This would suggest that \u201cresistance training\u201d per se could not only be beneficial, but it could be very beneficial, even if started at young ages. There is a misconception that resistance training is all about barbells and dumbbells \u2013 but that is not true. Resistance training in the early stages involves learning movement patterns and coordination, and light resistance before the youth can progressively overload the patterns with more load or volume. Resistance training is fundamental for increasing bone density, aiding in the development of movement patters specific for training, improving cognitive health, and overall wellbeing (Faigenbaum, 2013). Both participation in resistance training and exposure to different sports are important \u2013 and resistance training can act to help develop youth athletes in a more well-rounded way, changing up the areas of the body that are loaded, and helping to prevent repetitive injuries associated with certain sports. There is a massive misconception that the participation in resistance exercise is purely to put on muscle. The activation of muscle groups, increasing the mind-muscle connection, movement pattern development such as when performing deadlifts and squats, will only benefit the young athlete when the coaches are trained in appropriate starting points for the lifts and appropriate rates of overload for children and youth. This position statement is reflected in the Long Term Athletic Development (LTAD) model by Balyi (2003). \u201cHow young is too young?\u201d is likely a question about the ability of the child to be stay focused and be motivated to try new movement skills involved in strength training and conditioning. For youth, games are likely the most motivating which is why the position statement calls training between the ages of 6-9 the \u201cFUNdamentals\u201d stage.<\/p>\n\n\n\n
Strength training does not appear to have negative implications for muscular adaptations in children, however, the stunting of growth has been raised as a fear of strength training in children in the past (Kr\u00f6ger, Kotaniemi, Kr\u00f6ger, & Alhava, 1993).At the onset of puberty, ossification overruns the growth plate, fusing the primary growth centre to the secondary growth centres, resulting in a mostly unchanged length of bone thereafter (Mackie, Ahmed, Tatarczuch, Chen, & Mirams, 2008). But, contrary to the belief that \u201cstrength training\u201d could negatively affect childhood development, no evidence directly supports the claim that resistance training would cease the growing of children\u2019s growth plates (Guy & Micheli, 2001). In fact, dynamic exercise, especially resistance training, has been shown to have clear benefits for the skeleton (Turner & Robling, 2003). Studies examining the bone mineral content (BMC) of competitive tennis and squash players, have shown that the dominant arm used to hold the racket not only had much higher BMC than the non-dominant arm, but also that this difference is observed significantly more pre-menarcheal than in adults (Turner & Robling, 2003). This is important for skeletal health because the mechanism underpinning the addition of osteocytes to the periosteal surface occurs from loading the bone (Robling, Hinant, Burr, & Turner, 2002). In turn, this improves the bending and torsional strength of the bone. As well, resorption of bone from the periosteal surface (outside layer of our bone) is extremely rare in adults (it is usually trabecular bone that gets reabsorbed\/lost), so this additional layer can add a protective effect later into life (Robling, Hinant, Burr, & Turner, 2002). When mechanical compressions of the ulna was evaluated in rodent models over 16 weeks, tests revealed that bone mineral density (BMD) and content improved by 5-6%, yet there was a 64% increase in ultimate force (i.e., maximal amount of force the bone could support before failing) and a 94% increase in energy failure (i.e., amount of energy absorbed by the bone before failure). Interestingly, mechanical loading was found to be more effective if loads were applied in discrete bouts separated by recovery periods rather than if loads were applied in a single session. Though this study was done on rats, this information can be translated to humans as bone formation and adaptations occur via similar mechanisms. <\/p>\n\n\n\n
Additionally, dynamic loading as opposed to static loading appears to be more beneficial due to the sensitivity of bone cells to shear stresses (Hert & Landa, 1971). Although these studies were in rabbits or rats, recent studies that have since confirmed this response in humans (Turner & Robling, 2003). Importantly, engaging in exercise during skeletal growth is shown to be more osteogenic (bone-forming) than exercise after skeletal maturation (Turner & Robling, 2003), so loading children\u2019s bones during times of growth, even without the corresponding large hypertrophic \u201cstrength\u201d increases in their musculature that we typically associate with \u201cstrength training\u201d, could result in long term bone health implications!<\/p>\n\n\n\n
