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November 2003 Vol.5 No.9   Conference/Workshop Calendar
 Editorial

The recent role of physical activity is changing rapidly in schools. It is very well known that regular physical activity provides many health benefits for participants. Despite the recent emphasis on physical activity in children, according to Surgeon General’s Report (2002), the increase in child obesity was recognized as a number one threat to the lives of children in the USA. 

Integration of health and fitness concepts into school curriculum with individual and lifetime activities as well as cognitive and affective development may promote to "Physically active and healthy life styles" for all youngsters. We believe that developmentally age appropriate plyometric training programs and Olympic lifts can be an essential parts of all physical education and athletic programs

Children and adolescents get many cardiovascular and musculoskeletal health benefits with participation to daily physical activities. One of the most frequently asked questions is about the risk of strength and resistance training for children. Contrary to beliefs research shows that youngsters are having significantly the benefits of plyometric exercises combined with resistance training (Faigenbaum, 2001; Faigenbaum & Chu, 2001). In addition, Faigenbaum and Chu state that participation to a plyometric training program may promote bone strength and weight control as wells as decreased risk of sport injuries if they are applied very well during preseason period.

Ferman Konukman
Andrew Jenkins
Coaching Section Editors


  Featured Article

"Plyometric Training for Children " Dangerous or Beneficial?

Dr. Ferman Konukman, Abant Izzet Baysal University, School of PE & Sports, Bolu, TURKEY

Dr. Andrew Jenkins, Central Washington University, Department of Health Human Performance & Recreation, Ellensburg, WA,

Considering the recent arguments by practitioners, researchers, and families on the risk and effectiveness of the plyometric training for children, the main purpose of this article is to provide practical guidelines and examples of plyometric exercises for children with an emphasize on developmentally appropriate physical education practices.

MECHANICAL PRINCIPLES OF PLYOMETRIC TRAINING

Plyometric exercises stimulate a muscle to reach maximal force in a short time period. Plyometric is a Greek terminology that has two meanings: Plio = more; Metric = to measure (Potach & Chu, 2000). Although this terminology is newly emphasized in training, It was first used by American track and field coach Fred Wilt to explain the training methodology of the Eastern European athletes during mid 70s (Woronczak, 1998).

Elastic energy and stretch reflex are the two mechanical and physiological basics of plyometric training. During exercise, elastic energy is produced when the muscle filaments have stretch on them with a tendency to return to their resting length. This type of muscle training leads to muscular force production and performance enhancement. The stretch-shortening cycle is the main cause of plyometric exercise and involves three phase (Chu, 1992; Potach & Chu, 2000; Woronczak, 1998)

Phase I is eccentric phase that provides a preloading against to agonist muscle groups. Eccentric phase stores the energy and the muscle spindles are stimulated. During a single leg hop, a foot placement on the ground until removal is a good example of this phase.

Phase II is amortization phase that involves the time period or pause between the eccentric and concentric phases. This is the most important period of plyometric training because if it is too long stored energy can be lost as a heat (Potach & Chu, 2000). Therefore, this phase should be very quick for quality of training program. During a single leg jump, the pause period before removal of foot from ground is an example of this phase.

Phase III is concentric phase in which body propels itself. Elastic energy stored during eccentric phase is the main cause of phase III with a muscle contraction

PHYSIOLOGICAL ADAPTATIONS TO TRAINING

There are three main physiological adaptations to plyometric training (Blazazevich, 2000):

First, plyometric training stimulates more motor units and greater tension. As a result of this, muscles reach a higher level of activation in the concentric phase of movement when the eccentric phase is performed.

Second, elastic energy is stored in the structures of muscle-tendon combination during eccentric phase. At the end this is recovered during concentric phase to produce muscle power output and movement efficiency.

Third, although speed and force of muscle contractions can still be improved after prolonged types of training such as resistance training. One of the advantages of Plyometric training is that providing both variability and overload to a training program.  This means that plyometric training provides a connection between resistance and speed training. Therefore, plyometric training has been widely accepted for development of speed and power.

Speed Stacks

 References

Blazevich, A. (2002). Plyometric training for PDHPE. [On-line] Available: www.members.ozemail.com.au/
~cjhay/pdhpe/conference2000/
anthonyblazevich/anthony.html

Chu, D. A. (2002). Plyometric training for youth. [On-line] Available: www.donchu.com/articles/
plyo_train_youth.html

Faigenbaum, A., & Chu, D. A. (2001-December). Plyometric training for children and adolescents. American College of Sport Medicine, Current Comment.

Faigenbaum, A. (2001). Strength training and children’s health. Journal of Physical Education Recreation and Dance, 72, (3), 24-30.

Potach, D. H., & Chu, D. A. (2000). Plyometric training. In T. R. Baechle, & R.W. Earle (Eds.). Essentials of strength training and conditioning. (pp. 427-470) Human Kinetics. IL: Urbana Champaign.

