Oh yeh, just some studies for whoever is interested. I'd like to see a study or something showing how weightlifiting can stunt growth rather then "Seriously I know guys this happened to":
"Increased bone density in teenagers, male or female submited to resistance traning or other sports (1,2,3,4,5,14,15).
Resistance training is indicated to healthy subjects of all ages (6).
Resistance training indicated to children above the age of 6 (8).
Properly supervised weight traning doesn't pose higher injury risk to children than any other sport(7).
Recent evidence suggests that strenght traning and consequent strength increases help to prevent injuies to the growth plates (9,10,12,13). Go figure.....
Increased height in girls that are physically active (11), not weightlifting but I just threw it in too....
And with all this research not a single word about possible concerns that weight training might stunt growth in teenagers.
All the concerns raised about damages to growth plates are related to high impact sports and this doesn't include weightlifting.
1-Effects of high-intensity resistance training on bone mineral density in young male powerlifters.
Tsuzuku S, Ikegami Y, Yabe K.
Department of Epidemiology, National Institute for Longevity Sciences, 36-3 Gengo, Morioka-cho, Obu-city, Aichi pref, 474-8522 Japan.
The effects of high-intensity resistance training on bone mineral density (BMD) and its relationship to strength were investigated. Lumbar spine (L2-L4), proximal femur, and whole body BMD were measured in 10 male powerlifters and 11 controls using dual-energy X-ray absorptiometry (DXA). There were significant differences in lumbar spine and whole body BMD between powerlifters and controls, but not in proximal femur BMD. A significant correlation was found between lumbar spine BMD and powerlifting performance. These results suggest that high-intensity resistance training is effective in increasing the lumbar spine and whole body BMD.
2-[Exercise increases bone mass in children but only insignificantly in adults]
[Article in Swedish]
Ortopediska kliniken, Universitetssjukhuset MAS, Malmo. firstname.lastname@example.org
Data supporting the notion that exercise during growth built a stronger skeleton is compelling. Exercise during growth, especially during the pre-pubertal years, increases bone mineral density (BMD) and perhaps also bone size, each independently conferring bone strength. In adulthood, exercise at best halts bone loss or increases BMD by a few percentage points, an increase of questionable biological significance. High lifelong work load and high leisure time activity level are associated with high BMD. The Achilles heel of exercise is its cessation. Most BMD benefits achieved by exercise during growth are lost with cessation of exercise. Exercise at a lower level, after a period of high intense activity, may retain residual BMD benefits into old age. A reduced rate of fragility fractures in the population could perhaps be achieved by promoting a physically active lifestyle with lifelong high activity level during work and leisure time, leading to high BMD and fewer fractures.
3-Bone mineral density in adolescent female athletes: relationship to exercise type and muscle strength.
Duncan CS, Blimkie CJ, Cowell CT, Burke ST, Briody JN, Howman-Giles R.
University of Sydney, Sydney, Australia.
PURPOSE: This study investigated the influence of different exercise types and differences in anatomical distribution of mechanical loading patterns on bone mineral density (BMD) in elite female cyclists, runners, swimmers, triathletes, and controls (N = 15 per group). Associations between leg strength and BMD were also examined. METHODS: Areal BMD (g x cm(-2)) was assessed by duel-energy x-ray absorptiometry (DXA) (total body (TB), lumbar spine (LS), femoral neck (FN), legs, and arms). Right knee flexion and extension strength was measured using a Cybex Norm isokinetic dynamometer at 60 degrees x s(-1). RESULTS: Runners had significantly higher unadjusted TB, LS, FN, and leg BMD than controls (P < 0.05); higher TB, FN, and leg BMD than swimmers (P < 0.05); and greater leg BMD than cyclists (P < 0.05). Absolute knee extension strength was significantly (P < 0.01) correlated (0.33 < or = r < or = 0.44) with TB, FN, LS, and leg BMD for all groups combined. Weaker but still significant correlations (0.28 < or = r < or = 0.33) existed for normalized (per leg lean tissue mass) knee extension strength and all BMD sites, except FN BMD. There were no significant correlations between absolute or normalized knee flexion strength and any of the BMD variables. Absolute knee extension strength was entered as the second independent predictor for LS and leg BMD in stepwise multiple linear regression analysis (MLRA), accounting for increments of 4% and 12%, respectively, in total explained variation. CONCLUSION: We conclude that running, a weight bearing exercise, is associated with larger site-specific BMD than swimming or cycling, that the generalized anatomical distribution of loads in triathlon appears not to significantly enhance total body BMD status, and that knee extension strength is only a weak correlate and independent predictor of BMD in adolescent females.
