Muscle Metabolic Adaptations to Endurance and Sprint Training

Vocabulary-style flashcards covering physiological and metabolic adaptations in muscle tissue resulting from aerobic endurance and anaerobic sprint training programs.

Mitochondrial adaptations (Endurance)

An increase in both the number and size of mitochondria, along with increased activities of oxidative enzymes in the Krebs cycle, electron transport chain, and fatty acid oxidation.

Fuel Substrate changes (Endurance)

Changes that include an increase in muscle glycogen stores and muscle triglyceride stores.

GLUT4

Glucose transporters in the cell membrane that increase in density following both endurance and sprint training.

MCT1

Lactate/$H^+$ co-transporters in the cell membrane that increase with training to facilitate lactate transport and reduce intramuscular accumulation.

Lactate shuttle

The mechanism where there is an increase in lactate and $H^+$ uptake in non-contracting fibres.

Muscle-fibre type (Endurance)

Adaptations involving an increased cross-sectional area of slow-twitch fibres and a small transition of fast-twitch (type $IIb$) to fast-twitch (type $IIa$) fibres.

Myoglobin (Mb)

A protein that facilitates $O_2$ transport from the cell membrane to the mitochondria; endurance training increases its content by $75\text{-}80\text{\%}$ in rodent muscle.

Na-K pump density

Increases in the sarcolemma with training to blunt the rise in extracellular $K^+$ and reduce $K^+$-induced muscle fatigue.

Glycogen sparing

A functional adaptation of endurance training characterized by an increased capacity to oxidise fat, resulting in less glycogen use during prolonged exercise.

Creatine Kinase (CK)

An enzyme in the ATP-PCr system that catalyzes the reaction $PCr + ADP + H^+ \rightarrow ATP + Cr$; its activity increases with anaerobic training.

Myokinase

An enzyme that increases with anaerobic training and catalyzes the reaction $ADP + ADP \rightarrow ATP + AMP$.

Glycolytic system enzymes (Sprint)

Key enzymes that increase to allow a higher rate of glycolysis/glycogenolysis, including Phosphorylase, Phosphofructokinase (PFK), Lactate dehydrogenase (LDH), and Hexokinase.

Muscle-fibre type (Sprint)

Adaptations involving an increased cross-sectional area mainly of fast-twitch (type $IIa$ and $IIb$) fibres, and a potential transition of slow-twitch to fast-twitch (type $IIa$) fibres.

Na+/H+ exchanger

A cell membrane transporter that increases with sprint training to manage muscular pH by exporting $H^+$ ions.