tiramisu
10-08-2010, 09:14 AM
What is Strength Really?
by Mel Siff
Extracts from PTonthenet
Date Released : 02 Feb 2002
Some years ago while I was on the mechanical engineering staff at my former
university (University of Witwatersrand, S Africa), I was asked if I could
co-supervise the research of a postgraduate student from the physiotherapy
department, because she had opted to study changes in strength with certain
types of conditioning and one of my specialisations is the biomechanics of
strength.
My first questions to her were: "What type of strength do you wish to study and
how are you going to measure it?". Her response was one of amazement. After all
isn't all strength the same? Isn't strength just the ability of the body to
produce maximum force? Wouldn't it just be measured with some isokinetic machine
like the 'Cybex'? I attempted to explain that strength is not that simple, even
though everyone appears to have a very adequate intuitive grasp of the concept.
Furthermore, I stressed that strength as measured isokinetically does not
necessarily relate directly to strength as exhibited in real sport. During the
hours that we spent discussing this issue, this poor student expressed her utter
frustration that, despite having studied all about strength during her basic
degree at a top university, she had never been taught any of the finer details
of what strength really is.
This student's experience is by no means unique. From my involvement with
thousands of other students, personal trainers and coaches throughout the world,
I have found that the full scope of strength and strength training is very
superficially understood and that many struggle to define strength beyond the
belief that it "is the ability of the body to produce maximum force." While some
may think that accurate definitions are pedantic and unnecessary, it is
essential to point out that what is left out of a simplistic definition may be
precisely what hinders you from fully understanding and applying any given
method of training and testing...
Let us first correct that basic definition that strength is the ability of the
body to produce maximum force. It is not! Strength is the ability of the body to
produce force; the ability of the body to produce maximum force is maximum
strength. Even then, this implies that strength is some sort of general property
of human capability, which totally ignores the fact that strength depends on the
way in which it is produced or measured. After all, we frequently are exposed to
arguments about who is the strongest type of person - the weightlifter, the
powerlifter, the wrestler, the footballer, the manual labourer, the Highland
Games contestant, a world Strongman competitor....?
If we are quite objective we have to recognise that there is no universal way of
proving strength superiority because one may be strong in one test, but
relatively weak in another. It is apparent that the production of "strength"
depends on the test, the movements involved, motor skill, the duration of the
test, the weight of the person, and several other such factors. In short, all
strength is contextual or situational.
So what does one generally do when a client approaches you to develop sport
specific"strength", "functional strength", "core strength" or rotator cuff
strength? Well, you design a programme based upon your personal education and
experience, often almost reflexively choosing to use Olympic lifting methods,
circuit training, machine training, HIT ("High Intensity Training"), plyometrics
and so forth, depending more often on personal bias than a thorough, objective
analysis of what is involved.
Your client might be an experienced athlete like a gymnast, boxer or martial
artist who challenges you with the very real point that most of the best
performers in their sports never use weights, so how can doing a power clean,
balancing on a ball or using a resistance machine really improve their sport
specific strength? Anecdotes about all the results you have achieved may be to
no avail because your client might detect that you do not fully understand the
nature of the specific forms of strength (and power) required. This is yet
another reason why it is vital to understand the whole spectrum of what strength
really is.
DEFINING STRENGTH
Accurately speaking, strength is the result of muscular action initiated and
orchestrated by electrical processes in the nervous system of the body.
Classically, it may be defined as "the ability of a given muscle or group of
muscles to generate muscular force under specific conditions." Thus, "maximal
strength" is the ability of a particular group of muscles to produce a maximal
voluntary contraction in response to optimal motivation against an external
load. This strength is usually produced in competition and may also be referred
to as the "competitive maximum strength." It is not the same as "absolute
strength", which Dr Zatsiorsky calls "maximum maximorum strength", the maximum
of all maxima, and which usually is associated with the greatest force which can
be produced by a given muscle group under involuntary muscle stimulation by, for
example, electrical stimulation of the nerves – supplying the muscles or
recruitment of a powerful stretch reflex by sudden extremes of loading.
For practical purposes, "absolute strength" may be regarded as roughly
equivalent to maximal eccentric strength, which is difficult or impractical to
measure, because a maximum by definition refers to the limit point preceding
structural and functional failure of the system. Thus, it is apparent that
special feedback mechanisms, like governors in a mechanical engine, exist in the
nervous system to prevent a muscle from continuing to produce force to the point
of mechanical failure. This is why it probably would be more practical to use
the "maximum explosive isometric strength" (produced under so-called maximum
plyometric conditions or explosive thrusting against an isometric maximum load)
as an approximation to absolute strength. To prevent confusion, we also need to
note that the term "absolute strength" sometimes is used to define the maximum
strength which can be produced irrespective of one's body mass.
