There has been so much discussion during recent Puzzles & Paradoxes
(P&Ps) on the nature of strength that a little further elaboration on this
topic may be appropriate:


THE NATURE OF STRENGTH

The design of a successful strength training programme depends on a thorough
understanding of the factors which influence the development of strength. The
next task is to determine which of these factors can be modified by physical
training and which methods do so most effectively and safely. Some of these
factors are structural and others, functional. Structural factors, however, only
provide the potential for producing strength, since strength is a neuromuscular
phenomenon which exploits this potential to generate motor activity.
        
It is well known that strength is proportional to the cross-sectional area of
a muscle, so that larger muscles have the potential to develop greater strength
than smaller muscles. However, the fact that Olympic weightlifters can
increase their strength from year to year while remaining at the same
bodymass reveals that strength depends on other factors as well.
        
The most obvious observation is that a muscle will produce greater
strength if large numbers of its fibres contract simultaneously, an event which
depends on how efficiently the nerve fibres send impulses to the muscle fibres.
Moreover, less strength will be developed in a movement in which the
different muscles are not coordinating their efforts. It is also important to note
research by Vredensky which has shown that maximum strength is produced
for an optimum, not a maximum, frequency of nerve firing (Vorobyev, 1978).
Furthermore, this optimal frequency changes with level of muscle fatigue
(Kernell & Monster, 1982).

DETERMINANTS OF STRENGTH

In general, the production of strength depends on the following major factors:

A. STRUCTURAL FACTORS

(a) The cross-sectional area of the muscle
(b) The density of muscle fibres per unit cross-sectional area
(c) The efficiency of mechanical leverage across the joint

B. FUNCTIONAL FACTORS

(d) The number of muscle fibres contracting simultaneously
(e) The rate of contraction of muscle fibres
(f) The efficiency of synchronisation of firing of the muscle fibres
(g) The conduction velocity in the nerve fibres
(h) The degree of inhibition of muscle fibres which do not contribute to the
       movement
(i) The proportion of large diameter muscle fibres active
(j) The efficiency of cooperation between different types of muscle fibre
(k) The efficiency of the various stretch reflexes in controlling muscle tension
(l) The excitation threshold of the nerve fibres supplying the muscles
(m) The initial length of the muscles before contraction

With reference to the concept of synchronising action among muscle fibres
and groups, it is important to point out that synchronisation does not appear to
play a major role in increasing the rate of strength production (Miller et al,
1981). Efficiency of sequentiality rather than simultaneity may be more
important in generating and sustaining muscular force, especially if stored
elastic energy has to be contributed at the most opportune moments into the
movement process. Certainly, more research has to be conducted before a
definite answer can be given to the question of strength increase with increased
synchronisation of motor unit discharge.

STRENGTH AND CONNECTIVE TISSUE

Besides its role in ballistic and rapid movements, connective tissue can also
increase the overall bulk of the muscle complex and aid it in producing usable
strength. Recently, it has been found that increases in the quality (or type) and
quantity of connective tissue may improve the transmission of force from
individual muscle fibres to the skeletal system.
        
For example, an insufficiently strong or extensive sheath of connective
tissue will allow the muscle to dissipate some of its force in a direction which
is perpendicular to its line of action and thereby lower its efficiency in
overcoming a load.
        
The connective tissues which are not structurally linked to the muscles,
such as those in the ligaments, joint capsules, skin and cartilages play the vital
role of passively stabilising the joints, facilitating contact between moving
parts and absorbing shock. The importance of this passive role should not be
forgotten in overall training, since it is pointless to develop bulk and strength if
the remainder of the musculoskeletal system is not equipped to handle the
increased strength. One must condition muscle, bone and connective tissue if
overall performance and safety is to be enhanced.
       
 Overemphasis on muscle strengthening at the expense of tendon and
other connective tissue strengthening can produce a muscle complex which is
prone to injury and inefficient in generating reactive strength. This is one of
the reasons why use of anabolic steroids can be harmful: this tends to
hypertrophy and increase the strength of the muscles relative to the tendons, so
that musculo-tendinous injuries become far more common among steroid
users.
        
Moreover, muscle tissue adapts to increased loading within several days,
whereas the connective tissues (such as tendons, ligaments and joint capsules)
or systems which contain a high proportion of connective tissue (such as bone
and cartilage) only display significant adaptation and hypertrophy after several
weeks or months of progressive loading (McDonagh & Davies, 1984). It is
vital that the prescription of training takes into account the different rates of
adaptation of all the systems involved and avoids overtraining the systems with
the slowest rates of adaptation. Gradual increase in training load and
avoidance of impulsive or explosive methods is essential for minimising the
occurrence of connective tissue soreness and injury, particularly during the
general physical preparation phase (GPP) and by relative novices to strength
training.
       
 It is important to note that most of the above factors underlying strength
production are functional rather than structural. Those determined by
efficiency of the nervous system are of fundamental concern to the
development of strength, since the muscular 'motors' are operated by
synchronised electrical impulses supplied to the muscles by the nerves.
  
Current preoccupation with the use of anabolic steroids to produce physical
bulk thus may be seen to be misplaced, unless bodybuilding bulk is the sole
objective. The development of specialised training regimes to enhance
nervous system conditioning would be scientifically and morally more
advisable, particularly in view of the side effects of drugs and the ethics of
their use.

REFERENCE

The above notes on the nature of strength are based on material from the
following textbook:

Siff MC & Verkhoshansky YV "Supertraining" 1996
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Dr Mel C Siff
School of Mechanical Engineering
University of the Witwatersrand
WITS 2050 South Africa
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