In this study, the test-retest reliability of the valuably quantitative measures (i.e. VAS, BF, CPT, HPT, PPT, and LPST) was determined for the study of low back pain using a series of ICC, percent agreement, CV, SEMs, and one-way repeated measures ANOVA. These measurement outcomes were evaluated in an attempt to utilize these measures for exploring characteristics and examining effectiveness of an intervention in both clinical and research settings among athletes or individuals with low back pain. The results of this current study showed that the data from the local site of symptoms (i.e. back pain area) was more precise and relatively consistent than the non-symptomatic remote sites (i.e. deltoid, tibialis anterior). These findings were supported by the previous studies in which the local primary area of injury was sensitive to both mechanical (e.g., PPT) and thermal stimuli (i.e. CPT, HPT), but the remote site was mainly sensitive to mechanical stimulus [6,22]
. A previous study of the test-retest reliability for pressure pain threshold measurements of the upper limb and scapular region also reported a high reliability of test-retest with a 2-day interval between sessions (i.e. ICC ranged from 0.90–0.98) 
. This range of ICC value was similar to our current study (i.e. ICC at deltoid site ranged from 0.92–0.95) which is considered as an acceptable level of reliability. Interestingly, the reliability of the PPT at the remote site on tibialis anteria (TA) seemed to show a relatively lesser ICC value (i.e. ICC of 0.88–0.91) and larger variability than the remote site on the deltoid (i.e. ICC of 0.92–0.95) as well as the local area of lumbar region (i.e. ICC of 0.99). Some explanations were that the symptomatic lumbar area might be more sensitive to mechanical stimulus than the asymptomatic deltoid and leg areas. In addition, the leg might to some degree relate to an impairment of lumbo-sacral nerve roots which are distributed along the dermatome of lower limb. Another interesting point from this present study was that the pain intensity as described by the VAS scale remained relatively stable within a 2-day interval of an evaluation for the individuals with chronic low back pain. This finding was supported by the recent study which found that pain and symptoms were relatively unchanged with the chronic conditions[6,24]
The tissue blood flow (BF) showed that its reliability was suitable, this result was similar to the laser Doppler flowmetry study by Roeykens et al 
which found that blood flow of the pulpal tissue was reliable (i.e. agreement of blood flux ranged from 0.85–0.88) with an interval of 1 week. However, a minimal diurnal variation of tissue blood flow might also be evident as it was influenced by the sympathetic tone and psychological stage 
. For lumbo-pelvic stability test, its intratester reliability in this study was considerably acceptable with percent agreement (kappa's score) of 83.1%. Harris and Lahey 
suggested that agreement scores of greater than 80% were adequate and considered as a conventional level for most scientific studies. However, the percent agreement of the lumbo-pelvic stability test in our current study seemed to be less than the study previously reported by Phrompaet et al 
, which reported kappa's score of 95%. One factor which might contribute to the different result was that the subjects in Phrompaet's study were healthy volunteers, therefore they might perform lumbo-pelvic stability test better than the individuals with low back pain in our current study.
It should be mentioned that the CV of CPT was relatively large (22% – 45%) for all testing sites. Park and colleagues 
studied the reliability of the sensory testing on the volar aspect of forearm in 19 healthy subjects. They found that the variability of the CPT was approximately 25.5% and the 95% confidence interval (95% CI) for the CPT was 18–24 times higher than hot pain threshold. Large variability of the CPT was also evidenced in subjects with spinal cord injury and neuropathic pain 
. Khamwong et al 
also found the similar result of greater in CV (i.e. 27 %) with the CPT measurement. Although, many studies suggested that CPT is more sensitive in detecting changes than the HPT 
, the CPT should be applied with caution because it had a large variation among individuals. This might be due the fact that cold sensation is activated in a wide range (e.g., from less than 15 °C) and signals are transmitted via the complicated pathways including C- and A-delta myelinated nerve fibers 
It should be considered that this preliminary study might have some limitations such that the subject of this study was a non-specific low back pain. Further studies are warranted to evaluate the reliability of outcome measurements in a specific pathologic condition, as well as in a specific group of athletes with low back pain. In addition, further studies should include the other quantitative measures for the study of low back pain such as the measurements of transabdominal muscles using the modern techniques of real-time ultrasonic imaging or magnetic resonance imaging (MRI).