It is also vital to recognise a "training maximum" or training 1RM (single
repetition maximum), which is always less than the competition maximum in
experienced athletes, because optimal motivation invariably occurs under
competitive conditions. Zatsiorsky states that the training maximum is the
heaviest load which one can lift without great emotional excitement, as
indicated by a very significant rise in heart rate before the lift. It is
noteworthy that, in the untrained person, involuntary or hypnotic conditions can
increase strength output by up to 35%, but by less than 10% in the trained
athlete. The mean difference between training maximum and competitive is around
12% in experienced weightlifters, with larger differences being exhibited by
lifters in heavier weight classes.
The merit of identifying the different types of strength or performance maximum
lies in enabling one to prescribe training intensity more efficiently. Intensity
is usually defined as a certain percentage of one's maximum and it is most
practical to choose this on the basis of the competitive maximum, which remains
approximately constant for a fairly prolonged period. The training maximum can
vary daily, so, while it may be of value in prescribing training for less
qualified athletes, it is of limited value for the elite competitor.
It is relevant to note that competitions involve very few attempts to reach a
maximum, yet they are far more exhausting than strenuous workouts with many
repetitions, since they involve extremely high levels of psychological and
nervous stress. The high levels of nervous and emotional stress incurred by
attempting a competitive maximum require many days or even weeks to reach full
recovery, even though physical recuperation would appear to be complete much
quicker. So this type of loading is not recommended as a regular form of
training.
In other words, any attempt to exceed limit weights requires an increase in
nervous excitation and interferes with the athlete's ability to adapt, if this
type of training is used frequently. In attempting to understand the intensity
of loading prescribed by the apparently extreme Bulgarian coaches who are
reputed to stipulate frequent or daily use of maximum loads in training, one has
to appreciate that training with training maxima (which do not maximally stress
the nervous system) is very different from training with competitive maxima
(which place great stress on nervous processes).
Strength is a relative phenomenon depending on numerous factors, so it is
essential that these conditions are accurately described when strength is being
assessed. For instance, muscular strength varies with joint angle, joint
orientation, speed of movement, muscle group and type of movement, so it is
largely meaningless to speak of "absolute strength" without specifying the
conditions under which it is generated. Sometimes, the term "relative strength"
is introduced to compare the strength of subjects of different body mass. This
is a topic we will address a little later.
It is also useful to recognise that one may define isometric, concentric and
eccentric strength maxima, since every sport requires distinct levels of each
one of these types of maximum. As a matter of interest, these maxima given in
order of magnitude are: eccentric, isometric, concentric, which most of us
already know from training experience - we can always handle between 25-40
percent more load during the eccentric phase of most movements.
STRENGTH AND FITNESS
Now that we have dissected strength in greater depth we can define "fitness"
("the ability to cope effectively with a given stress") in more detail. Fitness
comprises a series of interrelated structural and functional factors, which
conveniently may be referred to as the basic S-factors of fitness (Siff,
"Supertraining"): Strength, Speed, Stamina (general endurance or local muscular
endurance), Suppleness (flexibility), Skill (neuromuscular efficiency),
Structure (somatotype, size, shape) and Spirit (psychological preparedness).
Within the scope of skill, there is also a fitness quality known as Style, the
individual manner of expressing a particular skill.
We can now construct a comprehensive model of physical fitness from the
functional motor elements of fitness, as shown in Figure 1.
The diagram illustrates that strength, endurance and flexibility may be produced
statically or dynamically, unlike speed, which changes along a continuum from
the static to the dynamic state. However, this convenient picture could be
expanded by including the "quasi-isometric" state, which can influence
production of any of the motor qualities at very slow speeds. For this and other
reasons, this model should be viewed as one that represents or describes rather
than scientifically analyses.
