Effect of Exercise on Individuals with Chronic Neck Pain and Central Sensitisation

INTERVENTION: This study is a randomised crossover trial, investigating the effect of a single‐bout (30 minutes) of high intensity sub‐maximal aerobic cycling exercise versus a low intensity aerobic cycling exercise. Intensity of exercise is determined by the a priori criteria of age‐predicted max heart rate. High intensity exercise will have a targeted 75% age‐predicted max heart rate, and low intensity will have a target of 50% age‐predicted max heart rate. Intervention will be delivered in a face‐to‐face supervised setting, by a researcher with a background in clinical exercise physiologist with 5 years experience. Participants will attend two sessions of assessments with a 1‐2 week 'washout' period between each session. The study will be conducted at the Physiotherapy Rehabilitation Gym located at The University of Adelaide. CONDITION: Chronic Neck Pain;Central Sensitisation; ; Chronic Neck Pain ; Central Sensitisation Musculoskeletal ‐ Other muscular and skeletal disorders Neurological ‐ Other neurological disorders SECONDARY OUTCOME: Blood lactate concentration. Blood lactate will be obtain through fingerprick, and measured using a lactate analyser. ; [Baseline ; Immediately post‐exercise] INCLUSION CRITERIA: *Chronic neck pain (3/10 pain NPRS rating) *Chronic neck pain duration >12 weeks *Age 19 to 65 years old PRIMARY OUTCOME: Exercise‐induced hypoalgesia (EIH). EIH will be assessed through pain pressure threshold (PPT) measurement, followed by a fatigue‐inducing exercise stimulus, and lastly, the same PPT measurements. PPT will be measured using Echo Wireless Algometer (JTECH Medical, Utah, United States). PPT will be measured at two sites; (1) over the C5/6 spinous process in the cervical spine, and (2) over the muscle belly of the left tibialis anterior. To ensure accurate measurement, a ‘x’ will be marked on the testing site with a marker during baseline assessment, the same site will be used for post‐exercise PPT assessment. Pressure will be applied on the testing site at a rate of approximately 5 N/s. Participants will be asked to verbally state when the sensation change from “comfortable” pressure to “unpleasant” pain sensation. Triplicate reading, with a 30s interstimulus interval, will be taken at each site and the mean values will be used for analysis. PPT measures will be taken prior to and following the fatigue‐inducing exercise stimulus. The fatigue‐inducing exercise stimulus will be an isometric wall‐squat. Participants will be asked to maintain in a wall‐squat position until fatigue or for a maximum of 3‐mins.; ; [Baseline; Immediately post‐exercise ] Conditioned pain modulation (CPM). CPM will be measured using PPT as the test stimulus and cold pressor test as the conditioning stimulus. PPT will be measured using Echo Wireless Algometer (JTECH Medical, Utah, United States). The baseline PPT (PPTbase) is obtained from EIH assessment. The participants will be instructed to immerse their non‐dominant hand in an ice‐bath (up to the wrist), and will be motivated through verbal encouragement to maintain immersion for the duration of the defined period of 120s. Participants are instructed to verbally state when he/she began to feel pain. Cold pain threshold is the time, in seconds, that passed between the immersion and the verbal confirmation of pain sensation. Cold pressor pain tolerance is the total time, in seconds, in immersion. Single PPT will be measured over the previously marked site on the tibialis anterior, at 30s, 60s, 90s, and at the time of cold pain threshold occurring during immersion. [Baseline; Immediately post‐exercise] Temporal Summation (TS). TS will be induced using a 256mN punctate needle stimulator or “PinPrick” (MRC Systems GmbH, Heidelberg, Germany) as the noxious stimuli, at two sites: (1) over the C5/6 spinous process in the cervical spine, and (2) dorsal surface of the dominant hand between the second and third metacarpals. A ‘x’ will be marked at the testing site to ensure accuracy for baseline and post‐exercise assessment. In the test, a single stimulus will first be applied, participants will be instructed to verbally rate the pain intensity. Then after a period of 10s, a series of ten identical punctate stimuli will be applied at a frequency of 1Hz, which has been shown to be sufficient to induce TS. The participant will verbally state the pain rating immediately following the last stimulus. A printed numerical pain rating scale (NPRS), labelled with digits from 0 to 10, with ‘0’ indicating ‘no pain’ and ‘10’ being ‘extremely painful’, will be displayed in front of the participant.[Baseline; Immediately post‐exercise]