Contrary to popular belief, resistance training can provide benefit to all populations regardless of age. Safety is by and large the greatest concern regarding children’s’ participation in resistance training. The current research has shown no evidence that an age-appropriate resistance training program, done with proper supervision, is dangerous for a child. However, research has shown that resistance training can help children maintain a healthy body composition, improve skeletal and joint health, and improve sport performance. As long as a safe and detailed program is utilized, there seems to be no evidence to suggest that resistance training is detrimental to children.
Before we delve any further, resistance training needs to be defined to avoid confusion or misunderstanding. Resistance training is a method of exercise or conditioning that involves external loading to increase an individual’s capacity to produce force. Although resistance training is a common form of conditioning, as is running, most parents do not approve of resistance training because of misconceptions such as:
- Resistance training will stunt a child’s growth by sealing off growth plates
- Children have no testosterone so they won’t see benefits from strength training
- Children will ‘get in shape’ just by playing their sport(s)
- Speed/ speed-agility is the only training that is safe for children
- Strength training should only be done once the child is fully developed
Although there is no minimum age requirement at which a child can begin resistance training, several factors must be considered. One of those factors is the child’s age. Not necessarily chronological age but biological or physiological age. By that, I mean that not all ten year olds are the same; they differ in height, weight, coordination, and physical ability. One ten-year-old might be physically ready for resistance training while another may not. A child’s willingness to participate, psychological maturity, ability to pay attention and follow direction must also be considered. Generally, I would argue that if a child is ready for sport, they are ready for some type of resistance training. Research has shown that children as young as 6 years old have benefited from resistance training [1][2].
Participation in organized sport is generally accepted as being safe for young children. What many parents don’t realize is the amount of stress that is put on a child’s body during sport. Children are expected and encouraged to “go all out” during sport; you would never hear a parent or coach tell a kid to slow down on the field. This is where things get a bit backwards in my opinion. To further explain my reasoning, let’s discuss the topic of ground reaction force (GRF). Put simply, anytime you exert force on the ground, like when you land from a jump or push off to sprint, the ground exerts the same amount of force onto your body. This force is known as ground reaction force. The magnitude of ground reaction force is determined by how much you weigh and how fast you move. Just while walking, forces can reach 1.5x body weight. During running, forces can be up to 6x body weight, and even up to 11x body weight when landing from a jump.
To put that in perspective, if we have an average 10-year-old that weighs about 70lbs:
- Walking: ~105lbs of force on a single leg
- Running: ~210-420lbs of force on a single leg
- Jumping: ~280-770lbs of force on a single leg
If children are playing sport they should also be resistance training. Resistance training will not cause harm to children, but better allow their bodies to absorb the magnitude of the GRF. Sure, there are inherent risks that come along with resistance training, but those risks are no greater (and I would argue they are less) than the risk involved in sports. The forces placed on the joints during sport are greater than any forces that would likely be put on a child during resistance training. Resistance training takes place in a controlled environment; participants are closely supervised and safety precautions in terms of equipment and quality of movement are enforced. Any external loading of an athlete would be gradually progressed based on individual capability. Sport on the other hand is very unpredictable. That is not to say that children should not participate in sport. If a resistance training program is utilized alongside sport participation, we can improve athletic development and decrease risk of injury. In fact, it has been estimated that 15-50% of injuries sustained by children can be prevented with better physical preparation [3].
One of the biggest concerns is the presumable damage to a child’s growth plates. Injuries to the growth plate may disrupt the bone’s blood and supply of nutrients and result in growth disturbances. Although this is a definite concern, there is very little evidence of this occurring from resistance training. Only a few case studies that involved heavy overhead lifting in an unsupervised environment have reported injuries to the growth plates [4][5]. No fractures to the growth plate have been reported in youth resistance training studies when established training and safety guidelines were followed. Even 1-RM testing has shown no negative effects for children assuming proper 1-RM testing guidelines are followed [6]. From the research that has been done with children, it seems that resistance training is safe so long as they are taught how to resistance train properly and are under proper supervision.
Some argue that since kids do not have enough testosterone that they will not see strength benefits from resistance training. If that were true, women and elderly adults would not see strength benefits from resistance training. From preadolescent to teenage years, natural maturity of the body results in strength increases. Studies in the past have concluded that resistance training shows no strength benefits beyond the natural increases that occur due to growth and maturation. However, these studies were short (not long enough to elicit adaptation) and training volume was likely not high enough [7][8]. In studies done with appropriate duration (8-20 weeks) in untrained preadolescent children, results indicated 30-40% increases in strength and even up to 73%, beyond strength gains seen through normal maturation [9].
Some other benefits of RT include improved strength and density of connective tissue. RT can increase the strength of ligaments (tissue that connect one bone to another at a joint) and tendons (tissue that connect muscle to bone). Weight-bearing activity have been shown to generate compressive forces that are essential for bone formation and growth (i.e. bone mineral density). The effects of resistance training on the tissue (muscle, ligaments, tendons, bones) will help prepare the body to handle the stresses placed upon it through sport and everyday activity. Contrary to what many people may think, children cannot “play” themselves into shape because the demands of sport do not develop enough strength in the muscle and connective tissue.
Resistance training for children is a controversial topic. Until recently, we did not have a lot of evidence against or in support of resistance training in youth populations. If resistance training is done under proper supervision by a qualified strength and conditioning coach, and if appropriate progression is utilized, the benefits both on and off the field are innumerable.
References
- Faigenbaum, A. D., Westcott, W. L., Loud, R. L., & Long, C. (1999). The effects of different resistance training protocols on muscular strength and endurance development in children. Pediatrics, 104(1), e5-e5.
- Falk, B., & Mor, G. (1996). The effects of resistance and martial arts training in 6-to 8-year-old boys. Pediatric exercise science, 8(1), 48-56.
- Micheli, L. (2006). Preventing injuries in sports: What the team physician needs to know. F.I.M.S. Team physician manual, 2nd ed., K. Chan, L. Micheli, A. Smith, C. Rolf, N. Bachl, W. Frontera, & T. Alenabi, eds. Hong Kong: CD Concept. 2006. pp. 555-572.
- Gumbs, V. L., Segal, D., Halligan, J. B., & Lower, G. (1982). Bilateral distal radius and ulnar fractures in adolescent weight lifters. The American journal of sports medicine, 10(6), 375-379.
- Ryan, J. R., & Salciccioli, G. G. (1976). Fractures of the distal radial epiphysis in adolescent weight lifters. The American journal of sports medicine, 4(1), 26-42.
- Faigenbaum, A. D., Milliken, L. A., & Westcott, W. L. (2003). Maximal strength testing in healthy children. The Journal of Strength & Conditioning Research, 17(1), 162-166.
- Docherty, D. (1987). The effects of variable speed resistance training on strength development in prepubertal boys. J. Human Movement Studies, 13, 337-382.
- Hetherington, M. R. (1976). Effect of isometric training on the elbow flexion force torque of grade five boys. Research Quarterly. American Alliance for Health, Physical Education and Recreation, 47(1), 41-47.
- Faigenbaum, A. D., Zaichkowsky, L. D., Westcott, W. L., Micheli, L. J., & Fehlandt, A. F. (1993). The effects of a twice-a-week strength training program on children. Pediatric Exercise Science, 5(4), 339-346.