The quality of flexibility has been placed at the centre of the base of the
pyramid, because the ability to exhibit any of the other qualities generally
depends on existence of some range of movement (ROM). It should be noted that
static or dynamic flexibility refers to the maximum ROM that may be attained
under static or dynamic conditions, respectively. The line joining all adjacent
pairs of primary fitness factors depicts a variety of different fitness factors
between each of the two extremes. The model thus allows us to identify an
extended list of fitness factors, as follows (the factors bearing an asterisk
are various types of special strength):
• Static strength*
• Static strength-endurance*
• Dynamic strength*
• Dynamic strength-endurance*
• Strength-speed*
• Speed-strength*
• Speed-strength endurance*
• Strength-speed endurance*
• Speed
• Endurance
It is sometimes convenient to identify various flexibility qualities, namely:
• Flexibility (static and dynamic)
• Flexibility-strength*
• Flexibility-endurance
• Flexibility-speed
A series of skill-related factors may also be identified, although it should be
noted that skill forms an integral part of the process of exhibiting all of the
above fitness or motor qualities:
• Skill
• Strength-skill*
• Flexibility-skill
• Speed-skill
• Skill-endurance
All of the primary and more complex fitness factors should be viewed as
convenient descriptors of qualities which are involved in different proportions
in a particular physical activity. Nevertheless, this pyramidal model enables us
to understand sport specific fitness and training far more effectively than with
a simplistic model based only on the primary functional fitness factors of
strength, endurance, speed and flexibility.
One may also consider the concept of "relative strength" (e.g., how much you
lift divided by your bodyweight), especially since a client may grow stronger in
terms of absolute strength, but her bodymass may also increase, so that in
relative terms, she has grown weaker. The improvement in other fitness factors
relative to bodymass may also be highly relevant. For instant, "relative power"
(power per unit bodymass) is very important in cases where the athlete has to
increase power without increasing bodymass (e.g. a weightlifter or boxer in a
specific bodymass division). In sports which require the athlete to increase
muscle endurance without increasing bodymass, "relative endurance" needs to be
enhanced. In this case, one might even distinguish between "relative static
endurance" and "relative dynamic endurance". Depending on the sport, improvement
of "relative speed-strength endurance" (or relative strength endurance) under
repeated cyclic or acyclic conditions, may also be relevant.
Some of the above terms may require elaboration. For example, "static
strength-endurance" refers to muscle endurance under isometric conditions;
"strength-speed" and "speed-strength" describe power produced under heavily
loaded and very lightly loaded conditions, respectively; "speed-strength
endurance" refers to the ability to produce great power continuously without
serious decrement; "flexibility-speed" refers to flexibility which must be
exhibited at high speed; and "speed-skill" refers to an action which must be
produced skillfully at high speed.
STRENGTH FACTORS IN ACTION
So far, we have discussed different types of strength or strength qualities as
components of fitness, but it is also very informative to analyse strength at
the level of individual actions. This is best done by studying the curve of how
the force changes with respect to time for any given movement, such as the
idealised and simplified graph in Figure 2
Analysis of this curve reveals several characteristics associated with the
production of strength, some of which we have not discussed yet, namely:
1. Starting Strength
2. Acceleration-Strength
3. Rate of Force Development (RFD)
4. Explosive Strength (Maximum RFD)
5. Maximum Strength
6. Strength-Endurance
7. Deceleration Strength
Here, "starting-strength" refers to the ability of the muscles to develop force
at the beginning of the working contraction before external movement occurs and
is always produced under conditions of isometric muscle action. This fact alone
has important consequences for strength training, because it dispels the opinion
that the once-popular method of isometric training should be completely
abandoned in modern training. On the contrary, the ability to generate starting
strength rapidly can exert a profound effect on the dynamics of an entire
movement, not only in terms of the magnitude of the impulse, but also regarding
the psychological sensation of "lightness" that it creates during the crucial
initial stage of a highly resisted movement. "Acceleration-strength", describes
the ability to quickly achieve maximal external muscle force once dynamic
movement has begun.
"Explosive Strength" characterizes the ability to produce maximal force in a
minimal time. It is most commonly displayed in athletic movements when the
contraction of the working muscles in the fundamental phases of the exercise is
preceded by mechanical stretching (such as any plyometric, throwing, kicking,
striking or rebounding action in many sports). In this instance, the switch from
stretching to active contraction uses the elastic energy of the stretch to
increase the power of the subsequent contraction. Mathematically, it is given by
the maximum value of the slope of the force-time curve (where this slope is
called the Rate of Force Development, RFD).
"Strength-Endurance" characterizes the ability to effectively maintain muscular
activity under work conditions of long duration. In sport this refers to the
ability to produce a certain minimum driving force for a prolonged period.
(Examples: any longer sprint events in running, cycling, swimming for dynamic
strength-endurance, and any prolonged grappling in wrestling and scrumming in
rugby for static or quasi-isometric strength-endurance).
"Deceleration-Strength" refers to the ability to slow down any movement whenever
necessary, especially as a joint is reaching its end of range of movement. It
occurs under eccentric conditions and frequently is called into play by
reflexes, which are activated to prevent injury to the joints. It is vital that
this quality be adequately developed in anyone who takes part in any rapid,
ballistic or powerful sports, as well as in "plyometric" or rebound training,
because many injuries can result from inefficiency in slowing down or halting a
forceful movement.
