As little as 120 minutes of walking or other exercise per week was associated with biomarkers of bone strength in premenopausal women, according to the results of a cross-sectional study. An eight-week physical activity intervention program significantly increased biomarkers of bone strength compared with sedentary control patients.
Mohammed-Salleh M. Ardawi, PhD, FRCPath, from King Abdulaziz University Hospital in Jeddah, Saudi Arabia, and colleagues report their results in an article published online August 3 in the Journal of Clinical Endocrinology and Metabolism.
"Physical activity is good for bone health and results in lowering sclerostin, a known inhibitor of bone formation and enhancing IGF-1 levels, a positive effector on bone health," Dr. Ardawi said in a news release. "We also found physical activity training that enhances mechanical loading in combination with anabolic therapeutic agents will have added positive effect on bone health, particularly bone formation."
The cross-sectional study of 1235 randomly selected premenopausal women included a subgroup of 58 women followed up longitudinally during an eight-week course of physical activity training (4 days/week) who were compared with 62 control patients.
In the cross-sectional study, women were classified into four groups according to average walking or exercising level: less than 30 minutes, 30 to 60 minutes, 60 to 120 minutes, and 120 minutes or longer per week. The researchers found that women who were active more than 120 minutes/week had 36.8% lower serum sclerostin and 107% higher serum IGF-I levels than sedentary control patients. They also had higher levels of bone formation markers such as serum osteocalcin, serum procollagen type 1 N terminal propeptide, and serum bone-specific alkaline phosphatase.
In the eight-week longitudinal intervention study, sedentary women assigned to the intervention group completed eight weeks of exercise training consisting of 120-minute sessions four days per week. The structured session included 20 minutes of walking at increased speed and an endurance regimen of 25 minutes running, 20 minutes walking on a treadmill, 10 minutes cycling, and 10 minutes doing step-ups, followed by 35 minutes doing spine flexion-extension exercises and mobility exercises for the lower and upper trunk.
Compared with the women who had fewer than 30 minutes of exercise per week, the women in the exercise group had an average 33.9% decrease in serum sclerostin (P < .0001) and an average 74.2% increase in bone-formation markers and IGF-I (P < .0001).
According to the researchers, this research was inspired by data showing "significant hypersclerostinemia associated with bone loss in long-term immobilized patients [which] suggested that sclerostin could be a link between mechanical unloading and disuse osteoporosis in humans."
The researchers conclude, "To our knowledge, this study is the first to report a significant association between low serum sclerostin levels and increased [physical activity] duration and [serum]-IGF-I levels in premenopausal women. These cross-sectional observations were confirmed by our longitudinal study in which increasing the [physical activity] of sedentary premenopausal women for eight consecutive weeks (four d/wk) resulted in marked changes in serum sclerostin (decrease) and [serum]-IGF-I levels (increase).... The increase in BFM [bone formation markers] and the lack of concomitant changes in resorption markers observed in the longitudinal study parallels the findings of previous studies that showed that BFM are more responsive to short-term exercise training than bone resorption markers."
The authors have disclosed no relevant financial relationships.
J Clin Endocrinol Metabol. Published online August 3, 2012. Abstract
Janis C. Kelly • Medscape Medical News © 2012 WebMD, LLC