Differences in biomechanical and metabolic factors between patients with frozen shoulder and asymptomatic individuals. A cross-sectional study.

BACKGROUND: the pathogenesis of frozen shoulder (FS) is thought to be one of inflammation and fibrosis possibly influenced by hyperglycemia. Biomechanical changes of the shoulder joint in terms of muscle strength, scapular kinematics and proprioception might occur in FS. OBJECTIVES: to compare muscle strength, scapular kinematics, proprioception, and blood glucose levels within patients with FS and to asymptomatic individuals. DESIGN: cross-sectional study. METHOD: Thirty-five patients with FS and 35 asymptomatic age and gender-matched individuals underwent physical assessment to determine muscle strength (abduction, external and internal rotation), scapular kinematics (both visually and with a plurimeter), proprioception (joint position sense), and blood glucose level. RESULTS: Patients with FS showed a decrease in muscle strength in their affected shoulder compared to both the unaffected shoulder and asymptomatic individuals. Significant differences were found between the affected and unaffected shoulder in the FS group and between groups (FS versus controls) in scapular upward rotation (plurimeter) at 30° and 60° abduction. No difference in scapular kinematics (visual observation), proprioception, and blood glucose levels was found neither between shoulders in the FS group nor between groups. CONCLUSION: A clinically relevant difference in muscle strength and increase in scapular upward rotation were found in the affected shoulder of patients with FS compared to their unaffected side and controls. However, no evidence of different levels of scapular kinematics (visual observation), proprioception, and blood glucose levels in the affected shoulder compared to the unaffected shoulder or controls is lacking.

Exploration of the clinical course and longitudinal correlations in frozen shoulder: The role of autonomic function, central pain processing, and psychological variables. A longitudinal multicenter prospective observational study.

BACKGROUND: Altered central pain processing (CPP) and dysautonomia might play a role in the clinical course of frozen shoulder and psychological factors, like pain catastrophizing and hypervigilance, might influence clinical variables in frozen shoulder. OBJECTIVES: To explore the clinical course of frozen shoulder regarding CPP, dysautonomia, pain catastrophizing, and hypervigilance and to explore whether longitudinal correlations between these outcomes and pain intensity were present. DESIGN: prospective longitudinal observational study. METHOD: Participants with frozen shoulder were recruited at hospitals and general practitioner practices and followed for 9 months. They completed six questionnaires (about demographics, shoulder pain and disability, pain intensity, pain catastrophizing, pain hypervigilance, and autonomic symptoms) and underwent tactile sensitivity (allodynia), pressure pain thresholds (hyperalgesia), temporal summation, and conditioned pain modulation during four timeframes (3-month intervals). RESULTS: Initially, 149 participants with frozen shoulder were recruited and 88 completed all the measurements. An improvement from baseline to at least one follow-up measurement was found for shoulder pain and disability, pain intensity, pain catastrophizing, hypervigilance, and dysautonomia. A fair longitudinal correlation was found between pain intensity and catastrophizing and hypervigilance (r = 0.301-0.397). Poor longitudinal correlations were found between pain intensity and allodynia and hyperalgesia (r = -0.180-0.193), between pain catastrophizing and dysautonomia (r = 0.209) and between hypervigilance and hyperalgesia (r = -0.159). CONCLUSION: Patients with frozen shoulder showed an early improvement that flattened with time in several pain and psychological variables over the course of 9 months. However, autonomic symptoms rather showed a late improvement over 9 months.

Exploration of the clinical course of frozen shoulder: A longitudinal multicenter prospective study of functional impairments.