If the load is near maximal, then the initial slope of the Force-Time curve is
small and the time taken to produce movement is prolonged. This requires the
exhibition of the motor quality of "static strength-endurance", (Examples:
wrestling or rugby scrumming) as opposed to "dynamic strength-endurance", which
refers to the muscle endurance required to maintain movement over a given
interval (Examples: gymnastics, track running, longer sprint swimming ). This
quality may be involved in carrying out a set of repetitions with a load or by
maintaining cyclic work of various intensities
Suppose that we now wish to use this information to compare the performances of
two different athletes in executing the same exercise. Athlete A may not be able
to produce the same maximum force as athlete B, but he can produce his maximum
faster than A, so that if they are to compete against one another in a contact
sport, A may well defeat B in very short duration, explosive encounters. In
general, if the sport concerned requires rapid Rate of Force Development, then
athlete A will often have the advantage. This quality is essential in any sports
that involve jumping, hitting or throwing, such as basketball, martial arts,
American football and track-and-field. In this case, any training aimed at
increasing B's maximal strength or bulk will be misdirected, because he needs to
concentrate more on
explosive strength (RFD) training. If the sport requires a high maximal force or
a large amount of momentum to be exerted irrespective of time (Examples: as in
powerlifting or prolonged scrummaging or strongman contests), then athlete B
will prove to be superior. In such a situation, athlete A will not improve
unless he trains to increase maximal strength.
THE NATURE OF STRENGTH
It is our final task to briefly examine some of the physiological and anatomical
features that explain the phenomenon of strength, since the design of a
successful strength training programme depends on a thorough understanding of
the factors which influence strength development. The 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. (this means that maximum strength
production is not necessarily the result of activating as many muscle fibres as
possible, but just the right quantity in a given situation at a given time).
Furthermore, this optimal frequency changes with level of muscle fatigue.
DETERMINANTS OF STRENGTH
In general, the production of strength depends on the following major factors:
1. Structural Factors
• The cross-sectional area of the muscle
• The density of muscle fibres per unit cross-sectional area
• The efficiency of mechanical leverage across the joint
2. Functional Factors
• The number of muscle fibres contracting simultaneously
• The rate of contraction of muscle fibres
• The efficiency of synchronisation of firing of the muscle fibres
• The conduction velocity in the nerve fibres
• The degree of inhibition of muscle fibres which do not contribute to the
movement
• The proportion of large diameter muscle fibres active
• The efficiency of cooperation between different types of muscle fibre
• The efficiency of the various stretch reflexes in controlling muscle tension
• The excitation threshold of the nerve fibres supplying the muscles
• 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. 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. What this
means in simple terms is that it often used to used to be believed that
synchronising several muscle groups to operate at the same time was more
important than how the different muscle actions followed one another in
producing force. Research has now shown that the way in which muscle actions
follow one another in a given movement may even be of greater or equal
importance in this regard. 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 firing.
CONCLUSION
I trust that this short overview of what I struggled to condense into a
voluminous textbook ("Supertraining") has conveyed some of the exquisite
complexity and deeper nuances of the quality of strength which has been admired
since time immemorial and which has captured the attention of many of us today.
It will have achieved its goals if it in some measure enables readers to improve
their ability to work more effectively and appreciatively in the world of
strength training and rehabilitation. My personal fascination with strength
training began when I was a young student at university wishing to enhance my
track and field performances, a quest which led to my becoming a competitive
weightlifter and ultimately a career which wedded my sporting affection with my
postgraduate studies in biomechanics and physiology. Not for one moment did I
imagine that those elementary forays into Olympic weightlifting would lead to
the International Olympic Council (IOC) inviting me to write a major chapter for
one of its volumes, which is published to coincide with every Olympic Games. In
fact, much of the information that I am sharing here is based upon that chapter
("Biomechanical Foundations of Strength and Power Training" in Biomechanics in
Sport, edited by Zatsiorsky, 2000). May the quest for a better understanding and
application of human strength bear similar rewards for all of you!
REFERENCES
Siff M C Supertraining 2000 This 500 page textbook contains all of the
references upon which this article was based.