4-Resistance training and bone mineral density in adolescent females.
Nichols DL, Sanborn CF, Love AM.
Institute for Women's Health, Texas Woman's University, Denton, Texas 76204, USA.
OBJECTIVE: To examine the effects of 15 months of resistance training on bone mineral density (BMD) in female adolescents (aged 14 to 17 years). STUDY DESIGN: Participants were randomly assigned to either a training (n = 46) or control group (n = 21). BMD and body composition were measured by using dual-energy x-ray absorptiometry. Strength was assessed by means of one-repetition maximums for the leg press and bench press. The exercise group trained 30 to 45 minutes a day, 3 days per week, using 15 different resistance exercises. Control participants remained sedentary (<2 hours of exercise per week). RESULTS: Leg strength increased significantly (40%) in the exercise group, but there were no changes in the control group. Femoral neck BMD increased significantly in the training group (1.035 to 1.073 g/cm(2), P <.01) but not in the control group (1.034 to 1.048 g/cm(2)). No significant changes were seen in either group in lumbar spine BMD (1.113 to 1.142 g/cm(2) and 1.158 to 1.190 g/cm(2), respectively) or total body BMD (1.103 to 1.134 g/cm(2) and 1.111 to 1.129 g/cm(2), respectively). CONCLUSION: Resistance training is a potential method for increasing bone density in adolescents, although such a program would be best done as part of the school curriculum.
5-[Physical activity in children and adolescents in relation to growth and development]
[Article in Norwegian]
BACKGROUND: Physical activity may influence the performance and health of children and adolescents. The purpose of this article is to give a review of present knowledge in this field. MATERIAL AND METHODS: Literature was searched using Medline and the Norwegian University of Sports library. RESULTS: Related to body mass, boys have an aerobic capacity like young adults. Girls show a reduction from prepuberty until adulthood. Their trainability seems to be lower than in adults. Anaerobic capacity and muscle strength are lower than in adults, but increase during puberty, especially in boys. The trainability is good at all ages. There are small differences in performance between boys and girls before puberty. Physical activity has favourable metabolic effects and influences the development of fat tissue, skeleton and probably tendons, ligaments and cartilage. INTERPRETATION: Physical activity is important for performance and health during the growing years and later. It is a factor in the prevention of artheriosclerotic disease, hypertension, obesity, diabetes type 2, some types of cancers, osteoporosis, and muscular problems. Specialisation in sports should normally be postponed until late puberty, even by those who aim at high performance.
6-Prescription of resistance training for healthy populations.
Hass CJ, Feigenbaum MS, Franklin BA.
Department of Exercise and Sports Science, College of Health and Human Performance, University of Florida, Gainesville, USA. email@example.com
Although there are well documented protective health benefits conferred by regular physical activity, most individuals of all ages are not physically active at a level for sufficient maintenance of health. Consequently, a major public health goal is to improve the collective health and fitness levels of all individuals. The American College of Sports Medicine (ACSM) and other international organisations have established guidelines for comprehensive exercise programmes composed of aerobic, flexibility and resistance-exercise training. Resistance training is the most effective method available for maintaining and increasing lean body mass and improving muscular strength and endurance. Furthermore, there is an increasing amount of evidence suggesting that resistance training may significantly improve many health factors associated with the prevention of chronic diseases. These health benefits can be safely obtained by most segments of the population when prescribed appropriate resistance-exercise programmes. Resistance-training programmes should be tailored to meet the needs and goals of the individual and should incorporate a variety of exercises performed at a sufficient intensity to enhance the development and maintenance of muscular strength and endurance, and lean body mass. A minimum of 1 set of 8 to 10 exercises (multi-joint and single joint) that involve the major muscle groups should be performed 2 to 3 times a week for healthy participants of all ages. More technical and advanced training including periodised multiple set regimens and/or advanced exercises may be more appropriate for individuals whose goals include maximum gains in strength and lean body mass. However, the existing literature supports the guidelines as outlined in this paper for children and adults of all ages seeking the health and fitness benefits associated with resistance training.