BACKGROUND: Contradictory evidence exists regarding the clinical course of frozen shoulder (FS). OBJECTIVES: To explore the clinical course of FS regarding disabilities, pain, range of motion (ROM), muscle strength, scapular upward rotation, and proprioception and to establish longitudinal correlations between these variables. METHODS: Patients with FS were prospectively followed for 9 months at 3-month intervals. Assessment included the Disabilities of the Arm, Shoulder and Hand questionnaire; visual analogue scale for pain; an inclinometer for shoulder external rotation (ER), internal rotation (IR), flexion, and abduction ROM, and scapular upward rotation and proprioception, as well as handheld dynamometry for muscle strength in shoulder abduction, ER, and IR. RESULTS: Initially, 149 patients (98 females; mean (SD) age 53 (9) years) were included, with 88 completing all follow-up assessments. Most variables showed early improvement in the clinical course of FS, particularly ER and IR at 90° abduction, which continued to improve from 6 to 9 months of follow-up. Associations were observed between disabilities and pain (r = 0.61), disabilities/pain and ROM (r=-0.62 to -0.59 and r=-0.47 to -0.39, respectively), disabilities/pain and muscle strength (r=-0.24 to -0.35 and r=-0.36 to -0.17, respectively), and between disabilities/pain and scapular upward rotation below shoulder level (r = 0.23 to 0.38 and r = 0.24 to 0.30, respectively). ROM correlated with muscle strength (r = 0.14 to 0.44), while both ROM and ER muscle strength correlated with scapular upward rotation below shoulder level (r=-0.37 to -0.23 and r=-0.17 to -0.12, respectively). Muscle strength correlated with scapular upward rotation above shoulder level (r = 0.28 to 0.38) and lift-off muscle strength correlated with joint repositioning (r=-0.17 to -0.15). CONCLUSION: Almost all factors improved in the early phase (3-6 months) after baseline assessment, while ER and IR ROM at shoulder level continued to improve long term.

Identification of Metabolic Factors and Inflammatory Markers Predictive of Outcome after Total Knee Arthroplasty in Patients with Knee Osteoarthritis: A Systematic Review.

OBJECTIVE: To identify metabolic factors and inflammatory markers that are predictive of postoperative total knee arthroplasty (TKA) outcome. METHOD: A systematic search of the existing literature was performed using the electronic databases PubMed, Web of Science and Embase until the 1st of August 2022. Studies that evaluated the influence of metabolic or inflammatory markers (I) on postsurgical outcome (O) in end-stage knee osteoarthritis patients awaiting primary TKA (P) were included in this review. RESULTS: In total, 49 studies were included. Risk of bias of the included studies was low for one study, moderate for 10 studies and high for the remaining 38 studies. Conflicting evidence was found for the influence of body mass index, diabetes, cytokine levels and dyslipidaemia on pain, function, satisfaction and quality of life at more than six months after TKA. CONCLUSIONS: Several limitations such as not taking into account known confounding factors, the use of many different outcome measures and a widely varying follow-up period made it challenging to draw firm conclusions and clinical implications. Therefore large-scaled longitudinal studies assessing the predictive value of metabolic and inflammatory factors pre-surgery in addition to the already evidenced risk factors with follow-up of one year after TKA are warranted.

Understanding the clinical profile of patients with frozen shoulder: a longitudinal multicentre observational study.

INTRODUCTION: There is a large diversity in the clinical presentation of frozen shoulder (FS) and the clinical outcome is not always satisfactory. The aim of the current study was to examine to what extent range of motion (ROM) limitation, metabolic factors (diabetes mellitus and thyroid disorders), autonomic symptoms and pain sensitivity may contribute to the prognosis in terms of shoulder pain and disability and quality of life in patients with FS. METHODS: Patients with stage 1 or 2 FS were longitudinally followed-up during 9 months after baseline assessment. They completed six questionnaires and underwent quantitative sensory testing (pressure pain thresholds, temporal summation and conditioned pain modulation) and ROM assessment. RESULTS: One hundred and forty-nine patients with FS were initially recruited and 121 completed at least one follow-up measurement. Shoulder pain and disability improved over time and diabetes mellitus was found to be a prognostic factor for final outcome. Several domains of quality of life also improved over time and external rotation ROM, diabetes mellitus, thyroid disorder and autonomic symptoms were found to be prognostic factors for final outcome. These prognostic factors explained 2.5%-6.3% of the final outcome of shoulder pain and disability and quality of life. DISCUSSION AND CONCLUSION: In patients with FS, prognostic variables were able to predict different outcomes, indicating that outcomes in this population can be variable-dependent. Other variables not explored in this study might contribute to the prognosis of patients with FS, which should be investigated in future research. In clinical practice, baseline assessment of prognostic factors and focusing on a more holistic approach might be useful to inform healthcare practitioners about progression of patients with FS during a 9-month period.

