 10–15%).

Myoglobin concentration

Oxygen-binding protein in muscle; increases with endurance training (up to ~75–80%).

Mitochondrial adaptations

Endurance training increases the number and size of mitochondria, enhancing aerobic metabolism.

Citrate synthase

Krebs cycle enzyme; activity increases with endurance training.

Succinate dehydrogenase (SDH)

Krebs/SDH enzyme; activity increases with endurance training.

Beta-oxidation enzymes

Enzymes involved in fatty acid oxidation; their activity increases with endurance training.

Lipid pool

Muscle triglyceride stores that increase with endurance training, supporting greater fat oxidation.

Glycogen synthesis/storage

Endurance training increases muscle glycogen storage.

Muscle fiber type I (slow-twitch)

Slow-twitch fibers; endurance training may cause a small decrease in size.

Muscle fiber type IIa

Fast-twitch oxidative fibers; endurance training shifts IIx toward IIa and IIa toward Type I.

Muscle fiber type IIx

Fast-twitch glycolytic fibers; endurance training reduces IIx in favor of IIa.

W’ (W-prime)

Finite store of anaerobic energy available at the start of exercise.

Critical Power (CP)

An exercise intensity between LT and VO2max, roughly equivalent to MLSS; highly individual.

CP testing protocol

Three tests to exhaustion on separate days (or with rest), targeting exhaustion at approximately 1, 6, and 10 minutes.

CP and performance correlations

CP is closely related to performance across running, cycling, and swimming; stronger correlations with race times.

VO2max adaptation time

Most VO2max gains occur in the first 6–12 months of training.

LT adaptation specificity

LT improvements are specific to the exercise mode performed.

Dietary supplements for LT

Caffeine, beta-alanine, creatine, sodium bicarbonate, and citrulline malate can influence buffering and perceived fatigue.

LT and economy after VO2max gains

After initial VO2max gains, improvements in LT and economy often drive further performance gains.

Skeletal muscle fiber adaptations (general)

Endurance training can alter fiber size and the balance of fiber types (I, IIa, IIx) toward more oxidative properties.

Capillary and mitochondrial adaptations (training effects)

Increases in capillary density, myoglobin, mitochondrial number/size, and oxidative enzyme activity.

Capillary density increase

Capillaries around muscle fibers can increase by about 10–15% with endurance training.

Myoglobin increase

Myoglobin concentration can rise by ~75–80% with endurance training.

Mitochondrial changes

Endurance training increases both the number (~15%) and size (~35%) of mitochondria.

Enzyme activity increases (CS and SDH)

Citrate synthase and SDH activities rise with endurance training, boosting aerobic metabolism.

Lipid oxidation adaptations

Endurance training increases lipid availability and oxidation capacity via greater triglyceride stores and enzyme activity.

Glyogen storage adaptations

Endurance training enhances glycogen synthesis/storage in muscle.

Exercise fatigue mechanisms in endurance

Increased acidosis, accumulation of Pi and K+, glycogen depletion, central fatigue, and possible dehydration.

Post-exercise recovery concepts

EPOC and sustained elevated heart rate/ventilation contribute to recovery and oxygen consumption.