The following article is by Ken Mannie
Head Strength & Conditioning Coach at Michigan State University
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The subject of explosive weight training is one that has been in the center
of a maelstrom among strength and conditioning practitioners for quite
some time. Many individuals and some associations advocate the use of
so-called explosive weight training movements, which purportedly offer
trainees a distinct advantage in speed and power development over those
who choose to incorporate more controlled movements.
It is also suggested by some that explosive weight training movements
prepare the body for the exorbitant, potentially traumatic forces of
competition more so than other strength training techniques.
For the purpose of this article, only the explosive lifts will be discussed.
These include-but are not solely restricted to-the Olympic lifts (i.e., the
snatch and clean and jerk), power clean, speed-squats, push jerks and
any variations of these movements. Basically any movement performed in
a rapid, jerky manner where momentum plays a key role in the execution
and or completion of the movement would be included.
The intent of this article is three-fold:
1) to elucidate the fact that ballistic weight training movements carry with
them the highest injury potential of any resistance exercises performed in
the weight room setting;
2) to dispute the erroneous notion that there exists a definitive
physiological or biomechanical mechanism by which ballistic weight training
movements result in a distinct and irrefutable advantage over controlled,
high tension resistance exercises in producing and/or enhancing speed,
power or athletic skill development; and
3) to offer safer more efficient and more productive training alternatives.
The Risk Factor
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It is a an accepted premise that all types of resistance modes and/or
ideologies will have a certain degree of risk attached to them. This
is why instruction and supervision are paramount in resistance training
programs, regardless of the lifting movements being performed. There
will also be contradictions regarding exercise prescription in isolated
cases due to past injuries, structural abnormalities and other physical
impediments. As with any physical activity, there exists an assumption
of risk with strength training and this is why the participants must
be well-schooled regarding lifting/spotting techniques and the myriad
of safety guidelines which are of utmost importance in the weight room
setting. With judicious care, the majority of the environmental risks
associated with the weight room can be effectively controlled.
However, the aforementioned ballistic lifts are immersed in inherent dangers
even when supervision and correct techniques are evident. There exists
a prepoderance of evidence (4,5,8,9,10,14,17,21,22,23,29,33,34,38)
indicating that so-called explosive weight training movements carry a
high risk of injury, both acutely and cumulatively, to muscle tissue,
fascia, connective tissue and bony structures. Westcott (38) states that
the acceleration and deceleration forces placed on involved tendons,
ligaments, muscle fascia and bone create both initial and terminal stresses
on these structures which are likely to produce training injuries.
Several of the lifts being examined here - primarily the Olympic lifts,
power cleans and their analogs - cause repetitive forced hyperextensions
of the lumbar spine. This forced hyperextension can lead to any number
of physical anomalies and injury defects including lumbar sprain, strain,
disc injury or a condition known as spondyloysis which consists of a
fracture of the pars interarticularis (an area between the superior
and inferior articulating facet on a single vertebra). Dangles et al. (3)
noted a 44% incidence of spondolysis in a group of 47 Olympic lifters,
while Kotani et al. (22) identified the condition in 30.7% of 26 male
lifters. It is important to note that these were *experienced lifters*.
Dr. Lyle Micheli, past president of The American College of Sports Medicine
(ACSM) has also indicated that ballistic weight training contributes to
spondolysis (14).
While the low back region is a major concern with regard to the injury
potential of these lifts, their nature embodies concern for other areas
of the body as well. Dr. Fred Allman, another past president of the ACSM,
has commented on numerous occasions on the danger in performing Olympic
lifts, as well as the hazards of introducing speed to weight lifting
movements. Dr. Allman has also stated that the performance of the
Olympic lifts provides little benefit to athletes in their training programs
for any sport other than Olympic lifting (9).
Kulund (23) has mentioned injuries to the wrist, elbow and shoulder while
performing Olympic lifts - injuries which were obviously related to the
acceleration and/or deceleration forces imposed on these areas.
Hall (17) concluded from her study on the clean and jerk that fast lifting
speeds generate dramatic increases in compressive force, shear force, torque
and myoelectric activity in the lumbar region.
Matt Brzycki, {who used to post to this newsgroup for anyone who didn't know
that} the Strength and Conditioning Coach at Princeton University, offers
this perspective:
"Using momentum to lift a weight increases the internal forces encountered
by a given joint: the faster a weight is lifted, the greater these forces
are
amplified - especially at the points of acceleration and deceleration. When
these forces exceed the structural limits of a joint, an injury occurs in
the muscles, bones or connective tissue. No one knows what the exact
tensile
strength of ligaments and tendons are at any given moment. The only way
to ascertain tensile strength is when the structural limits are surpassed"
(11).
