power

Examples of power in the following topics:

• Velocity and Duration of Muscle Contraction

  • The force-velocity relationship in muscle relates the speed at which a muscle changes length to the force of this contraction and the resultant power output (force x velocity = power).
  • Maximum power is generated at approximately one-third of maximum shortening velocity.
  • As velocity increases force and power produced is reduced.
  • Although force increases due to stretching with no velocity, zero power is produced.
  • Maximum power is generated at one-third of maximum shortening velocity.

• Force of Muscle Contraction

  • The force-velocity relationship in muscle relates the speed at which a muscle changes length with the force of this contraction and the resultant power output (force x velocity = power).
  • Maximum power is generated at approximately one-third of maximum shortening velocity.
  • As velocity increases force and therefore power produced is reduced.
  • Although force increases due to stretching with no velocity, zero power is produced.
  • Maximum power is generated at one-third of maximum shortening velocity.

• Muscular Atrophy

  • Muscle atrophy can occur from disuse (decreated activity) or disease, resulting in power loss or immobility.
  • Even minor muscle atrophy usually results in some loss of mobility or power.

• Membrane Potentials as Signals

  • The membrane potential allows a cell to function as a battery, providing electrical power to activities within the cell and between cells.
  • First, it allows a cell to function as a battery, providing power to operate a variety of "molecular devices" embedded in the membrane.

• The Role of the Kidneys in Acid-Base Balance

  • To maintain this narrow range of pH the body has a powerful buffering system.
  • The kidneys are slower to compensate than the lungs, but renal physiology has several powerful mechanisms to control pH by the excretion of excess acid or base.

• Energy Requirements

  • Cardiomyocytes contain large numbers of mitochondria, the power house of the cell, enabling continuous aerobic respiration and production of ATP, which is required for mechanical muscle contraction.
  • The heart derives energy from aerobic metabolism via many different types of nutrients. 60% of the energy to power the heart is derived from fat (free fatty acids and triglycerides), 35% from carbohydrates, and 5% from amino acids and ketone bodies from proteins.

• Muscle Fatigue

  • However, loss of desire to exercise in the face of increasing muscle soreness, respiration, and heart rate can have a powerful negative impact on muscle activity.
  • Depletion of required substrates such as ATP or glycogen within a muscle result in fatigue as the muscle is not able to generate energy to power contractions.

• Motor Units

  • For instance, thigh muscles, responsible for large powerful movements, can have a thousand fibers in each unit, while eye muscles, requiring small precise movements, might only have ten.

• Liposuction

  • Power-assisted liposuction (PAL) uses a specialized cannula with mechanized movement, so that the surgeon does not need to make as many manual movements .
  • The aspirating inner cannula reciprocates within the slotted outer cannula to simulate a surgeon's stroke of up to 5 cm (2 in) rather than merely vibrating 1–2 mm (1/4 in), as other power assisted devices, removing most of the labor from the procedure.

• Artificial Pacemakers

  • Since a pacemaker uses batteries, the device itself will need replacement as the batteries lose power.