Modulation after Development of Chronic Neck Pain

Numerous studies demonstrate elevated pain sensitivity and impaired conditioned pain modulation (CPM) in patients with chronic musculoskeletal pain compared to healthy individuals; however, the time course of changes in pain sensitivity and CPM after the development of a chronic pain condition is unclear. Secondary analysis of data from a prospective investigation examined changes in evoked pain sensitivity and CPM before and after development of chronic neck pain (CNP). 171 healthy office workers participated in a baseline assessment, followed by monthly online questionnaires to identify those who developed CNP over the subsequent year. These individuals ( = 17) and a cohort of participants ( = 10) who remained pain-free during the follow-up period returned for a 12-month follow-up assessment of mechanical and thermal pain sensitivity and CPM. Pain sensitivity measures did not differ between groups at baseline; however, cold pain threshold decreased in the CNP group at follow-up ( < 0.05). CPM was lower at baseline in the CNP group compared to those who reported no neck pain ( < 0.02) and remained unchanged one year later. These findings indicate that CPM is reduced in healthy individuals prior to the development of chronic neck pain and the subsequent reduction of thresholds for cold but not pressure pain

Adaptations in Evoked Pain Sensitivity and Conditioned Pain Modulation after Development of Chronic Neck Pain

Numerous studies demonstrate elevated pain sensitivity and impaired conditioned pain modulation (CPM) in patients with chronic musculoskeletal pain compared to healthy individuals; however, the time course of changes in pain sensitivity and CPM after the development of a chronic pain condition is unclear. Secondary analysis of data from a prospective investigation examined changes in evoked pain sensitivity and CPM before and after development of chronic neck pain (CNP). 171 healthy office workers participated in a baseline assessment, followed by monthly online questionnaires to identify those who developed CNP over the subsequent year. These individuals (N=17) and a cohort of participants (N=10) who remained pain-free during the follow-up period returned for a 12-month follow-up assessment of mechanical and thermal pain sensitivity and CPM. Pain sensitivity measures did not differ between groups at baseline; however, cold pain threshold decreased in the CNP group at follow-up (p<0.05). CPM was lower at baseline in the CNP group compared to those who reported no neck pain (p<0.02) and remained unchanged one year later. These findings indicate that CPM is reduced in healthy individuals prior to the development of chronic neck pain and the subsequent reduction of thresholds for cold but not pressure pain

Discharge behaviors of trapezius motor units during exposure to low and high levels of acute psychosocial stress

This study investigated the effects of acute psychosocial stress on trapezius single motor unit discharge behaviors. Twenty-one healthy women performed feedback-controlled isometric contractions under conditions of low and high psychosocial stress in the same experimental session. Psychosocial stress was manipulated using a verbal math task combined with social evaluative threat that significantly increased perceived anxiety, heart rate, and blood pressure (P 0.121, N = 103] and derecruitment [6.0% (4.4%) maximal voluntary isometric contraction and 6.5 pps (4.1 pps), P > 0.223, N = 99], the mean [11.3 pps (2.3 pps), P = 0.309, N = 106] and variability [2.5 pps (0.91 pps), P = 0.958, N = 106] of discharge rate, and the proportion of motor units exhibiting double discharges (21%, P = 0.446) did not change across stress conditions. Discharge rate modulation with changes in contraction intensity was highly variable and similar across stress conditions (P > 0.308, N = 89). Rate-rate modulation of concurrently active motor units was also highly variable (r = -0.84 to 1.00, N = 75). Estimates of [DELTA]F for motor unit pairs with rate-rate modulation >=0.7 were positive and similar across stress conditions [4.7 pps (2.0 pps), P = 0.405, N = 16]. The results indicate that acute psychosocial stress does not alter trapezius motor unit discharge behaviors during a precisely controlled motor task in healthy women

Discharge rate modulation of trapezius motor units differs for voluntary contractions and instructed muscle rest

This study examined discharge rate modulation at respiratory (0–0.5 Hz) and beta (16–32 Hz) frequencies in trapezius motor units active during voluntary contractions and during periods of instructed rest under conditions of low and high psychosocial stress. In separate sessions, single motor unit activity was recorded from the trapezius muscle of healthy women during low-intensity voluntary contractions and during periods of instructed muscle rest that followed voluntary contractions. The level of psychosocial stress during periods of instructed muscle rest was manipulated using a verbal math task combined with social evaluative threat which increased perceived anxiety, heart rate, and blood pressure (P ≤ 0.002). Discharge rate modulation was quantified by the mean power of motor unit discharge rate profiles within frequency bands of interest. Under low stress conditions, motor units active during instructed rest had greater power at 0–0.5 Hz (P = 0.002) and less power at 16–32 Hz (P = 0.009) compared to those active during voluntary contraction. Exposure to the stressor increased the amount of motor unit activity during instructed rest (P = 0.021) but did not alter the power of discharge rate modulation at 0–0.5 Hz (P = 0.391) or 16–32 Hz (P = 0.089). These results indicate that sustained motor unit activity during periods of instructed muscle rest has a lesser contribution from inputs at beta frequencies and a greater contribution from inputs at respiratory frequencies than present during low-intensity voluntary contractions. Furthermore, increases in motor unit activity when exposed to stressors during periods of instructed rest are not caused by changes in inputs at respiratory or beta frequencies

