QUS measures the SOS values which reflect bone properties and bone health. In the machine that we used, the SOS values were measured. The T-score was calculated by the machine taking the difference between the patient's SOS result and the peak average SOS of young healthy population. We used quantitative ultrasound as a method of measuring bone mass as it has a T-score equivalence similar to that of dual-energy X-ray absorptiometry (DXA) 
We had hypothesized that as young educated women, most of our volunteers had the circumstances that would be optimal for bone health. Specifically, they had access to healthy nutrition as well as would be involved in adequate physical activity in the form of walking on a large campus. However we found that incidence of low bone mass in the range of osteopenia was high among these women. 13.46% of the women had low bone mass corresponding to the osteoporotic range whereas 47.11% in osteopenic range and 39.43% normal. This indicates that these young women had low bone mass which was much lower than the peak average values expected for young women that age. A limitation of this study is the fact that we used a convenience sample of university students and the sample is not representative of the general population.
It has been recently observed that young females are also prone to low bone mineral density despite the fact that osteoporosis is usually seen in postmenopausal women. Fatima et al, 2009 also concluded that the prevalence of osteoporosis and osteopenia is high among young Pakistani women i.e. 43.4% were osteopenic and 12.9% were osteoporotic as measured using QUS 
. Another study also observed that frequency of decreased BMD was 64% in women < 30 years, 55% in women between 31 – 45 years and 73.9% in women > 45 years as measured with QUS 
. A study including elite Iranian female athletes having female athlete triad showed that there is negative changes in BMD and cardiovascular biomarkers in these female athletes which may be due to functional hypothalamic menstrual dysfunction 
The observation of a high incidence of low bone mass critical enough to be considered osteopenia in this young population deserves further attention. On one hand it signifies that they are at a greater risk of developing osteoporosis in later life. On the other hand it may simply imply that this young population was in general slow to mature and perhaps has not developed adequate bone mineralization. On the other hand factors such as increasing sedantarism and the preference for physical inactivity due to greater hours spent indoors with computers and television could also be responsible 
for the prevalence of low bone mass in this population. Assuming that the status of risk factors for these women does not change, a large proportion of young women will develop osteoporosis-related fractures in the future. Prevention is the only cost effective approach for identification of young people at high risk of osteoporosis by improving bone accretion at this age that will further improve health related quality of life and will reduce the personal and economic burden of osteoporosis.
The present study was also undertaken with an objective of comparing the efficacy of exercise regimen and calcium supplementation on BMD at two sites i.e. distal radius and midshaft tibia. For confirming the hypothesis that exercise regimen was better than calcium supplementation to improve BMD, 60 osteopenic and osteoporotic young women were included in the study.
The results of the study showed that the trend for SOS T score distal radius curve had increased with a 22.02% increase observed in the exercise group followed by an 8.6% increase in the calcium supplementation group. Compared to these percentage increases the control group showed a non significant increase in BMD.
The findings that exercise has a positive effect on the SOS T score is consistent with a previous study by Wang et al, 2004 which reported that impact load from dynamic impact loading exercises accounted for 58% of the variance in BMD change at the distal radius and 66% of the variance in BMD change at total distal radius site 
. These results may be attributed to the loading characteristics i.e. dynamic impact loading exercises produce impact loads approximately 33% of body weight 
The results of our study showed that the values for SOS T scores at midshaft tibia had also increased with a 44.44% increase in exercise group followed by 16.09% increase in calcium supplementation group. Comparatively, control group also showed an increase in T score with 8.18% increase.
Further irrespective of the causative factors involved in the observation of the a large percentage of our population demonstrating low bone mass, the fact that exercise training using high impact loading did increase the bone mass confirms the potent role of exercise training parameters related with bone health. Further it also strengthens the notion that these young women though physically active did not meet adequate thresholds for physical activity to stimulate mineralization. It is possible that the recommendations that suggest population specific guidelines for defining cutoffs for osteopenia and osteoporosis need further analysis based on the fact that several studies, though not related to bone health have observed that Asians in general have lower levels of physical activity and are the most cause of concern when it comes to meeting the recommended guidelines [25–27]
The results of our finding confirmed the previous information by Kato et al., 2005 that jumping intervention significantly increased BMD at the femoral neck whereas BMD in the control group remained unchanged after 6 months of exercise intervention 
. Loading with many repetitions at one time had a relatively small additional effect on bones compared with loading of only 10–40 repetitions 
. So, we instructed the subjects to do 25-30 jumps per day. These results suggested that exercise training during adulthood, as well as youth, is very important for bone health.
The effect of calcium supplementation in our study was consistent with the previous finding that calcium supplementation significantly increases bone mineral content at various sites 
and Daniele et al, 2004 also showed the positive effect of calcium and Vitamin D supplementation in women both peri- and post-menopausal status 
The improvement in BMD noted in our study despite the intervention of 3 months was due to the age group of the subjects recruited and the fact that peak bone mass is thought to be attained by the end of the third decade, the early adult years are the final opportunity for its augmentation. Since our participants did not involve themselves in any sporting activity, the sudden stimuli to the bone by increasing physical activity as well as the fact that they were still young, the osteogenic response and increase in accrual of bone mineral in young women may have been greater.
In our study, almost all the subjects showed an improvement in BMD but were not able to reach normal values; only two of the osteopenic subjects reached normal values and two of the osteoporotic reached osteopenic values in the exercise group. A longer study would have indicated the average time for remineralisation of the measured sites to achieve SOS T scores considered normal for their age.