Zatsiorsky V Science and Practice of Strength Training 1994
Supertraining Web Forum. The archives of this list contain many articles that I
and others have written on many aspects of strength as art and science. It is a
free educational service, which anyone may join at:
http://groups.yahoo.com/group/Supertraining/ (http://groups.yahoo.com/group/Supertraining/)
=======================
Jamie Carruthers
Wakefield, UK
by Mel Siff
Extracts from PTonthenet
Date Released : 02 Feb 2002
Some years ago while I was on the mechanical engineering staff at my former
university (University of Witwatersrand, S Africa), I was asked if I could
co-supervise the research of a postgraduate student from the physiotherapy
department, because she had opted to study changes in strength with certain
types of conditioning and one of my specialisations is the biomechanics of
strength.
My first questions to her were: "What type of strength do you wish to study and
how are you going to measure it?". Her response was one of amazement. After all
isn't all strength the same? Isn't strength just the ability of the body to
produce maximum force? Wouldn't it just be measured with some isokinetic machine
like the 'Cybex'? I attempted to explain that strength is not that simple, even
though everyone appears to have a very adequate intuitive grasp of the concept.
Furthermore, I stressed that strength as measured isokinetically does not
necessarily relate directly to strength as exhibited in real sport. During the
hours that we spent discussing this issue, this poor student expressed her utter
frustration that, despite having studied all about strength during her basic
degree at a top university, she had never been taught any of the finer details
of what strength really is.
This student's experience is by no means unique. From my involvement with
thousands of other students, personal trainers and coaches throughout the world,
I have found that the full scope of strength and strength training is very
superficially understood and that many struggle to define strength beyond the
belief that it "is the ability of the body to produce maximum force." While some
may think that accurate definitions are pedantic and unnecessary, it is
essential to point out that what is left out of a simplistic definition may be
precisely what hinders you from fully understanding and applying any given
method of training and testing...
Let us first correct that basic definition that strength is the ability of the
body to produce maximum force. It is not! Strength is the ability of the body to
produce force; the ability of the body to produce maximum force is maximum
strength. Even then, this implies that strength is some sort of general property
of human capability, which totally ignores the fact that strength depends on the
way in which it is produced or measured. After all, we frequently are exposed to
arguments about who is the strongest type of person - the weightlifter, the
powerlifter, the wrestler, the footballer, the manual labourer, the Highland
Games contestant, a world Strongman competitor....?
If we are quite objective we have to recognise that there is no universal way of
proving strength superiority because one may be strong in one test, but
relatively weak in another. It is apparent that the production of "strength"
depends on the test, the movements involved, motor skill, the duration of the
test, the weight of the person, and several other such factors. In short, all
strength is contextual or situational.
So what does one generally do when a client approaches you to develop sport
specific"strength", "functional strength", "core strength" or rotator cuff
strength? Well, you design a programme based upon your personal education and
experience, often almost reflexively choosing to use Olympic lifting methods,
circuit training, machine training, HIT ("High Intensity Training"), plyometrics
and so forth, depending more often on personal bias than a thorough, objective
analysis of what is involved.
Your client might be an experienced athlete like a gymnast, boxer or martial
artist who challenges you with the very real point that most of the best
performers in their sports never use weights, so how can doing a power clean,
balancing on a ball or using a resistance machine really improve their sport
specific strength? Anecdotes about all the results you have achieved may be to
no avail because your client might detect that you do not fully understand the
nature of the specific forms of strength (and power) required. This is yet
another reason why it is vital to understand the whole spectrum of what strength
really is.
DEFINING STRENGTH
Accurately speaking, strength is the result of muscular action initiated and
orchestrated by electrical processes in the nervous system of the body.
Classically, it may be defined as "the ability of a given muscle or group of
muscles to generate muscular force under specific conditions." Thus, "maximal
strength" is the ability of a particular group of muscles to produce a maximal
voluntary contraction in response to optimal motivation against an external
load. This strength is usually produced in competition and may also be referred
to as the "competitive maximum strength." It is not the same as "absolute
strength", which Dr Zatsiorsky calls "maximum maximorum strength", the maximum
of all maxima, and which usually is associated with the greatest force which can
be produced by a given muscle group under involuntary muscle stimulation by, for
example, electrical stimulation of the nerves – supplying the muscles or
recruitment of a powerful stretch reflex by sudden extremes of loading.
For practical purposes, "absolute strength" may be regarded as roughly
equivalent to maximal eccentric strength, which is difficult or impractical to
measure, because a maximum by definition refers to the limit point preceding
structural and functional failure of the system. Thus, it is apparent that
special feedback mechanisms, like governors in a mechanical engine, exist in the
nervous system to prevent a muscle from continuing to produce force to the point
of mechanical failure. This is why it probably would be more practical to use
the "maximum explosive isometric strength" (produced under so-called maximum
plyometric conditions or explosive thrusting against an isometric maximum load)
as an approximation to absolute strength. To prevent confusion, we also need to
note that the term "absolute strength" sometimes is used to define the maximum
strength which can be produced irrespective of one's body mass.
