A randomized clinical trial will be conducted. 130 subjects diagnosed with lateral epicondylitis will be studied. 3 intervention groups will be formed. Experimental group 1 will receive a 1000mg daily vitamin C supplement along with the usual practice of manual therapy and TENS. Group 2 will undergo high-speed vertebral manipulations along with manual therapy and TENS. In group 3 or control, manual therapy and transcutaneous electrotherapy (TENS) will be applied. All groups will receive the same manual therapy program and TENS, one session per week for 6 consecutive weeks. Data analysis: The data will be entered in the SPSS statistical package (version 21.0) for analysis). Statistical analysis will be performed with a 95% confidence interval, meaning that those whose P is <0.05 will be considered significant values.

The 130 subjects will be randomized into 3 groups: Experimental group 1 will receive a supplement of vitamin C (ascorbic complex) of the Bonusan brand, a daily dose of 1000mg should be consumed along with the usual practice of manual therapy and TENS. This group will maintain the daily intake of vitamin C for the 6 weeks that the treatment lasts, they will be informed of the possible side effects of adaptation to the supplement, such as, for example, diarrhea since excess vitamin C, in the case if there is, it lodges in the large intestine, which attracts fluid and produces osmotic diarrhea. This group will have direct communication with the doctor who collaborates in this investigation for any situation, query or unwanted symptom. Vitamin C has been used in other degenerative-type pathologies of collagen tissue such as Achilles tendinopathies and supraspinatus musculature. The investigators have also found references to the effect of vitamin C as pain treatment. Group 2 will undergo high-speed vertebral manipulations along with manual therapy and TENS. Vertebral manipulations would seek a reflexogenic effect through the sympathetic nerve pathway of the lower cervical ganglion. The transcutaneous TENS-type stimulation is evidenced to have an analgesic effect using self-adhesive patches placed longitudinally at the myo-junction. tendon with a size of 50X50 mm, a frequency of 100 Hz and a pulse duration of 200μs for 25 minutes. Both the vertebral manipulation intervention and the TENS placement will be performed by a professional health physiotherapist with 27 years of clinical experience in the application of the aforementioned techniques.

In group 3 or control, manual therapy and transcutaneous electrotherapy (TENS) will be applied. All groups will receive the same manual therapy program and TENS, one session per week for 6 consecutive weeks.

All the aforementioned interventions will be included in a 45 minute session for the 3 groups alike. They will be in charge of a highly qualified physiotherapist for all the therapies when carrying out which expresses his consent for the study in. Said professional uses all these therapies in consultation daily.

8 The aforementioned therapies can generate some adverse effects that the participants should be aware of and that is reflected in the informed consent that they must complete before the start of the evaluation and the interventions. In the first place, in the TENS, no bibliography has been found that warns of any unwanted effect, which it can refer to is an increase in skin tone under the patch due to the local effect and heat conduction of the same. which should disappear within 30 minutes after application.

In high-speed vertebral manipulation in the cervical region, in 6% of cases, post-manipulation dizziness may occur due to the local vascular change that occurs . The vitamin C supplement can produce some type of heartburn diarrhea, especially in the first days of taking, since this vitamin is absorbed in the intestine .

Alterations at the elbow can cause pain and functional limitation. To quantify these effects, there are different measurement scales. The evaluation to quantify the pain will be carried out with the numerical pain scale (0-10). The Disabilities of the Arm Shoulder and Hand (DASH) questionnaire will be used to determine the functionality of the upper limb, the Shoulder Pain and Disability Index SPADI will be used to assess shoulder function, Global perception of change will also be evaluated, Global Rating of Change Scale (GROC) a 15-point scale where -7 indicates much worse than before, 0 the same as before and +7 much better than before . Finally, the pressure pain threshold (PDU) will be evaluated using a digital algometer .

Measurement variables will be analyzed before treatment, after it, and at 3 and 6 months after the last treatment session.

Inclusion Criteria:

• Elbow pain patients medically diagnosed with epicondylitis by ultrasound of more than 4 weeks of evolution.
• Age between 35 and 55 years (both inclusive).
• Have signed the informed consent.

Exclusion Criteria:

• Have received corticosteroid infiltrations in the previous 3 months. Having received physical therapy treatment for the same reason in last 3 months.
• Bilateral symptoms.
• Fibromyalgia syndrome.
• Previous trauma to the upper limb.
• Fractures or prior dislocation of the shoulder or elbow.
• Previous surgeries on the shoulder or elbow.
• Psychiatric treatment.
• Cognitive deficit.
• Owning defibrillator or pacemaker.
• Acute infectious diseases.
• Uncontrolled systemic pathologies (heart disease, pacemaker, coagulation disorders).
• Pregnant women.
• History of rheumatic disease affecting the elbow such as rheumatoid arthritis, gout, reflex sympathetic dystrophy, plaque psoriasis. • Oncological processes.
• Aversion or fear of the application of currents.