An Instrument-Assisted Coracoid Pain Test: An Exploratory Diagnostic Accuracy Study.

The coracoid pain test (CPT) could contribute to the diagnosis of frozen shoulder (FS) with palpation. However, due to assessor performance these values might be unreliable. Therefore, the aim was to explore the diagnostic accuracy of an instrument-assisted CPT and two alternative approaches (pain severity and side comparison) for assistance in the diagnosis of FS. Patients with FS and healthy age-matched controls were recruited. All participants underwent the instrument-assisted CPT on both shoulders with a pressure algometer. Sensitivity, specificity, and likelihood ratios were determined for the three approaches. In total, 35 patients with FS and 35 healthy participants were included. The original approach was positive in eight participants (11.4%), with only sufficient specificity to draw a conclusion. The pain severity approach was positive in 31 participants (44.3%) with sufficient sensitivity, specificity and likelihood ratios. The side comparison approach was positive in 10 participants (14.3%) with excellent specificity and positive likelihood ratio. The specificity of the instrument-assisted CPT can be used to increase the probability of FS with both the original and alternative approaches. Only the pain severity approach can draw a conclusion with a negative test result. This study should be repeated with a cross-sectional design to strengthen and confirm the conclusions.

Autonomic Nervous System Function and Central Pain Processing in People With Frozen Shoulder: A Case-control Study.

OBJECTIVES: The pathophysiology of a frozen shoulder (FS) is thought to be related to chronic inflammation. Chronic inflammation may disturb the immune system and consequently the nervous system as part of an overarching system. The aim of this study was to determine the presence of disturbed autonomic nervous system function and altered central pain processing (CPP) in patients with FS. Secondarily, the presence of psychological variables (catastrophizing and hypervigilance) and self-reported associated symptoms of altered CPP in patients with FS were investigated. METHODS: Patients with FS and healthy controls completed the Composite Autonomic Symptom Score (autonomic function) and underwent quantitative sensory testing to assess tactile sensitivity (ie, allodynia), pressure pain thresholds (PPTs, ie, hyperalgesia), temporal summation of pain, and Conditioned Pain Modulation (CPM). Psychological issues were explored with the Pain Catastrophizing Scale and the Pain Vigilance and Awareness Questionnaire, and self-reported symptoms associated with altered CPP were determined with the Central Sensitization Inventory. RESULTS: Thirty-two patients with FS and 35 healthy controls were analyzed in the study. Patients with FS showed more self-reported autonomic symptoms and symptoms of altered CPP, higher levels of pain catastrophizing and hypervigilance, and are more sensitive to tactile touches and mechanical pressure compared with controls. DISCUSSION: On the basis of the effect sizes, between-group differences in allodynia, hyperalgesia, catastrophizing, and hypervigilance were clinically relevant, but only local allodynia, hyperalgesia, catastrophizing, and hypervigilance were statistically different. Therefore, obvious altered CPP was not present at the group level in patients with FS compared with controls.

Are psychosocial variables, sleep characteristics or central pain processing prognostic factors for outcome following rotator cuff repair? A protocol for a prospective longitudinal cohort study.

