Resistance training or weight training for children and adolescents has been a topic of great debate for the last two decades among scientists and physicians, coaches, young athletes and their parents. The general opposition to prepubescent resistance training has been based on three areas of concern: (1) children lack sufficient circulating androgens to make any significant improvements in muscle strength or muscle endurance; (2) no greater sport performance achievements may be reached; and (3) the incidence of injury may reach an unacceptably high level (Payne et. al., 1996). Since these concerns have been exposed, many studies have set out to examine the effects of resistance training on children. The purpose of this study is to review current literature and examine whether resistance training is appropriate and safe for children, how and why this form of activity should be executed, what benefits could result from participation in it, and what type is most beneficial for younger individuals.
The Health Education Authority (Biddle et. al., 1998) published primary and secondary guidelines for younger individuals who participate in physical activity. The primary guideline recommends an hour of physical activity each day. The secondary guideline recommends that young people partake in exercise that promotes muscular strength, flexibility and bone health twice weekly. Studies have shown that strength training, when properly structured with regard to mode, duration of programme, intensity and frequency, can increase strength in adolescents and pre-adolescents (Falk & Tenenbaum, 1996 and Payne et. al., 1996). Much concern is placed on the focus of children partaking in maximal loads during testing and training, however, Faigenbaum et. al. (2003) found in a study evaluating one repetition maximum lifting in children that very little risk exists when a qualified trainer is present to supervise the exercise. They evaluated that, if qualified instructors are present and children have been educated in the technique correctly, very little risk of injury exists in participating in maximal loading. Recommended guidelines include participants having a medical examination before commencing a programme; an opportunity to discuss training goals, techniques, and expectations; and the issue of supplements, especially the use of anabolic steroids in adolescents who want to become bigger and stronger (Committee on Sports Medicine and Fitness, 2001). Overall well-supervised and appropriately prescribed resistance exercise provides no greater chance of injury than other sports activities (BASES, 2004).
The benefits that have been proposed of children participating in resistance training include improving sports performance through motor-skill development, preventing injuries and increasing skeletal health. A study by Cahill (1990) concluded that increases in muscular strength and endurance contribute greatly to improved motor-skill and injury prevention.
It is clear from previous studies that children do not gain strength through hypertrophy but that main strength gains are through neuromuscular adaptations where learning of the task is required, where training increases the number of motor neurons that will fire with each muscle contraction (Ozmun et. al.,1994 and Ramsay et. al., 1990). These studies found a significant increase in neural activity from pre-training to post-training. This increase in neural activity leads to an increase in strength in children. However, can this increase in strength contribute to an improved movement skill? Flanagan et. al. (2002) tested two different strength training modes on motor performance; one included machine-based training and another included body-weight-based training. They concluded that significant differences came about from body-weight trained individuals in increasing motor performance and that no significant difference was found through the other form of resistance training even though strength and muscle endurance gains were increased in both modes of training. However, there are limitations to this study as the test of motor performance included medicine-ball put, long jump and shuttle run all of which have minimal external load, therefore the machine training may not have been the most appropriate mode of resistance training for this study. Plyometric training, combined with machine training, may have been a more valid comparison. However, increases in muscle strength and endurance have been shown to increase motor performance in children. Also, benefits from strength and endurance through training can improve sport performance as many sports that children participate in have strength or power components; however, the link between resistance exercise and performance has not been fully established as few investigations have robust scientific procedures to address this question (BASES, 2004).
Another benefit of strength training that has been studied is that of injury prevention. Amongst adults the prescription of resistance exercise is common to help reduce the risk of joint and soft tissue injuries and also to aid recovery following an injury. Recently, Jones (2002) demonstrated that a twice-weekly resistance exercise programme lasting eight weeks reduced the participants perception of pain and increased function in adolescent sufferers of recurrent low back pain. Hejna et. al. (1982) studied high-school athletes over one year with three groups being examined: one control, one classified as experienced in resistance training and another with not such an experienced background. The study showed that individuals in the control group who participated in little resistance training had the greatest injury rate and rehabilitation time where those who regularly participated in resistance training had the lowest rate of injury under a third less and the shortest rehabilitation time by under a half compared with those who did not participate in resistance training as regularly. Although this study was significant in its findings, a lack of scientific significance in sample sizes and definition of injuries causes it not to be of high scientific significance, however, the basis of the study shows simply that those who participate in resistance training regularly are less likely to be injured during sports performance.
