Strength & Conditioning for Kids: How and Why?

An overview for parents and physical therapists


Heather Williams, DPT
Rehabilitation Department
Hospital for Special Surgery


Introduction

The number of children participating in sports at early ages is higher than ever before. While it is important for children and young adults to engage in athletic activities, it is equally important to closely monitor their preparations for strength and conditioning training.

“Strength” in Numbers

  • 50% of boys and girls between the ages of eight and sixteen compete in an organized sports program sometime during the year.
  • 75% of junior high schools and middle schools have competitive interscholastic sports programs.
  • There are 32 male and 27 female competitive sports at the high school level, in which 7,000,000 high school students participate.

Beyond organized sports programs, millions more compete and participate in physical education classes, church and community intramural programs, and other recreational athletic activities.

(American Academy of Orthopaedic Surgeons brochure: The young athlete, 2002 Feb)


What is Strength Training?

Strength training, or resistance training, is a form of physical conditioning used to increase the ability to resist force. By increasing muscle strength, strength training can improve sports performance in young athletes. Different types of exercises are used in strength training in young athletes, including weight machines, free weights, and exercises which use a body’s own resistance. By using different combinations of exercise repetitions, ranging from one set of ten repetitions, to five sets of fifteen repetitions, young athletes can achieve increases in strength from 30-40% over an eight to twelve week training program.


How Does Strength Training Work in Young Athletes?

Prepubescent children cannot increase the amount and size of their muscles as adults can. When considering strength and conditioning training for children, an increase in muscle fiber size should neither be expected nor considered desirable.

It is thought that strength increase in children who participate in strength training involves changes in the muscle that already exists. A muscle works by nerve firing, and strength training in children and adolescents changes the way the nerves fire, such that more muscle fibers are activated by each nerve. This increases muscle strength in children without changing the composition of the actual muscle.


Who should participate?

Questions the parent and physical therapist need to consider before starting a child on a strength and conditioning program include:

  • Is the child of appropriate age?
  • Does the child believe it is worthwhile?
  • Does he or she want to participate?
  • Are they mature enough to listen and follow directions?
  • Do they work well in a group setting?

Since some children are very shy around other kids, it might be more beneficial for them to start their training in a one-on-one setting. However, particularly young children (six or seven years old) might have more fun in a group setting with kids their own age; in this environment, it becomes an after school activity with their friends rather than a weight training session.

Conversely, some of the older athletes (15-16 years old) who are particularly serious and looking to get a college scholarship may want more individual attention from a therapist. At any age, the child should be mature and be able to follow directions. First and foremost, the parent should know these things about their child before bringing them in for an initial evaluation, at which point the therapist does her own assessment.

The importance of the parents’ involvement in their child’s conditioning program cannot be overstated. It must be emphasized that if parents appear to be either aggressively involved to a fault (where it becomes apparent that the child is being forced to train excessively) or disinterested in their child’s regimen (where the child could be at risk of overworking themselves without supervision), then the conditioning should be stopped immediately.


Reasons for Participating

Reasons for participating in strength and conditioning training include:

  • Promotion of a healthy lifestyle:
      Physical well-being is also a state of mind, and physical exercise commonly facilitates the incorporation of other aspects of a healthy lifestyle into a comprehensive regimen. It can also aid in body composition and the loss of body fat, countering childhood obesity.
  • Injury prevention:
      Studies by the American College of Sports Medicine show that training may prevent injury from occurring during the sports season. Since kids are at risk of repetitive injury and physical overuse, body strengthening and education from the physical therapist, i.e., how to land from a jump or a rebound or to properly cut on the field can prevent injuries during and after game time. It also gives children a basic level of fitness by using a wide range of exercises to promote flexibility and coordination, decreasing the number of injuries.
  • Improvement of sports performance, physical fitness, and mental self-image:
      Perhaps most importantly, a child’s self esteem, self confidence, mental discipline, performance, and coordination can all be expected to improve as a result of strength and conditioning training.
  • Resistance to life-threatening conditions:
      Exercise and proper training also have a positive effect on a child’s cardiopulmonary/cardiorespiratory status and bone mineral density, helping to reduce the risk of serious illnesses in adulthood, such as heart disease and osteoporosis.
    (Janz, Kathleen F., Burns, Trudy L., Levy, Steven M., Torner, James C., Willing, Marcia C., Beck, Thomas J., Gilmore, Julie M., Marshall, Teresa A. Everyday activity predicts bone geometry in children: the iowa bone development study. Medicine & Science in Sports Exercise. (36)7:1124-1131)


Is Strength Training Safe for Kids?

