Strength Training For Children
Introduction The efficacy, benefits and possible risk associated with strength training for children has been a topic of great interest for the past decade among scientists, physicians, coaches, young athletes and their parents. The aims of this review are to draw attention to a number of recent studies reporting on the benefits of strength training for children, and dispel some old myths that have resulted in disputation. More and more children are preparing for rigorous sports competition with strength training. The term strength training Tanner (1993) refers the use of one’s own body weight, barbells, dumbbells or machines to promote muscular strength and improve athletic performance. For children as for adults the principle of progressive overload is the key. The term child refers to prepubescent, male or female subjects. Prepubescence: Schafer (1991) time from early childhood to onset of secondary sex characteristics. From a scientific perspective Blimkie (1992) states that the very nature of the studies conducted relating to strength training and children vary in terms of the sport and athletic background of the subjects and the total volume of work (product of frequency and intensity of training, and the number of repetitions and sets of exercise) completed during the course of training. These differences in training approach have contributed to some of the uncertainty and controversy regarding strength training during childhood.
Effectiveness of Strength Training in Children In a Meta Analysis of 28 studies on the effectiveness of resistance training in children Falk & Tenenbaum (1996) concluded that resistance training can be effective in prepubescents. Significant improvements in strength after a training inventory were evident in 25 of the 28 studies, improvement ranged between 13 and 30%. Pfeiffer & Francis (1986) reported the effects of 9 weeks of isotonic resistance training on isokinetic strength in groups of prepubertal, pubertal and young adult males. The prepubertal group showed larger % increase in 11 of 16 specific strength measures compared to pubertal and young adult groups.
Weltman et al (1996) studied the effects of concentric hydraulic resistance training over a 14 week period on isokinetic elbow and knee flexion and extension strength. The results showed a significant increase in concentric strength throughout the full range of flexion and extension. Nielsen et al. (1980), studied the effects of three training modes on groups of girls aged 7 to 19 years. The girls were divided into groups according to height. Training groups were, isometric strength training (24 maximal double knee extensions per session), running training (100 steps in 10 starts per session), and vertical jumping
demonstrated a significant increase in voluntary isometric knee extension strength compared to controls, and only the jump trained group improved vertical jump performance. These training adaptations imply that the principle of specificity of training applies. Other studies, Rians et al (1987), Duba (1986), Schafer (1991), Faigenbaum (1993), Blimkie (1992), Ozmun et al (1993), Metcalf & Roberts (1993), Tanner (1993), Blimkie (1993) support the hypothesis that strength training is effective and beneficial for children. (see appendix A).
Neuromuscular Adaptations In a study of 16 prepubescent boys and girls, Ozmun et al. (1993) found that after an 8 week strength training program isokinetic and isotonic strength increased significantly. With the use of integrated electromyographic data Ozmun et al found there was a significant increase in neural activity from pretest to posttest scores in the trained subjects while the control group showed no significant change. The corresponding strength and IEMG increases in trained subjects may reflect an enhancement in motor unit recruitment, improvement in the firing rate of activated motor units, alteration of EMG firing patterns. In addition analysis of pretest and posttest arm anthropometrics (girth and skinfolds) showed no significant changes in arm size or composition in either the trained or control groups. The corresponding strength and EMG increases along with the absence of hypertrophy supports the statement by Tanner (1993) that “Prior to puberty, neuromuscular adaptations rather than muscle hypertrophy
more likely accounts for strength increases”.
A number of studies
Blimkie (1993) support the findings of Ozmun et al.
Osseous Tissue & Considerations for Children In order for someone to properly supervise prepubescent strength training, he or she should understand the differences between adults and children in osseous growth structures. Schafer (1991) states that during athletic activity , the greatest load falls on the weakest link during the entire movement. An overload at that point creates a potential injury. In the immature skeleton growth cartilage is located at three sites: the epiphyseal plate, the epiphysis or joint surface and the muscle tendon insertion or apophyseal insertions. Because the strength of cartilage is less than that of bone, the growth plate is a weak link. It is possible to damage all three growth cartilage sites by accident, operations, disease or repeated microtrauma.
Is Strength Training In Children Safe Rians C, et al. (1987) evaluated various aspects of safety during a 14 week concentric
surveillance was conducted by a physician, which revealed one strength training injury; six injuries occurred in sport and activities of daily living. The strength training injury was diagnosed as a shoulder strain, the symptoms resolved with one week of rest. While no other injuries occurred there were an number of musculoskeletal complaints which were resolved by correction of technique. Many such corrections were required, indicating the high level of supervision necessary to avoid incorrect technique and potential injury. Subclinical deleterious effects on the musculoskeletal system were investigated using biphasic musculoskeletal scintigraphy (bone, epiphysis, and muscle). No evidence of damage was detected. Radiopharmaceutical avidity at epiphysial plates was compared before and after strength training and between control and experimental groups. No differences were found by visual or computer-assisted interpretation. All sports place some degree of demand on the musculoskeletal system.
Faigenbaum (1993) states that the potential for injury due to strength training is no greater (and may even be less) than the risk of associated with activities and organised sports. There is general agreement among medical and sports medicine experts that increasing the strength of the athlete will enhance performance and decrease the risk of injury in adults Metcalf & Roberts (1993). Since it has been demonstrated that children can increase muscle strength following resistance training, encouraging them to participate in resistance training to reduce potential injuries is justified. A review by Brady, Cahill & Bodnar (1982) of 80 young athletes with weight training related injuries treated between Aug 1976 and Aug 1980 highlights the risk of injury to the young (in fact any) athlete if they are exposed to programs with inadequate supervision, inappropriate equipment, or unsuitable lifts and movement patterns. In 37 of the 80 athletes it was difficult to pinpoint the cause of the injury since the history revealed, in addition to weight training, either a program of running excessive mileage or repetitive lap running. However 63% of the injuries reported in this paper could be directly attributable to the Leaper machine. (The Leaper is indicative of two potential problems, use of improper technique and the machine is too dangerous for skeletally immature lifters to use, resulting in a causative factor in lumbosacral and cervical spine injuries) Other perpetrators were dead weight lifts and back hyperextension exercises on the Universal Gym.
When And How To Start A safe, appropriate age for a child to start a strength training program can not be cited. However, readiness for a strength training program Tanner (1993) depends on a child having a desire to participate, a belief that it is worthwhile, maturity to closely follow coaching and instructions, and discipline to lift weights several days per week. Ideally, coaches should incorporate strength training into periodised conditioning programs designed to increase motor skills and fitness levels and which vary in intensity and volume throughout the year. Faigenbaum (1993), Duda (1986), & Blimkie (1993) outline a set of guidelines based on NSCA and AOSSM review articles, such guidelines should be evaluated and adapted to the requirements of the children in question. In addition to issues already raised the following are key points from the guidelines; strength
training equipment should be of appropriate design to accommodate the size and degree of maturity of the child; emphasis should be on dynamic concentric contractions; all exercises should be carried through the full range of motion; no maximum lifts should ever be attempted.
Conclusion The benefits gained by weight training for children include increased strength, increased protection from potential athletic injuries, enhancement in motor unit recruitment, improvement in the firing rate of activated motor units. There are potential risks due to the relative fragility of the osseous growth structures, however, with proper supervision, appropriate technique instruction and exercise prescription, training related injury can be avoided.
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