INTRODUCTION: Prognosis following surgical rotator cuff repair (RCR) is often established through the assessment of non-modifiable biomedical factors such as tear size. This understates the complex nature of recovery following RCR. There is a need to identify modifiable psychosocial and sleep-related variables, and to find out whether changes in central pain processing influence prognosis after RCR. This will improve our knowledge on how to optimise recovery, using a holistic rehabilitation approach. METHODS AND ANALYSIS: This longitudinal study will analyse 141 participants undergoing usual care for first time RCR. Data will be collected 1-21 days preoperatively (T1), then 11-14 weeks (T2) and 12-14 months (T3) postoperatively. We will use mixed-effects linear regression to assess relationships between potential prognostic factors and our primary and secondary outcome measures-the Western Ontario Rotator Cuff Index; the Constant-Murley Score; the Subjective Shoulder Value; Maximal Pain (Numeric Rating Scale); and Quality of Life (European Quality of Life, 5 dimensions, 5 levels). Potential prognostic factors include: four psychosocial variables; pain catastrophising, perceived stress, injury perceptions and patients' expectations for RCR; sleep; and four factors related to central pain processing (central sensitisation inventory, temporal summation, cold hyperalgesia and pressure pain threshold). Intercorrelations will be assessed to determine the strength of relationships between all potential prognostic indicators.Our aim is to explore whether modifiable psychosocial factors, sleep-related variables and altered central pain processing are associated with outcomes pre-RCR and post-RCR and to identify them as potential prognostic factors. ETHICS AND DISSEMINATION: The results of the study will be disseminated at conferences such as the European Pain Congress. One or more manuscripts will be published in a peer-reviewed SCI-ranked journal. Findings will be reported in accordance with the STROBE statement and PROGRESS framework. Ethical approval is granted by the Ethical commission of Canton of Zurich, Switzerland, No: ID_2018-02089 TRIAL REGISTRATION NUMBER: NCT04946149.

Personal influencing factors for pressure pain threshold in healthy people: A systematic review and meta-analysis.

All studies that investigated personal factors influencing pressure pain threshold (PPT) in healthy people were synthesized. Data was summarized, and risk of bias (RoB) and level of evidence were determined. Results were pooled per influencing factor, grouped by body region and included in meta-analyses. Fifty-four studies were eligible. Five had low, nine moderate, and 40 high RoB. Following meta-analyses, a strong conclusion was found for the influence of scapular position, a moderate for the influence of gender, and a weak for the influence of age (shoulder/arm region) and blood pressure on PPT. In addition, body mass index, gender (leg region), alcohol consumption and pain vigilance may not influence PPT. Based on qualitative summary, depression and menopause may not influence PPT. For other variables there was only preliminary or conflicting evidence. However, caution is advised, since the majority of included studies showed a high RoB and several were not eligible to include in meta-analyses. Heterogeneity was high in the performed meta-analyses, and most conclusions were weak. More standardized research is necessary.

Factors associated with better treatment outcome of physical therapy interventions after shoulder arthroplasty: A systematic review.

OBJECTIVE: To summarize factors that are associated with a better treatment outcome after post-operative physical therapy in patients with shoulder arthroplasty. DATA SOURCES: PubMed, Cochrane, and Web of Science. REVIEW METHODS: Studies examining factors that are associated with a better outcome after post-operative physical therapy interventions in patients with shoulder arthroplasty were included. Two independent reviewers performed screening, extracted data, and assessed the risk of bias and level of evidence, using the Quality In Prognosis Studies tool and Evidence-Based Guideline Development checklist. PRISMA guidelines were followed. RESULTS: In total, 460 articles were found and 14 studies were included. Two of the included articles had a moderate risk of bias, 12 high. The overall number of patients in the included studies varied from 20 to 2053. Patients had either a reverse (N = 1863), an anatomic total shoulder arthroplasty (N = 1029) or, a hemiarthroplasty (N = 133). Anatomic total shoulder arthroplasty patients with a neutral rotation sling position showed less night pain and greater range of motion, which was awarded moderate evidence. Other modifiable and non-modifiable factors such as telemedicine, immediate range of motion exercises, and pre-operative function were only awarded preliminary or conflicting evidence. CONCLUSION: Mainly preliminary and conflicting evidence was found. The possible causes of the conflicting evidence were the different measurement methods, implant types, and follow-up times used. The methodological quality was low and physical therapy protocols differed greatly. More high-quality research with standardized protocols is needed to determine the association of various factors with treatment outcomes after post-operative physical therapy in patients with shoulder arthroplasty.

