Force-Velocity Relationship

Examples of Force-Velocity Relationship in the following topics:

• Velocity and Duration of Muscle Contraction

  • The shortening velocity affects the amount of force generated by a muscle.
  • 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).
  • Though they have high velocity, they begin resting before reaching peak force.
  • As velocity increases force and power produced is reduced.
  • Although force increases due to stretching with no velocity, zero power is produced.

• Force of Muscle Contraction

  • The force a muscle generates is dependent on its length and shortening velocity.
  • The force a muscle generates is dependent on the length of the muscle and its shortening velocity.
  • 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).
  • As velocity increases force and therefore power produced is reduced.
  • Although force increases due to stretching with no velocity, zero power is produced.

• Velocity of Blood Flow

  • A key first understanding is the difference between velocity and flow.
  • Velocity refers to the distance an object moves over time, for example in blood this measurement is often given as cm/sec.
  • Where F = flow, v = velocity and a = cross-sectional area.
  • Resistance is the force which  must be overcome by pressure in order for flow to occur and is a factor of vessel length, diameter and surface composition and the viscosity of the liquid flowing through.
  • As resistance increases the difference in pressure which influences velocity decreases which in turn reduces flow.

• Heart Murmurs

  • The term murmur only refers to a sound believed to originate within blood flow through or near the heart; rapid blood velocity is necessary to produce a murmur.
  • Abrupt standing or squatting may cause changes in murmur sounds, as does the valsalva maneuver, a forceful attempted exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose while pressing out as if blowing up a balloon.

• Ataxia

  • People with cerebellar ataxia may have trouble regulating the force, range, direction, velocity, and rhythm of muscle contractions.

• Exercise and Bone Tissue

  • Bones adapt to the muscle force loads placed on them, becoming thicker and stronger under stress/use and weaker and thinner when unused.
  • Muscle forces are a strong determinant of bone structure, particularly during the process of growth and development.
  • The gender divergence in the bone-muscle relationship becomes strongly evident during adolescence.
  • In females, growth is characterized by increased estrogen levels and increased mass and strength of bone relative to that of muscle; whereas in men, increases in testosterone fuel large increases in muscle, resulting in muscle forces that coincide with a large growth in bone dimensions and strength .

• Patellofemoral Stress Syndrome

  • The cause of pain and dysfunction often results from either abnormal forces or prolonged repetitive compressive or shearing forces (running or jumping) on the PF joint .
  • This image shows the relationship of the patella to the femur.

• Orthodontics

  • Soft, processed foods put less force on the developing jaw, resulting in a smaller jaw than would a diet of harder foods that requires more dental processing.
  • Orthodontics is the first specialty of dentistry that is concerned with the study and treatment of malocclusions (improper bites), which may result from tooth irregularity, disproportionate jaw relationships, or both.
  • Functional appliances, for example, are used in growing patients (age 5 to 14) with the aim of modifying the jaw dimensions and relationship if these are altered.

• Temporomandibular Joint Syndrome (TMJ)

  • Impaired tooth mobility and tooth loss can be caused by destruction of the supporting bone and by heavy forces being placed on teeth.
  • The movement of the teeth affects how they contact one another when the mouth closes; the overall relationship between the teeth, muscles, and joints can be altered.

• Male Sexual Response

  • The muscles of the pelvic floor, the ductus deferens (between the testes and the prostate), the seminal vesicles, and the prostate gland may begin to contract in a way that forces sperm and semen into the urethra inside the penis.
  • The relationship between erection and arousal is not one-to-one.