Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 180

The predominant exercise training factor that influences bony adaptation is the intensity and novelty of the load, rather than the number of repetitions, sets, or days per week or even the total duration of the programme. This observation is also true for animal models of mechanical loading, in which bone is most sensitive to short periods of loading characterised by unusual strain distribution, high strain magnitudes, and rapid rate of loading.

The relative efficacy of aerobic versus resistive exercise regimens for postmenopausal women may perhaps be best assessed via studies that have directly compared various intensities of these two exercise modalities in randomised subjects. Kohrt et al.⁷¹ found that both aerobic activities with high ground‐reaction forces (walking, jogging, stair climbing) and exercises with high joint‐reaction forces (weight‐lifting, rowing) significantly increased the BMD of the whole body, lumbar spine, and Ward’s triangle, whereas only the ground‐reaction group increased BMD at the femoral neck.⁷¹ The weight‐lifting group preserved femoral‐neck BMD relative to controls, as has been seen in other resistance training studies. However, lean mass and muscle strength increased only in the weight‐lifting group, leaving overall benefits of these two types of exercise for ultimate fall and fracture prevention still unresolved. Kerr et al.⁷² randomised 126 postmenopausal women to two years of high‐intensity weight‐lifting exercise, moderate‐intensity aerobic training (circuit training and stationary cycling), or sedentary control condition. Total hip and intertrochanteric BMD were improved only by strength training and were significantly different from aerobic training or control groups (+3.2% at two years). As most comparative studies other than those of Kohrt et al.⁷¹ and Kerr et al.⁷² have not sought to optimise both exercise modalities, it is still not possible to choose definitively one best modality for all bone sites. In general, the older the individual, the more favourable the resistance training appears, due to its broader benefits on muscle, bone, balance, and fall risk, relative to aerobic training. If aerobic training is used, however, activities that are weight‐bearing and higher impact have greater efficacy for bone health than non‐weight‐bearing or low‐impact aerobic activities.

It is important to consider not only the optimal modality of exercise but also the relative intensity, as the skeletal adaptation is critically linked to the intensity of the loading (whether due to increased amount of weight lifted during resistance training or higher ground‐reaction forces during aerobic/jumping activities). Interesting results have been reported by Cussler et al.⁷³ in a randomised trial of 140 postmenopausal women participating in a multimodal exercise programme (high‐intensity resistance training and a weight‐bearing circuit of moderate‐impact activities including walking/jogging, skipping, hopping, and stair climbing/stepping with weighted vests). Bone density improvements at the femoral trochanter were significantly and linearly related to total weight lifted during the 12 months, and also total weight lifted in leg press, squat, and military press exercises, but not to the volume or quality of the non‐resistance training components of the programme. High‐intensity resistance training is also more beneficial than low‐intensity training for muscle strength gains and muscle hypertrophy, in addition to associated gait disorders, functional impairments, and disability, making it ideal as a multiple risk factor intervention strategy for injurious falls prevention in osteopenic women.