Original Full Length ArticleHigh impact exercise increased femoral neck bone mineral density in older men: A randomised unilateral intervention
Highlights
► We examined the influence of a 12 month high impact, unilateral exercise programme on bone density. ► Participants were 50 healthy, community dwelling men aged 65–80 years. ► The brief daily exercises increased to 50 multidirectional hops, on one randomly selected leg. ► Femoral neck BMD, BMC and geometry improved significantly in the exercise leg compared to the control leg. ► Carefully targeted high impact exercises may reduce risk of hip fracture in healthy older men.
Introduction
Osteoporotic fractures are a major public health problem amongst older adults. One in two women and one in five men aged fifty and over in the UK will suffer a fracture in their lifetime [1]. Osteoporotic fractures commonly occur at the hip, spine, and wrist and of these hip fractures have the highest short-term mortality, morbidity and associated socio-economic impact [2], [3], [4]. Regular exercise is widely recommended as the most effective non-pharmacological method for improving and maintaining BMD [5] and can also reduce the risk of falling. As such, exercise has an important role in reducing the predisposition to osteoporotic hip fracture.
Although older people are the population at most immediate risk of osteoporosis, it has been suggested that exercise may be less effective in older, than younger, people [6], [7]. This may be related to the type and intensity of the exercise interventions studied, as lower neuromuscular function [8] or greater injury risk may limit exercise intensity in older people. Meta analysis of exercise intervention studies suggests that mixed loading interventions including low to moderate impact exercises in the form of jogging, walking and stair climbing, together with resistance training, can maintain BMD at the femoral neck in postmenopausal women [9]. However, evidence from animal experiments suggests that the optimal loading regimens are high in magnitude, high in strain rate and provide novel stress on the bone [10], [11], [12], [13]. In children and young adults, high impact jumping exercises that exert a high magnitude of loading at the hip have produced the greatest increases in femoral neck BMD [6]. Therefore, interventions that incorporate brief but regular high impact exercise could potentially increase femoral neck BMD (rather than just preventing bone loss) in older adults.
Few studies have investigated the effects of interventions consisting only of high impact loading in the form of vertical jumping on femoral neck BMD in older people [14], [15]. These studies found no change in femoral neck BMD following the intervention but these findings pertain to postmenopausal women, whose adaptive response to mechanical loading is thought to be impaired by estrogen deficiency and reduced estrogen receptor number [16], [17].
Older men are at risk of osteoporotic fractures, and hip fracture related morbidity and mortality are higher for men than women [18]. However, there is little information concerning the effects of long-term exercise interventions on BMD in this population [19], [20]. One exercise intervention including high impact exercises (single and double foot landings, bench stepping, and jumping off 15- and 30-cm benches) increased femoral neck BMD in middle aged and older men (50–79 years) [21], [22]. However, the high impact exercises in this intervention formed only a very small component of a progressive resistance training programme, requiring over 3 h of exercise per week. High impact exercise alone may be more feasible, as exercises are less time-consuming and can be performed at home, without requiring any special equipment. Brief, high impact exercises performed at home can increase BMD in premenopausal women [23], but the effectiveness of high impact exercise alone on femoral neck BMD in older men is unknown.
Individual differences and lifestyle modifications such as genotype, physical activity, diet and age-related change may confound longitudinal exercise intervention trials in older people [24]. The effect of these confounders can be minimised by using a within-subjects unilateral design (exercise leg [EL] vs. control leg [CL]) that has greater statistical power than studies comparing changes between individuals. Recently, it was demonstrated that high impact unilateral exercise increases femoral neck BMD in premenopausal women [25]. Therefore, the aim of this study was to investigate the influence of a 12 month high impact unilateral exercise intervention on femoral neck BMD in healthy community dwelling older men, using a within-subjects unilateral design.
Section snippets
Experimental overview
The study was conducted as a longitudinal, randomised trial of a high impact exercise intervention in older men. The men were prescribed a 12 month, high impact unilateral exercise intervention which increased to 5 sets of 10 multidirectional hops, 7 days a week on one randomly allocated exercise leg, with the contralateral leg being untrained to provide a control leg. Randomisation was performed using the minimisation method so that half of participants exercised on the left leg and half on the
Reproducibility
CVs for percentage total body fat and lean soft tissue were 1.2% and 0.5%. CVs for femoral neck BMD, BMC, CSMI, section modulus and minimum neck width were 1.0%, 1.0%, 4.7%, 3.4% and 1.4% respectively. CVs for absolute peak and mean GRF during take-off and during landing were 6.4%, 5.9%, 8.5% and 7.0%.
Intervention adherence and adverse events
Of the fifty men that took part in the study, thirty-five men exercised for 12 months. Fourteen (28%) of the 50 men withdrew from the study, whilst BMD data were missing for one man. Three men
Discussion
This is the first study to document the influence of high impact, unilateral exercise on femoral neck BMD in older men in a longitudinal, randomised trial. The study demonstrated that a 12 month high impact exercise intervention increased femoral neck BMD and BMC in healthy community-dwelling older men. The within-subjects unilateral design of the study (EL vs. CL) reduces the possibility that our findings have been influenced by individual differences in exercise response, lifestyle
Acknowledgments
The authors wish to thank the men who took part in the study. The authors also acknowledge that funding for this study was provided by a Loughborough University Studentship and Medical Research Council (MRC) Interdisciplinary Bridging Award.
Conflict of interest statement
None declared.
References (51)
- et al.
Epidemiology of fractures in England and Wales
Bone
(2001) - et al.
Bone mechanotransduction may require augmentation in order to strengthen the senescent skeleton
Ageing Res Rev
(2012) Functional strain in bone tissue as an objective, and controlling stimulus for adaptive bone remodelling
J Biomech
(1987)- et al.
Strain rate as a controlling influence on adaptive modeling in response to dynamic loading of the ulna in growing male rats
Bone
(1998) - et al.
Osteoporosis in men: update 2011
Rheum Dis Clin North Am
(2011) - et al.
Optimum frequency of exercise for bone health: randomised controlled trial of a high-impact unilateral intervention
Bone
(2010) - et al.
A short questionnaire for the measurement of habitual physical activity in epidemiological studies
Am J Clin Nutr
(1982) - et al.
Weight bearing exercise and bone mineral accrual in children and adolescents: a review of controlled trials
Bone
(2007) - et al.
Biomechanical characteristics of elderly individuals walking on land and in water
J Electromyogr Kinesiol
(2008) - et al.
Effects of gender, anthropometric variables, and aging on the evolution of hip strength in men and women aged over 65
Bone
(2003)