Exercise as it relates to Disease/The relationship between exercise frequency and bone mineral density development in exercising postmenopausal osteopenic women

This is an analysis of the journal article "Exercise frequency and bone mineral density development in exercising postmenopausal osteopenic women. Is there a critical dose of exercise for affecting bone? Results of the Erlangen Fitness and Osteoporosis Prevention Study" by Kemmler, W., Stengal, S., & Kohl, M. (2016)

This fact sheet was created by student u3099853

What is the background to this research?

Osteoporosis is a medical condition where bones become brittle and fragile due to a loss of bone structure. This bone structure is made up of minerals, such as calcium, and in osteoporosis is lost faster than the bone can restore them. The loss of strength in the bones can lead to increased fracture rates. Osteopenia is range of low bone density between normal and osteoporosis.

Osteoporosis is currently estimated to affect 23% of Australian women over the age of 50. In this population, between the ages of 50 and 60, there is an estimated future lifetime risk of acquiring a minimal trauma fracture of 42-56%. Hence it is imperative that steps are taken to prevent this avoidable condition.

It is well established in the literature that exercise can help prevent osteoporosis , but as people grow older the less frequently they are likely to exercise. This study aims to determine the minimum exercise frequency for there to be a benefit for bone mineral density in postmenopausal osteopenic women.

This research will allow osteopenic postmenopausal women to have a guideline of how many times a week they need to be exercising to increase their bone density and prevent osteoporosis.

Where is the research from?

The original study by Kemmler et al (2014) that the research is based on was conducted by the Institute of Medical Physics, University of Erlangen (FAU), Germany, from 1998 to 2014.

All three authors have done prior research together into osteoporosis and fractures, with Kemmler and von Stengel having their specialities lie in physical rehabilitation and osteoporosis. There were no sponsorship links that may have affected the bias in this study.

What kind of research was this?

This is a retrospective study, using the results of the Erlangen Fitness and Osteoporosis Prevention Study at 16 year follow up. This study has a level of evidence of III.

What did the research involve?

137 early postmenopausal (1–8 years post) women elected to join either the non-exercise (n=51) or exercise group (n=86). The exercise group performed 4 exercise sessions; 2 supervised group session and 2 home exercise sessions 49–50 weeks/year for 16 years.

	Group Session	Home Session
Frequency	2x/week	2x/week, starting from month 5
Intensity	Mixture of low and high intensity, with sets between 1-4 and rep ranges between 4-12, 50-90% 1RM	Not mentioned
Time	65 mins	20-25 mins
Type	Aerobic Dance Multilateral Jumping Periodised resistance exercises (machines and free weights)	Running Rope skipping Isometric and dynamic resistance exercises Stretching and flexibility exercises

Both groups were also provided with calcium and Vitamin D supplements to ensure an intake of at least 1000 mg/day of calcium and 500IU/day of Vit D.

Attendance for the supervised exercise groups was recorded by the instructors and the participants also recorded their participation at the groups and in the home exercise program in a log which was collected every 12 weeks. As home participation was self reported, subjects of the study may have over reported the frequency of their participation in the home exercise component in the 16 years this study was run.

Unfortunately, only 55 participants made it into the final analysis. Two-thirds of the participants dropped out or had to be excluded from the study for a large variety of reasons such as death, disinterest, serious diseases, injuries unrelated to the study, or the commencement of biophosphonate therapy. As the follow up was at 16 years, it is only natural to have so many lost to follow up.

Bone mineral density (BMD) was reported in mg/cm² rather than T-score value, which compares a patient's BMD to healthy adult norms, making it difficult to see the change in BMD in this study.

What were the basic results?

It was found throughout this study that exercise participation dropped significantly from 2.41 sessions per week in the first 2 years to 2.15 sessions per week in the final 2 years of the study (p<0.001)

It was found that a minimum of 2.11 sessions/week and 2.22 sessions/week was required for an improvement in Lumbar Spine BMD (p<.001) and Hip BMD (p<.005) respectively and anything less than that was no better than the sedentary control group.

What conclusions can we take from this research?

This research tells us several things. Firstly exercise participation seems to decrease as one ages. Secondly to improve BMD, there is a required minimum of 2 sessions per week of exercises including weight bearing aerobic activity as well as resistance exercise. However this exercise frequency may not be generalisable to all forms of exercise or all population groups.

This research is new being published in April 2016, and is the first study to look at the relationship of exercise frequency and bone mineral density.

Practical advice

With the information from this article, we can see that there is a general trend of decreasing exercise frequency even with a structured exercise program. However we may be able to offset this by educating our clients or patients that by setting aside just 2 hours a week to exercise they can improve their bone strength and decrease their risk of having bone fractures. This is something that can be a big motivational boost and can have a significant effect on their quality of life and health. A caveat is that this exercise would have to consist of some high impact activities and resistance exercises however. Exercise modalities such as swimming, cycling and water aerobics may not have the same effect as they are either no or very little impact.

Before starting this exercise program, readers should ensure that they are medically cleared by their GP to do this sort of exercise as it involves relatively high intensity and high impact exercises such as jumping and skip rope. Readers may need to start with lower impact exercises such as brisk walking and step ups depending on functionality and health.

Further information/resources

Diagnosis of osteoporosis: http://www.osteoporosis.org.au/diagnosis
Exercise information for osteoporosis: http://www.osteoporosis.org.au/exercise
Prevention information for osteoporosis: https://www.choice.com.au/health-and-body/conditions/muscles-bones-and-joints/articles/preventing-and-treating-osteoporosis