Influence of experimental pain on the perception of action capabilities and performance of a maximal single-leg hop

Changes in an individual's state - for example, anxiety/chronic pain - can modify the perception of action capabilities and physical task requirements. In parallel, considerable literature supports altered motor performance during both acute and chronic pain. This study aimed to determine the effect of experimental pain on perception of action capabilities and performance of a dynamic motor task. Performance estimates and actual performance of maximal single-leg hops were recorded for both legs in 13 healthy participants before, during, and after an episode of acute pain induced by a single bolus injection of hypertonic saline into vastus lateralis of 1 leg, with the side counterbalanced among participants. Both estimation of performance and actual performance were smaller (

Motor Adaptations to Pain during a Bilateral Plantarflexion Task: Does the Cost of Using the Non-Painful Limb Matter?

During a force-matched bilateral task, when pain is induced in one limb, a shift of load to the non-painful leg is classically observed. This study aimed to test the hypothesis that this adaptation to pain depends on the mechanical efficiency of the non-painful leg. We studied a bilateral plantarflexion task that allowed flexibility in the relative force produced with each leg, but constrained the sum of forces from both legs to match a target. We manipulated the mechanical efficiency of the non-painful leg by imposing scaling factors: 1, 0.75, or 0.25 to decrease mechanical efficiency (Decreased efficiency experiment: 18 participants); and 1, 1.33 or 4 to increase mechanical efficiency (Increased efficiency experiment: 17 participants). Participants performed multiple sets of three submaximal bilateral isometric plantarflexions with each scaling factor during two conditions (Baseline and Pain). Pain was induced by injection of hypertonic saline into the soleus. Force was equally distributed between legs during the Baseline contractions (laterality index was close to 1; Decreased efficiency experiment: 1.16±0.33; Increased efficiency experiment: 1.11±0.32), with no significant effect of Scaling factor. The laterality index was affected by Pain such that the painful leg contributed less than the non-painful leg to the total force (Decreased efficiency experiment: 0.90±0.41, P<0.001; Increased efficiency experiment: 0.75±0.32, P<0.001), regardless of the efficiency (scaling factor) of the non-painful leg. When compared to the force produced during Baseline of the corresponding scaling condition, a decrease in force produced by the painful leg was observed for all conditions, except for scaling 0.25. This decrease in force was correlated with a decrease in drive to the soleus muscle. These data highlight that regardless of the overall mechanical cost, the nervous system appears to prefer to alter force sharing between limbs such that force produced by the painful leg is reduced relative to the non-painful leg

Comparison of location, depth, quality and intensity of experimentally induced pain in six low back muscles

Introduction: The pattern of pain originating from experimentally induced low back pain appears diffuse. This may be because sensory information from low back muscles converges, sensory innervation extends over multiple vertebral levels, or people have difficulty accurately representing the painful location on standardized pain maps

Neuromotor control during stair ambulation in individuals with patellofemoral osteoarthritis compared to asymptomatic controls

Patellofemoral OA is characterized by PF pain during activities that load a flexed knee. Stair stepping ability is frequently impaired, yet little is known of the muscular recruitment strategies utilized during this task. Altered recruitment strategies may provide targets for clinical interventions. We aimed to determine if people with PFOA ascend and descend stairs with different muscular recruitment strategies compared to similar aged healthy individuals.Twenty-two people with PFOA and 20 controls were recruited. Electromyographic recordings from gluteus maximus and medius, medial and lateral hamstrings, vastus medialis and lateralis, medial and lateral gastrocnemius and soleus were acquired during stair ascent and descent. Force plate data was acquired to determine timing of foot placements and characterize dynamic stability.Seventeen people with PFOA (59 ± 10 years, 73 ± 13 kg, 167 ± 9 cm) and 15 controls (57 ± 10 years, 73 ± 16 kg, 171 ± 11 cm) had complete data. People with PFOA demonstrated: longer vastii activation duration during descent (lateralis: p = 0.01; medialis: p = 0.02); earlier onset of vastus lateralis for ascent (p

The effects of acute experimental hip muscle pain on dynamic single-limb balance performance in healthy middle-aged adults

