Lactate Response and MLSS in Swimming

Lactate Metabolism and Exercise

• The enzyme responsible for converting pyruvate to lactate is lactate dehydrogenase.
• After training, there is an increase in neurohormonal responses.
• The monocarboxylate transporter (MCT) is responsible for facilitating lactate transport across cell membranes.

Exercise and Lactate Levels

• Higher lactate levels are reported during high-intensity, anaerobic exercises.
• Fast-twitch muscle fibers are mostly used during high lactate exercise.
• PCr levels decrease after stress.

Lactate Production and Removal

• The primary factor contributing to lactate production during resistance exercise is the high intensity of the exercise.
• The lactate threshold for a trained person is around 50-60% of VO2max.
• Endurance training enhances lactate production and removal systems.
• PCr levels decrease by 50-70% after exercise.

Energy Sources and Exercise

• The rate of ATP hydrolysis increases after sprint training.
• At a very high power output, ATP is primarily generated from phosphocreatine (PCr).
• During exercise, substrate utilization shifts from fatty acids to carbohydrates.

Glucose and Lactate Transport

• GLUT-4 transporters are responsible for glucose uptake into muscle cells.
• Slow-twitch muscle fibers utilize lactate better.
• A limitation of fatty acids as a fuel source during exercise is their slow oxidation rate.

Glycolysis and Lactate Dehydrogenase

• The rate-limiting enzyme for glycolysis is phosphofructokinase (PFK).
• The A and B isoforms of lactate dehydrogenase increase with sprint training.

Mitochondrial Function

• The glycerol phosphate shuttle is responsible for transporting reducing equivalents across the mitochondrial membrane.
• ATP production in the electron transport chain generates most of the ATP during oxidative phosphorylation.

Maximal Lactate Steady State (MLSS)

• MLSS is the highest intensity at which lactate levels remain stable during exercise.
• As swimming speed increases during MLSS, lactate levels also increase.
• During recovery after exercise, lactate levels decrease rapidly.

Recovery and Lactate Removal

• The initial concentration of lactate at the end of exercise affects the rate of recovery.
• Active recovery with massage/stretching enhances lactate removal.
• The intensity range for cycling with minimal lactate buildup is 30-50% of VO2max, while for jogging it is 40-60% of VO2max.
• The purpose of lactate adaptation is to enhance lactate production and removal during high-intensity exercise.