7-Strength training for children and adolescents.
Guy JA, Micheli LJ.
Boston Children's Hospital, Boston, MA, USA.
Strength, or resistance, training for young athletes has become one of the most popular and rapidly evolving modes of enhancing athletic performance
. Early studies questioned both the safety and the effectiveness of strength training for young athletes, but current evidence indicates that both children and adolescents can increase muscular strength as a consequence of strength training. This increase in strength is largely related to the intensity and volume of loading and appears to be the result of increased neuromuscular activation and coordination, rather than muscle hypertrophy. Training-induced strength gains are largely reversible when the training is discontinued. There is no current evidence to support the misconceptions that children need androgens for strength gain or lose flexibility with training. Given proper supervision and appropriate program design, young athletes participating in resistance training can increase muscular strength and do not appear to be at any greater risk of injury than young athletes who have not undergone such training.
8-Strength training for children and adolescents.
Department of Human Performance and Fitness, University of Massachusetts, Boston, USA. firstname.lastname@example.org
The potential benefits of youth strength training extend beyond an increase in muscular strength and may include favorable changes in selected health- and fitness-related measures. If appropriate training guidelines are followed, regular participation in a youth strength-training program has the potential to increase bone mineral density, improve motor performance skills, enhance sports performance, and better prepare our young athletes for the demands of practice and competition. Despite earlier concerns regarding the safety and efficacy of youth strength training, current public health objectives now aim to increase the number of boys and girls age 6 and older who regularly participate in physical activities that enhance and maintain muscular fitness. Parents, teachers, coaches, and healthcare providers should realize that youth strength training is a specialized method of conditioning that can offer enormous benefit but at the same time can result in serious injury if established guidelines are not followed. With qualified instruction, competent supervision, and an appropriate progression of the volume and intensity of training, children and adolescents cannot only learn advanced strength training exercises but can feel good about their performances, and have fun. Additional clinical trails involving children and adolescents are needed to further explore the acute and chronic effects of strength training on a variety of anatomical, physiological, and psychological parameters.
9-trength training and the immature athlete: an overview.
Metcalf JA, Roberts SO.
The developing musculoskeletal structures of the immature athlete are uniquely susceptible to injury, particularly at the physes. These growth plates are present in arm and leg bones, and some may not close until the late teen years. Early literature suggested that weight training might be inappropriate for these athletes. However, recent evidence suggests that, properly done, strength/resistance training may not only be safe, it may also help reduce the risk of injury for the young athletes. Nurses are often called upon to advise coaches of formal and community athletic programs, and need to know the underlying physiology of developing bone and muscle as well as the current recommendations related to training.
10-[Overuse injury syndromes in children and adolescents]
[Article in Serbo-Croatian (Roman)]
Dapic T, Anticevic D, Capin T.
Klinika za ortopediju Medicinskog fakulteta Sveucilista u Zagrebu, KBC Zagreb, Zagreb.
More and more children participate in sports competitions. The main difference between children and adults is that the former still grow and develop. An immature musculoskeletal system is less able to cope with repetitive biomechanical stress. Sites of overuse injury are the sites of rapid growth: epiphysis, apophysis, and growth plates. Overuse injuries in children most commonly affect the cartilage where it meets with the tendons (nonarticular chondrosis), cartilage and bone at the joints surfaces (primary and secondary osteochondrosis), or the bone and its physis (stress fractures). The most characteristic overuse injuries in children are physeal stress fracture and osteochondrosis. The basic diagnostic and treatment principles in children greatly correspond to those in adults. The prevention of overuse injuries in children is very important. To minimise the injuries, children should be encouraged to limit the length of exercise, use high-quality equipment properly, cross train, and participate in conditioning programs to develop strength and flexibility.
