Effect of Isometric Exercise on Pain Perception in Rotator Cuff Related Shoulder Pain

The aim of this study is to compare the immediate effects of an acute bout of isometric exercise of the shoulder external rotator muscles above and below pain threshold on pain intensity, pain threshold, conditioned pain modulation and pain free force in external rotation. To evaluate the results of the exercise, the subjects will be assessed at pre-intervention, immediately post-intervention and after and 45 minutes after each experimental condition.

The aim of this study is to compare the immediate effects of an acute bout of isometric exercise of the shoulder external rotator muscles above and below pain threshold on pain intensity, pain threshold, conditioned pain modulation and pain free force in external rotation. It will consist of a randomized three-treatment parallel-design study. The sample will consist of subjects with rotator cuff related shoulder pain (RCRSP). Once the sample is selected, subjects will participate in three experimental sessions, which will occur in a randomized order: two exercise sessions (supra-threshold and infra-threshold isometric exercise) and one control session. In the first session, information regarding clinical and demographical aspects will be collected. A washout period of approximately 48 hours will separate each of the experimental sessions. To evaluate the results of the exercise, the subjects will be assessed at pre-intervention, immediately post-intervention and 45 minutes after each experimental condition. Pain intensity, Pressure Pain Thresholds (PPT), Conditioned Pain Modulation (CPM), maximal voluntary isometric contraction (MVIC) and pain free isometric strength (PFIS) will be measured.

Participants will perform 10 isometric external rotation supra-threshold contractions of the affected shoulder, each held for 15 seconds, with resting intervals of 15 seconds between contractions.

Participants will perform 10 isometric external rotation infra-threshold contractions of the affected shoulder, each held for 15 seconds, with resting intervals of 15 seconds between contractions.

The supra-threshold intensity will be stablished at 120% of participant's PFIS pre-session measurement (20% above the individual's pain threshold).

The infra-threshold intensity will be stablished at 80% of participant's PFIS pre-session measurement (20% bellow the individual's pain threshold).

Shoulder pain intensity reported by the patient will be assessed using a 100-mm visual analogue scale (VAS, 0-100, 0=minimum score, 100=maximum score). Higher values represent a better outcome (less pain).

Shoulder pain intensity reported by the patient will be assessed using a 100-mm visual analogue scale (VAS, 0-100, 0=minimum score, 100=maximum score). Higher values represent a better outcome (less pain).

Shoulder pain intensity reported by the patient will be assessed using a 100-mm visual analogue scale (VAS, 0-100, 0=minimum score, 100=maximum score). Lower values represent a better outcome (less pain).

PPTs will be recorded using an electronic algometer at the ipsilateral m. infraspinatus, the contralateral resting m. infraspinatus and the contralateral resting m. quadriceps. Higher values represent a better outcome.

PPTs will be recorded using an electronic algometer at the ipsilateral m. infraspinatus, the contralateral resting m. infraspinatus and the contralateral resting m. quadriceps. Higher values represent a better outcome.

PPTs will be recorded using an electronic algometer at the ipsilateral m. infraspinatus, the contralateral resting m. infraspinatus and the contralateral resting m. quadriceps. Higher values represent a better outcome.

MVIC will be measured at both m. infraspinatus and m. quadriceps of the non-affected side using a digital force gauge.

MVIC will be measured at both m. infraspinatus and m. quadriceps of the non-affected side using a digital force gauge.

MVIC will be measured at both m. infraspinatus and m. quadriceps of the non-affected side using a digital force gauge.

Inclusion Criteria: aged 18-80 years (likelihood of patients > 80 having degenerative changes in the shoulder is increased) pain localised to the proximal anterolateral shoulder region positive for pain on at least one of the following three impingement tests: Hawkins-Kennedy, Neer's, Jobe's positive for pain on resisted external rotation and/or abduction. Exclusion Criteria: shoulder surgery within last 6 months reasons to suspect systemic pathology including inflammatory disorders, cervical repeated movement testing affects shoulder pain and/or range of movement, passive external rotation deficit greater (less than 30º or a range of motion reduction of 50% or more as compared to the contralateral side), upper limb tension test A for cervical radiculopathy atraumatic degenerative rotator cuff tear based on the cluster of clinical tests (painful arc, drop arm test, and marked weakness into ER all three positive)

Luime JJ, Koes BW, Hendriksen IJ, Burdorf A, Verhagen AP, Miedema HS, Verhaar JA. Prevalence and incidence of shoulder pain in the general population; a systematic review. Scand J Rheumatol. 2004;33(2):73-81. doi: 10.1080/03009740310004667.

