Elsevier

Bone

Volume 40, Issue 1, January 2007, Pages 14-27
Bone

Review
Weight-bearing exercise and bone mineral accrual in children and adolescents: A review of controlled trials

https://doi.org/10.1016/j.bone.2006.07.006Get rights and content

Abstract

Introduction

Osteoporosis is a serious skeletal disease and as there is currently no cure, there is a large emphasis on its prevention, including the optimisation of peak bone mass. There is increasing evidence that regular weight-bearing exercise is an effective strategy for enhancing bone status during growth. This systematic review evaluates randomised and non-randomised controlled trials to date, on the effects of exercise on bone mineral accrual in children and adolescents.

Methods

An online search of Medline and the Cochrane database enabled the identification of studies. Those that met the inclusion criteria were included in the review and graded according to risk for bias.

Results

Twenty-two trials were reviewed. Nine were conducted in prepubertal children (Tanner I), 8 in early pubertal (Tanner II–III) and 5 in pubertal (Tanner IV–V). Sample sizes ranged from n = 10 to 65 per group. Exercise interventions included games, dance, resistance training and jumping exercises, ranging in duration from 3 to 48 months. Approximately half of the trials (n = 10) included ground reaction force (GRF) data (2 to 9 times body weight). All trials in early pubertal children, 6 in pre pubertal and 2 in pubertal children, reported positive effects of exercise on bone (P < 0.05). Mean increases in bone parameters over 6 months were 0.9–4.9% in prepubertal, 1.1–5.5% in early pubertal and 0.3–1.9% in pubertal exercisers compared to controls (P < 0.05).

Conclusions

Although weight-bearing exercise appears to enhance bone mineral accrual in children, particularly during early puberty; it remains unclear as to what constitutes the optimal exercise programme. Many studies to date have a high risk for bias and only a few have a low risk. Major limitations concerned selection procedures, compliance rates and control of variables. More well designed and controlled investigations are needed. Furthermore, the specific exercise intervention that will provide the optimal stimulus for peak bone mineral accretion is unclear. Future quantitative, dose–response studies using larger sample sizes and interventions that vary in GRF and frequency may characterise the most and least effective exercise programmes for bone mineral accrual in this population. In addition, the measurement of bone quality parameters and volumetric BMD would provide a greater insight into the mechanisms implicated in the adaptation of bone to exercise.

Introduction

Osteoporosis is a systemic, skeletal disease characterised by low bone density and micro-architectural deterioration of bone tissue, with a consequent increase in bone fragility [1]. It is a serious disease that is increasing at an epidemic rate and it is predicted that osteoporosis and osteoporotic fractures will rise exponentially over the next 50 years, as the population ages [2]. Thus, there is a large emphasis on preventative measures to combat or offset osteoporosis and fracture. One major preventive measure is the optimisation of peak bone mass in the early years. Peak bone mass can be defined as the greatest amount of bone mass achieved during life at a given skeletal site and is based on observations that bone mass increases during childhood and puberty, consolidates during young adulthood and declines with age [3], [4]. One strategy to increase peak bone mass is through regular, weight-bearing exercise [5], [6], [7]. The definition of weight-bearing exercise that has been adopted for this review is that of a structured, force-generating activity that provides loading to skeletal regions, above that provided by activities of daily living [8]. Weight-bearing exercises can include aerobics, circuit training, jogging, jumping, volleyball and other sports that generate impact to the skeleton. There is evidence to suggest that the years of childhood and adolescence represent an opportune period during which bone adapts particularly efficiently to such loading [9], [10].

Evidence supporting the role of weight-bearing exercise in bone health has accumulated from cross sectional, retrospective, prospective and intervention studies. Cross sectional studies report higher bone mass in athletes than non athletes [11], [12], and in highly active children compared to those who are more sedentary [13], [14]. Retrospective studies report greater bone mass in retired dancers compared to controls [15], and an increase in physical education (PE) within the school curriculum is associated with positive skeletal effects in children [16]. Prospective studies following children with different physical activity levels also report greater increases in the bone mass of active children compared to those who are less active [17], [18], [19]. Although such studies have contributed to the literature, they do not provide robust and causal inferences between exercise and bone mineral accrual. As such, there is a need to assess randomised controlled trials (RCT), which are regarded as the primary source for more valid and reliable evidence. The number of investigations has increased over the last 5 years [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33] therefore the purpose of this review was to evaluate this literature to date.

