Self-regulation of acute experimental pain with and without biofeedback using spinal nociceptive responses

Pain Perception in Contact Sport Athletes: A Scoping Review

Contact sports athletes are regularly facing acute physical pain in part of their sport; however, the literature investigating pain perception in these athletes remains scarce. This scoping review aimed to explore the literature surrounding pain perception in contact sport athletes and to compile and understand how it is studied. The search strategy consisted of using index terms and keywords in the MEDLINE, EMBASE, SPORTDiscus, Web of Science, PsycINFO, CINAHL and ProQuest Dissertations & Theses Global search engines. Results from 11 studies revealed that a mix of team contact sports and combat sports are studied and are included under the umbrella of contact sports. These athletes are being compared with non-athletes as well as athletes from non-contact sports. The cold pressor test and the pain pressure test are the two predominant methods used to investigate physical pain. This review highlights the need to clearly define sports based on contact levels expected in play to better define the types of pain athletes are facing in their practice. Athletes' level of play as well as years of experience should also be more rigorously reported. While contact sport athletes seem to have a higher level of pain tolerance than both active controls and non-contact athletes, the methods of pain testing are not always justified and appropriate in relation to the pain induced during contact sports. Future experimental studies should use pain testing methods relevant to the pain experienced during contact sports and to better justify the rationale for the choice of these methods.

Modulation of the nociceptive flexion reflex by conservative therapy in patients and healthy people: a systematic review and meta-analysis

ABSTRACT

The nociceptive flexion reflex (NFR) is a spinally mediated withdrawal response and is used as an electrophysiological marker of descending modulation of spinal nociception. Chemical and pharmacological modulation of nociceptive neurotransmission at the spinal level has been evidenced by direct effects of neurotransmitters and pharmacological agents on the NFR. Largely unexplored are, however, the effects of nonpharmacological noninvasive conservative interventions on the NFR. Therefore, a systematic review and meta-analysis was performed and reported following the PRISMA guidelines to determine whether and to what extent spinal nociception measured through the assessment of the NFR is modulated by conservative therapy in patients and healthy individuals. Five electronic databases were searched to identify relevant articles. Retrieved articles were screened on eligibility using the predefined inclusion criteria. Risk of bias was investigated according to Version 2 of the Cochrane risk-of-bias assessment tool for randomized trials. The evidence synthesis for this review was conducted in accordance with the Grading of Recommendations Assessment, Development and Evaluation. Thirty-six articles were included. Meta-analyses provided low-quality evidence showing that conservative therapy decreases NFR area and NFR magnitude and moderate-quality evidence for increases in NFR latency. This suggests that conservative interventions can exert immediate central effects by activating descending inhibitory pathways to reduce spinal nociception. Such interventions may help prevent and treat chronic pain characterized by enhanced spinal nociception. Furthermore, given the responsiveness of the NFR to conservative interventions, the NFR assessment seems to be an appropriate tool in empirical evaluations of treatment strategies.PROSPERO registration number: CRD42020164495.

Emotion regulation and peripheral psychophysiological correlates in the management of induced pain: A systematic review

Cognitive reappraisal and acceptance strategies have been shown to be effective in reducing pain experience and increasing pain tolerance. However, no systematic reviews have focused on the relationship between the use of these two strategies and peripheral physiological correlates when pain is experimentally induced. This systematic review aims to summarize the existing literature that explores the relationship between emotion regulation strategies (i.e., cognitive reappraisal and acceptance) and peripheral correlates of the autonomic nervous system and facial electromyography, such as affect-modulated responses and corrugator activity, on laboratory tasks where pain is induced. The systematic review identifies nine experimental studies that meet our inclusion criteria, none of which compare these strategies. Although cognitive reappraisal and acceptance strategies appear to be associated with decreased psychological responses, mixed results were found for the effects of the use of both strategies on all the physiological correlates. These inconsistencies between the studies might be explained by the high methodological heterogeneity in the task designs, as well as a lack of consistency between the instructions used in the different studies for cognitive reappraisal, acceptance, and the control conditions.

