Heidi M. Weingart, MA, and Len Kravitz, PhD
Resistance Training and Bone Mass
esearch has begun to emphasize the potential benefits of adding resistance training to an exercise regimen, especially for elderly persons. Among the benefits for seniors are improved strength, bone mineral density and daily living performance, which can raise independence for this population while lowering the risk of falls and other injuries. Controversy remains, however, about what training method is best suited for individuals in their advanced years. The research study reviewed in this article attempts to address the contro-
versy by comparing high-intensity, standing free-weight resistance training to moderate-intensity, seated machinebased resistance training. The study also compared how the two training regimens impacted elderly men versus elderly women in regard to strength, bone mineral density and body composition. First, some background material on bone mineral density must be discussed.
Morphology of Bone Mineral Density Bone is a complex tissue that provides lifelong structural support for muscles, protection for vital organs and storage
for calcium, which is essential for bone density (Nieman 1998). All living bones are constantly breaking down and building up, referred to as remodeling. Specific chemical signals direct some bone cells--referred to as osteoclasts--to break down and remove bone--referred to as bone resorption, which is the act of absorbing. Different chemical messages tell other bone cells--known as osteoblasts--to deposit new bone. Shortly after puberty, bone mineral density reaches its peak (Robergs & Roberts 1997). The remodeling process is regulated by a variety of factors, including physical stress and a multiple-hormone
SUMMARY OF PAST RESEARCH ON BONE MINERAL DENSITY (BMD)
SUBJECTS/ METHODS RESULTS
Lloyd, T., et al. 2000. Adult female hip bone density reflects teenage sports exercise patterns but not teenage calcium intake. Pediatrics, 106, (1), 40-4.
81 premenarchal, white, adolescent females 6-year study
calcium intake did not affect total body BMD; no significant positive relationship between sports activity and hip BMD
Andersen, R. E., et al. 1997. Changes in bone mineral content in obese dieting women. Metabolism, 46, (8), 857-61.
21 obese women: 13 premenopausal, 4 perimenopausal, 4 postmenopausal 24-week resistance training and low-calorie diet study
no reductions in total BMD; did not prevent loss of BMD from femoral neck and greater trochanter
Hawkins, S. A., et al. 1999. Eccentric muscle action increases site-specific osteogenic response. Medicine & Science in Sports & Exercise, 31, (9), 1287-92.
20 women, 20-23 years old, with no current participation in exercise programs 18-week eccentric resistance vs. concentric resistance study
eccentric resistance exercise was more effective in increasing BMD than concentric resistance exercise
Dornemann, T. M., et al. 1997 Effects . of high-intensity resistance on bone mineral density and muscle strength of 40-50-year-old women. Journal of Sports Medicine and Physical Fitness, 37, 246-51.
26 women, 40-50 years old, with regular menstruation and no estrogen therapy 6-month heavy resistance training study
slightly significant increase in vertebral BMD in women who participated in heavy resistance training
Chilibeck, P. D., et al. 1996. Twenty weeks of weight training increases lean tissue mass but not bone mineral mass or density in healthy, active young women. Canadian Journal of Physiology Pharmacology, 74, (10), 1180-5.
30 young women, about 20 years old, with no menstrual irregularities or regular exercise 20-week resistance training study
significant increases in strength and lean tissue mass; no change in BMD
IDEA PERSONAL TRAINER
system (Robergs & Roberts 1997). The multiple-hormone system is sensitive to blood calcium levels. When these levels drop, the parathyroid hormone is released, which activates the osteoclasts. When calcium levels are high, the thyroid gland releases the hormone calcitonin, which inhibits the osteoclasts and activates the osteoblasts, resulting in bone deposition (Robergs & Roberts 1997). In females, estrogen tends to inhibit osteoclast activity and, therefore, helps retain bone mineral (Robergs & Roberts 1997). Maintaining bone mineral density levels is important for postmenopausal women, because they no longer have the protective effects of estrogen. Interestingly, though elderly women are more prone to bone loss, testosterone in men tends to have the same effects as estrogen on bone remodeling (Robergs & Roberts 1997). Therefore, it is also important for elderly men to maintain bone mineral density, because testosterone levels decline with age. One of the best methods to maintain bone mineral density is through physical activity, which accelerates physical stresses on the bone. These stresses help activate the osteoblasts and favor bone deposition (Robergs & Roberts 1997). Resistance training is one activity being advocated for retaining, and even possibly increasing, bone mineral density. Still, the question remains: What type of resistance training is best? The following research study review examines this question as it relates to elderly men and women.
Recent Investigation Study: Maddalozzo, G. F., & Snow, C.
healthy older men and women. Methods: Twenty-four elderly men (54.6
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