Surgeon General Report. (2002). Overweight and obesity fact sheet: Overweight in children and adolescents. [On-line] Available: www.surgeongeneral.gov/topics/obesity/
calltoaction/fact_adolescent.htm

Woronczak , M. (1998). Plyometric training for the lower limb. [On-line] Available: www.Alphalink.com.au/~zack/
exercise.html



Phi Epsilon Kappa
 Featured Article #1 Cont'd

PROGRAM DESIGN

Three important factors should be considered very carefully before any plyometric training for children (Blazevic, 2002).

First, plyometric training should not be start immediately at the beginning of semester. Four to five weeks period of pretraining with children emphasizing low impact to moderate running and jumping activities should be planned because this will help muscles and bones to strength sufficiently to cope with the real intense training and load during plyometric training.

Second, it is very important to have enough flexibility before performing any plyometric training because of the rapid stretching of muscles and tissues in the nature of plyometric training.  Therefore, flexibility training should be performed before plyometric training schedule.

Third, children with weight management problems should not force to perform intensive plyometric drills.

In addition to this, followings are highly recommended:

-Proper warm up activities should be performed before any plyometric training.

-Plyometric training should be performed early part of training before fatigue

-Plyometric training should not be performed after very high intensive training

Using the principles of training theory, the following guidelines adopted from Chu (2002) provides some information about designing affective and developmentally appropriate plyometric training for children.

Volume Of Training

  • If athletes are very young several session of practice should be organized to teach appropriate plyometric techniques
  • Proper performance and skill is much more important than number of repetitions
  • It is very important to have a pretraining plan according to traits of athlete and sport

Intensity Of Training

  • Maximal effort should be used after children had the proper execution of drills
  • Jumping from relatively lower heights can be used
  • Once the learning of appropriate skills occurred children can force maximal effort during training

Frequency Of Training

  • Maximal effort days need to perform twice a week during training period
  • 48-72 hours of recovery period should be provided between training days
  • Three days a week is appropriate for juniors if there is no competition at the end of week
  • If there is a competition in the week or at the end of week, this should be twice a week
  • If children having an active warm up as a part of each workout, 4-5 plyometric exercise could be included as a part of this warm up activity rather than having a separate work out for plyometric training

Resting Period

  • Full recovery should be provided between execution of repetitions
  • Without full recovery performance decrement will occurred
  • Plyometric training uses the ATP-PC and Anaerobic glycolytic systems. This systems needs brief but intense work periods followed by long active recovery periods
  • Walking, jogging, are active ways of recovery between sets

Progression

  • Progression of plyometric drills depends on the type or traits of sport that emphasized
  • Changing range of motion such as from 90 degree angle of motion to 120 degree
  • Increasing the intensity such as using different equipments in height or size

EXAMPLES

Plyometric training drills should be very sport specific and they are very helpful when the exercise similar to sport practiced. Using the framework of Blazevic (2002) examples of plyometric training should be categorized in three stages:

Stage 1:Low impact workouts. These exercised are performed two legs or arms such as double leg jumps for height, distance, double leg lateral jumps, single leg bounding, push ups, push ups with clap, light medicine ball forward throws and twits are good examples of stage one workouts for children.

Stage 2: Moderate impact workouts. These exercises are executed with one leg and have greater pre-stretch loads. Such as single leg jumps for height, distance, hopping for distance, standing triple jump, lateral bounding, overhead medicine ball throw, push up onto box or other equipments.

Stage 3: High impact workouts. These exercises are formation of pre-stretch loads. Such as single leg bounds onto obstacles, drop-jumps of a box for height, drop-jumps for distance, push-up over obstacles.

However, it is very important to emphasize that majority of sport events occurs in a dynamic environment that requires speed, strength and explosive power in a combination. Therefore, having quality and diverse training methods are necessary for plyometric training. At this point, plyometric-training drills can be taught in fun ways using obstacle games. Children can perform wide variety of plyometric drills around and above the objects.


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If you have ideas, comments, letters to share, or questions about particular topics, please email one of the following Coaching Section Editors:

Sporttime
 Featured Article #2

"Teaching The Olympic Lifts for Children"

Dr. Andrew Jenkins, Central Washington University, Department of Health Human Performance & Recreation, Ellensburg, WA,

Olympic lifts can be an essential program in physical education and athletic programs as long as youngsters trained age appropriate and modified equipment. This kind of developmentally appropriate Olympic lift programs can lead to injury prevention and safety for all youngsters in the gym. Therefore, the purpose of this article is to provide information about how to teach the Olympic lifts in a simple progression for physical education teachers and coaches.

Basic Principles

  • Begin each lifting lesson from the ground up.  For example, teach proper positioning beginning with the feet, legs, grip, elbows, shoulders, and head. 
  • Begin with low-level skills and work up to high level skills.
  • Always be prepared to use remedial work to bring a lifter back up to high-level skill.
  • Emphasize power, speed, and momentum not slow strength.

