The inclusion
of strength and power training as a component of a total sports training
program has become an integral component in the developmental process when coaching youth athletes.
Once believed to be ineffective for developing strength in the young athlete
and unsafe due to a high risk of injury, empirical
evidence and research has demonstrated that strength and power training
is not only safe and effective but also beneficial to a young athlete’s
health, performance, and general development.
To be successful an appropriate strength and power training must consider
the influences of body type, age, stage of physical development, sensitive
periods, level of performance, and prior or current training status.
The selection of an age-appropriate program along with methods and
means are
also dependent on the desired adaptations in physiology and performance,
as each will provide the young athlete with a specific training effect.
The purpose of this chapter is to provide the athlete, coach, trainer,
and parent with foundational information in regard to understanding
the adaptations
associated with the proper design and application of a strength and
power training program for young athletes.
Types of Strength and Power Training
A number of training methods are utilized in the design of strength and
power programs for young athletes. The following will provide a brief description
of the most common methods and their derivatives as they are used to develop
the young athlete.
Powerlifting
Powerlifting is a competitive strength sport; the goal is to lift the
most weight possible in a one repetition maximum lift. The competitive
lifts are limited to the squat, the bench press, and deadlift (97,8). Because
the methods utilized to develop the powerlifting athlete are specific to
developing maximal strength, many sports training programs will include
similar methods. Weights lifted in training and competition at a high level
frequently require lifting maximal and near-maximal loads in excess of
two to three times bodyweight (15).
Weightlifting
Weightlifting is frequently referred to as “Olympic weightlifting” to
distinguish it from the common term of weight lifting. Weightlifting is
a competitive, skilled power sport with a goal of lifting the most weight
possible in a one repetition maximum lift. The competitive lifts are limited
to the clean and jerk and the snatch (8, 97). Derivatives of the competition
lifts are frequently used to assist in the development of the competitive
lifts. Examples of the derivatives of the competitive lifts include the
power clean, power snatch, the jerk, and the push press. Because of the
higher power outputs developed and the mechanical specificity to many power-based
sports demonstrated in the competitive lifts and their derivatives, these
methods are frequently included in sports training programs (97).
Bodybuilding
Bodybuilding is a sport based on the aesthetic development of the skeletal
muscles. There are no competitive lifts in the sport of bodybuilding, although
it does rely primarily on the lifting of weights with the intention of
increasing muscular hypertrophy in a proportionate manner (8, 97). The
methods utilized to develop hypertrophy may be beneficial in the development
of some athletes as gains in muscle mass frequently result in increased
strength; however, hypertrophy alone is rarely beneficial. Theses methods
are rarely beneficial to very young athletes who lack the hormonal environment
necessary for muscle hypertrophy (34).
Strength Training
Strength training is a non-competitive use of progressive resistance exercise
in an effort to improve physical abilities such as strength, power, and
endurance (97). Body weight, elastic bands, free weights, and strength
training machines may provide resistances in such methods. Sports training
programs typically include a component of strength training with method
and exercise selection, dependent on the sport in question (8).
Plyometrics
Plyometrics, shock training, is a method of training designed to improve
explosive strength and rate of force development (8). Activities typically
emphasize the application of the stretch-shortening cycle that consists
of a lengthening muscle contraction providing enhancement to the immediately
following shortening contraction (51). Jumping, bounding, and medicine
ball throws can be considered plyometric forms of training.
Weight Training
Weight training is a non-competitive activity that utilizes methods similar
to strength training but tends to be less formalized training with a goal
of general conditioning (8). Body weight, elastic bands, free weights,
and strength training machines may provide resistances in such methods.
Physiological Concepts in the Programming of Strength Training for the
Young Athlete
A brief examination of scientific and popular literature clearly shows
an infinite variety of loading parameters and training strategies that
have been successful in increasing strength, power, and muscular hypertrophy
in an adult population. Because of physiological differences in the development
of children and adolescents, it cannot be assumed that exercise programming
which is successful for adults will be successful in younger athletes.
The following section will examine the physiological considerations in
the programming and organization of strength and power training exercises
in an effort to determine useful principles that coaches and trainers can
apply to their own programs utilized to improve performance and prevent
injury in young athletes.
Sensitive Periods
Physiological changes, in the muscular and nervous systems, progress in
a predictable manner throughout a young athlete’s growth and development
from childhood to adolescence (52). Because of this fact, there are periods
of development when a young athlete’s physiology is more adaptable to a
specific form of training stimulus. This period of training is most effective
when programming targets a specific ability that is developing rather than
one that is already matured (26). Drabik defines these periods of physiological
development as “sensitive periods.” He further stresses the importance
of these periods by indicating the result of not developing ability at
the optimal time will result in a permanent loss of fitness and athletic
potential (26, 54). Sensitive periods differ between males and females
due to the differing rates of biological development (26).
Muscular Hypertrophy Adaptations to Training
A young athlete will naturally gain muscle mass and strength as he or
she grows and develops via natural maturation processes. In comparing body
composition in children at 8 years of age and teenagers at 15 years of
age, 27% of the children’s body composition consists of muscle mass and
the teenagers’ body composition consists of 33% muscle mass (27). With
increasing natural body weight and total muscle mass, young athletes will
obviously demonstrate greater absolute strength (90).
The natural increases in muscle mass and body weight are typically associated
with the normal increases in anabolic hormones associated with puberty
and adolescence (52). These changes in muscle mass are typically more
pronounced in males than female to the larger secretion of testosterone
which is 10
to 30 times greater in males than females (52). The increase in muscle
mass can also be augmented via strength training in the 12-16 year old
age bracket (27).
Because of these hormonal differences in pubertal and adolescent athletes
compared to children, muscular hypertrophy with training may occur
(63), but is atypical.
For instance, in a comparison between ten year old gymnasts who had
undergone intensive gymnastics training and ten year old untrained
controls measurable,
but not significant, increases in maximum force and muscle mass were
indicated (40). It was also indicated that the measured increases
in force could
not be associated entirely with the gains in muscle cross-sectional
area (40), therefore, training programs designed to increase muscle
mass in
children are not typically recommended.
Neural Adaptations to Strength Training
In general, the younger the athlete the less able the athlete is able
to fully activate his or her neuromuscular system. (40, 4, 48, 39, 82).
Natural growth and development improves this ability as it has been shown
that adolescent males are better able to activate the nervous system than
prepubescent males (40). Comparisons to adults also show higher contractile
speeds in favor of the adults over children (4).
A summary of the neuromuscular limitations during maximum muscle action
in children in comparison to adolescents and adults is as follows:
• Longer electromechanical delay (time from onset of EMG activity to muscle
tension) (4)
• Less eccentric EMG activity for the same amount of concentric force
(82)
• Restricted eccentric capabilities (48)
• Decreased motor unit activation (39)
• Decreased muscle coordination (73)
In direct comparisons of strength-trained versus untrained athletes, the
strength-trained athletes demonstrate improved abilities that off-set these
limitations. A summary of the benefits of a strength training program for
young athletes are as follows:
• Increased motor unit activation (73, 40)
• Greater percent recruitment of fast-twitch motor units during maximum
voluntary contractions (40)
• Increased motor skill and coordination (73)
• Increased spatial and/or temporal recruitment of motor units (40)
As the potential for increased speed of movement, coordination, flexibility,
and technique is greatest during the early periods of athletic development
(27), the value and importance of a properly designed strength and conditioning
program becomes clear from these comparisons.