Section snippets

Search strategy to identify relevant trials

The aim of the literature search was to identify all available RCTs and controlled studies concerning the effects of weight-bearing exercise on bone mineral accrual in children and adolescents, aged 8 and 17 years. To do so, a computerised search of the MEDLINE database was performed on articles published between the years 1964 and 2005. The keywords entered were: ‘exercise, children, girls, boys, adolescents, bone, bone mineral and bone mass’. A total of 573 articles were found, and their

Results

Table 2 summarises the design, execution and outcomes of the studies reviewed. These are grouped according to the participants' Tanner Stage because maturity status is critical when evaluating the effects of exercise on growing bone [8], [9]. Results are given as the percentage increase in bone mass parameters (bone mineral content (BMC), areal bone mineral density (aBMD) and volumetric BMD (vBMD) in exercisers compared to controls. When provided by the authors, absolute changes in bone mass

Optimal exercise intervention for bone mineral accrual

It is known that the skeletal response to weight-bearing exercise is site-specific and studies to date support this, reporting the most significant effects at the femoral neck (Table 2). However, a major question arising from this review is what constitutes the optimal exercise programme to improve bone mineral accrual in children?

Intervention trials that have achieved successful results have used a range of exercise protocols. These have included (a) activities such as aerobics, football and

Conclusions

To conclude, positive skeletal effects from weight-bearing exercise can be attained in girls and boys. The long term effects are unknown, but maximising peak bone mass is likely to offset future development of osteoporosis and bone fragility. The evidence indicates that early puberty potentially represents an opportune maturity stage to augment bone mineral accrual through exercise, although definitive conclusions cannot yet be made. Many studies to date have a high risk for bias, with only a

References (46)

  • R.P. Heaney et al.

    Peak bone mass

    Osteoporos. Int.

    (2000)
  • H.K. Genant et al.

    Short report: interim report and recommendations of the World Health Organisation task-force for osteoporosis

    Osteoporos. Int.

    (1999)
  • O.M. Rutherford

    Is there a role for exercise in the prevention of osteoporotic fractures?

    Br. J. Sports Med.

    (1999)
  • M.C. Kai et al.

    Exercise interventions: defusing the world's osteoporosis time bomb

    Bull. World Health Organ.

    (2003)
  • K.J. MacKelvie et al.

    Is there a critical period for bone response to weight-bearing exercise in children and adolescents? A systematic review

    Br. J. Sports Med.

    (2002)
  • S.L. Bass

    The prepubertal years: a uniquely opportune stage of growth when the skeleton is most responsive to exercise?

    Sports Med.

    (2000)
  • A. Andreoli et al.

    Effects of different sports on bone density and muscle mass in highly trained athletes

    Med. Sci. Sports Exerc.

    (2001)
  • J.E. Dook et al.

    Exercise and bone mineral density in mature female athletes

    Med. Sci. Sports Exerc.

    (1997)
  • H. Haapasalo et al.

    Effect of long-term unilateral activity on bone mineral density of female junior tennis players

    J. Bone Miner. Res.

    (1998)
  • R.M. Daly et al.

    Influence of high impact loading on ultrasound bone measurements in children: a cross-sectional report

    Calcif. Tissue Int.

    (1997)
  • K.M. Khan et al.

    Self-reported ballet classes undertaken at age 10–12 years and hip bone mineral density in later life

    Osteoporos. Int.

    (1998)
  • M. Sundberg et al.

    Peripubertal moderate exercise increases bone mass in boys but not in girls: a population-based intervention study

    Osteoporos. Int.

    (2001)
  • D.A. Bailey et al.

    A six-year longitudinal study of the relationship of physical activity to bone mineral accrual in growing children: the University of Saskatchewan bone mineral accrual study

    J. Bone Miner. Res.

    (1999)
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