Watts AR, Williams B, Kim SW, Bramwell DC, Krishnan J. Shoulder impingement syndrome: a systematic review of clinical trial participant selection criteria. Shoulder Elbow. 2017 Jan;9(1):31-41. doi: 10.1177/1758573216663201. Epub 2016 Aug 20.

Maenhout AG, Mahieu NN, De Muynck M, De Wilde LF, Cools AM. Does adding heavy load eccentric training to rehabilitation of patients with unilateral subacromial impingement result in better outcome? A randomized, clinical trial. Knee Surg Sports Traumatol Arthrosc. 2013 May;21(5):1158-67. doi: 10.1007/s00167-012-2012-8. Epub 2012 May 12.

Luime JJ, Koes BW, Miedem HS, Verhaar JA, Burdorf A. High incidence and recurrence of shoulder and neck pain in nursing home employees was demonstrated during a 2-year follow-up. J Clin Epidemiol. 2005 Apr;58(4):407-13. doi: 10.1016/j.jclinepi.2004.01.022.

Lewis J. Rotator cuff related shoulder pain: Assessment, management and uncertainties. Man Ther. 2016 Jun;23:57-68. doi: 10.1016/j.math.2016.03.009. Epub 2016 Mar 26.

Littlewood C, Malliaras P, Chance-Larsen K. Therapeutic exercise for rotator cuff tendinopathy: a systematic review of contextual factors and prescription parameters. Int J Rehabil Res. 2015 Jun;38(2):95-106. doi: 10.1097/MRR.0000000000000113.

Littlewood C, Ashton J, Chance-Larsen K, May S, Sturrock B. Exercise for rotator cuff tendinopathy: a systematic review. Physiotherapy. 2012 Jun;98(2):101-9. doi: 10.1016/j.physio.2011.08.002. Epub 2011 Oct 5.

Smith BE, Hendrick P, Smith TO, Bateman M, Moffatt F, Rathleff MS, Selfe J, Logan P. Should exercises be painful in the management of chronic musculoskeletal pain? A systematic review and meta-analysis. Br J Sports Med. 2017 Dec;51(23):1679-1687. doi: 10.1136/bjsports-2016-097383. Epub 2017 Jun 8.

Holmgren T, Bjornsson Hallgren H, Oberg B, Adolfsson L, Johansson K. Effect of specific exercise strategy on need for surgery in patients with subacromial impingement syndrome: randomised controlled study. BMJ. 2012 Feb 20;344:e787. doi: 10.1136/bmj.e787.

Littlewood C, Bateman M, Brown K, Bury J, Mawson S, May S, Walters SJ. A self-managed single exercise programme versus usual physiotherapy treatment for rotator cuff tendinopathy: a randomised controlled trial (the SELF study). Clin Rehabil. 2016 Jul;30(7):686-96. doi: 10.1177/0269215515593784. Epub 2015 Jul 9.

Coombes BK, Wiebusch M, Heales L, Stephenson A, Vicenzino B. Isometric Exercise Above but not Below an Individual's Pain Threshold Influences Pain Perception in People With Lateral Epicondylalgia. Clin J Pain. 2016 Dec;32(12):1069-1075. doi: 10.1097/AJP.0000000000000365.

Naugle KM, Fillingim RB, Riley JL 3rd. A meta-analytic review of the hypoalgesic effects of exercise. J Pain. 2012 Dec;13(12):1139-50. doi: 10.1016/j.jpain.2012.09.006. Epub 2012 Nov 8.

Rio E, Kidgell D, Purdam C, Gaida J, Moseley GL, Pearce AJ, Cook J. Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy. Br J Sports Med. 2015 Oct;49(19):1277-83. doi: 10.1136/bjsports-2014-094386. Epub 2015 May 15.

Balasch-Bernat M, Lluch E, Vaegter HB, Duenas L. Should Exercises be Painful or not? Effects on Clinical and Experimental Pain in Individuals with Shoulder Pain. J Pain. 2021 Oct;22(10):1246-1255. doi: 10.1016/j.jpain.2021.03.153. Epub 2021 Apr 20.