Acta of Bioengineering and Biomechanics Vol. 10, No. 2, 2008 Effect of treadmill exercise on lumbar vertebrae in ovariectomized rats: anthropometrical and mechanical analyses P.A. SIMÕES*, A. ZAMARIOLI, P. BLÓES, F.C. MAZZOCATO, L.H.A. PEREIRA, J.B. VOLPON, A.C. SHIMANO Laboratory of Bioengineering and Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, Faculty of Medicine of Ribeirão Preto, University of São Paulo. The purpose of this study was to examine the preventive effect of exercise on lumbar vertebrae in ovariectomized rats. Three-month- old female Wistar rats were divided into 3 groups: control group (A, n = 10); non-exercised ovariectomized group (B, n = 7) and exer- cised ovariectomized group (C, n = 7). The rats from group C were subjected to treadmill exercise (15 m/minute in the initial six weeks and 19 m/minute in the next six weeks, 1 hour/day, 4 days/week) for 12 weeks. At death, the fourth lumbar vertebrae were removed and an anthropometrical analysis by a paquimeter and a mechanical compression test by a universal test machine were performed. After 12 weeks, the ovariectomy decreased the superior–inferior vertebral height and the maximal braking load in group B compared to group A, while the exercise increased the vertebral mass in group C compared to both groups A and B ( p < 0.01) and the stiffness compared to group B. We concluded the physical activity has an important role to prevent the osteopenia in lumbar vertebrae. Key words: spine, ovariectomy, osteopenia, biomechanics 1. Introduction Bone is a dynamic tissue in the continuous processes of formation and resorption which are stimulated by osteoblasts and osteoclasts, respectively [1]. After meno- pause, the reduction of estrogen concentration increases the osteoclastic resorption that exceeds the rate of osteo- blastic formation, resulting in a bone mass loss (osteope- nia or osteoporosis). In the last years, these diseases have extensively been researched all over the world, since they became a serious health problem – one of the most dangerous diseases of the women and elderly people. The most usual fractures caused by the osteoporosis are those of hips and vertebrae [2]. Physical exercises are widely used as a preventive method that minimizes the decrease of the bone min- eral density [3]–[10]. The physical activity increases the bone mineral density in rats and in women after menopause [11]. 2. Purpose This study is aimed to verify the influence of the treadmill running on mechanical and structural proper- ties of the forth lumbar vertebrae by means of biome- chanical analysis with compression test and anthro- pometrical measurements of ovariectomized rats. 3. Material and methods Three-month-old female Wistar rats (n = 30), weighing approximately 250 g, were used. Animals ______________________________ * Corresponding author: P.A. Simões, University of São Paulo, Faculty of Medicine of the Departament of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, Santos Dumont Street, 564 – Bairro Vila Tibério, CEP 14050-060 Ribeirão Preto – São Paulo – Brazil, e-mail: arianezamarioli@usp.br Received: April 22, 2008 Accepted for publication: June 4, 2008