VO2 Max, Muscle Contraction, and Energy Systems

Posted on Mar 17, 2025 in Biology

Factors Influencing VO2 Max

Several factors determine a person’s maximum oxygen consumption (VO2 max):

  • Inheritance
  • Muscle mass
  • Age
  • Sex
  • Training level
  • Motivation

Basic Formula for VO2 During Exercise

VO2 = Vs x HR x (a-v)O2 difference

  • VO2: Oxygen consumed by cells
  • Vs: Systolic volume
  • HR: Heart rate
  • (a-v)O2 difference: Arteriovenous oxygen difference

Gas Exchange and Dead Space

Underlying Physical Process of Gas Exchange

Diffusion in gas exchange.

Respiratory Dead Space

The respiratory system contains a volume of air that does not participate in gas exchange.

Arteriovenous Oxygen Difference

Reflects the difference between oxygen in arterial and venous blood, indicating oxygen extraction by tissues.

Mechanism of Muscle Contraction

The mechanism involves:

  1. ATP hydrolysis: ATP → ADP + Pi + Energy
  2. Calcium ions bind to troponin, exposing active sites on actin.
  3. Myosin heads bind to actin, using ATPase to power contraction.
  4. Calcium removal inactivates troponin, stopping contraction.

Motor Unit

A motor unit consists of a motor neuron and all the muscle fibers it controls.

Heat Transfer Mechanisms

The human body uses these mechanisms to maintain body temperature:

  • Radiation
  • Conduction
  • Convection
  • Evaporation

Hypothalamic-Pituitary Axis

The anterior pituitary is a small gland located below the hypothalamus in the brain. The hypothalamus secretes two hormones that, in turn, stimulate the pituitary gland to secrete growth hormone and prolactin.

ATP-PC System: Advantages and Disadvantages

Advantages

Rapid energy production, essential for short-duration, high-intensity activities.

Disadvantages

Limited energy reserves of ATP and PC, leading to significant oxygen debt.

Aerobic vs. Anaerobic Glycolysis

Anaerobic glycolysis provides a rapid supply of ATP without requiring O2, but it can only resynthesize a small amount of ATP from glucose. The presence of O2 inhibits the formation of lactic acid from pyruvic acid.

Oxygen Debt

When physical effort begins from rest, there’s an initial oxygen deficit. Components include O2, ATP-PC, and lactic acid.

Levels of Organization in Living Things

The levels, from lowest to highest, are:

  1. Atomic-Molecular Level: All living beings share a similar chemical composition of atoms and molecules (organic and inorganic).
  2. Cellular Level: Molecules combine to form cells, the basic unit of life. In unicellular organisms, this is the highest level of organization.