The present study is aimed to assess the LTP-like pain amplification in chronic low back pain patients to explore the central and peripheral effect for pain LTP.

This study is a cross-sectional study. Two groups, including low back pain group and healthy subjects group will be arranged in this study. 50 subjects will be recruited in each group, The healthy subjects were matched for sex and age in relation to the low back pain group. Conditioning electrical stimulation (100 Hz, repeated 5 times with 10 s intervals, 500 impulses) using circular pin electrodes will be used in both groups to induce LTP-like pain amplification. The pain intensity changes to pinprick and light touch stimuli will be compared between two groups.

1. Chronic low back pain patients

   Inclusion Criteria:

   • Age 21-80 years old.
   • People must have experienced low back pain for at least 3 months and have reported a minimal pain level of 30 (pain threshold) on the 0-100 pain numerical rating scale (NRS) in the last 7 days.

   Exclusion Criteria:

   • Age below 21 or over 80 years old.
   • Patients were excluded if they had taken pain medications on the day of the assessment or if they had serious spinal pathologies, such as fractures, tumors or inflammatory diseases, such as ankylosing spondylitis, nerve root compromise confirmed by clinical neurological tests or severe cardiorespiratory diseases. Those who were pregnant, patients with cancer and those with a cardiac pacemaker were also excluded.

2. Healthy volunteers.

Inclusion Criteria:

• Age 21-80 years old.
• These participants must not have presented episodes of low back pain for more than 7 days in the last 12 months.

Exclusion Criteria:

• Age below 21 or over 80 years old.
• These participants have presented episodes of low back pain for more than 7 days in the last 12 months.

1. Chronic low back pain patients Age 21-80 years old.People must have experienced low back pain for at least 3 months and have reported a minimal pain level of 30 (pain threshold) on the 0-100 pain numerical rating scale (NRS) in the last 7 days.Patients were excluded if they had taken pain medications on the day of the assessment or if they had serious spinal pathologies, such as fractures, tumors or inflammatory diseases. Those who were pregnant, patients with cancer and those with a cardiac pacemaker were also excluded.
2. Healthy volunteers. Age 21-80 years old.These participants must not have presented episodes of low back pain for more than 7 days in the last 12 months.