Causes of Shoulder Dysfunction in Diabetic Patients: A Review of Literature.

Objective: Understanding the underlying mechanisms behind shoulder dysfunctions in patients with diabetes mellitus. Study Design: Systematic qualitative literature review. Participants: Patients with shoulder dysfunctions and diagnosed with impaired glucose tolerance or diabetes mellitus. Intervention: Published scientific literature containing evidence about the mechanisms of shoulder dysfunctions in the diabetic population. Articles were selected based on criteria containing diabetic population, shoulder dysfunction, methodological quality ≥ 6/9 and >20 subjects. Main Outcome measures: range of motion; questionnaires (QoL, UCLA-m, SPADI, DASH); blood glucose, blood HbA1C; calculated capsular stiffness (Kcap); calcification shoulder joint; shoulder dysfunction in patients with glucose metabolism disorders and diabetes mellitus. Results: We found 17 published articles with level 2 and 3 evidence. Multiple factors such as age, duration of diabetes mellitus (DM), glycated hemoglobin (HbA1c), advanced glycation end products (AGE), vascular endothelial growth factor (VEGF), interleukin-1ß (IL-1ß) were shown to be associated with tendon changes and increased capsular stiffness (Kcap) conceivably leading to limited range of motion (ROM) or frozen shoulder. Decreased ROM and frozen shoulder have a significantly higher prevalence in DM than in non-DM. Conclusions: Based on the current literature we confirm a high prevalence of shoulder dysfunctions in patients with diabetes mellitus. The cause of the shoulder complications is unknown, and more research is mandatory to shed more light on the complex interplay between the multifactorial causes of shoulder dysfunction in diabetes mellitus.

A Central Nervous System Focused Treatment Program for People with Frozen Shoulder: A Feasibility Study.

Background: Frozen shoulder (FS) is a highly disabling pathology of poorly understood etiology, which is characterized by the presence of intense pain and progressive loss of range of motion (ROM). The aim of this study is to evaluate the feasibility and clinical impact of a CNS-focused treatment program for people with FS. Methods: 10 subjects with primary FS received a 10-week CNS-focused intervention including sensory discrimination training and graded motor imagery techniques delivered as clinic sessions (60 min) and home therapy (30 min five times per week). Measurements were taken at baseline, after a 2-week "washout" period, after treatment, and at three months follow-up. The Shoulder Pain and Disability Index (SPADI) was the primary outcome. Secondary measures were feasibility-related outcomes, self-reported shoulder pain, active and passive range of motion, two-point discrimination threshold (TPDT), left/right judgement task (LRJT), fear-avoidance (Tampa Scale for Kinesiophobia), pain catastrophization (Pain Catastrophizing Scale), and pain sensitization (Central Sensitization Inventory). A Student's t-test was used to assess the "washout" period. A repeated measure analysis of variance (ANOVA) was used to evaluate within-subjects' differences for all outcome measures in the different assessment periods and a pairwise analysis was used to compare between the different assessment points. Statistical significance was set at p < 0.05. Results: 70% of participants completed the treatment. No significant changes were found after "washout" period except for TPDT (p = 0.02) and SPADI (p = 0.025). Improvements in self-reported shoulder pain (p = 0.028) and active shoulder flexion (p = 0.016) were shown after treatment (p = 0.028) and follow-up (p = 0.001) and in SPADI at follow-up (p = 0.008). No significant changes were observed in TPDT, LRJT, fear-avoidance, pain catastrophization, and pain sensitization. Conclusions: a CNS-focused treatment program might be a suitable approach to improve pain and disability in FS, but further research is needed to draw firm conclusions.

Exercise Therapy Is Effective for Improvement in Range of Motion, Function, and Pain in Patients With Frozen Shoulder: A Systematic Review and Meta-analysis.

