Physical and psychosocial correlates of test-retest isometric torque variability in patients with chronic low back pain

Could Self-Control and Emotion Influence Physical Ability and Functional Recovery after Stroke?

Background and Objectives: This study was conducted to determine whether self-control and emotions could influence patients' physical ability and functional recovery after stroke. Materials and Methods: Twenty-four patients within eight weeks after a stroke were included in this study (age: 54.04 ± 10.31; days after stroke: 42.66 ± 8.84). The subjects participated in tests at the baseline, four weeks later, and eight weeks later. Subjects were asked to complete the following: (1) self-control level test, (2) positive and negative emotion test, (3) knee muscle strength testing, (4) static balance test, (5) gait measurement, and (6) activities of daily living evaluation. Results: The muscle strength of the knee, static balance, gait ability, and the Functional Independence Measure score increased significantly in the stroke patients over time. A significant correlation was noted between the emotion and physical variables in stroke patients. The self-control level was significantly associated with the change in the physical variables in stroke patients over time. Conclusions: The self-control level was positively related to the increases in functional recovery of stroke patients with time, while the emotions were related more to the physical abilities.

Which instruments can detect submaximal physical and functional capacity in patients with chronic nonspecific back pain? A systematic review

STUDY DESIGN

Systematic review.

OBJECTIVE

To evaluate the validity of instruments that claim to detect submaximal capacity when maximal capacity is requested in patients with chronic nonspecific musculoskeletal pain.

SUMMARY OF BACKGROUND DATA

Several instruments have been developed to measure capacity in patients with chronic pain. The detection of submaximal capacity can have major implications for patients. The validity of these instruments has never been systematically reviewed.

METHODS

A systematic literature search was performed including the following databases: Web of Knowledge (including PubMed and Cinahl), Scopus, and Cochrane. Two reviewers independently selected the articles based on the title and abstract according to the study selection criteria. Studies were included when they contained original data and when they objectified submaximal physical or functional capacity when maximal physical or functional capacity was requested. Two authors independently extracted data and rated the quality of the articles. The included studies were scored according to the subscales "Criterion Validity" and "Hypothesis Testing" of the COSMIN checklist. A Best Evidence Synthesis was performed.

RESULTS

Seven studies were included, 5 of which used a reference standard for submaximal capacity. Three studies were of good methodological quality and validly detected submaximal capacity with specificity rates between 75% and 100%.

CONCLUSION

There is strong evidence that submaximal capacity can be detected in patients with chronic low back pain with a lumbar motion monitor or visual observations accompanying a functional capacity evaluation lifting test.

Critical issues in the use of muscle testing for the determination of sincerity of effort

Over the past 20 years, there have been numerous attempts to identify methodologies that are capable of the determination of sincerity of effort during muscle testing. The ensuing paper reviewed this literature and drew several conclusions. Injured patients and healthy volunteers do produce less force and more variable force while performing submaximal contractions than maximal contractions. However, submaximal efforts during strength testing can be reproduced and the use of force variability is not adequate to distinguish sincerity of effort. Visual examination of the shape of force output curves is also not adequate for distinguishing sincerity of effort. Furthermore, much of the research using strength ratios, difference scores, and an assortment of different parameters derived during strength testing has not established reliable and clinically useful methods of differentiating effort levels. Methods examining motion variability, radial/ulnar force output ratios, difference scores of eccentric-concentric ratios, and electromyography offer some promise, but numerous critical issues need to addressed. The use of the coefficient of variation, for example, is statistically untenable given the number of trials appropriate for clinical samples. Several studies have inadequate sample size to number of variable ratios. Many studies have questionable or at least unknown generalizability to patient samples and actual functional capacity. It is critical that other explanatory variables such as fear of injury, pain, medications, work satisfaction, and other motivational factors be considered. It is our opinion that there is not sufficient empirical evidence to support the clinical application of muscle testing to determine sincerity of effort.

Variability of isometric and isotonic leg exercise: Utility for detection of submaximal effort

A number of studies have investigated the use of variability measures in the detection of submaximal or insincere efforts in strength testing. The underlying assumption of these approaches is that submaximal efforts will be more variable than maximal efforts. Previous studies have investigated the variability of torque production in isometric or isokinetic tasks with mixed results. The present study investigated the variability of torque production and velocity in isometric and isotonic leg extension tasks, respectively. Fifteen asymptomatic subjects participated in a within-subject counterbalanced design in which they were asked to perform maximally and submaximally in both isometric and isotonic leg extension tasks. Results indicated that both isometric and isotonic tasks showed greater variability (measured by coefficient of variation) in the submaximal effort condition. However, the sensitivity to detect submaximal efforts was much greater for the isotonic velocity variability condition. It was concluded that the isotonic approach showed promise for clinical application, but that the isometric task had unacceptably poor classification rates, consistent with previous research.