Spinal and supraspinal modulation of pain responses by hypnosis, suggestions, and distraction

The mechanisms underlying pain modulation by hypnosis and the contribution of hypnotic induction to the efficacy of suggestions being still under debate, our study aimed, (1) to assess the effects of identical hypoalgesia suggestions given with and without hypnotic induction, (2) to compare hypnotic hypoalgesia to distraction hypoalgesia and (3) to evaluate whether hypnotic suggestions of increased and decreased pain share common psychophysiological mechanisms. To this end, pain ratings, nociceptive flexion reflex amplitude, autonomic responses and electroencephalographic activity were measured in response to noxious electrical stimulation of the sural nerve in 20 healthy participants, who were subjected to four conditions: suggestions of hypoalgesia delivered with and without hypnosis induction (i.e. hypnotic-hypoalgesia and suggested-hypoalgesia), distraction by a mental calculation task and hypnotic suggestions of hyperalgesia. As a result, pain ratings decreased in distraction, suggested-hypoalgesia and hypnotic-hypoalgesia, while it increased in hypnotic-hyperalgesia. Nociceptive flexion reflex amplitude and autonomic activity decreased during suggested-hypoalgesia and hypnotic-hypoalgesia but increased during distraction and hypnotic-hyperalgesia. Hypnosis did not enhance the effects of suggestions significantly in any measurement. No somatosensory-evoked potential was modulated by the four conditions according to strict statistical criteria. The absence of a significant difference between the hypnotic hypoalgesia and hyperalgesia conditions suggests that brain processes as evidenced by evoked potentials are not invariably related to pain modulation. Time-frequency analysis of electroencephalographic activity showed a significant differentiation between distraction and hypnotic hypoalgesia in the theta domain. These results highlight the diversity of neurophysiological processes underlying pain modulation through different psychological interventions.

Electrophysiological investigation of the contribution of attention to altered pain inhibition processes in patients with irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder associated with chronic abdominal pain and altered pain processing. The aim of this study was to examine whether attentional processes contribute to altered pain inhibition processes in patients with IBS. Nine female patients with IBS and nine age-/sex-matched controls were included in a pain inhibition paradigm using counter-stimulation and distraction with electroencephalography. Patients with IBS showed no inhibition of pain-related brain activity by heterotopic noxious counter-stimulation (HNCS) or selective attention. In the control group, HNCS and selective attention decreased the N100, P260 and high-gamma oscillation power. In addition, pain-related high-gamma power in sensorimotor, anterior cingulate and left dorsolateral prefrontal cortex was decreased by HNCS and selective attention in the control group, but not in patients with IBS. These results indicate that the central pain inhibition deficit in IBS reflects interactions between several brain processes related to pain and attention.

Stimulus predictability moderates the withdrawal strategy in response to repetitive noxious stimulation in humans

Innate defensive behaviors such as reflexes are found across all species, constituting preprogrammed responses to external threats that are not anticipated. Previous studies indicated that the excitability of the reflex arcs like spinal nociceptive withdrawal reflex (NWR) pathways in humans are modulated by several cognitive factors. This study assesses how the predictability of a threat affects the biomechanical pattern of the withdrawal response, showing that distal and proximal muscles are differentially modulated by descending control.

Learned control over spinal nociception: Transfer and stability of training success in a long-term study

OBJECTIVE

Healthy subjects can learn to use cognitive-emotional strategies to suppress their spinal nociception, quantified by the nociceptive flexor reflex (RIII reflex), when given visual RIII feedback. This likely reflects learned activation of descending pain inhibition. Here, we investigated if training success persists 4 and 8 months after the end of RIII feedback training, and if transfer (RIII suppression without feedback) is possible.

METHODS

18 and 8 subjects who had successfully completed feedback training were investigated 4 and 8 months later.

RESULTS

At 4 months, RIII suppression during feedback and transfer was similar to that achieved at the final RIII feedback training session (to 50 ± 22%, 53 ± 21% and 52 ± 21% of baseline, all differences n.s.). At 8 months, RIII suppression was somewhat (not significantly) smaller in the feedback run (to 64 ± 17%) compared to the final training session (56 ± 19%). Feedback and transfer runs were similar (to 64 ± 17% vs. 68 ± 24%, n.s.). Concomitant reductions in pain intensity ratings were stable at 4 and 8 months.

CONCLUSIONS

RIII feedback training success was completely maintained after 4 months, and somewhat attenuated 8 months after training. Transfer was successful.

SIGNIFICANCE

These results are an important pre-requisite for application of RIII feedback training in the context of clinical pain.