Lactate Threshold & Acid–Base Balance

These flashcards cover key concepts related to lactate threshold and acid-base balance, critical for understanding physiological responses during exercise.

What is an acid?

An acid is a substance that donates hydrogen ions (H⁺) in solution, lowering pH.

What are examples of acids?

Lactic acid, carbonic acid, hydrochloric acid, phosphoric acid.

What is a base?

A base is a substance that accepts hydrogen ions (H⁺), raising pH.

What are examples of bases?

Bicarbonate, proteins, hemoglobin, phosphate.

What is a buffer?

A buffer is a weak acid/base system that resists changes in pH by binding or releasing H⁺.

What is the primary buffer reaction in blood?

H⁺ + HCO₃⁻ ⇄ H₂CO₃ ⇄ CO₂ + H₂O.

Where are intracellular buffers found?

In proteins, phosphate system, and carnosine.

Which buffer is most important in extracellular fluid?

Bicarbonate (HCO₃⁻) is the most important extracellular buffer.

How does ventilation (VE) affect acid-base balance during exercise?

VE regulates blood pH by removing CO₂, which is linked to H⁺ production.

What happens to pH during intense exercise?

H⁺ concentration increases, lowering pH.

What is lactate threshold (LT)?

The exercise intensity at which lactate accumulation exceeds clearance.

What is ventilatory threshold (VT)?

The point where VE increases disproportionately to VO₂.

How are LT and VT related?

LT and VT occur at nearly the same exercise intensity due to bicarbonate buffering.

Why is pH regulation important at rest and during exercise?

Low pH impairs enzyme function, muscle contraction, and ATP production.

What is the normal blood pH range?

7.35–7.45.

What physiological changes occur with high-intensity training?

Increased glycolytic enzyme activity, lactate production, and muscle buffering capacity.

How does training affect acid-base balance during exercise?

Training increases LT %VO₂max, bicarbonate buffering, and lactate clearance.

What does blood lactate testing measure?

It measures lactate levels to determine lactate threshold.

What does the Talk Test indicate about exercise intensity?

Inability to speak full sentences indicates near lactate threshold.

What is OBLA?

Onset of Blood Lactate Accumulation, defined at 4 mmol/L lactate.