Discussion
This study presents an aquatic exercise program named HydrOS, in reference to specific high-intensity aquatic exercises for the prevention and treatment of osteoporosis. As far as we are concerned, no study involving aquatic exercises has shown significant changes in neuromuscular variables, together with an expressive fall reduction among postmenopausal women. To set up the present aquatic exercise program, we combined many different exercise methodologies that other studies have indicated to be useful for enhancing physical function and for preventing falls among older women: high-intensity strength/power training performed with a low number of repetitions in each set of exercises and a high speed of movements.
Our results showed that 6 months of high-intensity aquatic exercises could significantly improve all neuromuscular variables measured in the study. The flexibility of the participants in the AEG increased by 26.6%, and although there was also a significant improvement in the CG (12.2%), the AEG presented a 14.4% better result. In the same way, Colado et al investigated the effects of a 24-week resistance training in water on the physical capacity of healthy sedentary postmenopausal women and found that the flexibility measured through FLEX improved by 27.94%—very similar to the results observed in our study.
Although the CG also presented a significant progress in TUG (10.1%), the mobility of the participants showed a more expressive improvement (23.7%) in the AEG (13.6% more than in the CG; P<0.001). After menopause, as women grow older, some physiological capacities, such as body balance and muscle strength, start to decline; as a consequence, mobility impairments may cause falls and difficulties in performing activities of daily living. Hence, the mobility improvement seen in the AEG probably contributed to the reduction of falls also observed in this group.
Some studies involving aquatic exercises and postmenopausal women did not succeed in showing enhancements in muscle strength in this population. Taunton et al showed that a general aquatic exercise program, including aerobic training and endurance muscle training, was not able to enhance handgrip strength among women aged 70 years after a 12-week period. In the same direction, Rizzi et al studied the effects of an aquatic exercise protocol on the muscle strength of 23 postmenopausal women (mean age, 68 y). The program designed to develop the endurance of the main muscles lasted for 8 weeks and did not imply any significant differences in muscle strength tests. These two studies failed to show enhancements in muscle strength probably because of their general characteristics: they were not designed to develop muscle strength, that is, participants had to repeat one exercise too many times in a row (usually more than 25), with moderate to low intensity in each repetition.
As in our study, other researchers followed a different physiological basis for physical training in water. Graef et al studied women older than 60 years who submitted to 12 weeks of a specific resistance training based on aquatic exercises that included four mesocycles of 3 weeks, respectively: four sets of 15 repetitions, four sets of 12 repetitions, five sets of 10 repetitions, and five sets of 8 repetitions at maximal speed, using resistive equipment. This type of training increased the muscle strength of shoulder horizontal flexion by 11%. In another trial, Takeshima et al studied older women in a 12- week aquatic exercise program, including resistance exercises; the results showed an increase in SKE by 8% and an increase in SBE by 6%. Our results found a comparable increase for SKE (7.7%) but a much higher enhancement for SBE (26.25%). This difference could be explained by the periodization of our training protocol and the specificity of the exercises. As it is already known that strong back extensor muscles are associated with less vertebral fractures in women with osteopenia and osteoporosis, we designed our exercise protocol to include movements that require the precise action of these muscles, which certainly contributed to the expressive gain in the strength of the back muscles.
The volunteers who participated in the exercise protocol proposed in this study showed an improvement in SHF that was 12.8% better than the one observed in the CG. Also, the measurements of SKE in the AEG confirmed an enhancement of 7.7%, whereas in the CG, there was a significant reduction (4%) in the strength of this muscle group that was important to walking biomechanics.
The negative correlations observed in this study between TUG and the other neuromuscular variables indicate that older women who have better body balance and greater strength of the back, hip, knee, and hand muscles present better mobility, spending less time in walking short distances (TUG). These data confirm the importance of physical activity programs aimed to develop mobility, strength, and balance in postmenopausal women, such as the aquatic exercise protocol
Another main concern when dealing with postmenopausal women are falls. Studies demonstrate that a third of people older than 65 years fall annually, with approximately 10% to 15% of falls in this population resulting in fracture, and with almost 60% of those who fell the previous year falling again. These data point to the importance of identifying the women who fall (the fallers) so that we can make use of all possible fall prevention strategies to avoid recurrent falls. Trombetti et al showed that participation in music-based multitask exercise classes once a week for a 6-month period could improve gait performance and reduce both the rate of falls (54% less) and the risk of falling among at-risk older community-dwelling adults. Another study, a systematic review, confirmed that Tai Chi interventions could promote up to a 37% fall reduction in older persons. In the present study, we analyzed the number of falls and fallers before and after the protocol to estimate the effects of aquatic exercises on these variables. The results showed that the number of falls was significantly reduced only in the AEG (P<0.001), and the number of postmenopausal women who fell after the protocol diminished by 44% in the AEG, whereas no significant change was seen in the CG. The 14.1% increase in static balance after the aquatic exercises—together with calcium + vitamin D supplementation and the improvement in SBE (26.2%), SKE (7.7%), SHF (18.5%), and HGS (13.4%)—certainly contributed to the reduced number of falls and fallers in the AEG.
An interesting finding of the present trial was the high number of fallers (65.8%) among the not-so-old women (considered a whole group) studied, notably higher than the 40.1% found by Siqueira et al in a Brazilian population of older people. Analyzing the factors that could explain these results, we found certain conditions in the studied group that had already been recognized by some authors as risk factors for falls, such as low visual acuity (91.7%), economic problems (100%), sedentary lifestyle (100%), and impaired physical function, especially low levels of balance and muscle strength at baseline. In a previous study, we measured SHF and SKE in institutionalized persons 60 years or older using exactly the same dynamometer and procedures used in the present study. Upon comparison of the institutionalized and community-dwelling women, the results for SKE were very similar (11.6 and 11.25 kg, respectively), whereas SHF was notably higher in institutionalized women than in the women studied here (9.8 and 5.1 kg, respectively). The weakness of hip flexor muscles among the postmenopausal women of the present study, as well as the low levels of static balance presented in the group, might have contributed to falls. Domínguez-Carrillo et al reported that the static balance measured through UST in older persons should result in scores higher than 30 seconds, and they concluded that results lower than that—as the ones we found (22.8 s)—should be interpreted as an indicator of falls in older people.
It is important to point out that the main muscle groups, including the abdominals (mainly as an isometric stabilizer of other movements), were targeted in the aquatic exercise program that we proposed. However, no intentional flexion or rotation of the spine was performed by the participants in the AEG because it was already known that postmenopausal women with osteoporosis may develop vertebral fractures due to the stress imposed on the vertebrae by these movements.
In this trial, because the initial serum vitamin D levels of the participants were not very low, the daily cholecalciferol supplementation (1,000 IU) implemented seemed to be efficient in correcting 25(OH)D deficiency, considering that most participants reached the sufficiency level after the study. Both groups significantly raised initial serum 25(OH)D levels and improved TUG (10.1%), and the mild increase in UST (4.5%) and SHF (5.7%) in the CG can be explained by the enhancement in serum vitamin D levels. In the same way, various researchers have found increases in neuromuscular parameters, such as balance, functional mobility, and muscle strength, after vitamin D supplementation in older persons without regular physical activity. Although serum iPTH levels showed a significant increase after the protocol in the CG, the final results were within the reference range for this parameter.
A limitation of this trial was the fact that, for ethical reasons, we could not have a CG without any calcium + vitamin D supplementation. If thiswere possible, we would certainly have a better understanding of the isolated effects of supplementation on the measured variables. Another limitation would be the self-reported data on falls, especially the falls that happened before the beginning of the study—data that might have been misrelated by the participants.