Perfect practice leads to perfect performance: Do not allow your lifters to develop bad habits that need to be "un-learned" later

Lesson 1 Addressing the Bar

ü     On all beginning, remedial, and advanced lifts the bar is "addressed" in the same manner:

ü     Place feet in the "jump" position.  Jump position is established by asking the lifter to close his eyes and perform a series of full effort vertical leaps.  Chalk the start position on the floor that yields the strongest, highest leap.

ü     bar is over the balls of the feet

ü     grip is pronated and overhand or hook grip..  No "monkey"( thumbless) grip! 

ü     hands are  snatch width (elbow width) or clean grip (shoulder width) is also acceptable for Olympic lifters)

ü     buttocks are down, low back is "set position,"

ü     elbows are always fully extended and never bent

ü     shoulders are slightly ahead of the bar

ü     head is face-forward or slightly up.

Lesson 2 Establishing Grip width on the Bar

Clean Grip:  For clean and jerk related exercises, the standard width is 'shoulder width."  This is established by having the lifter lean forward over the bar and allow her arms to dangle loosely from the shoulders.  Have the lifter grip the bars directly where the hands hang.  An inch or so in or outward should establish the most comfortable and powerful width.

Snatch Width:  For snatch related exercises the wide snatch grip is used.  Stand behind the lifter and have him laterally raise is elbows until his upper arms form a straight line and his forearms dangle vertically (resembling a scarecrow).  Mark his/her elbow positions on the bar.  Have lifter turn around and grasps the bar with his hands just outside of these marks.  Allow adjustments up to 2 inches wider grip for comfort and power.

Lesson 3  The Power Deadlift.

The lifter addresses the bar in the standard fashion.  The lifter uses the overhand or hook grip not the alternating grip used in powerlifting. Note that there is to be no flexion in the elbows (a common error) --the arms should remain perfectly straight.  Tell the lifter that her arms and hands are merely ropes attached to the bar.

Lesson 4  The Power Shrug

The power shrug can be performed with either the clean or the snatch width grips.  The lifter addresses the bar in the standard fashion.  From a normal standing position, the bar is shrugged forcefully until the shoulders are snugged up beside of the lifter's neck and ears.  Note that there is to be no flexion in the elbows--the arms remain perfectly straight.

Lesson  5 The Power Pull

The lifter begins with a strong power shrug and then continues the motion of the bar by flexing the elbows and power pulling the bar to mid-chest level.  Note that the athlete should employ rapid extension of the hips, legs, and feet to add to the momentum of the bar.  The upper-most position should have the lifter with his elbows high, bar in close to the chest, legs and ankles extended.  The lifter should lower the bar controlled and bring it to rest on his thighs.  Encourage rapid, explosive movement and full body, leg, and ankle extension.

Lesson 6a  Racking the Bar

The rack position is the finishing position of the clean.  Following the power pull phase of the clean, the lifter will dip his knees and "scoop" up the bar during the millisecond of "hang time" where the bar is neither traveling upward nor downward.  The bar should remain close to the lifter's chest as he dips and scoops.  From the side, the coach should see his elbows rotating rapidly counterclockwise around the bar as a pendulum might swing around an axis.  The most common mistakes in racking the bar are a) reverse curling the bar, b) hopping into a lateral "splits" with the legs.  Both of these errors are caused by a lack of dipping speed and depth.  The finishing position of a good rack has the lifter holding the bar tightly to his collarbones and resting on his frontal delts, elbows are out not down, wrists are fully extended.

Lesson 6b Snatching Overhead

A the top of the second pull (called the “hit”) and high pull phase the snatch lifter will drop rapidly into a squat and press himself down away from the bar.  The lifter should finish in a half squat with his arms fully extended overhead in a wide snatch grip.

The Jerk

The jerk lift is usually combined with the clean or power clean but can be used by itself.  The lift begins from the “rack" position.  The lifter bends his knees in a slight dip and then accelerates the bar from his chest using combined leg, glute, and shoulder force.  As the bar passes the lifter's face, he begins his split while pressing his body downward from the bar (as in the snatch) until his arms are extended fully overhead.   Recovery is performed by taking one or two baby-steps back with the lead leg until the lifter's feet are parallel.

Progression

Begin with the standard shoulder press.  Add weight and tell the lifter to now use his legs and "cheat" the weight up by accelerating the bar first with the legs, then the arms.  This is called Push Press.  When the push press is mastered, add in the split or a two-legged dip and you have a jerk.

Teaching the split

The jerk split serves to lower the lifter under the bar rapidly.  Begin with the lifter's feet in the jump position.  Have the lifter place one foot directly in front of the other.  Mark the toes 1 1/2 feet from the starting line (that's the lifter's foot not 12 inches!).  This is the mark he should hit with his lead leg during his split.  Practice rapid splitting from the jump to the split position while extending the arms rapidly overhead.

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