Human body composition: measurement and relationship with exercise, dietary intakes and cardiovascular risk factors

This thesis describes studies related to human body composition, concentrating upon methodology of measurement, and a study on the influence of brisk walking programme upon healthy, previously sedentary middle-aged men. In chapter I, the principles of the techniques used for measurement of body composition in this thesis are discussed. The limitations and potential sources of error associated with each are discussed. The response of body composition to exercise, and the relationship of this response to changes in cardiovascular risk factors are considered. General methods are described in chapter 2. Techniques suitable for measurement of body composition in "field" conditions are evaluated in chapters 3 and 4. Near infra-red interactance was found to under-estimate fatness, to an increasing extent with increasing fatness. Bio-electrical impedance estimates of body composition from different sets of prediction equations from the literature differed significantly. Most overestimated fatness, to an increasing extent with increasing fatness. In chapter 5 techniques for measurement of subcutaneous adipose tissue are evaluated by comparison with A-mode ultrasound. Skinfold thicknesses were better correlated with subcutaneous adipose tissue thickness than were interactance data. Chapters 6 and 7 describe a year-long study on the effects of a brisk walking programme on healthy, previously sedentary middle-aged men. Volunteers were randomly allocated to walking or control groups (n = 42 and 23 respectively). Brisk walking for on average 27 minutes per day was not found to influence body composition, although significant changes in lower limb skinfold thicknesses were observed. The relationship of changes in blood pressure and blood concentrations of total cholesterol, lipoprotein-cholesterol subfractions and triglycerides with changes in body composition and fat distribution is examined. Energy intake did not change during the study, despite the expected increase in energy expenditure, and lack of change in body composition. Changes in dietary cholesterol and fatty acid intakes during the year are described, and related to changes in cardiovascular risk factors. In conclusion, newer field techniques were not found to be a better predictor of body composition than skinfold thicknesses. Participation in the walking programme did not significantly influence body composition or energy intake

Vibration therapy

Whole body vibration training (WBV) involves standing or exercising on a vibrating platform. WBV has been suggested to benefit bone strength and neuromuscular function, so could potentially reduce risk of fracture by preventing falls as well as increasing bone strength. Whilst some potential has been demonstrated, findings have been mixed, perhaps in part due to the variation in vibration interventions that have been delivered and the groups of participants studied

Risks and benefits of whole body vibration training in older people

Risks and benefits of whole body vibration training in older peopl

Optimum frequency of exercise for bone health: randomised controlled trial of a high-impact unilateral intervention

Introduction: Exercise can increase bone strength, but to be effective in reducing fracture risk, exercise must be feasible enough to be adopted into daily life and influence potentially vulnerable skeletal sites such as the superolateral cortex of the femoral neck, where thinning is associated with increased fracture risk. Brief, high-impact exercise increases femoral neck bone density but the optimal frequency of such exercise and the location of bone accrual is unknown. This study thus examined (1) the effectiveness of different weekly frequencies of exercise on femoral neck BMD and (2) whether BMD change differed between hip sites using a high-impact, unilateral intervention. Methods: Healthy premenopausal women were randomly assigned to exercise 0, 2, 4, or 7 days/week for 6 months. The exercise intervention incorporated 50 multidirectional hops on one randomly selected leg. BMD was measured by DXA at baseline and after 6 months of exercise. Changes in the exercise leg were compared between groups using ANCOVA, with change in the control leg and baseline BMD as covariates. RM-MANOVA was conducted to determine whether bone changes from exercise differed between hip sites. Results: 61 women (age 33.6±11.1 years) completed the intervention. Compliance amongst exercisers was 86.7±10.6%. Peak ground reaction forces during exercise increased from 2.5 to 2.8 times body weight. The change in femoral neck BMD in the exercise limb (adjusted for change in the control limb and baseline BMD) differed between groups (p=0.015), being −0.3% (−1.2 to 0.6), 0.0% (−1.0 to 1.0), 0.9% (−0.1 to 2.0) and 1.8% (0.8 to 2.8) in those exercising 0, 2, 4 and 7 days per week, respectively. When BMD changes at upper neck, lower neck and trochanter were compared using RM-MANOVA, a significant exercise effect was observed (p=0.048), but this did not differ significantly between sites (p=0.439) despite greatest mean increases at the upper femoral neck. Conclusions: Brief, daily hopping exercises increased femoral neck BMD in premenopausal women but less frequent exercise was not effective. Brief high-impact exercise may have a role in reducing hip fragility, but may need to be performed frequently for optimal response

Letter to the Editor: On epidemiology of fractures and variation with age and ethnicity

Letter to the Editor: On epidemiology of fractures and variation with age and ethnicit

Bone mineral density and hip structure analysis of UK Bangladeshi women compared with indigenous British women [Abstract]

Bone mineral density and hip structure analysis of UK Bangladeshi women compared with indigenous British women [Abstract

High and odd impact exercise training improved physical function and fall risk factors in community-dwelling older men

High impact exercise programmes can improve bone strength, but little is known about whether this type of training further benefits fracture risk by improving physical function in older people. Objectives: This study investigated the influence of high impact exercise on balance, muscle function and morphology in older men. Methods: Fifty, healthy men (65-80 years) were assigned to a 6-month multidirectional hopping programme (TG) and twenty age and physical activity matched volunteers served as controls (CG). Before and after training, muscle function (hop performance, leg press and plantar- and dorsiflexion strength) and physiological determinants (muscle thickness and architecture) as well as balance control (sway path, one leg stance duration) were measured. Resting gastrocnemius medialis (GM) muscle thickness and architecture were assessed using ultrasonography. Results: Significant improvements in hop impulse (+12%), isometric leg-press strength (+4%) and ankle plantarflexion strength (+11%), dorsiflexor strength (+20%) were found in the TG compared to the CG (ANOVA interaction, P<0.05) and unilateral stance time improved over time for TG. GM muscle thickness indicated modest hypertrophy (+4%), but muscle architecture was unchanged. Conclusion: The positive changes in strength and balance after high impact and odd impact training would be expected to improve physical function in older adults

Multidirectional hopping exercise improved balance and ankle plantarflexion strength in community-dwelling older men [Abstract]

Multidirectional hopping exercise improved balance and ankle plantarflexion strength in community-dwelling older men [Abstract

The reproducibility of T2 relaxation time measurement of knee cartilage in women aged over 50 [Abstract]

The reproducibility of T2 relaxation time measurement of knee cartilage in women aged over 50 [Abstract

Effect of high impact exercise on femoral neck bone mineral density and T2 relaxation times of articular cartilage in postmenopausal women [Abstract]

Effect of high impact exercise on femoral neck bone mineral density and T2 relaxation times of articular cartilage in postmenopausal women [Abstract