11-Age differences in growth and physical abilities in trained and untrained girls 10-17 years of age.
Loko J, Aule R, Sikkut T, Ereline J, Viru A.
Institute of Sport Pedagogy, University of Tartu, Estonia.
The purpose of the present study was to assess the age differences in growth characteristics and physical abilities of physically active adolescent girls and to compare them to corresponding data for girls nonactive in sport. The cross-sectional study was carried out on 643 Estonian girls, 10-17 years of age, who were regularly training track and field, and 902 nonactive girls. The organized physical activity of the studied girls consisted of lessons in the school curriculum (2 x 45 minutes per week) for both groups and special track and field training for the first group. Height, weight, and the body mass index (BMI) were used to characterize growth status. Physical ability was assessed with the 30-m dash, standing long jump, medicine ball throw (2 kg), standing quintuplet jump, isometric strength of back extensor muscles, and 1-minute ergocycling at the highest possible rate. Girls active in track and field were taller in all the age groups (P < 0.05-0.001) and lighter except at 17 years, when they were heavier (P > 0.05), but the differences at 12 and 13 years were not significant. BMI was also significantly lower in active girls (P < 0.05-0.001) in all age groups, except at 17 (P > 0.05). The actively training girls had higher physical abilities at all ages from 10-17. The annual differences in performance scores were significant (P < 0.05-0.001) up to 15 years except for the standing long jump. Differences in mean scores of most motor abilities were minimal or reduced significantly at 13-14 years in nonactive girls, but were significant in active girls. Copyright 2002 Wiley-Liss,
12-Strength training and nutritional supplement use in adolescents.
Department of Medicine, Hospital for Special Surgery, Cornell Medical College, New York, New York, USA. MetzlJ@HSS.EDU
The "win at all costs" mentality is becoming increasingly common in youth sports, and young athletes are often looking for methods to improve sports performance and avoid injury. As organized sports participation continues to increase among American adolescents, questions related to sports medicine are more frequently encountered in the pediatric and adolescent office setting. Concerned with the improvement of athletic performance and the prevention of injury, adolescents are turning to strength training to help improve bone density and muscle strength. These efforts should be encouraged if the strength program is properly designed and supervised. Another topic of concern to many adolescents is nutritional supplement use. Products known as ergogenic aids are designed to chemically improve sports performance and are currently being used by many adolescent athletes. Of these products, nutritional supplements
are presented as a natural and safe method of improving athletic ability. None of these products has been tested in or approved for use in pediatric or adolescent subjects. Recommendations regarding the use of these products should be approached with a significant amount of trepidation in the pediatric and adolescent health communities.
13-Efficacy of strength training in prepubescent to early postpubescent males and females: effects of gender and maturity.
Lillegard WA, Brown EW, Wilson DJ, Henderson R, Lewis E.
Orthopedic Department, Center for Sports Medicine, Duluth, MN 55805, USA.
There has been considerable debate concerning the benefits of children participating in weight training programs. With the potential benefits of such training in specific rehabilitation regimens, the safety/efficacy of weight training is a topic in need of scientific study. Fifty-two experimental and 39 control subjects participated in this study. A 2 x 2 x 2 (gender by treatment by Tanner stage) ANOVA was used to examine pre- to post-test differences in six strength measures, eight anthropometric measures, five motor performance measures, and one flexibility measure associated with participation in a 12-week progressive resistance programme. In addition, safety of the weight training programme was examined. For strength differences, there were two significant main effects favouring strength gains in males and four favouring the experimental group. For anthropometric changes, 3-way interactions occurred that were not easily explained. However, the predominant main effect was treatment; the experimental group generally experienced gains in body segment girths with decreases in skinfold thickness. For motor performance, the experimental group had greater improvements in three of five parameters. The experimental group also had significantly greater gains in flexibility. The weight training programme was associated with only one injury. These findings support the general observation that physical benefits can be gained safely by children who participate in a weight training programme.
