Sports Medicine: Just the Facts

preexercise states, after having borrowed ATP at the

beginning of exercise. This term, O 2 debt, was coined

by AV Hill in the early 1900s, but is transitioning to

excess postexercise oxygen consumption (see

below).

• Excess postexercise oxygen consumption:Excess
  postexercise oxygen consumption(EPOC), the inte-
  gral of VO 2 during recovery after the termination of
  exercise, consists of a fast and slow component. It is
  highly correlated with exercise intensity, and the fast
  portion may reflect resynthesis of stored PC and
  restoration of muscle and blood O 2 stores. The slow
  component may reflect elevated body temperature,
  catecholamines, accelerated metabolism (conversion
  of lactic acid to glucose/gluconeogenesis) and other
  hormonal/metabolic processes.

RESISTANCE EXERCISE

• Resistance exercise is used to improve muscular fit-
  ness, which is a combination of strength, endurance,
  and power. Strength is the greatest force a muscle can
  exert in one effort; endurance is the muscle’s ability to
  make repeated efforts; and power is a measure of how
  quickly muscular strength can be applied.

WEIGHTTRAININGPARAMETERS
•When training with weights, the magnitudes of
increase in muscle strength and endurance depend on
the specific training parameters: repetitions, sets,
volume, and intensity.

• Repetition maximum:The amount of force a subject
  can lift a given number of repetitions defines repeti-
  tion maximum(RM). For example, 1RM is the maxi-
  mal force a subject can lift with one repetition and
  5RM would be the maximal force someone could lift
  five times. Resistance training with weights represents
  isotonic strength.


• Repetitions:Repetitions reflect the number of con-
  secutive times a particular weight is lifted without a
  rest period. For examples, repetitions could be 5, 10,
  12, 25, or 50.


• Sets:The number of sets delineates how many times
  the repetitions are repeated after a rest period. For
  example, a training session could consist of three sets
  of 12 repetitions.


• Volume:Volume equates to the total number of times
  a weight was lifted (Sets ×Reps). For example, if the
  session was three sets of 12 repetitions, the volume
  would be 3 ×12 or 36 repetitions. Volume indicates
  how much work was done: the greater the volume, the
  greater the total work.
  
  
  • Intensity:Intensity reflects the actual resistance
    lifted, and is expressed as a percent of the maximum
    weight (1RM). If the 1RM for a particular exercise
    is 80 kg, then a weight of 40 kg would be a 50% and
    60 kg a 75% intensity.
  
  
  
  

RESISTANCETRAININGCONCEPTS

• SAID or Specific adaptation to imposed demand:
  The specificity principle states that physiological, neu-
  rological, and psychological adaptations to training are
  specific to the “imposed demand.” For example, to
  develop speed, power, and specific metabolic path-
  ways, the imposed demand must target those specific
  areas.


• Strength-endurance continuum:A weight training
  concept based on the premise that muscle strength and
  muscle endurance exist on a continuum, with muscle
  strength being 1RM and muscle endurance represent-
  ing the ability to exert a lower force repeatedly over
  time. Low numbers of repetitions (6–10 RM) are
  associated with increases in strength and high num-
  bers (20–100 RM) are associated with increases in
  endurance. As repetitions increase, there is a transi-
  tion from strength to endurance.


• Muscle hypertrophy:Compensatory growth in skele-
  tal muscle in response to a specifically imposed load.
  The primary components to muscle hypertrophy
  include a neural response, followed by an upregulation
  of second messenger systems to activate the family of
  immediate early genes that dictate the responses of
  contractile protein genes, and message passing down
  to alter protein expression.


• Muscle hypertrophy may take 2 months to begin. The
  new contractile proteins appear to be incorporated
  into existing myofibrils and there may be a limit to
  how large a myofibril can become: they may split at
  some point. Hypertrophy results primarily from
  growth of each muscle cell, rather than an increase in
  the number of cells.


• Muscle hypertrophy is observed in all three major
  fiber types (Types I, IIa, and IId(x/b) when low, but
  not high, numbers of repetitions are performed.
  Physiologic adaptations and performance are linked
  to both the volume and intensity of resistance training.

BIOMECHANICALFACTORS INMUSCLESTRENGTH

• Neural control, muscle cross-sectional area, arrange-
  ment of muscle fibers, muscle length, joint angle,
  velocity of muscle contraction, joint angular veloc-
  ity, strength-to-mass ratio, body size, joint motion
  (joint mobility, dexterity, flexibility, limberness, and
  range of motion), point of tendon insertion, and the
  interactions of these factors influence muscle
  strength.

44 SECTION 1 • GENERAL CONSIDERATIONS IN SPORTS MEDICINE