The Palliative Effect of TENS-WAA on 'Capsaicin/Heat' Induced Acute Lower Back Pain: a Self-controlled Clinical Study

Content of the study Phase 1 trial: subjects were randomly divided into Left1 group (n=15) and Right1 group (n=15), subjects in the Left1 group were intervened in the left lower ankle after capsaicin/heat pain modelling in the left region adjacent to the lumbar vertebrae of L2-L4; subjects in the Right1 group were intervened in the right lower ankle after capsaicin/heat pain modelling in the right region adjacent to the lumbar vertebrae of L2-L4. Intervention.

Phase 2 trial: subjects in the Left1 and Right1 groups of the Phase 1 trial were crossed over, i.e., the Left1 group was assigned to the Right2 group and the Right1 group was assigned to the Left2 group. the Left2 group intervened in the right lower ankle after capsaicin/heat pain modelling was established in the left region adjacent to the lumbar vertebrae of L2-L4, and the Right2 group intervened in the right lower ankle in the right region adjacent to the lumbar vertebrae of L2-L4. After establishing the capsaicin/heat pain model, the intervention was performed on the left lower ankle.

Research Methods

• Experimental environment A quiet, dark and undisturbed indoor environment was selected, with a constant room temperature of 26°C, and the subjects were kept in a sitting position throughout the experiment to facilitate the acquisition of functional near infrared spectroscopy (fNIRS) signals.
• Test materials Functional near infrared spectroscopy (fNIRS) signal acquisition equipment, transcutaneous electrical nerve stimulation equipment based on the theory of carpal and ankle needling, capsaicin cream (CAPZASIN-HP, 0.1% capsaicin), medical alcohol disinfectant wet wipes, cling film, and temperature-controlled hot packs.
• Capsaicin sensitivity test Capsaicin sensitivity test was first performed on the included subjects by applying capsaicin cream on the inner left forearm of the subjects 1cm×1cm, with a thickness of about 1mm. retaining the capsaicin for 5min, and subjects with allergic reactions and capsaicin intolerance were excluded from the test.
• Lower back capsaicin-heat pain model In this experiment, the capsaicin-thermal pain model was established by applying hot compresses with capsaicin cream: capsaicin cream (CAPZASIN-HP, 0.1% capsaicin) was applied to two symmetrical areas of 5 cm × 10 cm on either side of the alcohol sterilised lumbar paraspinal region of L2-L4, at a thickness of approximately 2 mm, and covered with cling film, and a hot compress bag with a constant temperature of 40°C was used to apply hot compresses on the area for for 10 minutes, and the application position was as shown in Figure 1. Capsaicin was retained throughout and wiped off at the end of the trial.
• Methods Using an own-crossover controlled study, subjects (n=30) included in the trial were subjected to two phases of the trial, separated by a washout period of more than 7 days. Before the start of the trial, the subjects were educated about the trial process and pain assessment methods. The transcutaneous electrical nerve stimulation (TENS-WAA) action site based on the theory of wrist and ankle acupuncture (TENS-WAA) was selected from the lower 5 or 6 sites on the lateral side of the ankle according to the records of Practical Wrist and Ankle Acupuncture and literature references, which can treat low back pain, lumbar spine and paravertebral pain, and sciatica.

Inclusion criteria

• Healthy adult males between the ages of 18-44 years;
• The dominant hand is the right hand;
• No persistent pain in the last month;
• No acute pain in the last week;
• Good health with no medical condition for which he/she is receiving treatment;
• Subjects agreed to participate in this trial and signed an informed consent form.

Exclusion criteria

• With malignant tumours and serious heart, liver and kidney diseases;
• Those with skin breakage at the site of capsaicin application;
• Those with a history of lumbar spine surgery, spinal fracture, rheumatic disease, cancer, pacemaker, or congenital anomalies of the spine;
• Any other medical condition that may affect pain perception, including neurological and psychiatric disorders;
• Taking sedative and sleep-aiding drugs within one week;
• Those who are allergic to capsaicin;
• Currently participating in another clinical trial concerning lower back pain or pain.