Dr. Ken Leistner who has long excoriated ballistic lifting in training
programs, points out that the inclusion of these movements in strength
programs may, in fact be the genesis of injuries incurred later in
practise in games. As Dr. Leistner states, "...the continuous exposure
to acceleration/deceleration forces present when doing cleans, snatches
and jerks can produce tissue damage which literally is an *accident waiting
to happen*" (26). In younger athletes, the risks of damage to the
epiphyseal are on the bones is also a cause for concern, as complete
ossification may not take place until the late teens or older.
Some individuals take to task the injury potential of this type of weight
training by citing the Zemper et al. study (40), which looks at time-loss
injuries incurred in the weight room. These same individuals have
interjected, "Many of the exercises used by those players would be
considered speed-strength exercises...the average team can expect
one time-loss injury from the weight room every three years."
The unanswered questions, however, include:
1) How many of the injuries incurred were a result of *ballistic* training?;
2) This survey measured acute injuries; what about cumulative trauma which
was *aggravated* on the field and not attributed to the weight room?; and
3) Is *any* injury in the weight room acceptable?
Many proponents of explosive training ignore the *single most* vulnerable
area subected to the compressive and shear forces propagated by the majority
of the ballistic lifts - the lower back region.
Some authors have suggested that explosive weight training movements are
necessary in increasing the tensile strength of viscoelastic tissue as
well as increasing bone density and strength. While it has been shown that
progressive resistance training, in general, can accomplish these goals,
there exists *no* definitive scientific finding indicating that explosive
lifting induces a better adaption than high tension, velocity-controlled
repetitions - relative to the parameters of the repetition scheme, safe
range of motion, and controlled movement speed will strengthen the
aforementioned tissues without the introduction of unnecessary momentum
(6,7,11,15,21,25,26,31,32,38). You need not perform ballistic weight
training movements for injury prevention purposes ANY MORE THAN YOU NEED
TO POUND YOUR HEAD WITH A HAMMER IN ORDER TO PREPARE FOR A
CONCUSSION {my emphasis}
Contrary to the suggestions of some individuals, injuries do occur in
the weight room and have been documented in the literature
(5,9,10,29,33,34).
Many of these injuries can be directly contributed to ballistic lifting,
not merely the failure of the participants to comply to safety guidelines.
Also, it is categorically unacceptable to compare weight room injuries with
sports-related injuries and to subsequently state that there are fewer
injuries in the weight room. Strength training for athletes is NOT a sport,
nor is it an activity where injuries should be commonplace. The comparison
is ludicrious.
It should also be noted that certain sports, especially football, place
inherent technique stresses on the lumbar spine (16,18,19,26,36). In light
of this, performing ballistic lifts which have proven to be traumatic
to the same region is hardly the prudent thing to do. For example, the
Zemper study noted a total of 18 injuries involving either the lower
or upper back. The majority of the total injuries were incurred by
defensive
linemen and offensive linemen/tight ends (19 total). It would be
interesting
to note the type of lifting which was being performed when these injuries
were sustained, but the study fails to examine those important specifics.
Zemper states that the most likely explanation for the higher incidence of
injury positions is that "...they spend more time in the weight room and
generally are lifting more total weight" (40). Could the actuality that
these positions are also the ones most persistently directed by their
coaches to perform cleans, snatches, etc., be a factor as well?
The underlying tone of explosive lifting proponents, when discussing
injuries,
is that they are a part of athletics, therefore the fact that certain lifts
may carry inherent risks must be accepted. This thinking represents a
negligent haphazard approach in the training of athletes who are not
competitive weightlifters.
It is important to note that the American Orthopedic Society for Sports
Medicine, an organization which happens to distinguish between *strength
training* and *weightlifting* in it's position paper, contraindicates the
Olympic lifts in training regimens. Also, the ACSM, the world's
foremost authority on training protocol since being founded in 1954,
recommends safer movements in their position paper and makes no mention
of the inclusion of the Olympic lifts in training (6).
There is no question that the medical community needs to become more
actively involved in this controversy. It is my personal belief that,
with their continuous input, we will be able to slam the door on this
dangerous and unnecessary type of lifting for the general athletic
population.
Ballistic Weight Training is Unnecessary
----------------------------------------
It is the contention of explosive lifting proponents that ballistic lifting
movements are necessary in enhancing athletic performance in addition to
"simulation movement patterns and velocity and acceleration of many
sports movements." These claims are *not* supported with definitive,
conclusive research data. Some individuals make numerous "suggestions"
taken from its and pieces of the scientific literature which fit into
their ideology, but the smoking gun is nonexistent. At best, the
conflicting
data and/or lack of irrefutable findings on these matters render the
entire controversy inconclusive.