Further examination of modifying patient-preferred movement and alignment strategies in patients with low back pain during symptomatic tests.

Abstract Our purpose was to examine the effect of modifying symptomatic movement and alignment tests in a sample of people with LBP referred to physical therapy. Fifty-one patients (19 males, 32 females; mean age 37AE10.59 yr) with LBP and a mean Oswestry Disability Index score of 34AE18% were examined. The examination included 28 primary tests in which patients used their preferred movement or alignment strategy and reported symptoms. Symptomatic tests were followed by a secondary test in which the patient&apos;s strategy was standardly modified to correct the spinal alignment or movement that occurred with the primary test. Symptoms and directions of movement or alignment modified were recorded. For 82% of the secondary tests, the majority of the patients&apos; symptoms improved. For 54% of the secondary tests, some patients required modification of more than one direction of movement or alignment to eliminate symptoms. The findings suggest that the modifications described are generalizable across a number of tests with a moderately involved group of patients, and for individual tests there is variability in the numbers and directions of movements or alignments that appear to contribute to symptoms. Information obtained from the modifications is important because it can be used to confirm the patient&apos;s LBP classification and, within the context of the examination, immediately be used to teach the patient strategies to change movements and positions that appear to be contributing to his LBP

Further examination of modifying patient-preferred movement and alignment strategies in patients with low back pain during symptomatic tests.

Abstract Our purpose was to examine the effect of modifying symptomatic movement and alignment tests in a sample of people with LBP referred to physical therapy. Fifty-one patients (19 males, 32 females; mean age 37AE10.59 yr) with LBP and a mean Oswestry Disability Index score of 34AE18% were examined. The examination included 28 primary tests in which patients used their preferred movement or alignment strategy and reported symptoms. Symptomatic tests were followed by a secondary test in which the patient&apos;s strategy was standardly modified to correct the spinal alignment or movement that occurred with the primary test. Symptoms and directions of movement or alignment modified were recorded. For 82% of the secondary tests, the majority of the patients&apos; symptoms improved. For 54% of the secondary tests, some patients required modification of more than one direction of movement or alignment to eliminate symptoms. The findings suggest that the modifications described are generalizable across a number of tests with a moderately involved group of patients, and for individual tests there is variability in the numbers and directions of movements or alignments that appear to contribute to symptoms. Information obtained from the modifications is important because it can be used to confirm the patient&apos;s LBP classification and, within the context of the examination, immediately be used to teach the patient strategies to change movements and positions that appear to be contributing to his LBP

Reflex responsiveness of a human hand muscle when controlling isometric force and joint position

Objective: This study compared reflex responsiveness of the first dorsal interosseus muscle during two tasks that employ different strategies to stabilize the finger while exerting the same net muscle torque

Modulation of intracortical inhibition in response to acute psychosocial stress is impaired among individuals with chronic neck pain

ObjectivePsychosocial stress has been associated with a variety of chronic pain disorders although the mechanisms responsible for this relationship are unknown. The purpose of this study was to compare the excitability of intracortical and corticospinal pathways to the trapezius muscle in individuals with and without chronic neck pain during exposure to low and high levels of psychosocial stress.MethodsSingle and paired-pulse transcranial magnetic stimulation was used to assess motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) during mental math performed in the presence and absence of social evaluative threat.ResultsAll participants demonstrated higher amplitude MEPs in the high stress compared to the low stress condition (p < 0.01). Participants with chronic neck pain had significantly greater SICI than healthy participants in the low stress condition (p = 0.03). During exposure to the stressor, healthy participants showed an increase in SICI, whereas participants with neck pain showed no change (group difference for change in SICI, p < 0.01).ConclusionsThese findings suggest that individuals with chronic neck pain inhibit motor output to the trapezius in the presence of minor stressors, and are unable to compensate for additional stress-evoked increases in corticospinal excitability through further modulation of SICI. This observation has potential implications for the management of patients who have difficulty relaxing painful muscles during times of stress