This study showed that the elderly patients who experienced more than 4 weeks of low-intensity “upper-body yoga” training may show higher FVC, PCF, and daily living activity than those who experienced the same period of abdominal breathing training. And such yoga exercise is safe and feasible in the acute phase of hip fracture and subsequent rehabilitation.
Age-related sarcopenia (or decreased muscle mass) is a noticeable problem for elderly patients. Aging reduces respiratory functions as manifested by the decline of pulmonary volume and respiratory muscle tone . Upon hip fracture, the vital capacity and forced expiratory flow in elderly patients confined in a supine position are further reduced. In this study, on the first day of admission elderly patients with healthy lungs showed significantly lower FVC (2.14 ± 0.54 L) and FVC% (71.66% ± 12.53%) than the normal range specified in the guideline of the American Thoracic Society and the values of Cebria et al.’s  study on sedentary frail older women (77.7~83.0%). It has been well proven that lower position reduces spirometric values [11, 12]. The low FVC of patients with healthy lungs and hip fracture in the present study may be attributed to postural limitations, physical pain, and stress weakness. As it went to 1 month later, FVC% in both CG and YG increased gradually with the recovery of the disease and the progress of respiratory training. However, the FVC% in YG showed an even bigger increase.
The effective role of yoga in improving pulmonary functions of healthy elderly people and COPD patients has been well recognized [13,14,15]. However, the effects of different intensity and duration of yoga training on vital capacity and cough capacity are unclear. At present, yoga practices in immobilized elderly have not been well studied.
It is known that the training on abdominal breathing (belly breathing) is the most traditional breathing training method. When belly breathing is repeatedly practiced, the muscle of the diaphragm contracts forcefully to generate a higher tidal volume, thus helping to inflate the lungs and make the diaphragm stronger. Celli et al. , Baarends et al. , and Petta et al.  studied the physiological responses upon unsupported low-intensity static and dynamic exercises of upper limbs (limb elevation, flexion, and extension). These studies revealed that unsupported low-intensity exercises of upper limbs significantly increased ventilation and promotes respiratory muscle function. During arm exercise, accessory muscles of respiration are primarily recruited to positions, which forces the major inspiratory muscle (diaphragm) to increase its contribution to ventilation. Recently, unsupported arm exercises have been widely used in the immediate post-operative period of thoraco-abdominal surgery and in chronic stages of pulmonary diseases . The “upper-body yoga” exercise used in this study is a combination of upper body movement, respiration training (belly inhalation, slowly and fast forced exhalation), and relaxation. It is hypothesized that this training program may be more effective and suitable than traditional belly breathing program in peri-operative management of hip fracture. However, in prior studies, the duration of yoga in majority of the studies was designed over 2 months, these yoga sessions were performed 2~4 times per week [20, 21]. Four weeks seems too short of a time to observe a substantial improvement in respiratory muscles. In this study, the number of yoga sessions was more (2 times/day, 7 days/week). At present, several studies have confirmed the effects of short-term yoga on lung function. In some studies, 4 weeks of yoga have been shown to improve lung function in asthmatic patients [22, 23]. In another study, the elderly patients with COPD showed significantly higher vital capacity and better quality of life after 6 weeks of yoga (3 days/week) . Similarly, we observed that at the end of 4 weeks after surgery, the subjects in YG had higher FVC% than those in CG, indicating the presence of higher ventilation and stronger respiratory muscles in YG. Current research shows that expiratory muscle may be easier to get enhanced by short training sessions than inspiratory muscle. The advantage in YG may be due to a combination of subtle changes in inspiratory muscle and expiratory muscle strength. Unfortunately, we did not have an accurate estimate of respiratory muscle strength. The result above indicates that the combination of upper-body movements and respiration training (“upper-body yoga”) may be more beneficial to improving lung capacity than belly breathing alone.
PCF is the maximum airflow generated during a cough and is dependent on inhaling vital capacity and expiratory muscle tone. Bach et al.  suggested that in patients with muscle weakness, a minimum threshold for effective airway clearance was 160 L/min. According to Tzeng and Bach’s  experience, when the PCF is < 270 L/min, it is likely to fall below 160 L/min when a patient becomes frailer. In the present study, the baseline PCF in the 30° supine position was 193.13 ± 37.49 L/min in CG and 191.44 ± 33.96 L/min in YG, both of which were significantly lower than 270 L/min. Even after more than 4 weeks of training, the PCF of the patients was still less than 270 L/min. At present, there is no reference values of PCF for different age group, and there are few reports on PCF of the elderly. A study  on healthy Brazilian population’s PCF (aged 18~40) showed that PCF decreased significantly with age and the average PCF of men aged 18 and 40 was significantly different (499 L/min vs. 316 L/min). So, advanced age and postural restriction is the primary consideration for the low PCF in this study. These results suggested that when elderly patients were forced to stay in bed, they were at a high risk of sputum retention and lung infection, and hence, it was essential to help remove airway secretions.
