The aim of this study was to evaluate the influence of the intensity of Isometric Contraction of shoulder external rotators, comparing the effect of a high-level IC (80% maximal voluntary isometric contraction) versus a low-level Isometric Contraction (20% maximal voluntary isometric contraction) on pain intensity, pain thresholds, and function in chronic pain shoulder patients.
This was a single-blinded, randomized parallel study. Eighty-two patients presenting chronic musculoskeletal shoulder pain were allocated to two groups. Patients in group 1 (n= 41) received a five-series Isometric Contraction of shoulder external rotators at 20% maximal voluntary isometric contraction, while patients in group 2 (n= 41) received similar protocol but the intensity of contraction was set at 80% maximal voluntary isometric contraction. In both cases, each series of IC was done until exhaustion or up to a maximum of 5 minutes. Patients received five sessions of treatment during a two-week period. Outcome measures included muscle pain sensitivity (pressure pain thresholds) and pain intensity (pain intensity numerical rating score), and shoulder function (Constant Score).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
82
The intervention included the application of a series of isometric contraction for the external rotators shoulder muscles. The exercise protocol included two intensities; high-level isometric contraction (80% maximal voluntary isometric contraction) versus a low-level isometric contraction (20% maximal voluntary isometric contraction).
Hospital Traumatológico
Concepción, Bio Bio, Chile
Pain intensity Numerical Rating Scale
The Pain intensity Numerical Rating Scale is a self-reporting measure of pain intensity. This involves asking patients to rate their pain intensity by selecting a number on a horizontally depicted 11-point scale from 0 (no pain) to 10 (worst possible pain). Based on its several advantages (i.e. more responsive, sensitive and easy to administer) over other pain measuring scales, the PI-NRS has been recommended as a core outcome measure in clinical trials of chronic pain treatments. The minimal clinically important change for this scale has been reported to range from 1.5 to 3.2 points. Other authors have determined a meaningful clinical change of 2 points from baseline pain scores.
Time frame: Baseline through the end of the intervention (2 week period)
Shoulder function
The shoulder function was assessed by the Constant Score scale. This is a multi-item functional scale assessing pain, activities of daily living, range of motion and strength of the affected shoulder. Its score ranges from 0 to 100 points, representing worst and best shoulder function respectively. Pain and activities of daily living (subjective aspects receiving 35 points) are answered by the patient ; and range of motion and strength (objective aspects receiving 65 points) require a physical evaluation and are answered by the orthopaedic surgeon or the physiotherapist.
Time frame: Baseline through the end of the intervention (2 week period)
Muscle pain sensitivity
Muscle pain sensitivity was evaluated through the pressure pain threshold, or the minimum pressure that induces pain or discomfort. Pressure pain thresholds measurements have been shown to have good or excellent inter-rater intraclass correlation coeficient values ranging from 0.74 to 0.90, and intra-rater reliability interclass correlation coefficient values ranging from 0.75 to 0.99. The minimal clinically important change calculated for this outcome has been reported to be ≥ 1.10 Kg/cm2/s
Time frame: Baseline through the end of the intervention (2 week period)
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