Neuromuscular Response

1
Neuromuscular Response

• Exercise training should incorporate some form of
  resistance training. Examples of walking stairs,
  body toning, and weight resistance training may
  all serve purpose based on state of
  deconditioning.
• Number of motor units recruited and their rate of
  firing or activation leads to maximal force
  potential.
• "Low threshold" MUs recruited first, usually
  along the order of the size principle. Factors
  modifying this principle are 1) inhibitory
  signals from CNS as a protective mechanism 2)
  inability to recruit high threshold units due to
  conditioning state.
• Functional performance of skeletal muscle plays
  major role in ability of individual to perform
  prescribed exercise program and limit daily
  living chore fatigue.

2
Influence of Fiber Type

• Most of the improvements we hope our clients make
  in conditioning might be restricted or enhanced
  by fiber type profile Fig. 3-17.
• If our client wants to dramatically increase
  endurance capacity for cycling, running, etc., we
  hope they possess a reasonable percentage of Type
  I oxidative motor units.
• Gains made in resistance training likewise may be
  accentuated in subjects with higher percentage of
  Type IIa IIb motor units.
• Typical subject would benefit from split or 50/50
  distribution. Reasonable Type I to succeed in
  endurance yet can expect effective gains in
  strength.
• Capacity for fiber type conversion.

3
Qualities of NM system

• Endurance deals with repeated contractions-maintai
  n some submaximal effort-what daily work duties
  might be
• Strength deals with maximal efforts-may be few
  and far between.
• Power-rate at which work is performedRate of
  force development might be best singular
  improvement in NM training- how rapidly you are
  able to activate your muscles force
  potential-why does this matter?

4
Hemodynamic Response

• HR and BP rise a function of what of 1-RM the
  person is exercising and to what extent an
  isometric component is present.
• Exaggerated response with arm exercise at same
  workload as legs, but similar under relative
  conditions.
• Stroke volume only increases during eccentric
  phase of lift with no change from rest with
  concentric lift

5
NM Adaptations

• Table 23.1 Lobby for use of resistance training
  with all exercise programs.
• Hypertrophy-enlargement of skeletal fibers-real
  interest is in what effect on functional
  capacity, especially in terms of minimum
  power/strength requirements?
• Change in oxidative state? Does this negatively
  impact functional status?
• Neural Adaptations-improved neural drive,
  synchronization of motor units, activation of
  contractile elements (excitation-coupling),
  inhibition of Golgi tendon organs. This may lead
  to a more efficient recruitment of motor units.

6
NM Adaptations

• Neuroendocrine Adaptations-growth hormone,
  insulin-like growth factor I, testosterone
  influence hypertrophy while cortisol
  catecholamines are catabolic hormones.
• Manipulate intensity, rest interval, volume of
  work to get desired response.
• Health-related benefits-Serum Lipids,
  cardiovascular function, bone density, Data
  typically mixed.
• Left ventricular mass-wall thickness increases,
  however the relative change is consistent with
  change in body size.