It is also vital to recognise a "training maximum" or training 1RM (single
repetition maximum), which is always less than the competition maximum in
experienced athletes, because optimal motivation invariably occurs under
competitive conditions. Zatsiorsky states that the training maximum is the
heaviest load which one can lift without great emotional excitement, as
indicated by a very significant rise in heart rate before the lift. It is
noteworthy that, in the untrained person, involuntary or hypnotic conditions can
increase strength output by up to 35%, but by less than 10% in the trained
athlete. The mean difference between training maximum and competitive is around
12% in experienced weightlifters, with larger differences being exhibited by
lifters in heavier weight classes.
The merit of identifying the different types of strength or performance maximum
lies in enabling one to prescribe training intensity more efficiently. Intensity
is usually defined as a certain percentage of one's maximum and it is most
practical to choose this on the basis of the competitive maximum, which remains
approximately constant for a fairly prolonged period. The training maximum can
vary daily, so, while it may be of value in prescribing training for less
qualified athletes, it is of limited value for the elite competitor.
It is relevant to note that competitions involve very few attempts to reach a
maximum, yet they are far more exhausting than strenuous workouts with many
repetitions, since they involve extremely high levels of psychological and
nervous stress. The high levels of nervous and emotional stress incurred by
attempting a competitive maximum require many days or even weeks to reach full
recovery, even though physical recuperation would appear to be complete much
quicker. So this type of loading is not recommended as a regular form of
training.
In other words, any attempt to exceed limit weights requires an increase in
nervous excitation and interferes with the athlete's ability to adapt, if this
type of training is used frequently. In attempting to understand the intensity
of loading prescribed by the apparently extreme Bulgarian coaches who are
reputed to stipulate frequent or daily use of maximum loads in training, one has
to appreciate that training with training maxima (which do not maximally stress
the nervous system) is very different from training with competitive maxima
(which place great stress on nervous processes).
Strength is a relative phenomenon depending on numerous factors, so it is
essential that these conditions are accurately described when strength is being
assessed. For instance, muscular strength varies with joint angle, joint
orientation, speed of movement, muscle group and type of movement, so it is
largely meaningless to speak of "absolute strength" without specifying the
conditions under which it is generated. Sometimes, the term "relative strength"
is introduced to compare the strength of subjects of different body mass. This
is a topic we will address a little later.
It is also useful to recognise that one may define isometric, concentric and
eccentric strength maxima, since every sport requires distinct levels of each
one of these types of maximum. As a matter of interest, these maxima given in
order of magnitude are: eccentric, isometric, concentric, which most of us
already know from training experience - we can always handle between 25-40
percent more load during the eccentric phase of most movements.
STRENGTH AND FITNESS
Now that we have dissected strength in greater depth we can define "fitness"
("the ability to cope effectively with a given stress") in more detail. Fitness
comprises a series of interrelated structural and functional factors, which
conveniently may be referred to as the basic S-factors of fitness (Siff,
"Supertraining"): Strength, Speed, Stamina (general endurance or local muscular
endurance), Suppleness (flexibility), Skill (neuromuscular efficiency),
Structure (somatotype, size, shape) and Spirit (psychological preparedness).
Within the scope of skill, there is also a fitness quality known as Style, the
individual manner of expressing a particular skill.
We can now construct a comprehensive model of physical fitness from the
functional motor elements of fitness, as shown in Figure 1.
The diagram illustrates that strength, endurance and flexibility may be produced
statically or dynamically, unlike speed, which changes along a continuum from
the static to the dynamic state. However, this convenient picture could be
expanded by including the "quasi-isometric" state, which can influence
production of any of the motor qualities at very slow speeds. For this and other
reasons, this model should be viewed as one that represents or describes rather
than scientifically analyses.