Middle-aged adults with painful hip conditions show balance impairments that are consistent with an increased risk of falls. Pathological changes at the hip, accompanied by pain, may accelerate pre-existing age-related balance deficits present in midlife. To consider the influence of pain alone, we investigated the effects of acute experimental hip muscle pain on dynamic single-limb balance in middle-aged adults. Thirty-four healthy adults aged 40–60 years formed two groups (Group-1: n\ua0=\ua016; Group-2: n\ua0=\ua018). Participants performed four tasks: Reactive Sideways Stepping (ReactSide); Star Excursion Balance Test (SEBT); Step Test; Single-Limb Squat; before and after an injection of hypertonic saline into the right gluteus medius muscle (Group-1) or ∼5\ua0min rest (Group-2). Balance measures included the range and standard deviation of centre of pressure (CoP) movement in mediolateral and anterior-posterior directions, and CoP total path velocity (ReactSide, Squat); reach distance (SEBT); and number of completed steps (Step Test). Data were assessed using three-way analysis of variance. Motor outcomes were altered during the second repetition of tasks irrespective of exposure to experimental hip muscle pain or rest, with reduced SEBT anterior reach (−1.2\ua0±\ua04.1\ua0cm, P\ua0=\ua00.027); greater step number during Step Test (1.5\ua0±\ua01.7 steps, P\ua

Insight into motor adaptation to pain from between-leg compensation

Purpose: Although it appears obvious that we change movement behaviors to unload the painful region, non-systematic motor adaptations observed in simple experimental tasks with pain question this theory. We investigated the effect of unilateral pain on performance of a bilateral plantarflexion task. This experimental task clearly allowed for stress on painful tissue to be reduced by modification of load sharing between legs. Methods: Fourteen participants performed a bilateral plantarflexion at 10, 30, 50 and 70\ua0% of their MVC during 5 conditions (Baseline, Saline-1, Washout-1, Saline-2, Washout-2). For Saline-1 and -2, either isotonic saline (Iso) or hypertonic saline (Pain) was injected into the left soleus. Results: The force produced by the painful leg was less during Pain than Baseline (range -52.6\ua0% at 10\ua0% of MVC to -20.1\ua0% at 70\ua0% of MVC; P\ua

Reproducibility of the Kids Balance Evaluation Systems Test (Kids-BESTest) and the Kids-Mini-BESTest for children with cerebral palsy

To evaluate the reproducibility, including reliability and agreement, of the Kids Balance Evaluation Systems Test (Kids-BESTest) and short-form Kids-Mini-BESTest for measuring postural control in school-aged children with cerebral palsy.Psychometric study of intra-rater, inter-rater and test-retest reliability and agreement; SETTING: Clinical laboratory and home.Convenience sample of 18 children aged 8 to 17 years with ambulant cerebral palsy (Gross Motor Function Classification System I-II) with spastic or ataxic motor type.Not applicable.Postural control was assessed using the Kids-BESTest and the short-form Kids-Mini-BESTest. An experienced physiotherapist assessed all children in real-time and the testing session was videoed. The same physiotherapist viewed and scored the video twice, at least two weeks apart, to assess intra-rater reproducibility. Another experienced physiotherapist scored the same video to determine inter-rater reproducibility. Thirteen children returned for a repeat assessment with the first physiotherapist within 6 weeks and their test-retest performance was rated in real time and with video.Excellent reliability was observed for both the Kids-BESTest (ICC 0.96 to 0.99) and Kids-Mini-BESTest (ICC 0.79 to 0.98). The Smallest Detectable Change was good to excellent for all Kids-BESTest agreement analyses (5% to 9%), but poor to good for Kids-Mini-BESTest analyses (9% to 16%).The Kids-BESTest shows an excellent ability to discriminate postural control abilities of school-aged children with cerebral palsy and it has a low Smallest Detectable Change, suitable for use as a pre-post intervention outcome measure. Although the Kids-Mini-BESTest is 5-10 min shorter to administer, it has poorer reproducibility and focuses only on falls-related balance, which excludes two domains of postural control

Effects of prolonged and acute muscle pain on the force control strategy during isometric contractions

Musculoskeletal pain is associated with multiple adaptions in movement control. This study aimed to determine whether changes in movement control acquired during acute pain are maintained over days of pain exposure. On day 0, the extensor carpi radialis brevis muscle of healthy participants was injected with nerve growth factor (NGF) to induce persistent movement-evoked pain (n\ua0=\ua013) or isotonic saline as a control (n\ua0=\ua013). On day 2, short-lasting pain was induced by injection of hypertonic saline into extensor carpi radialis brevis muscles of all participants. Three-dimensional force components were recorded during submaximal isometric wrist extensions on day 0, day 4, and before, during, and after saline-induced pain on day 2. Standard deviation (variation of task-related force) and total excursion of center of pressure (variation of force direction) were assessed. Maximal movement-evoked pain was 3.3\ua0±\ua0.4 (0–10 numeric scale) in the NGF-group on day 2 whereas maximum saline-induced pain was 6.8\ua0±\ua0.3\ua0cm (10-cm visual analog scale). The difference in centroid position of force direction relative to day 0 was greater in the NGF group than in the control group (P\ua