Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Experimental glutamate and capsaicin-induced pain has not been described in tendon tissue despite the implications of addressing these receptors in pain management strategies. This study investigated pain induction and modulatory interactions by injecting glutamate (0.5 ml, 1 M) and capsaicin (0.5 ml, 5 microg, 33 microM) to human tendon tissue. Following the initial glutamate or capsaicin injection, a second injection of either glutamate (following capsaicin), capsaicin (following glutamate) or hypertonic saline (after both glutamate and capsaicin) was given. ⋯ The results indicate in tendon tissue a facilitation of response to capsaicin injection following glutamate injection. PPTs were only reliably reduced by capsaicin injection. These results emphasize the possible importance of peripheral glutamate receptor antagonists in pain management in musculoskeletal conditions.
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The modulation of the lower limb nociceptive withdrawal reflex elicited during late stance by a stimulus train with frequencies of 15 and 30 Hz delivered to the mid-forefoot, arch of the foot, and heel was investigated. Stimulation was delivered at four moments of the gait cycle between heel-off and toe-off. Stimulation at 15 Hz induced larger kinematic responses at the knee and hip. ⋯ The dorsiflexion response was largest when stimulating at toe-off and was larger for stimulation at 15 Hz than at 30 Hz. The muscle reflex responses were site modulated in tibialis anterior with largest responses evoked by stimulation at the arch of the foot and mid-forefoot, and phase and frequency modulated in soleus. This study presents a detailed assessment of the lower limb nociceptive reflex modulation and provides results, which might have application in the rehabilitation of the hemiparetic gait.
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Mechanisms and structures which are involved in eccentric exercise-induced delayed onset muscle soreness (DOMS) are not yet clarified. Tissue and site specificity may be important considerations in afferent sensitisation following eccentric exercise. This study investigated the nociceptive response to hypertonic sodium solution applied to fascial/epimysium tissue and mechanically sensitised sites in muscle by assessing (1) afferent recordings in animals and (2) psychophysical assessment in humans. ⋯ Fascial injection of the exercised muscle caused significantly higher pain intensity compared to all other injections. Response to deep muscle stimulation was not different between sides. This suggests that fascia rather than muscle tissue is important in DOMS associated sensitisation.
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Subjects with carpal tunnel syndrome (CTS) typically describe self-perceived pinch grip deficits, clumsiness sensations and difficulty with grasping small objects, which suggest the existence of a fine motor control deficit. No previous studies have investigated fine motor control and pinch grip force bilaterally in patients diagnosed with moderate CTS. Our aim was to investigate differences in fine motor control ability and pinch grip force between patients with unilateral CTS and healthy controls. ⋯ The ANOVA also revealed significant differences between groups (F = 141.2; P < 0.001), and fingers (F = 142.2; P < 0.001), but not between sides (F = 0.9; P = 0.4) for pinch grip strength: CTS patients showed bilateral lower pinch grip force levels in all fingers when compared to controls (P < 0.001). Fine motor control and pinch grip were negatively related to the hand pain intensity and duration of symptoms history (all, P < 0.01). Our findings revealed bilateral deficits in fine motor control ability and pinch grip force in patients with unilateral moderate CTS when compared to controls.
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We investigated age related changes in the control of precision grip in 29 healthy adults spanning early adulthood to middle age (21-67 years). Subjects performed a visually guided, isometric precision grip ramp-and-hold force-tracking task. Target force levels were 3, 6, and 9 N. ⋯ Age correlated positively with the amount of error at the lowest (3 N) force level in both phases. Force onsets were systematically earlier in middle-aged subjects and the average slope of the force during the ramp decreased with increasing age. The results show that precision during low grip force control decreases already during middle age and those subjects may modify their force generation strategies to compensate for early and subtle degenerative changes in the motor system before decline in grip strength is apparent.