How should we know what age to transition children and adolescents into weight training? Chronological and developmental ages can vary drastically in that two twelve-year-old\u2019s could be the same age, but in completely different stages of development of bone and puberty. It appears that peak BMD occurs around menarche in females (around age 12) and around ages 13-17 in males (adolescence) (Kr\u00f6ger et al., 1993), which is typically right after peak height velocity (PHV) occurs. PHV landmarks the start of the growth spurt and peak of the spurt, and they are key landmarks for design of training and competition programs. Soon after PHV, the growth plates will fuse, and this appears to be the best time to build muscular strength due to its sensitive period, outlined in the LTAD model, occurring 1-2 years after (Balyi et al., 2006; Kr\u00f6ger et al., 1993). This would be the optimal time to start building muscular strength because not only is the bone fully fused, but it has also reached its full potential for growth (Turner & Robling, 2003).<\/p>\n\n\n\n
From ages 0-6, the recommendations are to have kids start general exploration of movement, on all environments and surfaces (ice, snow, gravel, grass, water) (Balyi, 2006). Structured gymnastics and swimming programs usually begin this young. Between the ages of 6-9, depending on the child\u2019s mental cognitive and emotion development, we can start introducing the ABC\u2019s of athleticism (agility, balance, coordination, and speed) (Balyi, 2006). This would also be an appropriate time to start doing body weight exercises and slightly more structured programs. Between the ages of 8-12, Balyi (2006) recommends that we should further introduce resistance training, for example through body weight, medicine ball, and swiss ball exercises to progressively overload the developing sport patterns and movement skills. Between 11-16, most children will hit puberty, and attain their PHV, where introducing free weights to continue the progressive overload would be appropriate (Balyi, 2006).<\/p>\n\n\n\n
The Canadian Society for Exercise Physiology\u2019s (CSEP) recommendations for resistance training in youth and adolescents include low- to moderate-intensity resistance exercise 2\u20133 times a week on non-consecutive days, with 1\u20132 sets initially, progressing to 4 sets of 8\u201315 repetitions for 8\u201312 exercises (Behm, Faigenbaum, Falk, & Klentrou, 2008). They recommend that exercises including more advanced movements such as Olympic-style lifting, plyometrics, and balance training, which can enhance strength, power, co-ordination, and balance, should be used with gradual progression under qualified instruction and supervision with appropriately sized equipment. Resistance training can safely lead to functional (i.e., muscular strength, endurance, power, balance, and co-ordination) and health benefits in these populations (Behm et al., 2008).<\/p>\n\n\n\n
In conclusion, recommendations for strength training for children are to start with physical literacy and to let kids play as much as possible as often as possible while experiencing different planes of movement, upper and lower extremities, and different surfaces (ice, snow, gravel, grass, water). The goal here is to develop the neuromuscular system for a strong base of coordination as well as to enhance bone and cardiovascular development. The more fun a kid has with their \u201ctraining\u201d, in other words \u2013 how well we can disguise \u201ctraining\u201d as play \u2013 the more likely they will continue participating in the activity, even in the long term. As per the LTAD model, it is advantageous to cash in on the sensitive periods of trainability. Strength improvements are prominent after PHV is passed, because bones are at their peak lengths, are strong, and newly circulating hormones help develop the muscles as well as help lay down a protective layer of BMD during that sensitive period. Long term considerations of the LTAD model, although it is not completely evidence-based and is not an individualized approach, presents an advancement in the understanding of the developing athlete alongside their biological growth (Ford et al., 2011). If possible, improvements in sports systems would allow grouping of athletes according to developmental age rather than chronological age, and if this criterion could not be adapted to, then better alignment of strength and conditioning programs with growth could be a future solution. The take-home message is that resistance training in youth is safe and effective, and it can have many health-related benefits. Furthermore, the safety and effectiveness of training will be maximized under the supervision of a qualified strength and conditioning coach.<\/p>\n\n\n\n
So, yes, it is safe for youth and children to lift weights, when introduced in a safe, progressive, and movement pattern focused way!<\/p>\n\n\n\n
About the Author<\/strong><\/em><\/p>\n\n\n\n Carla Robbins, MKin, CSEP-CEP (High Performance), is the Owner of Vital Strength & Physiology<\/a> <\/strong><\/span>a company based in Calgary, Alberta. You can find information about her company HERE<\/span><\/strong><\/a><\/p>\n\n\n\n
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