14-Type of physical activity, muscle strength, and pubertal stage as determinants of bone mineral density and bone area in adolescent boys.
Nordstrom P, Pettersson U, Lorentzon R.
Department of Orthopedics, Umea University, Sweden.
The present study was conducted to evaluate the influence of different types of weight-bearing physical activity, muscle strength, and puberty on bone mineral density (BMD, g/cm2) and bone area in adolescent boys. Three different groups were investigated. The first group consisted of 12 adolescent badminton players (age 17.0 +/- 0.8 years) training for 5.2 +/- 1.9 h/week. The second group consisted of 28 ice hockey players (age 16.9 +/- 0.3 years) training for 8.5 +/- 2.2 h/week. The third group consisted of 24 controls (age 16.8 +/- 0.3 years) training for 1.4 +/- 1.4h/week. The groups were matched for age, height, and pubertal stage. BMD, bone mineral content (BMC, g), and the bone area of the total body, lumbar spine, hip, femur and tibia diaphyses, distal femur, proximal tibia, and humerus were measured using dual-energy X-absorptiometry. When adjusting for the difference in body weight between the groups, the badminton players were found to have significantly higher BMD (p < 0.05) of the trochanter and distal femur compared with the ice hockey players despite a significantly lower weekly average training. The badminton players had higher BMD compared with the control with the control group at all weight-bearing BMD sites, except at the diaphyses of the femur and tibia and lumbar spine. The independent predictors of bone density were estimated by adjusting BMC for the bone area in a multivariate analysis among all subjects (n = 64). Accordingly, the bone density of all sites except the spine was significantly related to muscle strength and height, and the bone density of the total body, neck, trochanter, distal femur, and proximal tibia was significantly related to type of physical activity (beta = 0.09-0.33, p < 0.05). The bone area values at different sites were strongly related to muscle strength and height and less strongly related to the type of physical activity and pubertal stage. In conclusion, it seems that during late puberty in adolescent boys the type of weight-bearing physical activity is an important determinant of bone density, while the bone area is largely determined by parameters related to body size. The higher BMD at weight-bearing sites in badminton players compared with ice hockey players, despite significantly less average weekly training, indicates that physical activity including jumps in unusual directions has a great osteogenic potential.
15-Effects of resistance training on bone mineral content and density in adolescent females.
Blimkie CJ, Rice S, Webber CE, Martin J, Levy D, Gordon CL.
Department of Kinesiology, McMaster University, Hamilton, ON, Canada.
Postmenarcheal adolescent girls performed resistance training (RT) for 26 weeks, which consisted of 4 sets of 13 exercises of varying and progressive intensity performed 3 times weekly on hydraulic resistance machines. Bone mineral was assessed by dual photon absorptiometry. Resistance training resulted in significant increases (pre-post) in biceps curl (21.4%), triceps press (21.5%), knee extension (25.1%), knee flexion (52.8%), and squat press (21.5%) strength. There were no significant differences between RT and control © groups initially, and no significant effects of training (pre-post) for total body (TB) or lumbar spine (LS) bone mineral content (BMC) or bone mineral density (BMD). The largest increases in LS bone mineral occurred during the first 13 weeks, and although not significant, the increases in LS BMC (g) (3.9 vs. 5.9%), LS BMC (g.cm-1) (2.6 vs. 5.9%), LS areal BMD (g.cm-2) (1.48 vs. 4.75%), and LS bone mineral apparent density (BMAD, g.cm-3) (0.47 vs. 4.13%) were greater in the RT compared with the C group during this period. In conclusion, resistance training resulted in a trend towards a transient increase in LS bone mineral during the first 13 weeks, but despite significant strength gains, there were no significant changes in TB or LS bone mineral after 26 weeks of training."