Low back pain is a musculoskeletal disease to cause problems in daily life if it lasts longer than three months (Sherafat et al., 2013). Although the cause of low back pain has not been clearly revealed yet, changes in the lumbar structure due to musculoskeletal damage and the biomechanical factors of surrounding tissues are considered to be the main causes of low back pain. In addition, muscles around the spinal column, which play an important role in maintaining the stability of the spinal column during movement, and muscles that help maintain the normal curvature of the spinal column such as the lumber muscles, the hip flexor muscles, and the hamstring muscle are reported to be muscles associated with low back pain (Kim et al., 2014).

Among the lower extremity muscles, the tensor fascia lata is used in hip joint flexion, adduction, and internal rotation and knee joint extension and external rotation and plays diverse roles in the hip and knee joints (Kendall et al., 2005). Gottschalk et al. (1989) reported that if the tensor fascia lata is shortened, the hip joint will be internally rotated leading to the rotation of the pelvis and that excessive internal rotation of the hip joint will cause the abnormal alignment of the lumbar spine and the hip joint leading to pain in the lumbar region and the pelvis (Gottschalk et al., 1989; Kim and Son, 2009; Schamberger et al., 2002). Therefore, the stretching of the tensor fascia lata should be considered for the treatment of low back pain because it improves the range of motion of the hip joint and the pelvis and reduces low back pain (Kippers and Parker, 1987). In a recent study, Lee et al. (2015) confirmed tension of anterior fibers of the gluteus medius muscle and the tensor fascia lata in patients with chronic low back pain. After exercise for relaxing and strengthening these muscles, pain was relieved.

As methods for low back pain treatment, exercise such as stretching, aerobic exercise, and sling are presented (Hertzman-Miller et al., 2002). Among them, stretching exercise relieves muscle tension, leads to improve blood circulation. Increase the movement in the trunk and legs by stretching improves muscle strength, alleviate low back pain, and help recovery of normal movements (Ylinen, 2008). Among many methods of stretching, static stretching is presented as a safer and more effective method because it does not exceed the normal range of motion of joints. It does not require a high level of fitness, and causes less muscle pain (Matsuo et al., 2015). In particular, static stretching using a load is known to maximize the effects to stretch muscles and tendons (Kim et al., 2015; Peck et al., 2014; Shrier and McHugh, 2012) compared effect of static stretching with or without a load on the shortened hamstring. They reported that the static stretching using a load improves flexibility within a shorter period of time. Most studies reported that stretching has positive effects in healthy individuals instead of patients with diseases. Therefore, the purpose of this study was to investigate the effect of static stretching using a load on the pain, flexibility, and the low back pain disability index on low back pain patients with the shortened tensor fascia lata.

Most people experience low one back pain at least once while they are living (Park et al., 2005). To effectively treat low back pain, reducing pain and increasing strength and flexibility are important (Rainville et al., 2004). The application of stretching to the lumbar and leg muscles is known to alleviate low back pain and help restoration (Paek et al., 2014). Among them, the stretching of the tensor fascia lata has been reported to improve the range of motion of the hip joint and pelvis and relieve low back pain (Kippers and Parker, 1987). Therefore, we investigated the effect of static stretching using a load on the tensor fascia lata on the on pain, flexibility, and low back pain disability index in patients with low back pain.

Pain is a primary symptom of low back pain or is an important to confirm treatment outcome. Patients with low back pain want to minimize movements to relieve pain. This is because the sensitivity of tissues increases around the pain region (Goubert et al., 2004). In particular, when movement patterns to avoid pain, such as the reduction of the range of motion of the lumbar spine and the reduction of tilting and curvature of the vertebrae appear, the patient becomes to experience difficulties even in basic activities of daily living (Faas, 1996; Zusman, 1992). In the present study, the application of stretching to the tensor fascia lata reduced pain in patients with low back pain and helped their return to daily life. These effects are attributable to the fact that the application of stretching relaxed surrounding muscles leading to the expansion of the capillaries, resulting in increased blood supply to the muscle cells, so that metabolites are reduced and sufficient oxygen is supplied to reduce pain (Park et al., 2005; West et al., 2014). In addition, pain can change activation of muscle and recruitment pattern (Hodges and Richardson, 1999). Therefore, we supposed that the application of stretching to the tensor fascia lata reduced the pain so that the tension of the lower extremity muscles was relieved and the unbalance in the functional aspect was improved to help recovery of daily life.

For the musculoskeletal system to function properly, not only all joints should maintain proper ranges of motion, but also the extensibility of the muscles, tendons, articular capsules, and ligaments (Shephard et al., 1990). Sahrmann (2002) reported that most low back pain would be relieved if the trunk muscles were controlled and the flexibility of the lower extremities was increased. Paek et al. (2014) reported that stretching and pinch lift and rubbing manual therapies applied to patient with lower back pain were effective for muscle strengthening, pain relief, and flexibility. The result of this study also showed that the application of stretching using a load on the tensor fascia lata connected from the pelvis to the lower extremity increased flexibility. Many researchers apply stretching with a load to increase flexibility. This method is known to maximize the effect to stretch muscles and tendons (Peck et al., 2014). Kim et al. (2015) also reported that the application of stretching using a load to the hamstring showed faster flexibility effects than group treated only stretching. In this case, 10% of one-repetition maximum (1RM) was applied as a load during stretching. This method has shortcomings as it is difficult to measure 1RM from the patient and it cannot be easily used by those who do not have the tool to apply the load suitable for them. In the present study, we used the weight of the lower extremity of the subject without any tool. It can be easily used by patient with low back pain for flexibility.

In conclusion, static stretching using a load on the tensor fascia lata affected the pain relief and flexibility increases in patients with low back pain and its positive effects for return to daily life were identified. Therefore, stretching using a load is considered to be utilizable as a more effective intervention method than applying only stretching to low back pain patients with the shortened tensor fascia lata. However, the results of this study cannot be sufficiently generalized because experiments were conducted with a small number of subjects and this study has a limitation as the effects of stretching applied to the tensor fascia lata on the pelvis and low back were not analyzed and observed in three dimensions.