S. Jayne Garland

Minimal Detectable Change in Quadriceps Strength and Voluntary Muscle Activation in Patients With Knee Osteoarthritis

OBJECTIVE To examine the test-retest reliability and quantify the minimal detectable change (MDC) in quadriceps strength and voluntary activation in patients with knee osteoarthritis (OA). DESIGN Repeated measures over a 1-week interval. SETTING Tertiary care center. PARTICIPANTS A convenience sample of patients (N=20) diagnosed with knee OA. INTERVENTION Isokinetic and isometric quadriceps strength testing and voluntary quadriceps activation testing using interpolated twitch technique. MAIN OUTCOME MEASURES Peak isokinetic and isometric knee extension torque (Nm) and percentage of voluntary quadriceps activation (%). RESULTS The mean differences with 95% confidence intervals between the 2 test sessions for quadriceps isokinetic strength, isometric strength, and percent of voluntary activation were -4.34Nm (-14.01 to 5.34Nm), 1.56Nm (-5.56 to 8.68Nm), and 1.34% (-.53 to 3.22%), respectively. The intraclass correlation coefficients for all measures ranged from .93 to .98. The standard errors of measurement (SEMs) for quadriceps isokinetic and isometric strength were 14.57Nm and 10.76Nm, respectively. The SEM for percentage of voluntary activation was 2.84%. Based on these values, the MDCs were 33.90Nm, 25.02Nm, and 6.60% for quadriceps isokinetic strength, isometric strength, and percentage of voluntary activation, respectively. CONCLUSIONS Maximal quadriceps isokinetic strength, isometric strength, and percentage of voluntary activation measures demonstrate excellent test-retest reliability in patients with knee OA. In addition to research applications, the present findings suggest these measures are appropriate for use when evaluating change in neuromuscular function of the quadriceps in individual patients.

Sway-dependent modulation of the triceps surae H-reflex during standing

Previous research has shown that changes in spinal excitability occur during the postural sway of quiet standing. In the present study, it was of interest to examine the independent effects of sway position and sway direction on the efficacy of the triceps surae Ia pathway, as reflected by the Hoffman (H)-reflex amplitude, during standing. Eighteen participants, tested under two different experimental protocols, stood quietly on a force platform. Percutaneous electrical stimulation was applied to the posterior tibial nerve when the position and direction of anteroposterior (A-P) center of pressure (COP) signal satisfied the criteria for the various experimental conditions. It was found that, regardless of sway position, a larger amplitude of the triceps surae H-reflex (difference of 9-14%; P = 0.005) occurred when subjects were swaying in the forward compared with the backward direction. The effects of sway position, independent of the sway direction, on spinal excitability exhibited a trend (P = 0.075), with an 8.9 +/- 3.7% increase in the H-reflex amplitude occurring when subjects were in a more forward position. The observed changes to the efficacy of the Ia pathway cannot be attributed to changes in stimulus intensity, as indicated by a constant M-wave amplitude, or to the small changes in the level of background electromyographic activity. One explanation for the changes in reflex excitability with respect to the postural sway of standing is that the neural modulation may be related to the small lengthening and shortening contractions occurring in the muscles of the triceps surae.

Electromyography and Kinematics of the Trunk during Rowing in Elite Female Rowers

PURPOSE The purpose of this study was to characterize the EMG of trunk muscles together with kinematics of the pelvis and the spine of elite female rowers during the rowing stroke. METHODS Nine Rowing Canada national team candidates performed a 2000-m race simulation. EMG activity of spinal and pelvic extensor and flexor muscles and kinematic data of the pelvis and the spine were collected and analyzed during the period of peak force production. RESULTS During this period, pelvic and spinal extensor muscles demonstrated similarities in the timing of muscle activity with minimal coactivation of flexors and extensors. Minimal excursion of spinal segments occurred during the stroke with most of the extension occurring at the pelvis. Flexor activity occurred toward late drive, suggesting that trunk extension is slowed by increasing activity of the flexor muscles. CONCLUSIONS This study provides data of trunk kinematics and muscle recruitment patterns in elite female rowers. During the period of peak force production, there is minimal coactivation of trunk flexor and extensor muscles and, of the spinal segments, L3-S1 shows the most movement, which may make it more susceptible to soft tissue injury.