In the right environment, and with proper supervision and technique, strength training for kids has been deemed safe and effective for kids and has been approved by the American College of Sports Medicine, the American Academy of Pediatrics, the American Society of Sports Medicine, and the National Strength and Conditioning Association.

The following are safety guidelines every parent and therapist must follow:

  • A qualified individual (physical therapist, Certified Strength and Conditioning Specialist [CSCS®], or athletic trainer) must be present.
  • There must not be too many other kids at the same session. The best ratios for training are one-on-one, -two, or -three, and there should never be more than three to four children to a trainer, especially in sessions for beginners.
  • Children should wear loose clothing and sneakers to train.
  • Set reasonable goals for each child, based on his or her desires and ability.
  • Perform aerobic exercise for 10 minutes before training begins.
  • Use different modes of training, including free weights, size-appropriate weight machines, body weight exercises, elastic bands, and medicine balls.
  • Start with six to eight exercises, 10 to 15 repetitions per set at a low weight level. Choose weight with which a child can succeed. Adults can spot children to help them finish a set.
  • Stress proper technique, rather than increased weight.
  • Rest between sets, and complete one to three sets, based on child’s needs.
  • Training should begin at an appropriate level, with adequate rest between exercises, to minimize injury and maximize fun. Proper form will decrease the risk of a soft-tissue injury.
  • Encourage use of workout cards, and review progress at each session.
  • Stress proper nutritional guidelines including the importance of calcium in a child’s diet.
  • Train in two to three sessions spread throughout the week.
  • Kids should use low weights and high repetition, with a qualified supervisor correcting their form and teaching them the proper technique. With proper early direction, children learn safety standards that can benefit them throughout their lives.

Contrary to prior understanding, new studies have shown that growth plates (the areas of primary growth at the ends of longer bones) in prepubescent children are not at high risk of epiphyseal fractures when the training adheres to these guidelines. Strength and conditioning training can actually enhance bone growth; the greatest amount of bone formation occurs during childhood, and strength training can serve to create stronger bones if done correctly and in the proper setting.

When considering competitive conditioning sports, including weight lifting (clean-and-jerk, snatch), power lifting (squat, bench press, dead lift), or bodybuilding (for esthetics), always consult the standards set by the American College of Sports Medicine, the American Academy of Pediatrics, the American Society of Sports Medicine, and the National Strength and Conditioning Association. Although these sources may have differing views on certain aspects of these controversial sports, it is important for every interested child and parent to be educated about the possible risks and benefits of competitive conditioning.


Is Strength Training Effective for Kids?

Studies: Then and Now

We now have a better understanding of the neurology behind muscle hypertrophy, and strength training in general, than was common 25-30 years ago. Studies done in the 1970s and 1980s which debunked the validity of strength training were later denounced by the American Academy of Pediatrics for using inaccurate parameters and excluding important studies on natural strength gained by children. For example, in the 1970’s, researchers didn’t realize that it took six weeks for the motor units to change in number and size.

Contemporary studies have altered that approach and have determined that children as young as six years old “can improve strength when following age-specific resistance training guidelines.”

(Benjamin, Holly J. MD; Glow, Kimberly M. MD, MPH, Strength training for children and adolescents. The Physician and Sports Medicine. 2003, Sept; (31)9)

Two studies used the twitch interpolation technique to determine the effects of changes in motor unit activation on strength increases in preadolescent boys when in a proper training environment. This technique involves delivering single electrical pulses to a muscle when the subject is at rest and while the subject attempts to produce a maximum voluntary contraction. The training sessions lasted ten weeks; when it was over, they saw a gain of 9% in the boys’ elbow flexors and 12% in their knee extensors. Strength gains were due to increased neuronal activation, intrinsic muscular adaptations, and motor coordination (learning). While muscle strength increased, the size of the muscle did not.