OBJECTIVE(S): To determine (1) the effect of exercise therapy alone or in combination with other interventions compared with solely exercises and programs with or without exercises and (2) what kind of exercise therapy or combination with other interventions is most effective. DATA SOURCES: PubMed, Web of Science and Cochrane Central Register of Controlled Trials. STUDY SELECTION: Studies were screened in a 2-phase approach by 2 independent reviewers (M.M. and L.M.). Reference lists of included studies and interesting systematic reviews were hand searched. DATA EXTRACTION: Two independent reviewers (M.M. and L.M.) extracted information about origin, characteristics of study participants, eligibility criteria, characteristics of interventions, outcome measures and main results in a pre-defined template. DATA SYNTHESIS: Thirty-three studies were included in the qualitative and 19 in the meta-analysis. Preliminary evidence was found for supervised exercises to be more beneficial than home exercises for ROM and function. Multimodal programs comprising exercises may result in little to no difference in ROM compared to solely exercises. Programs comprising muscle energy techniques show little to no difference in ROM when compared with programs with other exercises. Adding stretches to a multimodal program with exercises may increase ROM. There is uncertain evidence that there is a difference between those programs regarding function and pain. Preliminary evidence was found for several treatment programs including exercises to be beneficial for improvement in both passive and active ROM, function, pain, and muscle strength. No studies used patient satisfaction as an outcome measure. CONCLUSIONS: ROM, function, and pain improve with both solely exercises and programs with exercises, but for ROM and pain there was little to no difference between programs and for function the evidence was uncertain. Adding exercises improve active ROM compared with a program without exercises, whereas adding physical modalities has no beneficial effect. Muscle energy techniques are a beneficial type of exercise therapy for improving function compared with other types of exercise. Unfortunately, no conclusion can be drawn about the results in the long-term and most effective dose of exercise therapy.

An overview of effective and potential new conservative interventions in patients with frozen shoulder.

Frozen shoulder (FS) is a pathology that is difficult to understand and difficult to manage. Over the last ten years, contradictory and new evidence is provided regarding the recovery and its natural course. This narrative review provides new information about the diagnosis and conservative treatment of patients with FS and ongoing research hypotheses that might provide new insights in the pathology and treatment options. FS has a characteristic course. People with Diabetes Mellitus and thyroid disorders have a higher risk of developing a FS. The diagnosis FS is based on pattern recognition and physical examination. Additionally, 'rule-in' and 'rule-out' criteria can be used to increase the likelihood of the frozen shoulder diagnosis. Recommended and most common physical therapy interventions are mobilization techniques and exercises, in which tissue irritability can guide its intensity. In addition, physical therapy is often complementary with patient education and pharmacotherapy. The latest evidence-based practice related to FS is proprioceptive neuromuscular facilitation and mirror therapy. In addition, interventions like pain neuroscience education, high-intensity interval training and lifestyle changes are still hypothetical. Finally, better insight in the involvement of biochemical processes, function of myofibroblasts and matrix metalloproteinases can provide better understanding in the pathophysiology and will be addressed in current review.

Specific versus Non-Specific Exercises for Chronic Neck or Shoulder Pain: A Systematic Review.

The current systematic review aimed to compare the effect of injury-focused (specific) exercises versus more general (non-specific) exercises on pain in patients with chronic neck or shoulder pain. We searched PubMed, EMBASE, and Web of Science. Two reviewers screened and selected studies, extracted outcomes, assessed risk of bias, and rated the quality of evidence. A total of nine eligible studies, represented in 13 articles, were identified, with a considerable risk of bias. One article investigated the acute effect of single bouts of exercise on pain and reported an immediate pain reduction after non-specific exercise. Regarding short-term effects, seven out of the nine studies found no differences in pain between interventions, with inconsistent results among two other studies. Concerning the long-term effects, while pain reduction seems to be favored by specific exercises (two out of four articles), the best format is still unclear. Based on the acute effects, a single bout of non-specific exercise seems to be a better option for pain-relief for patients with chronic neck or shoulder pain. For short-term effects, there are no differences in pain between specific and non-specific exercises. Regarding long-term effects, specific exercises seem to be the best option. Nevertheless, more studies are warranted.

