Isometric exercise consisting of 1 session only. The session will last for around 5 minutes which will include asking the patient to do 1 repetition of wall squat for 3 min or to volitional fatigue at 100° knee angle.

Intervention: Other: Single bout of exercise

isometric exercise consisting of 1 session only. The session will last for around 10 minutes which will include asking the patient to perform 3 repetitions of wall squats (each time the exercise will be performed for 3 min or to volitional fatigue at 100°degree knee angle); the patient will be given 30-sec rest between repetitions.

Intervention: Other: Single bout of exercise

Will not receive any intervention

isometric wall squat at a knee joint angle of 100 degrees. Instruct participant to place their back against the wall with feet positioned parallel and spaced shoulder-width apart. Lower themselves down until they reached a knee joint angle of 100 degrees. Measure knee joint angle by placing a goniometer on the lateral epicondyle of the knee, in line with the femur whilst the anchor arm was in line with the lateral malleolus.

The pain will be measured using digital pressure algometer, FDX®️ (Wagner instrument, Greenwich, USA). All trials will be conducted on forearm, lumbar spine and calf sites. There will be at least 20 sec rest before an individual site is tested again. Two trials will be performed at each site. The raw values of each test will be recorded.

Because we are testing repeated times, we will use a marker to mark the location of each test site to ensure consistency in location.

Algometer must be positioned perpendicular to the measurement site for all trials.

It will be assessed using Visual Analogue Scale (VAS; 0-10). A rating of zero means that participant don't currently have pain at the low back. A rating of ten on this scale means that the pain at low back is the worst pain. So, the higher the number on this scale means the higher the pain intensity participant is experiencing.