Osteoporosis and alterations of the spine resulting from it lead to back pain. The causes of pain are many-faceted and not immediately related to vertebral deformation. Muscle loss and muscular imbalance may be one reason. The results of the present study show that a sling exercise program leads to upright posture and reduces the kyphosis angle. Markedly improved strength in the trunk (chair-rising test) and better mobility (timed up-and-go test) are responsible for significant pain relief during motion and at rest. To our knowledge, the data registered after sling therapy in patients with osteoporosis have not been previously reported.
The recent published literature contains reports on various types of training programs. In an investigation of 100 postmenopausal women with osteoporosis, aged between 55 and 75 years, Teixeira et al. [29] concluded that progressive muscle training of the quadriceps muscle and proprioception leads to muscular and coordinative adjustments; this exerts a positive effect on the risk of falls and quality of life in patients with osteoporosis. The authors did not register the patients’ intake of painkillers.
Iwamoto et al. [11] conducted a 5-month training program in 68 patients aged 76.4 years on average. After completion of the training program, marked improvements were registered in respect of muscle strength and walking ability, while the frequency of falls was significantly reduced.
In 69 postmenopausal women with osteoporosis, aged between 50 and 70 years, Siegrist et al. [26] found that strength training performed twice a week has effects on muscle strength, dynamic performance capacity, and well-being. No patient had been taking painkillers on a regular or permanent basis.
Franck et al. [10] report that a mere 4 weeks of exercise is sufficient to enhance functional abilities in patients with osteoporosis as well as reduce their physical symptoms (back pain, heavy legs).
The concept of sling exercise therapy has the same purpose, but the use of a sensomotor approach to treat pain in osteoporosis is new. The neuromuscular system is subjected to numerous stimuli because of the variability of the slings. Patients must concentrate and react very rapidly to regulate and control their movements with a small supporting surface. The purpose is to activate the deep and joint-supporting muscles of the spine (the multifidus and transversus abdominis muscles, the pelvic floor, and the diaphragm), which are very important for stabilization of the lumbar spine and alleviation of pain in this region [9, 14, 16, 17, 24].
Instability is a result as well as cause of degenerative disorders. Degeneration of intervertebral disks leads to instability, although it may not necessarily be accompanied by pain. Instability of the spine is associated with a high risk of injury due to external factors, such as lifting heavy weights [13, 14, 18].
All of the abovementioned training programs and exercises improved muscle strength and reduced pain. However, these studies contain no information about the kyphosis angle. Based on experimental data reported by Boeckh-Behrens and Buskies [5], who sought to optimize exercise programs on the basis of electromyographic recordings, it may be concluded that the exercises performed in the present study were effective.
We used the method of video raster stereography, which registers posture parameters such as the kyphosis or lordosis angle without the use of radiation. An interesting finding in the present study was the reduction of the kyphosis angle. This appears to have been due to the dorsal muscles of the musculus erector spinae. Especially the lateral muscles (musculus longissimus, musculus iliocostalis) have long muscle bundles that insert at every bone segment (rib or transverse process) and also form new origins. Extending from the sacral bone (os sacrum) to the occiput, the muscle’s fixation in the pelvis is responsible for its strong lifting arms. These are important for an erect trunk, its lateral inclination, and rotation [21]. Besides, we presume that the medial muscles (musculus multifidus, musculus spinales) were subjected to loads because of the intervention.
In a cross-section study, Sinaki et al. [28] proved that muscle strength in the extensors of the spine, the kyphosis angle, and vertebral fractures are closely interrelated. The authors conclude that stronger back muscles counteract advancing kyphosis of the chest and reduce the risk of vertebral fractures. Recent studies corroborate these concepts [6, 27].
However, the significant difference in the kyphosis angle between our groups at baseline is difficult to explain. We presume that this resulted from the size of the random sample on the one hand and the larger number of vertebral body fractures in the sling exercise group on the other.