(Ramsay JA, Blimkie CJ, Sale DF, et al.. Strength training effects in prepubescent boys. Medicine & Science in Sports & Exercise. 1990; 22(5):605-614)

Movement Intelligence

An instinctual factor in sports, called “movement intelligence”, has also been shown to increase after a course of strength and conditioning training. Movement intelligence is when all the parts of the body learn to coordinate movement together in the most effective way. With proper training, this state is achieved with no conscious thought, e.g., when a basketball player jumps up for a rebound or when a baseball player swings at a pitch. The muscles involved with these movements and responses become more inherently and instinctually conditioned to react quickly and properly, resulting in increased ability and a reduced risk of injury. Since movement intelligence is learned, and since children tend to learn quickly at an early age, it is best to teach it as early as possible.

(Ramsay JA, Blimkie CJ, Sale DF, et al.. Strength training effects in prepubescent boys. Medicine & Science in Sports & Exercise. 1990; 22(5):605-614)


Beginning a strength and conditioning program

  1. Initial Intake
    1. Interview
      1. Interview the child and/or parents and fill out an initial intake form in order to individualize a training program based on the data gathered from his/her responses as well as his/her medical history.
      2. Have the parents sign a consent/waiver form.
      3. Take baseline measurements, such as height, weight, blood pressure, and resting heart rate.
    2. Physical Tests
      • Have the child perform a standing long jump to monitor the development of his/her elastic leg strength. Take the average of three attempts, and compare the results every eight weeks during the course of training.


        Standing Long Jump

      • They should also attempt other exercises such as push-ups and sit-ups (for one min. max).
      • Have the child perform a Step Test. A Step Test is an aerobic capacity test involving repeatedly stepping up and down on a box for three minutes to the beat of a metronome, with the height of the box corresponding to the child’s gender. The test score is weighed by age, weight, and gender, and is based on the child’s altered post-test blood pressure and heart rate.


        Step Test

      • Test their lower body strength on a single leg press weight machine, using 40-,50-, and 60% of their body weight. Have them achieve maximum repetitions until a feeling of fatigue sets in.


        Single Leg Press

      • Use other standardized tests, which may include the following: the Straight Leg raise, Thomas Test, Craig’s Test, 8” Forward Step Down, Single Leg Squat, and Landing from a Jump.


      Forward Step Down

    3. Formulate a Training Program
      1. Review the results of the interview and physical tests.
      2. Design a training program reflecting the needs of the individual athlete in relation to their particular sport.
      3. Follow up with re-evaluation after eight weeks or ten training sessions.

  2. Following Proper Guidelines
    • Stress quality over quantity.
    • Constantly assess safety and progress, i.e., watch all movements to give proper feedback, and progress in a safe and reasonable manner – not too much too soon.
    • Keep it fun and innovative.
    • Maintain a balance of work and rest – proper rest is essential.
    • Be mindful of bad habits and/or red flags:
      • Pain/chronic pain
      • Fatigue/chronic fatigue
      • Weight loss or gain
      • A feeling of being “burned out”

    If warning signs, bad habits, complaints, and/or red flags do arise, the physical therapist needs to question the child further to conclude if it is a temporary, resolvable issue (e.g., fatigue because the child was up late studying), or if it’s a real problem. If serious issues arise, the physical therapist is required to inform the child’s doctor and/or parents.

  3. Training session: see slides

    Warm-up:
    • Utilize traditional aerobics and static stretching (standing and sitting and holding) in tandem with dynamic exercise (such as jumps, walking lunges, shuttle runs, etc.). Studies now show that combining these exercises improves performance.
    • For beginners, start with body-weight exercises (as opposed to weight machines).
    • Constantly observe form and technique and provide verbal and tactile cues to get desired movement response.
    • Teach “prehabilitation” techniques, which prevent overuse injuries and balance range of motion, strength, coordination and stabilization, focusing on coordination and stabilization of the hips, stomach and back.

