Pain and isometric Exercise for Tennis Elbow

INTERVENTION: Participants randomised to the exercise group will complete a daily home program of isometric exercise for 8 weeks. Following baseline examination, participants allocated to exercise will receive a 30 minute individualised session with the trial Physiotherapist who will provide written and verbal education about the exercise program as well as general advice regarding activity modification. Participants will be provided equipment (flask with handle) to begin their home program the following day. Isometric exercise will be performed by holding the water filled container in the affected arm, with the forearm resting on the edge of a table (elbow approximately 90 degrees flexion, forearm pronated, wrist 30 degrees extension). The water level will be initially filled to achieve a load equivalent to 20% of the maximal voluntary wrist extension capacity of the unaffected arm. Participants will be instructed to increase the load by 5% each fortnight (by adding a set volume of water). The following progressions will be adopted to enable a progressive increase in weekly exercise volume (load x hold time x sets). Week 1: 20% load, 4x30s isometric holds, 30s intervals Week 2: 20% load, 3x45s isometric holds, 30s intervals Week 3: 25% load, 4x30s isometric holds, 30s intervals Week 4: 25% load, 3x45s isometric holds, 30s intervals Week 5: 30% load, 4x30s isometric holds, 30s intervals Week 6: 30% load, 3x45s isometric holds, 30s intervals Week 7: 35% load, 4x30s isometric holds, 30s intervals Week 8: 35% load, 3x45s isometric holds, 30s intervals Participants will complete a daily exercise diary to evaluate compliance (load, duration and sets achieved) and symptoms (rating of perceived exertion (RPE‐CR10 and pain intensity (numercial rating scale, 0=no pain, 10=worst imaginable pain) during exercise. Exercise diaries will be sent to the trial Physiotherapist at the end of each week. CONDITION: tennis elbow (lateral epicondylalgia) PRIMARY OUTCOME: Global rating of change (6 point Likert scale with categories: Completely recovered, much improved, improved, same, worse, much worse) Pain free grip force (N) will be measured over the affected arm with participant supine, arm pronated and resting on the bed. The participant will grip an electronic hand held dynamometer, stopping when they first experience pain. Maximal grip force will be measured over the unaffected arm in the same position. An average of three repetitions will be used in analysis. Patient rated tennis elbow evaluation (PRTEE) ‐ 15 questions concerning pain and disability, equally summed to give a total score. INCLUSION CRITERIA: Aged 18 years or older; Elbow pain for 6 weeks or more, which is greater than 2/10 on NRS for average pain intensity; Clinical diagnosis of tennis elbow (lateral epicondylalgia): positive response to at least 2 of the following physical tests (resisted wrist, index or middle finger extension, stretch of wrist extensor muscles) and reduced pain free grip force. SECONDARY OUTCOME: Cold pain threshold (C) will be measured over the affected and unaffected elbows using a Thermotest system. Temperature will be decreased at a rate of 1 degrees per second, until the first onset of pain. An average of three repetitions will be used in analysis. Conditioned pain modulation will be assessed by immersing the foot in iced water (12degrees celcius) for at least 2 minutes to deliver a pain intensity between 4 and 6 out of 10 on a 11‐point NRS. Exercise induced analgesia will be assessed by performance of a submaximal endurance isometric exercise task of the wrist extensor muscles of the affected arm. Participants will hold a container filled with water to a load equivalent to 20% of the maximal voluntary wrist extensor capacity of the unaffected arm. Participants will be seated with the forearm resting on the edge of a table (approximately 90degrees elbow flexion, forearm pronation, 30 degrees wrist extension). Participants will be asked to maintain this position, until one of the following endpoints are reached: pain intensity >6 on a 11‐point NRS, rating of perceived exertion =10 (Borg's RPE‐CR10) or inability to maintain wrist position for >3s). Pressure pain threshold (KPa) will be measured over the affected and unaffected elbows using a handheld algometer with probe size 1cm2. Pressure will be applied at a rate of 40KPa/s until the first onset of pain. An average of three repetitions will be used in analysis. Resting and worst pain using 11‐point numerical rating scale (NRS), where 0=no pain; 10=worst imaginable pain