Mean (± SEM, N = 9) CoP displacement and velocity between CoP peak to peak averaged across the four baseline sessions.

<p>Ipsilateral (open bars), net CoP (grey bars) and contralateral (solid) displacements are illustrated. The symbol “*” indicates significant increase compared with the contralateral CoP.</p

Center of Pressure Displacement of Standing Posture during Rapid Movements Is Reorganised Due to Experimental Lower Extremity Muscle Pain

<div><p>Background</p><p>Postural control during rapid movements may be impaired due to musculoskeletal pain. The purpose of this study was to investigate the effect of experimental knee-related muscle pain on the center of pressure (CoP) displacement in a reaction time task condition.</p><p>Methods</p><p>Nine healthy males performed two reaction time tasks (dominant side shoulder flexion and bilateral heel lift) before, during, and after experimental pain induced in the dominant side vastus medialis or the tibialis anterior muscles by hypertonic saline injections. The CoP displacement was extracted from the ipsilateral and contralateral side by two force plates and the net CoP displacement was calculated.</p><p>Results</p><p>Compared with non-painful sessions, tibialis anterior muscle pain during the peak and peak-to-peak displacement for the CoP during anticipatory postural adjustments (APAs) of the shoulder task reduced the peak-to-peak displacement of the net CoP in the medial-lateral direction (P<0.05). Tibialis anterior and vastus medialis muscle pain during shoulder flexion task reduced the anterior-posterior peak-to-peak displacement in the ipsilateral side (P<0.05).</p><p>Conclusions</p><p>The central nervous system in healthy individuals was sufficiently robust in maintaining the APA characteristics during pain, although the displacement of net and ipsilateral CoP in the medial-lateral and anterior-posterior directions during unilateral fast shoulder movement was altered.</p></div

Target movement trajectory and three CoP displacements for the anterior-posterior and the medial-lateral CoP directions during the unilateral shoulder flexion task (A) and bilateral heel task (B).

<p>Onset of the target movement is illustrated as a vertical line.</p

Mean (±SEM, N = 9) time for the first negative and first positive peak of AP direction across the four baseline sessions of CoP displacement during unilateral shoulder flexion (A) and bilateral heel lift (C). The time for negative (open symbols) and positive (solid symbols) peaks are illustrated for the ipsilateral (circles), net CoP (triangles) and contralateral (squares). The symbol “*” indicates significant earlier peak time of contralateral compared with the ipsilateral CoP. Time duration between two peaks of AP direction across the four baseline sessions of CoP displacement during unilateral shoulder flexion (B) and bilateral heel lift (D).

<p>Ipsilateral (open bars), net CoP (grey bars) and contralateral (solid) are illustrated. The symbol “*” indicates significantly longer time of the ipsilateral side compared with the contralateral side is illustrated.</p

Center of Pressure parameters during quiet standing.

<p>Mean (± SEM) center of pressure parameters from the quiet standing posture during four sensory condition: eyes open and firm surface (EO), eyes closed and firm surface (EC), eyes open and soft surface (EO-soft) and eyes closed and soft surface (EC-soft). The CoP Standard Deviation (SD) and speed in medial–lateral (ML) and anterior–posterior (AP) directions are presented for the less severe (KL score 1 and 2), severe (KL score >2) groups. Significant increases in body sway during EC-soft compared with EO-soft condition are indicated (*, interaction between <i>surface</i> and <i>vision</i>; NK: <i>P<</i>0.01). Significant increase in body sway during EC compare EO condition is marked with “^#” (interaction between <i>surface</i> and <i>vision</i>; NK: <i>P = </i>0.02). Significant higher values during EC-soft compared with all other conditions (^¥, Interaction between <i>surface</i> and <i>vision</i>; NK: <i>P<0.01</i></p

Correlation between KL scores, Pain Intensity, and CoP Range in the medial-lateral direction during quiet standing (n = 42).

<p>Spearman (R) correlation coefficient between pain intensity immediately before each balance measurement, Kellgren and Lawrence (KL) score, Centre of Pressure (CoP) Range in medial-lateral (ML) during four different sensory conditions: (i) Eyes open and firm surface (ii) eyes closed and firm surface, (iii) eyes open and soft surface, and (iv) eyes closed and soft surface. Significant correlations are indicated by <i>p-values</i> smaller than 0.05 (*).</p

Representative examples of bidimensional center of pressure (CoP) trajectory for a representative subject from the “severe” (red line) and “less severe” (blue line) group during one minute of quiet standing with eyes closed on the soft (foam) surface.

<p>Representative examples of bidimensional center of pressure (CoP) trajectory for a representative subject from the “severe” (red line) and “less severe” (blue line) group during one minute of quiet standing with eyes closed on the soft (foam) surface.</p

Additional file 5: of The Strengthening Exercises in Shoulder Impingement trial (The SExSI-trial) investigating the effectiveness of a simple add-on shoulder strengthening exercise programme in patients with long-lasting subacromial impingement syndrome: Study protocol for a pragmatic, assessor blinded, parallel-group, randomised, controlled trial

Strengthen your shoulder, intervention leaflet 2. (PDF 557 kb

Additional file 3: of The Strengthening Exercises in Shoulder Impingement trial (The SExSI-trial) investigating the effectiveness of a simple add-on shoulder strengthening exercise programme in patients with long-lasting subacromial impingement syndrome: Study protocol for a pragmatic, assessor blinded, parallel-group, randomised, controlled trial

TIDieR intervention, strengthen your shoulder. (PDF 207 kb

Additional file 6: of The Strengthening Exercises in Shoulder Impingement trial (The SExSI-trial) investigating the effectiveness of a simple add-on shoulder strengthening exercise programme in patients with long-lasting subacromial impingement syndrome: Study protocol for a pragmatic, assessor blinded, parallel-group, randomised, controlled trial

Strengthen your shoulder, intervention leaflet 3. (PDF 588 kb