In the process of belly breathing program, expiration is passive, expiratory muscles are not activated and hence disuse-atrophy in bed. In the “upper-body yoga” training program, a forced expiratory technology (including slowly and fast forced exhalation) was adopted to improve the main expiratory muscle strength (abdominal and chest muscles). Moreover, upper-body exercises may make the majority of chest and back muscles (accessory expiratory muscles) stronger. Many studies revealed that the training on expiratory muscles increases the tone of expiratory muscles and the rate of voluntary expiratory flow. In Kim’s  4-week training of expiratory muscles in sedentary and healthy elderly subjects, the maximum expiratory pressure (MEP) generated by expiratory muscles quickly increased in the first week of training from 77.14 cmH2O to above 90 cmH2O, and then gradually increased to 110.83 cmH2O in the following weeks. In addition, the peak expiratory flow rate of reflexive cough induced by capsaicin increased from 298.8 ± 130.8 L/min to 480.0 ± 183.6 L/min. In another study, an increase in MEP was observed in 2~4 weeks of training on expiratory muscle strength . However, these studies were carried out using an expiratory pressure threshold device. A recent study  observed favorable effects of forced expiratory training on vital capacity and peak expiratory flow in frail and elderly subjects. In this study, the subjects practiced slow expiration using abdominal muscles and a resistance device for 20 min/day in 3 months. In the present study, more than 4 weeks of soothing yoga training increased PCF from 191.44 ± 33.96 L/min to 216.16 ± 39.29 L/min, and it was higher than that of the CG. The results are consistent with previous studies. The higher PCF in YG may be related to stronger inspiratory muscles and expiratory muscles. On the other hand, fast forced expiration maneuver in YG has been considered an effective method to induce tracheobronchial clearance [31, 32].
In the acute phase of fracture, a patient’s quality of daily living is seriously affected. In the first year after hip fracture, only 57% of body functions can be restored . The arms play a central role in daily activities, such as eating, dressing, and washing. In the present study, patients in YG showed higher BI at the points of T1 and T2 than those in CG. A possible explanation for the above results is that upper-limb movement in “upper-body yoga” training makes arms more flexible and stronger. On the other hand, active upper-limb movement can encourage bedridden older people to take care of themselves, thus improving the BI. However, this advantage is more pronounced in the early stages of the disease. With the improvement of the patient’s systemic mobility, the advantage was not more obvious with the extension of time.
In the postoperative follow-up, one in CG was diagnosed with pneumonia, and nobody suffered pulmonary complication in YG. On the one hand, the present study included a relatively small number of patients. On the other hand, the subjects included in this study all had healthy lungs, which put them at a low risk of pulmonary infection.
The most common injuries related to yoga are sprain, strain, and falls, which occur most often in strenuous and challenging training . The “upper-body yoga” program used in the present study was designed by three specialists and was low intensity and easy to learn. No discomfort and adverse events were observed. In addition to physiological changes, aging obviously impairs learning and cognitive functions. In YG, the elderly patients got face-to-face and audio coaching, which made the training easier. Hence, although a yoga program seems more complex than the training of belly breathing, a similar number of elderly patients mastered the yoga skills in this study. In the follow-up interview, most patients considered yoga training fun and relaxing. On the contrary, for people not enjoying the training on abdominal deep breathing, they thought the training was boring. An RCT study comparing the effects of short-term inspiratory threshold training with yoga training in institutionalized frail older adults showed that yoga respiratory training appears to be more effective and well-tolerated in frail older adults, and may therefore be a useful alternative to general breathing training, to improve respiratory function in older population, when whole-body exercise is not possible .
Limitation of the study
There are some limitations in this study. First, only the simplest variables were measured in this study, while more accurate indicators for lung function and respiratory muscle strength are needed. Second, the subjects included in the present study have healthy lungs. There, it is essential to further investigate the effect of “upper-body” yoga breathing program in patients with a high risk of pneumonia. In addition, the participants in this study were not strictly blinded, thus increasing the risk of bias.