The quality of flexibility has been placed at the centre of the base of the
pyramid, because the ability to exhibit any of the other qualities generally
depends on existence of some range of movement (ROM). It should be noted that
static or dynamic flexibility refers to the maximum ROM that may be attained
under static or dynamic conditions, respectively. The line joining all adjacent
pairs of primary fitness factors depicts a variety of different fitness factors
between each of the two extremes. The model thus allows us to identify an
extended list of fitness factors, as follows (the factors bearing an asterisk
are various types of special strength):
• Static strength*
• Static strength-endurance*
• Dynamic strength*
• Dynamic strength-endurance*
• Strength-speed*
• Speed-strength*
• Speed-strength endurance*
• Strength-speed endurance*
• Speed
• Endurance
It is sometimes convenient to identify various flexibility qualities, namely:
• Flexibility (static and dynamic)
• Flexibility-strength*
• Flexibility-endurance
• Flexibility-speed
A series of skill-related factors may also be identified, although it should be
noted that skill forms an integral part of the process of exhibiting all of the
above fitness or motor qualities:
• Skill
• Strength-skill*
• Flexibility-skill
• Speed-skill
• Skill-endurance
All of the primary and more complex fitness factors should be viewed as
convenient descriptors of qualities which are involved in different proportions
in a particular physical activity. Nevertheless, this pyramidal model enables us
to understand sport specific fitness and training far more effectively than with
a simplistic model based only on the primary functional fitness factors of
strength, endurance, speed and flexibility.
One may also consider the concept of "relative strength" (e.g., how much you
lift divided by your bodyweight), especially since a client may grow stronger in
terms of absolute strength, but her bodymass may also increase, so that in
relative terms, she has grown weaker. The improvement in other fitness factors
relative to bodymass may also be highly relevant. For instant, "relative power"
(power per unit bodymass) is very important in cases where the athlete has to
increase power without increasing bodymass (e.g. a weightlifter or boxer in a
specific bodymass division). In sports which require the athlete to increase
muscle endurance without increasing bodymass, "relative endurance" needs to be
enhanced. In this case, one might even distinguish between "relative static
endurance" and "relative dynamic endurance". Depending on the sport, improvement
of "relative speed-strength endurance" (or relative strength endurance) under
repeated cyclic or acyclic conditions, may also be relevant.
Some of the above terms may require elaboration. For example, "static
strength-endurance" refers to muscle endurance under isometric conditions;
"strength-speed" and "speed-strength" describe power produced under heavily
loaded and very lightly loaded conditions, respectively; "speed-strength
endurance" refers to the ability to produce great power continuously without
serious decrement; "flexibility-speed" refers to flexibility which must be
exhibited at high speed; and "speed-skill" refers to an action which must be
produced skillfully at high speed.
STRENGTH FACTORS IN ACTION
So far, we have discussed different types of strength or strength qualities as
components of fitness, but it is also very informative to analyse strength at
the level of individual actions. This is best done by studying the curve of how
the force changes with respect to time for any given movement, such as the
idealised and simplified graph in Figure 2
Analysis of this curve reveals several characteristics associated with the
production of strength, some of which we have not discussed yet, namely:
1. Starting Strength
2. Acceleration-Strength
3. Rate of Force Development (RFD)
4. Explosive Strength (Maximum RFD)
5. Maximum Strength
6. Strength-Endurance
7. Deceleration Strength
Here, "starting-strength" refers to the ability of the muscles to develop force
at the beginning of the working contraction before external movement occurs and
is always produced under conditions of isometric muscle action. This fact alone
has important consequences for strength training, because it dispels the opinion
that the once-popular method of isometric training should be completely
abandoned in modern training. On the contrary, the ability to generate starting
strength rapidly can exert a profound effect on the dynamics of an entire
movement, not only in terms of the magnitude of the impulse, but also regarding
the psychological sensation of "lightness" that it creates during the crucial
initial stage of a highly resisted movement. "Acceleration-strength", describes
the ability to quickly achieve maximal external muscle force once dynamic
movement has begun.
"Explosive Strength" characterizes the ability to produce maximal force in a
minimal time. It is most commonly displayed in athletic movements when the
contraction of the working muscles in the fundamental phases of the exercise is
preceded by mechanical stretching (such as any plyometric, throwing, kicking,
striking or rebounding action in many sports). In this instance, the switch from
stretching to active contraction uses the elastic energy of the stretch to
increase the power of the subsequent contraction. Mathematically, it is given by
the maximum value of the slope of the force-time curve (where this slope is
called the Rate of Force Development, RFD).
"Strength-Endurance" characterizes the ability to effectively maintain muscular
activity under work conditions of long duration. In sport this refers to the
ability to produce a certain minimum driving force for a prolonged period.
(Examples: any longer sprint events in running, cycling, swimming for dynamic
strength-endurance, and any prolonged grappling in wrestling and scrumming in
rugby for static or quasi-isometric strength-endurance).
"Deceleration-Strength" refers to the ability to slow down any movement whenever
necessary, especially as a joint is reaching its end of range of movement. It
occurs under eccentric conditions and frequently is called into play by
reflexes, which are activated to prevent injury to the joints. It is vital that
this quality be adequately developed in anyone who takes part in any rapid,
ballistic or powerful sports, as well as in "plyometric" or rebound training,
because many injuries can result from inefficiency in slowing down or halting a
forceful movement.