Some explosive lifting proponents have conceded that, "Slow movement speed
does not necessarily mean that an exercise is not explosive. A slow
movement may be considered explosive if the athlete applies maximal
force as rapidly as possible, although the weight moves slowly due to its
great inertia." If one performs a maximum or near maximum set of an
exercise within a given repetition range, this "controlled explosion"
will be in effect for the majority of the reps performed.
This type of training can be done with exercise machines, free weights
and the various velocity-controlled modes (i.e., isokinetic devices).
It is definitely a safer way to train and is a more efficient manner
in which to train.
ANY type of progressive strength training will elicit gains in muscle
hypertrophy and strength with concurrent enhancement in the contractile
properties of muscle tissue (6,8,11,27,39). However, high force/
low velocity movements produce longer periods of continuous muscle
tensition during both the concentric and eccentric phases, thereby
placing heavier demands on the target muscles (7,11,12,15,27,31,32,39).
There exists an inverse relationship between movement speed and muscle
force production, which dictates that maximal tension is developed at
slow velocities (though the "intent" to move rapidly is evident) and
decreases as the speed of contraction increases (7,8,12,15,27,31,32,38,39).
Low force/high velocity movements, are therefore less productive with
respect to maximal force production and concomitant strength development.
While there exists considerable controversy in the scientific literature
on the mechanisms of motor unit recruitment, the most widely accepted
precept is the "size principle" of activation (7,12,15,27,32,39,40).
Henneman (39) states that the size of the newly recurited motor unit
increases with the tension level at which it is recruited. Basically,
smaller motor units are recruited first, with successfully larger units
firing at increasing tension levels. Slow twitch units (Type I) ten
to be smaller and produce less overall force than the intermediate
and fast twitch units (Type II A, Type II AB, or Type II B). A major
difference in the speed of contraction between the Type I units and the
Type II units (including the intermediate Type II fibers) is the fact
that they have different degrees of myosin ATPase activity.
Myosin ATPase is intimately involved in the muscle contraction process
and the fibers that have more of this activity can contract more rapidly.
Also related to contractile speed is the fact that slow twitch fibers have
a very poorly developed sarcoplasmic reticulum when compared to fast
twitch fibers. This may help explain the response of slow twitch fibers to
stimulation, as the sarcoplasmic reticulum is important for the quick
release of calcium to trigger contraction. Couple this with the fact that
that the troponin of Type I fibers has a low affinity for calcium when
compared to the continuum of Type II fibers, and a clearer picture of
the differences in contraction capabilities surfaces.
There are also numerous metabolic differences between slow twitch and
fast twitch units, due to oxidative properties which dictate energy
production and endurance capacities (e.g., mitochondria supply, glycogen
stores, etc.).
The element most germane to this discussion, however is that of neural
innervation. Slow units are innervated by motor neurons that tend to
be much smaller - both in the diameter of their axons and in the size of
their cell bodies in the spinal cord - than that of fast motor units.
In addition, the net conduction velocity is much slower in the nerves of
slow motor units. These differences in innervation elicit a lower
threshold of activation in the slow motor units as compared to the
fast motor units. The net effect of this neural mechanism is that slow
units are recruited first for nearly all activities, regardless of
movement speed (7,8,11,15,27,32,39,40). It is only when the INTENSITY
of activation is very great or when the slow twitch units are fatigued
that the larger, more powerful fast motor units are brought into play.
Herein lies much of the controversy regarding fiber recruitment: Is
there a preferential recruitment of the fast motor units when fast
movement speeds are employed? Again, literature exists where
"implications" and/or "suggestions" are made in favor of
such an
occurence, but the preponderance of currently available data do not
support this viewpoint. Lesmes et al. (27) states that both muscle
fiber types are actively recruited during maximal muscular contractions,
regardless of the movement speed. The entire "size principle" of fiber
recruitment is predicated on *muscle force production* NOT the actual
*speed of movement*. Slow motor units are quite capable of inititating
fast speeds of limb movement if the force requirements are low. Therefore,
if the training goal is the recruitment and development of the fast
twitch muscle fibers, fast weight training speeds at low intensity
(i.e., high velocity/low resistance movements) represent the *least*
efficient approach. As stated by Pipes, "Speed of limb movement has
little to do with intensity. If anything there is an inverse
relationship...
you can have speed or you can have intensity; you cannot have both" (31).
Studies by Palmieri (30) and Wenzel et al. (37) measured training speed
and power development with no significant differences being found at
slow, fast or a combination of slow and fast speeds. The relevance
of these studies is in the conclusion of each that fast training speeds
are not needed for power improvements. If controlled speed is at least
as effective (if not more so) and safer than faster speed, wouldn't
the controlled movement speed be the more judicious option? More
importantly, if the safety and welfare of the athletes entrusted to
you truly superseded any personal preference or commercial bias in
training techniques, then the choice should be quite obvious.
