Journal of IMAB ISSN: 1312-773X https://www.journal-imab-bg.org SUMMARY Purpose: To develop and study the effectiveness of methods and algorithms using a specialized magnetotherapy with underwater water-jet massage for chronic lumbar pain. Material/Methods: 30 subjects from two experimental groups (EG-1 from 15 athletes and EG-2 from 15 non-athletes) were examined, all with chronic lumbar pain. Testing is performed-before and after one month of physiotherapy. The test battery includes: anthropometry (height, body weight); visual-analogue pain scale; Laseg test-for the neurodynamics of n.ischiadicus. Physiotherapy includes hydrotherapy, with a water temperature of 36 0-37 0 and magnetotherapy with a duration of 30-35 min-treatment of the paravertebral muscle in the lumbar region, gluteus and lower limbs-dorsal and ventral. The procedures are applied 3 times a week for one month. Results: Methods and algorithms using a specialized magnetotherapy with underwater water-jet massage for patients with chronic lumbar pain have been developed. Pain on the Visual-Ana-log Scale of EG-1 athletes was studied-before physiotherapy (with hydrotherapy) X = 4.93±1.39mm, V% = 28.12%, which is an indicator of severe pain in the lumbar region. After 30 days, physiotherapy was reduced to X = 1.53±0.99mm, at V% = 64.59%. Its decrease is 31.03%, P<0.01. Pain before physiotherapy was found in EG-2 X = 6.87±1.64mm, at V% = 23.91%. After physiotherapy, it is reduced to X = 1.93±1.49mm, at V%=76.89%, P<0.01. A study of the neurodynamics of n.ischiadicus, through the Laseg test, found that passive flexion in the hip joint of the healthy leg-before physiotherapy with EG-1 hydrotherapy was X =76.33±8.76 o , at V% = 11.47%. After hydrotherapy increased to X = 86.33±5.51 o , at V%=6.37%. Passive flexion in the hip joint of the injured leg before hydrotherapy was detected in EG-1. X = 69.67±10.43 o , which indicates its strong limit. Post-hydrotherapy X = 80.33±10.08 o , at V%=12.55%. P<0.0. In EG-2, the passive flexion in the hip joint-before hydrotherapy, the healthy leg was X = 71.67±14.1 o , V% = 19.67%. After hydrotherapy increased to X = 81.53±8.37 o. In V% = 10.26%. In the injured leg, passive flexion-before hydrotherapy was X = 71.00±11.37 o , after it X = 82.07±7.70 o , V% = 9.39%. P<0.01. Conclusion: The proven technique and algorithms of hy-drotherapy, with a specialized magnetotherapy with underwater water jet massage, is effective for the recovery of persons with chronic lumbar pain. The technique reduces the neurological and pain symptoms and the restoration of n.ischiadicus. INTRODUCTION: Chronic low back pain (CLBP) is a chronic pain syndrome in the lower back region, last 3 months. CLBP represents the second lead in the cause of disability worldwide, being major welfare and economic problem [1]. CLBP may be nociceptive or neuropathic or may incorporate both components. The presence of a neuropathic component is associated with the more intense pain of longer duration, and a higher prevalence of co-morbidities [2]. In sports training and competition, athletes suffer different severity of injuries, followed by a lengthy recovery process by physiotherapists. To maintain the athletic form of the athletes, it is important to speed up the recovery processes in the body and fully integrate them into the next stages of sports training [3]. This is mainly achieved through physiotherapy, including restorative massages, êinesiotape, hydrotherapy [4] and other means. The effect of water is multidirectional, by reducing edema, causing an effluent effect, increasing the range of motion of joints [5], activating regenerative processes , improving myo-articular laxity, relaxing spastic hyper-tonic muscles, improves the manifestation of strength and endurance [6] and dynamic joint stability [7]. Hydrotherapy is also suitable for non-sports, with other injuries of the mus-culoskeletal system, muscle weakness, limited mobility of traumatic joints, arthrosis, musculoskeletal deformities of the musculoskeletal system [8] and the like. The complex positive effect of hydrotherapy on the musculoskeletal system causes an increase in the range of motion in the joints, increases the elasticity of soft tissues, relaxes spastic and toned muscles, influences effluent, pain suppressant, improves the manifestation of strength and endurance , improves dynamic joint stability [9, 10]. Hydrotherapy (with a tangentor) also has a mechanical effect, a massage effect associated with suppression, a proprioceptive effect in impaired proprioception; weak neu-romuscular control, impaired neuromuscular synergism, impaired coordination and equilibrium, impaired dynamic joint stability and locomotor capacity [10], in which cases the restoration of dynamic proprioceptive reactivity is prioritized [9, 10]. Hydrotherapy has also been used as a cryo-effect [11] for the reduction of edema, pain and inflammatory response [12]. It affects the myo-articular tissues-tendons, tendons vagina, ligaments and bursa, muscles. In the presence of pain near the muscle, the reflex response of the muscle is a spasm, thus immobilizing the source of the pain [13].