Comparison of five conditioned pain modulation paradigms and influencing personal factors in healthy adults.

BACKGROUND: Conditioned pain modulation (CPM) methods are experimental procedures to assess presumed descending nociceptive modulatory pathways. Various CPM-methods are currently used, making the comparison of results difficult. The aim of this study was to compare five conditioning stimuli and to evaluate the influencing effects of personal factors on CPM-efficacy. METHODS: 101 healthy pain-free adults (50 males, 51 females) participated in this cross-sectional study with repeated measures design. The CPM-method consisted of hot water immersion (46°C, HWI), cold pressor test (12°C, CPT), cold pack application, and single and double ischemic occlusion as conditioning stimuli in randomized order. Pressure pain threshold was used as test stimulus at the mm. trapezius and quadriceps for all CPM-protocols. RESULTS: All CPM-protocols resulted in effective CPM, although cold pack application revealed smaller CPM-magnitudes compared to all other methods at both muscles, except single ischemic occlusion at the m. quadriceps. A smaller CPM-effect at the m. trapezius was shown when CPM was provoked by single ischemic occlusion compared to the CPT. Chronic stress, gender, attentional focus, age, physical activity and perceived pain are all influencing factors, in various conditioning stimuli at the mm. trapezius and quadriceps. CONCLUSIONS: CPT and HWI seem to be the most appropriate conditioned pain modulation paradigms for research settings, while single and double ischemic occlusion seem to be more useful for clinical settings. Influencing factors to be considered are gender, age, stress, physical activity, perceived pain and attentional focus to the conditioning stimulus, but depend on the test site and exerted method. SIGNIFICANCE: Hot water immersion, cold pressor test, and single and double ischemic occlusion result in comparable CPM-effects at the mm. trapezius and quadriceps. Anti-nociceptive effects of the cold pack are mainly a result of attention towards the cold pack. Chronic stress, attentional focus towards the conditioning stimulus and perceived pain of the conditioning stimulus influenced the anti-nociceptive effects at the m. trapezius. Gender and level of physical activity influenced the anti-nociceptive effects with the other methods at the m. quadriceps.

The Result of Acute Induced Psychosocial Stress on Pain Sensitivity and Modulation in Healthy People.

BACKGROUND: Pain can be influenced by several factors, including stress. Stress can have various reactions on pain. These reactions are influenced by several internal factors such as gender, age, and experience with stress or pain. OBJECTIVES: To determine the effect of acute stress on mechanical hyperalgesia (with pressure pain thresholds [PPT]), endogenous pain facilitation (measured by temporal summation [TS]), and inhibition (measured by conditioned pain modulation [CPM]) in healthy people and to determine which factors are responsible for this stress result. STUDY DESIGN: Pre-posttest design. SETTING: Healthy volunteers from Belgium. METHODS: One hundred and one healthy pain-free patients underwent a modified Trier Social Stress Test. Prior and following the stress manipulation, PPT, TS, and CPM efficacy were determined in the mm. trapezius and quadriceps and overall. Furthermore, possible explanatory factors, such as fear of pain, pain catastrophizing, pain hypervigilance, and daily activity levels, were assessed using questionnaires. RESULTS: We found a significant stress result on widespread pain sensitivity, with an increase of PPT (P < 0.001), unchanged TS (P > 0.05), and a decrease in CPM efficacy (P < 0.001). Factors associated with the stress result were age, previous surgery, attentional focus on the conditioning stimulus during CPM, fear of pain, and daily activity levels. LIMITATIONS: The efficacy of the stress manipulation was not examined, and the lack of a control group prevented to examine a real stress-effect. Furthermore, no physiologic parameters were measured as possibly influencing internal factors for the stress-result. CONCLUSIONS: The increase in PPT was not a clinically significant change, whereas the decrease in CPM was meaningful. None of the factors predicted the stress result in all experimental pain measurements, and the predictions that were observed only explained a small proportion of the observed effects.