By Robert D. Paras, M.D.
Weight training or resistance exercise has been long accepted as a method of increasing strength and enhancing sports performance in the high-school age athlete, but what about the younger prepubescent child? Are there benefits to weight training in the elementary aged athlete? Will weightlifting increase a young child’s risk of injury? Will it adversely affect their growth?
Many measurable benefits may be gained with regular participation in a youth resistance training program. In addition to enhancing motor skills, weight training helps to strengthen bone, facilitate weight control, enhance one’s sense of well-being, and may also help improve one’s cardiovascular risk profile. In contrast, despite the fact that strength training is common practice in sports in which size and strength are desirable, scientific studies have failed to consistently show that improved strength enhances running speed, jumping ability, or overall youth sports performance. In addition, evidence is inconclusive that strength training programs help to prevent sports related musculoskeletal injuries in preadolescents and adolescents. Furthermore, there is no evidence that strength training will reduce the incidence of catastrophic sports-related injuries.
Strength training programs should not start until a child achieves good balance and postural control skills. This often occurs by eight years of age. Children should have a certain level of skill proficiency in their sport before investing in a strength training program, in order for the strength gains to have potential value. Lastly, children also need to be mature enough to accept and follow training instructions.
In pre-adolescents, resistance training enhances strength without concomitant muscle hypertrophy or enlargement. Such gains in strength can be attributed to neuromuscular “learning” whereby training increases the number of motor neurons that are “recruited” to fire with each muscle contraction. This increases the number of muscle connections per nerve, which increases muscle power. This mechanism accounts for the increase in strength in populations with low androgen concentrations, such as females and pre-adolescent boys. In contrast, strength training augments the muscle growth and enlargement that normally occurs with puberty in boys and girls.
Multiple studies have shown that strength training, with proper technique and strict supervision can increase strength in pre-adolescents and adolescents. Frequency, mode (type of resistance), intensity, and duration all contribute to a properly structured program. Increases in strength occur with virtually all modes of strength training lasting at least 8 weeks in duration, and can occur with training as little as once a week, although training twice a week may be more beneficial. Appropriately supervised programs emphasizing strengthening of the core (focusing on the trunk muscles such as the abdominal, low back, and gluteal muscles) are appropriate for children, and may benefit sports-specific skill acquisition and postural control. Unfortunately, gains in strength, muscle size, and power are lost 6 weeks after resistance training is discontinued; therefore, it may be desirable to maintain a regular exercise routine.
Strength training programs may include the use of body weight, elastic tubing, weight machines, and free weights. The amount and form of resistance used, as well as the frequency of resistance exercises, are determined by specific program goals. Explosive and rapid lifting of weights during routine strength training is not recommended, because safe technique may be difficult to maintain, and body tissues may be stressed too abruptly. Because of the limited research regarding prepubertal injury rates in competitive weightlifting, the American Academy of Pediatrics does not support participation in competitive lifting events by skeletally immature children, and is opposed to childhood involvement in power lifting, body building, or use of the 1-repetition maximum lift as a way to determine gains in strength.
With regards to injuries, muscle strains account for the majority of all strength-training injuries, with the hand, low back, and upper trunk being the most commonly injured areas. Most injuries occur on home equipment using unsafe techniques, and in unsupervised settings. Injury rates in settings with strict supervision and proper technique are lower than those that occur in other sports or in general recess play at school.
A limited number of case reports have raised concern about growth plate injuries in the wrist and in the spine from weight lifting in skeletally immature individuals. Such injuries are uncommon and are believed to be largely preventable by avoiding improper lifting techniques, maximal lifts, and improperly supervised lifts.
Strength training programs do not seem to adversely affect a child’s growth and do not seem to have any long-term detrimental effect on cardiovascular health. Young athletes with hypertension may experience further elevation of blood pressure from the isometric demands of strength training and need to be periodically monitored.
When a child or adolescent undertakes a strength training program, he/she should begin with low-resistance exercises until proper technique is perfected. When 8 to 15 repetitions can be performed, it is reasonable to add weight in 10% increments. Increasing the repetitions at lighter resistance may be performed to improve endurance strength of the muscles in preparation for repetitive-motion sports. Exercises should include all muscle groups, including the muscles of the core, and should be performed through the full range of motion at each joint. For achievement of gains in strength, workouts need to be at least 20 to 30 minutes long, take place 2 to 3 times per week, and should continue to add weight or repetitions as strength improves. Strength training 4 times per week seems to have no additional benefit, and may increase the risk for an overuse injury. Proper technique and strict supervision are mandatory for safety reasons and to reduce the risk of injury. Proper supervision is defined as an instructor-to-student ratio no more than 1:10 and approved strength-training certification of the instructor. Proper 10 to 15 minute warm-up and cool down periods with appropriate stretching techniques also are recommended.
Weight training in children clearly provides measurable benefits to the health of the prepubertal child as long as appropriate training guidelines are followed. Keep in mind that the vast majority of children are not developmentally ready or mature enough to participate effectively until approximately 8 to 10 years of age. In general children who want to improve sports performance will benefit more from practicing and perfecting the skills of their sport than from strength training alone. Strength training should be part of a multifaceted approach to exercise and fitness. Addition of an aerobic training program should be added for long-term health benefits.
General Youth Resistance Training Guidelines
• Provide qualified instruction and supervision
• Ensure the exercise environment is safe and free of
hazards
• Begin each session with a 5 to 10 minute dynamic
warm-up period
• Start with 1 set of 8 to 15 repetitions with a moderate
load with a variety of exercises
• Progress to 2 or 3 sets of 6 to 15 repetitions depending
on needs and goals
• Increase the resistance gradually (5% to 10%) as
strength improves
• Focus on the correct exercise technique instead of the
amount of weight lifted
• Resistance train 2 to 3 times per week on nonconsecutive
days
• Use individualized workout logs to monitor progress
• Keep the program fresh and challenging by
systematically varying the training program
top of page