Welch, J. M., C. M. Weaver, and C. H. Turner. Adaptations to free-fall impact are different in the shafts and bone ends of rat forelimbs. Impact exercise can have beneficial effects on the growing skeleton. To understand what changes it promotes in the shafts and ends of weight-bearing bones, we measured the effects of impact from repetitive free falls in growing rats. Fischer 344 female rats, 6.5 wk old, were assigned to one of three groups (n ϭ 10 each). Controls were not dropped, whereas those subjected to impact were dropped from 30 or 60 cm. Rats in both free-fall groups were dropped 10 times per day for 8 wk. Leg bones were mechanically tested, and their cross-sectional area (CSA), cross-sectional moments of inertia, and volumetric bone mineral density (BMD) were measured by peripheral quantitative computed tomography. In the shafts of the forelimbs, but not the hindlimbs, free-fall impact resulted in greater ultimate breaking force, minimum and maximum second moments of area, and CSA but not BMD. In the bone ends of the forelimb and tibial bones, trabecular BMD increased but CSA did not. Landing from 30 and 60 cm produced peak impact forces of 12.0 and 16.7 times the standing forefoot weight for each front leg and of 4.5 and 7.7 times the standing hind foot weight for each hind foot. Overall, free-fall impact affected the forelimbs by increasing trabecular bone density in the bone ends and improving the strength at the shaft as a result of geometric improvements. These results indicate that adaptation to impact may occur by different mechanisms in bone end and shaft regions. exercise; bone strength; ground reaction force; peripheral quantitative computed tomography; rats Values are means Ϯ SE. ND, sufficient cortical bone not available for analysis of image by software. Significant difference from controls: a P Ͻ 0.05; b P Ͻ 0.01; c P Ͻ 0.001. Significant difference between F30 and F60: d P Ͻ 0.05. ADAPTATIONS TO IMPACT IN BONE
Soy isoflavones and their metabolites, with estrogenic activity, have been considered candidates for reducing postmenopausal bone loss. In this study, we examined the effect of dietary equol, a bioactive metabolite of the soy isoflavone daidzein, on equol tissue distribution, bone parameters, and reproductive tissue activity using an adult ovariectomized (OVX) rat model. An 8-wk feeding study was conducted to compare 4 dietary treatments of equol (0, 50, 100, 200 mg/kg diet) in 6-mo-old OVX female Sprague-Dawley rats. A dose response increase in tissue equol concentrations was observed for serum, liver, kidney, and heart, and a plateau occurred at 100 mg equol/kg diet for intestine. In OVX rats receiving 200 mg equol/kg diet, femoral calcium concentration was greater than those receiving lower doses but was still less than SHAM (P < 0.05), and other bone measures were not improved. Tibia calcium concentrations were lower in OVX rats receiving 100 and 200 mg equol/kg diet compared with the OVX control rats. Trabecular bone mineral density of tibia was also lower in equol-fed OVX rats. At this dietary equol intake, uterine weight was higher (P < 0.05) than in other OVX groups but lower than the SHAM-operated intact rats. The 200 mg/kg diet dose of dietary equol significantly increased proliferative index in the uterine epithelium. Dietary equol had no stimulatory effect on mammary gland epithelium. We conclude that in OVX rats, a dietary equol dose that had modest effect on bone also exerts mild uterotropic effects.
Calcium (Ca) supplements, especially Ca carbonate (CaCO3), are the main alternative sources of dietary Ca and an important part of a treatment regimen for osteoporosis, the most common metabolic bone disorder of aging and menopause. In a female ovariectomized (OVX) rat model for studying postmenopausal osteoporosis, we tested the hypothesis that a small compared with a large particle size of CaCO3 (13.0- vs. 18.5-mum geometric diameter) would result in increased Ca balance and subsequently bone mass and that this would be affected by dietary Ca level. We used 6-mo-old rats that were OVX either at 6 or 3 mo of age as models of early or stable menopausal status, respectively. The rats received semipurified diets that contained either 0.4 or 0.2% dietary Ca provided from CaCO3 of 2 particle sizes. A group of Sham-operated rats with intact ovaries served as control and were fed 0.4% dietary Ca from large particles. Estrogen deficiency as a result of ovariectomy had an adverse effect on bone density, mineral content, and bone mechanical properties (P < 0.001). Reducing dietary Ca from 0.4 to 0.2% resulted in significant adverse effects on bone density and mechanical properties (P < 0.001). The particle size of CaCO3 did not affect total Ca balance, bone dual energy X-ray absorptiometry and peripheral quantitative computed tomography indices, bone ash and Ca content, or the mechanical determinants of bone strength. We conclude that a decrease in particle size of CaCO3 to 70% of that typically found in Ca supplements does not provide a benefit to overall Ca metabolism or bone characteristics and that the amount of Ca consumed is of greater influence in enhancing Ca nutrition and skeletal strength.
A sedentary lifestyle is linked to many diseases, including diabetes and heart disease, as well as ailments such as obesity, which is becoming the major root cause of early death in most industrialized countries. The advent of the television, computers and videogames has resulted in a more sedentary lifestyle, with more time spent in front of a screen more than ever before. Exergaming is a term used to describe video games that provide encouragement to exercise, particularly for an audience that may be reluctant to engage in the more traditional forms of exercise. Exergames are a commonly accepted method of encouraging more physical activity to promote better health for those with high levels of sedentary screen time. In this work, we survey a number of quantitative exergame studies to define a general set of elements that make exergames effective from a physical standpoint. We also examine the intended audience and the incentive elements necessary for an exergame to meet the needs of its audience. Finally, we examine our own exergame system and how well it performs against commercial systems.
Bone and muscle weakness due to vitamin D deficiency is common among Muslim women who reside in sunny, equatorial countries. The purpose of this study was to determine if living in a northern maritime location additionally disadvantages women who wear concealing clothes. A cross-sectional matched pair design was used to compare women who habitually wore concealing clothing with women who dressed according to western norms. Each premenopausal hijab-wearing woman (n = 11) was matched by age, height, weight and skin tone with a western-dressed woman. Subjects were tested by hand grip dynamometry to assess muscular strength and by quantitative ultrasound at the calcaneus to assess bone status. Nutritional intake was obtained by 24 h recall. Serum 25-hydroxyvitamin D (s-25(OH)D) status was determined in seven matched pairs. The hijab group had lower s-25(OH)D than women who wore western clothes (40 ± 28 vs. 81 ± 32 nmol/L, p= 0.01). Grip strength in the right hand was lower in the hijab-wearing women (p = 0.05) but this appeared to be due to less participation in intense exercise. Bone status did not differ between groups (p= 0.9). Dietary intake of vitamin D was lower in the hijab-wearers (316 ± 353 vs. 601 ± 341 IU/day, p= 0.001). This pilot study suggests that women living in a northern maritime location appear to be at risk for vitamin D insufficiency and therefore should consider taking vitamin D supplements.
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