"Movement specifity" is a term that has long been misinterpreted by
some explosive training proponents. To say that "the snatch and
clean are very similar to other athletic movements such as "jumping",
is to contradict many of the basic principles of motor learning.
First of all, a clear definition of "specificity" is in order. The
*encoding principle of specificity* states that the closer the influence
of the practise on the test context characteristics (i.e., the competition
situation), the better the practised movements will be recalled during
the test (1,2,28). Simply put, your practise drills, situations, etc.,
should mirror the conditions under which you will be tested. Performing
a certain type of lifting movement with the hope that it will transfer
to a sport-specific or position-specific task is *useless*. The
central nervous system acquires, stores and uses only meaningful
information when movement is required (28).
As once stated by Dr. Lyle Micheli, "...strength training has the potential
to improve size and strength; skill development is something different"
(25). That brief, candid statement says it all.
Perspective On Proper Strength Training
---------------------------------------
Strength training programs should be comprehensive in nature with the
emphasis placed on exercising the major muscle complexes throughout their
fullest range of functional motion. The selected movements should include
a variety of multi-joint and single-joint exercises, utilizing a good
mix of machines and free weights whenever possible, and be safe and
relatively easy to perform in terms of technique.
Set and repetition schemes can be varied, but the program should strive
for intense efforts, accurate record keeping, a system for progressive
overload and time efficiency. Movements requiring excessive momentum
for the execution and/or completion of the lift should be avoided.
Conclusion
----------
This article was not written for individuals who are firmly entrenched
in their thinking one way or another, but rather for those who are
seeking to compare training information in order to make a rational,
educated decision. It must be repeated and emphasized that any type
of progressive overload strength training will elicit gains in
muscular size and strength with concurrent enhancement in the contractile
properties of muscle tissue. However, I caution the reader not to fall
prey to the notion that there is a distinct advantage in producing
"explosive" athletes by training them with ballistic weight movements.
This erroneous proposition continues to be force-fed to the coaching
community by organizations and individuals who, because of prejudiced
thinking based on their backgrounds or vested interests, are married to
this close-minded philosophy.
It is my personal opinion that many of the articles written by explosive
training proponents are rife with ambiguous suggestions, one-sided
half-truths, and incomplete misinterpretations of the scientific literature.
If accepted as doctrine by those in the coaching ranks who are searching
for training information, it could contribute to a higher incidence of
weight room injuries - a situation that is totally unacceptable, both
professionally and ethically.
References
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Learning Retention and Transfer of Human Motor Skills", Psychological
Bulletin, 101, 41-74 (1985)
2. Adler, J. "Stages of Skill Acquisition: A Guide for Teachers",
Motor Skills: Theory Into Practise, (1982)
3. Aggrawal, N.D., et al., "A Study of Changes in Weight Lifters and
Other Athletes", British Journal of Sportsmedicine, 13, 58-61, (1985).
4. Alexander, M.J.L., "Biomechanical Aspects of Lumbar Spine Injuries
in Athletes: A Review", Canadian Journal of Applied Sports Sciences,
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and Prescription, 4th Edition, Lea and Febiger, (1991)
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8. Birk, T., Assistant Professor Dept. of Med. and Rehab. Medicine,
The Medical College of Ohio, Conversation and Correspondence, (1992)
9. Brady, T., et al., "Weight Training Related Injuries in the High
School Athlete", American Journal of Sportsmedicine, 10:(1), 1-5, (1982)
10. Brown, T., "Lumbar Ring Apophyseal Fracture in an Adolescent
Weightlifter", The American Journal of Sportsmedicine, 18:(5), (1990)
11. Brzycki, M., "A Practical Approach to Strength Training", Masters
Press, 2nd Edition, (1991)
12. Costill. D., et al., "Adaptions in Skeletal Muscle Following Strength
Training", Journal of Applied Physiology, 46: (1), 96-99, (1979)
13. Drowatzky, J.N., Chairman & Professor, Health Promotion and Human
Performance, The University of Toledo, Conversation, (1992)
14. Duda, M., "Elite Lifters at Risk of Spondylolysis", The Physician
and Sportsmedicine, 5:(9), 61-67
15. Enoka, R.M., "Muscle Strength and Its Development", Sports Medicine,
6: 146-168, (1988)
16. Hall, S., "Effect of Lifting Speed on Forces and Torque Exerted
on the Lumbar Spine", Medicine and Science in Sports and Exercise,
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Sportsmedicine, 3: 75-78, (1980)
19. Jackson, D.W., "Low Back Pain in Young Athletes: Evaluation of
Stress Reaction and Discogenic Problems", American Journal of
Sportsmedicine, 7:(6), 364-366 (1979)
20. Jackson, D.W., et al., "L
