The investigators believe that blood flow-restricted training can result in increased caste hypertrophy and strength without stressing the tendon in lateral elbow tendinopathy, and that changes in local metabolic activities can be effective in the process of tendon healing. The researchers' aim in the study is to investigate the effectiveness of blood flow restriction training in lateral elbow tendinopathy for 8 weeks, in addition to the 2 days a week multi-modal physiotherapy program, which will be applied by limiting blood flow by 40-50% occlusion recommended for the upper extremity using the patient's systolic pressure to the severity of 20-30% of 1 maximum repetition, 75 repetitions including 30-15-15-15 repetitions and 30 seconds rest period between sets, remaining attached to the recommended 10-15 minutes period for the top extremity.

Physiotherapy is the first step in the treatment algorithm for lateral elbow tendinopathy (LET), which is characterized by pain in the lateral epicondyl of the humerus during wrist extension and which limits hand-to-hand movements such as grabbing and thinning and consequently negatively affects hand functions. Extender carpi radialis brevis (ECRB) and extender digitorum, communis (EDC) are the muscles that contribute most to the onset of symptoms. Exercise, either alone or as part of a multimodal physiotherapy program, is central to the management of many patients with LDT. Exercise in patients with chronic LDT has been shown to result in more and faster relief of pain, less use of illness, less medical consultation, and increased working capacity. In literature, loading with recommended exercises is considered necessary to re-form the tendon, while on the other hand some patients may not tolerate this loading. For rehabilitation practitioners, it is quite difficult to design optimal exercise programs that facilitate musculo-skeletal system (MSK) adaptations while also enabling biological healing and safe loading of the injured body. In these cases, there has been a search for a new method that can generate physiological benefits associated with higher intensity training with exercise at lower loads. Increasing evidence supports the use of resistance training at a reduced load along with blood flow restriction (BFR) therapy to increase hypertrophic and force responses in skeletal muscle. The American Association of Sports Physicians (ACSM) recommends that at least 65% of the 1 maximum repetition, similar to exercising at high intensity with 8-12 repetition resistant weight lifting strength training, can be used in low loads such as 20% to 30% of 1 maximum repeat in the treatment to caste hypertrophy and strength. Effects of blood flow-restricted training on muscle lithium excitement, mechanical tension, metabolic stress, systemic and local hormones, vascular endothelial growth factor (VEGF) and oxidative stress mechanisms have been. There have been no randomized controlled studies in the literature on the effectiveness of BFR training in tendinopathies. However, case studies and series of cases have been included and no contraindications of BFR have been for patients with tendinopathy. The increasing number of studies on various diseases in the literature is a proof of this.

Inclusion Criteria:

• Between 18 and 65 years of age,
• Lateral tendinopathy diagnosis,
• Have scored 33 or more out of 100 on the Patient Based Tennis elbow Assessment Test (PRTEE).

Exclusion Criteria:

• Dysfunction in the shoulder, neck and/or chest area,
• Local or generalized arthritis.
• The neurological deficit.
• Radial dysfunction,
• Limitation of arm functions,
• A history of shoulder or upper extremity pathology requiring surgery or treatment;
• Venous thromboembolism
• Inflammation or other hematological disorders.
• Coronary artery disease,
• Peripheral arterial disease or hypertension (systolic/diastolic blood pressure >140 mm Hg/90 mmHg),
• To be pregnant,
• Irritation of median nerves.
• Irritation of radial nerves.
• Irritation of the ulnar nerves,
• The pain score is less than 30 mm.

Treating therapists and patient will be aware of treatment. Grip strength objective measure will be performed by a clinician blinded to the participant's treatment group. All other outcome measures are patient-reported on outcome forms.