If the load is near maximal, then the initial slope of the Force-Time curve is
small and the time taken to produce movement is prolonged. This requires the
exhibition of the motor quality of "static strength-endurance", (Examples:
wrestling or rugby scrumming) as opposed to "dynamic strength-endurance", which
refers to the muscle endurance required to maintain movement over a given
interval (Examples: gymnastics, track running, longer sprint swimming ). This
quality may be involved in carrying out a set of repetitions with a load or by
maintaining cyclic work of various intensities
Suppose that we now wish to use this information to compare the performances of
two different athletes in executing the same exercise. Athlete A may not be able
to produce the same maximum force as athlete B, but he can produce his maximum
faster than A, so that if they are to compete against one another in a contact
sport, A may well defeat B in very short duration, explosive encounters. In
general, if the sport concerned requires rapid Rate of Force Development, then
athlete A will often have the advantage. This quality is essential in any sports
that involve jumping, hitting or throwing, such as basketball, martial arts,
American football and track-and-field. In this case, any training aimed at
increasing B's maximal strength or bulk will be misdirected, because he needs to
concentrate more on
explosive strength (RFD) training. If the sport requires a high maximal force or
a large amount of momentum to be exerted irrespective of time (Examples: as in
powerlifting or prolonged scrummaging or strongman contests), then athlete B
will prove to be superior. In such a situation, athlete A will not improve
unless he trains to increase maximal strength.
THE NATURE OF STRENGTH
It is our final task to briefly examine some of the physiological and anatomical
features that explain the phenomenon of strength, since the design of a
successful strength training programme depends on a thorough understanding of
the factors which influence strength development. The 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. (this means that maximum strength
production is not necessarily the result of activating as many muscle fibres as
possible, but just the right quantity in a given situation at a given time).
Furthermore, this optimal frequency changes with level of muscle fatigue.
DETERMINANTS OF STRENGTH
In general, the production of strength depends on the following major factors:
1. Structural Factors
• The cross-sectional area of the muscle
• The density of muscle fibres per unit cross-sectional area
• The efficiency of mechanical leverage across the joint
2. Functional Factors
• The number of muscle fibres contracting simultaneously
• The rate of contraction of muscle fibres
• The efficiency of synchronisation of firing of the muscle fibres
• The conduction velocity in the nerve fibres
• The degree of inhibition of muscle fibres which do not contribute to the
movement
• The proportion of large diameter muscle fibres active
• The efficiency of cooperation between different types of muscle fibre
• The efficiency of the various stretch reflexes in controlling muscle tension
• The excitation threshold of the nerve fibres supplying the muscles
• 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. 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. What this
means in simple terms is that it often used to used to be believed that
synchronising several muscle groups to operate at the same time was more
important than how the different muscle actions followed one another in
producing force. Research has now shown that the way in which muscle actions
follow one another in a given movement may even be of greater or equal
importance in this regard. 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 firing.
CONCLUSION
I trust that this short overview of what I struggled to condense into a
voluminous textbook ("Supertraining") has conveyed some of the exquisite
complexity and deeper nuances of the quality of strength which has been admired
since time immemorial and which has captured the attention of many of us today.
It will have achieved its goals if it in some measure enables readers to improve
their ability to work more effectively and appreciatively in the world of
strength training and rehabilitation. My personal fascination with strength
training began when I was a young student at university wishing to enhance my
track and field performances, a quest which led to my becoming a competitive
weightlifter and ultimately a career which wedded my sporting affection with my
postgraduate studies in biomechanics and physiology. Not for one moment did I
imagine that those elementary forays into Olympic weightlifting would lead to
the International Olympic Council (IOC) inviting me to write a major chapter for
one of its volumes, which is published to coincide with every Olympic Games. In
fact, much of the information that I am sharing here is based upon that chapter
("Biomechanical Foundations of Strength and Power Training" in Biomechanics in
Sport, edited by Zatsiorsky, 2000). May the quest for a better understanding and
application of human strength bear similar rewards for all of you!
REFERENCES
Siff M C Supertraining 2000 This 500 page textbook contains all of the
references upon which this article was based.
Zatsiorsky V Science and Practice of Strength Training 1994
Supertraining Web Forum. The archives of this list contain many articles that I
and others have written on many aspects of strength as art and science. It is a
free educational service, which anyone may join at:
http://groups.yahoo.com/group/Supertraining/ (http://groups.yahoo.com/group/Supertraining/)
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Jamie Carruthers
Wakefield, UK