Exercise as it relates to Disease/Cross sectional and longitudinal studies on the effect of water exercise in controlling bone loss in Japanese postmenopausal women

This Wikibooks page is an analysis of the journal article "Cross sectional and longitudinal studies on the effect of water exercise in controlling bone loss in Japanese postmenopausal women" by Tsukahara et al. (1994)

Introduction to Osteoporosis

Osteoporosis is a disease characterised by a decrease in bone mineral density and strength, making them brittle, fragile, and more susceptible to breaks and fractures. The loss of bone tissue is a result of hormonal changes, or deficiency of minerals such as calcium and vitamin D. Bone density is influenced by multiple factors such as heredity, oestrogen levels, physical activity, nutrition, and life style. In general, women are at higher risk than men, particular those of postmenopausal age. This study on Japanese postmenopausal women examines the effect of water exercise on bone mineral density, and whether an exercise program improves the awareness of health and daily life of the participants.

Prevalence in Japan

The prevalence of osteoporosis in Japan is estimated to be 11.6 million with 8.4 million women, and 3.2 million men. An average of 90 000 hip fractures are estimated to occur every year, with the incidence rate continuing to increase in both men and women.

Treatment methods

Treatment of osteoporosis include calcium and vitamin D supplements, and a range of medicines such as bisphosphonates, hormone replacement therapy (HRT), and selective estrogen receptor modulators (SERMs). Regular physical activity, especially weight-bearing exercises, is also known to play an important role in maintaining and improving BMD.

Where is this research from?

This research was carried out in September 1993 by the Department of Food and Nutrition at the Japan Women’s University in Tokyo. Subjects included 67 healthy postmenopausal women who did regular water exercises classes at a sports club in Tokyo, and 30 healthy postmenopausal women who did no particular regular exercise.

What kind of research was this?

This study on Japanese women involved a cross-sectional study and a longitudinal study. In the cross sectional study, the women were divided into 3 groups: Non-exercisers (n=30), Newcomers (n=40), and Veterans (n=27). The newcomers and veterans groups performed the water exercise, while the non-exercisers served as the control. The longitudinal study consisted of 30 non-exercisers, 15 newcomers, and 20 veterans. Anthropometry and BMD of the subjects were measured 1 year after initial the assessment.

Research Methods

Cross Sectional Study

The cross sectional study involved 97 healthy Japanese postmenopausal women with physical characteristics shown in Table 1 below (mean±SD).

Group	Non-Exerciser	Newcomer	Veteran
Number of Subjects	30	40	27
Age (year)	60.13±0.38	63.68±0.70	64.26±0.82
Height (m)	1.533±0.01	1.537±0.01	1.536±0.82
Weight (kg)	54.80±0.89	54.40±0.88	55.82±1.56
BMI (kg/m2)	23.36±0.41	23.03±0.34	23.64±0.61
Body fat (%)	30.36±1.12	30.19±0.81	30.96±1.46

The veteran group consisted of women who had an exercise history of 35.2 months on average, whilst the newcomer group consisted of women who had only begun exercise 3 or 4 weeks before. The non-exercisers served as the control group. Informed consent was obtained from all subjects. Body fat percentage was performed using Bioelectrical Impedance Analysis, while BMD of the lumbar spine (L1-L4) was measured using Dual X-ray Absorptiometry (DXA). The BMD was expressed either in g/cm2 or as a Z-score based on data from approximately 1000 Japanese normal women aged 20-80 years. Furthermore, nutritional analysis was estimated from 3 day dietary records, and calculated based on the Japanese Recommended Dietary Intake. General awareness of health and fitness in daily life was also investigated using questionnaires.

Water Exercise Protocol

The water exercise was performed once a week in a warm water pool (28-29^oC), and included waking, jumping, and light callisthenics. The 45min session consisted of:

• 10min warm up
• 20min of aerobic exercise and deep breathing
• 10min of swimming
• 5min cool down

The program included two Maximum Working Heart Rate Peaks (approximately 120bpm) during the 45min session.

Longitudinal Study

In the longitudinal study, anthropometry and BMD measurements were taken 1 year after the initial assessment. Participants included 15 newcomers, 20 veterans, and all 30 subjects in the non-exercisers group.

Results and findings from the study

The study found that consistently participating in water exercise can prevent bone loss in postmenopausal women. The veterans group who had been doing water exercises for 35.2 months on average, showed higher lumbar spine BMD Z-scores than the newcomers and non-exercisers groups. From the longitudinal study, the exercising groups maintained or showed an increase in BMD, while the non-exercising group showed a definite decrease at the 1 year point.

Nutritional analysis of the women from 3 day dietary records showed that in the exercising groups, intakes of all nutrients were adequate compared to the Japanese RDA. The non-exercising group however, showed a slight insufficient iron intake.

The result of the general awareness survey showed that there was an improvement in life and health after starting the water exercise program. Many said they had a more positive outlook on daily life and that their physical fitness had increased.

What conclusions can we take from this research?

From this study we can conclude that there is a positive effect of water exercise on bone mineral density in postmenopausal women. It is well known that regular physical activity is beneficial for bone density and strength, and that exercise is an effective means for preventing, delaying, and treating osteoporosis. This research shows that non weight-bearing activities can also be used to increase BMD. This is good news as it is often difficult for the elderly to perform weight-bearing exercises due to their decreased physical capabilities and fitness. Furthermore, the study shows that an exercise program indirectly improves the awareness of one’s health, and their outlook on daily life.

Implications and further suggestions

While results show improvements in BMD in the women, the sample size is quite small (n=97), and does not mention the duration of the water exercise intervention. It only stated that it was performed 45min once a week. While water exercise was found to be beneficial, the study could have included another group that performed weight-bearing exercises (such as walking, jogging or resistance training). This would show what form of exercise is most suitable for this age and gender group. The long term effectiveness (>1 year) of water exercise on BMD should also be further investigated.

Further information and resources

The followings links provide further information regarding osteoporosis and the benefits of exercise:

• Osteoporosis Australia: http://www.osteoporosis.org.au/
• Exercise Recommendations for Osteoporosis: https://www.iofbonehealth.org/exercise-recommendations
• Osteoporosis and Exercise: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1742726/pdf/v079p00320.pdf
• Journal of Osteoporosis and Physical Activity: http://www.esciencecentral.org/journals/osteoporosis-and-physical-activity.php