The influence of aerobic exercise on Conditioned Pain Modulation (CPM) and Manipulation Induced Pain Modulation (MIPM) effects in participants with tennis elbow.

Research Study Procedure: A randomized between-group design will be used in this study, Participants will be first randomized to receive either low (50% VO2 max) or moderate intensity (75% VO2 max) aerobic exercise . Participants in each group will be initially tested for pressure pain threshold (PPT) at both elbow and wrist measurement sites. They will then be randomized to undergo a precondition CPM assessment protocol and an MIPM assessment protocol, in two separate test sessions (i.e. two study days) separated by three days. All CPM and MIPM protocols will be performed by the same assessor who will remain blinded to the level of aerobic exercise subjects are completing. Following completion of the aerobic exercise, all subjects will be reassessed for CPM and MIPM. Description of Aerobic Exercise Intervention: All participants will undergo a 15 min session of stationary cycling at 2 different intensities: 75% or 50% VO2 heart rate reserve (HRR). Prior to the beginning of the session, the target heart rate (THR) matching 75% or 50% VO2 max will be determined using the Karvonen formula: THR = ((maximal HR - resting HR) × %Intensity) + resting HR), where maximal HR = 220-age. Heart rate will be regularly observed during rest and exercise using a heart rate monitor, which will be fitted at the start of the session. The targeted exercise intensity level will be achieved through controlling the speed and the resistance of the cycle ergometer. Participants will initially start warming up by cycling gradually to reach the desired exercise intensity during the first 5mins, they will then continue cycling for the following 10mins while maintaining the exercise intensity at 75%Vo2max. The heart rate will be continuously monitored to ensure that the exercise intensity is achieved and adequately maintained during the session. This intervention will be conducted under standardized conditions by a physiotherapy student, who is under the supervision of senior physiotherapy staff at Curtin University Physiotherapy Clinic. Conditioned Pain Modulation (CPM) Assessment Protocol Test stimulus: Pressure Pain Threshold (PPT) will be used as the test stimulus and measured by an electronic digital algometer (Somedic AB, Sweden). Participants will sit on a chair of adjustable height so the forearm is comfortably supported. PPT will be performed two marked locations of the affected arm, which will be positioned in pronation on a table. PPT will be tested at baseline prior to cold water immersion, after 1 min during immersion, and 1 min post immersion. At each time point, PPT will be measured three times with 10-15 s rest intervals in between. The mean value of the three measurements at each point will be used for analysis. Conditioning stimulus: The Cold Pressor Test (CPT) will be used as a conditioning stimulus to elicit the CPM response. The unaffected hand will be submerged 4 inches above the wrist crease in a cold water bath, with a temperature maintained at 7 degrees Celsius for a period of 2 min The water bath contains a mix of water and ice and it is supplied with a circulating pump to ensure uniformity of water temperature at the skin. The difference between PPT measurements taken before and after water immersion represents the CPM effect. This will be quantified as the percentage change in PPT relative to the baseline measure. Separate percentage change measures will be obtained for the wrist and elbow sites. Manipulation Induced Pain Modulation (MIPM) Assessment Protocol Test stimulus: PPT will be the test stimulus. The Pain Free Grip (PFG) test, Upper Limb Neurodynamic Test (ULNDT) with radial nerve bias and measures of PPT at both test sites will be carried out at baseline and then repeated immediately after the conditioning stimulus (C5/6 contralateral lateral glide mobilisation). Testing will be performed with the participants lying supine on a plinth. PFG and UNLDT will provide additional measures of the MIPM effect. Conditioning stimulus: a grade III passive oscillatory, contralateral lateral glide (CLG) mobilisation of the C5/6 motion segment of the cervical spine will be used to induce MIPM The participant will be comfortably lying supine with arms by their side and instructed to report if they feel any discomfort or pain during execution of the mobilisation. In contrast to CPM this conditioning stimulus should be painless. The therapist will depress the scapulae with one hand, while the other hand cradles the occiput and neck above the C5/6 segment. Using the cradling hand, the therapist will apply a grade III passive oscillatory CLG directed towards the unaffected upper limb. The CLG stimulus will be performed for 60 s, and will be repeated three times, with 60-s rest periods in between (5 min total). The difference between PTT measurements taken before and after CLG mobilisation represents the MIPM effect. This will be quantified as the percentage change in PPT relative to the baseline measure. Separate percentage change measures will be obtained for the wrist and elbow sites and the PFG and ULNDT measures. A Physiotherapy PhD student, who has a masters degree in manual therapy and 8 years post masters experience in manual therapy, will conduct all assessment procedures previously described. Experimental procedures will be conducted at the Physiotherapy Clinic at the School of Physiotherapy and Exercise Science at the Bentley campus of Curtin University.