In association with injury, resistance training has been found to be beneficial to skeletal health. Most researchers agree that an increase in bone mineral density in the early years of bone formation are important if people are to maintain skeletal integrity and mobility later in life (BASES, 2004). To maximise bone mass during skeletal maturation, the modelling process must be optimised. Therefore, the most apparent form of doing this would be to apply a mechanical load during the critical stages of bone maturation. Conflict between researchers over the mode of loading has occurred; weight-bearing activities have generally been considered to have a positive effect on bone health, however, there are conflicting results about non-weight-bearing activities which actively load the skeleton through muscle contraction. Grimston et. al. (1993) found that children who are competitively involved in sports producing impact loads to the skeleton of equal to or over three times of body mass had significantly greater bone mineral density than children in non weight-bearing activities (swimming). Therefore, the benefits of resistance training become beneficial in later years as the quality and quantity in adults is in part believed to be influenced by characteristics during childhood and early adulthood. Unfortunately, limitations in the literature due to studies not allowing for genetic make up and nutritional factors, and also whole body density rather than that at a specific site, does not allow for any firm conclusions to be made which does not, in turn, allow for prescription of a particular dose or type of physical activity to say whether resistance training positively enhanced skeletal health.
It has been proven in many studies that children can enhance muscle strength and muscle endurance through resistance training (Falk & Tenenbaum, 1996., Payne et. al., 1997., Committee on sports medicine and fitness, 2001., Sailors & Berg, 1987). However, what has not as yet been established in this article is the optimal training regime with regard to frequency, mode, intensity and duration of programme to increase muscular strength and endurance. Many studies that have found an increase in muscular strength and endurance have had flaws in their methodology by not providing a control group for comparison with strength gains through growth and maturity; however, a study by Sailors & Berg (1987) compared pubescent boys during strength training to a control group to measure the rate of increase. They successfully concluded that strength and muscular endurance were improved to the natural rate of maturation and growth. However, this does not help coaches and physical trainers with the training protocols that should be introduced. A study by Faigenbaum et. al. (1999) examined the effect of high repetition and a moderate weight, and low repetitions and a heavy load, in the development of strength and muscular endurance. The results concluded that gains were greater from a high repetition and moderate load, whereas there was no significant difference between the control group and the heavy load, low repetitions group. This study suggested that the reason why such little strength gains occurred in the high load, low repetition was due to the low volume of training, as most training gains are induced through neuromuscular adaptation, the greater volume enhances motor-unit activation and motor-skill coordination this, however, is not required in adults due to greater learning ability which is why adults are recommended to use a heavy load and low reps for strength, and moderate loads and high reps for muscular endurance (Fleck & Kraemer, 1997). Further research by Faigenbaum et. al. (2002) studying the effects of frequency of training demonstrated that strength gains could be achieved with just one training session per week but two sessions resulted in greater gains in one repetition max in seated leg and bench press. Another study by Faigenbaum et. al. (2001) also studying the effects of different training protocols, which included a group training using a medicine ball and a complex training combination, showed no significant gains in the medicine ball group but equally high gains between medium load and high reps and the complex training group who trained with low reps and heavy weights immediately followed by medicine ball chest exercises. The limitations of the stated studies are that they are in children with no recent history in resistance exercise and may not be applicable due to the lack of periodisation that has not been incorporated into the study, however, further study is required to examine the effect of periodised training on children. The conclusions from researchers suggest that a protocol of high reps and moderate load be incorporated in the initial adaptation period of a resistance training programme. The reason for this lies in the motor-unit activation and motor-skill coordination that is required in children unlike in adults. Lower reps may be a possibility as the participant develops, however, more research needs to be done in this area.
This article has reviewed current issues that surround resistance training in children. It has been established that it is safe for children to participate in such training as long as critical guidelines are put in place to ensure safety of the participants. It has also been established what the optimal protocols are that can be applied, and why resistance training should be applied to children. It is vital that coaches and qualified professionals implement resistance training in the correct way to get the optimal gains for childrens health or sport participation, or both.