    Weight Machines:
    • Only use plate-loaded machines
    • Only allow low weight to start
    • Focus on high repetitions
    • Do reps or by time, e.g.. 30 seconds

    a. Core strengthening

    Every movement you do comes from your core – your rectus and transverse abdominus, deep internal stabilizers, back extensors, back stabilizers, and trunk rotational muscles are all part of your muscle core.

    Begin on a stable surface and progress to unstable surfaces, such as training with a physioball to improve balance.


    Core Strengthening Using Physioball

    b. Proprioception

    This training teaches athletes how to instinctively detect joint position and movement in space and to respond appropriately to variations in forces received either during or prior to initiation of a deleterious, or harmful, movement. Much of this training involves balance conditioning, and as the athlete’s skill improves, more stimuli are needed to continue improvement in this area.

    • For example, a gymnast does a back tuck in the air on a balance beam just a few inches wide. There is less than a second for her body to know where to land, and proprioception enhances her body’s ability to determine how to land with two feet safely on the beam.

    c. Neuromuscular Training

    Neuromuscular training teaches athletes to make the proper decisions in order to avoid injury. It enhances unconscious motor responses during movements, especially when jumping, landing, cutting, pivoting, hopping, and decelerating. Training this continual feedback control system improves one’s ability to utilize proprioceptive information.

    • For example, when a soccer player makes a quick motion, or “cuts”, to the left, s/he doesn’t want his/her leg down with a straight knee, because the anterior translation of the tibia onto the femur will strain the ACL (anterior cruciate ligament). Instead, neuromuscular training will condition the athlete to bend slightly at the knees before cutting.

    d. Plyometrics

    Plyometrics involve the rapid stretching of a muscle (eccentric phase) and the rapid shortening of the same muscle (concentric phase). Using this technique, the nervous system is conditioned to react more quickly to the stretch-shortening cycle, thereby increasing the speed of movement and improving power production. When plyometric activity is incorporated into their regimen, athletes improve their reaction time, and their overall strength improves -- they learn how to jump and leap higher, run faster, and throw farther. It also improves hand-eye coordination.

    • For example, plyometrics would give a track athlete the ability to “explode” out of the starting block.


      Using Plyometrics to Rapidly Stretch and Shorten Muscles Used for Jumping

    e. Sport specific training

    The following exercises should be tailored for each sport with the help of trained physical therapists:

    • Baseball/Swimming
      • Rotator cuff strengthening
      • Theraband rotation
      • Core strengthening
      • Plyometrics
    • Basketball/Soccer
      • ACL prevention strategies
      • Box jumps
      • Hamstring flexibility
        o Plyoback chest pass, using a trampoline and a weighted ball
      • Medicine ball rebounds against wall
    • Tennis/Volleyball
      • Intrinsic shoulder and scapular stabilization
      • Lateral agility training
      • Hand-eye coordination
    • Track and Field/Cross Country
      • Sports cord
      • Hip/glutes strengthening (to prevent knee stresses and injuries)

    f. Cool Down

    • Emphasize stretching
    • Encourage rehydration
    • Review the athlete’s Home Exercise Program
    • Answer any questions posed by kids and their parents


        Conclusion:

        Strength and conditioning training for children can be safe and effective when proper safety guidelines are met and each child’s program is designed appropriately and individually. A pre-training evaluation by a personal trainer is necessary, along with a post-training evaluation, and the child must be supervised throughout the course of the training by the trainer. Likewise, the child’s parents must take an active interest in the regimen without resorting to forceful excess. The quality of each training session should be stressed over the quantity of sessions, and when applicable, the training should be as sport-specific as possible. Most importantly, a child undergoing strength and conditioning training should never stop having fun doing it.

        Posted: 9/15/2005

        summary by Mike Elvin