Factors That Influence Muscle Weakness Following Stroke and Their Clinical Implications: A Critical Review

PURPOSE To provide a comprehensive review of changes that occur in the muscle after stroke and how these changes influence the force-generating capacity of the muscle. METHODS A literature search of PubMed, CINAHL, MEDLINE, and Embase was conducted using the search terms stroke, hemiparesis, muscle structure, cross sectional area, atrophy, force, velocity, and torque. There were 27 articles included in this review. RESULTS Three changes occur in the muscle after stroke: a decrease in muscle mass, a decrease in fibre length, and a smaller pennation angle. In addition, the tendon is stretched and becomes more compliant. All of these factors reduce the affected muscles ability to generate forces similar to controls or to non-paretic muscles. The result is a leftward shift in the length-tension curve, a downward shift in the torque-angle curve, and a downward shift in the force-velocity curve. CONCLUSION Changes in muscle architecture contributing to weakness, such as muscle-fibre length, pennation angle, muscle atrophy, and tendon compliance, should be prevented or reversed by means of an appropriate rehabilitation programme.

Cardiorespiratory and neuromuscular deconditioning in fatigued and non-fatigued breast cancer survivors

PurposeFatigue is one of the most commonly reported side effects during treatment for breast cancer and can persist following treatment completion. Cancer-related fatigue after treatment is multifactorial in nature, and one hypothesized mechanism is cardiorespiratory and neuromuscular deconditioning. The purpose of this study was to compare cardiorespiratory and neuromuscular function in breast cancer survivors who had completed treatment and met the specified criteria for cancer-related fatigue and a control group of breast cancer survivors without fatigue.MethodsParticipants in the fatigue (n = 16) and control group (n = 11) performed a maximal exercise test on a cycle ergometer for determination of peak power, power at lactate threshold, and VO2 peak. Neuromuscular fatigue was induced with a sustained submaximal contraction of the right quadriceps. Central fatigue (failure of voluntary activation) was evaluated using twitch interpolation, and peripheral fatigue was measured with an electrically evoked twitch.ResultsPower at lactate threshold was lower in the fatigue group (p = 0.05). There were no differences between groups for power at lactate threshold as percentage of peak power (p = 0.10) or absolute or relative VO2 peak (p = 0.08 and 0.33, respectively). When adjusted for age, the fatigue group had a lower power at lactate threshold (p = 0.02) and absolute VO2 peak (p = 0.03). There were no differences between groups in change in any neuromuscular parameters after the muscle-fatiguing protocol.ConclusionsFindings support the hypothesis that cardiorespiratory deconditioning may play a role in the development and persistence of cancer-related fatigue following treatment. Future research into the use of exercise training to reduce cardiorespiratory deconditioning as a treatment for cancer-related fatigue is warranted to confirm these preliminary findings.

Reliability of center of pressure measures within and between sessions in individuals post-stroke and healthy controls

BACKGROUND Knowing the reliability of the center of pressure (COP) is important for interpreting balance deficits post-stroke, especially when the balance deficits can necessitate the use of short duration trials. The novel aspect of this reliability study was to examine the center of pressure measures using two adjacent force platforms between and within sessions in stroke and controls. After stroke, it is important to understand the contribution of the paretic and non-paretic leg to the motor control of standing balance. Because there is a considerable body of knowledge on COP reliability on a single platform, we chose to examine reliability using two adjacent platforms which has not been examined previously in stroke. METHODS Twenty participants post-stroke and 22 controls performed an arm raise, load drop and quiet stance balance task while standing on two adjacent force platforms, on two separate days. Intraclass correlations coefficient (ICC2,1) and percentage standard error of measurement (SEM%) were calculated for COP velocity, ellipse area, anterior-posterior (AP) displacement, and medial-lateral (ML) displacement. RESULTS Between sessions, COP velocity was the most reliable with high ICCs and low SEM% across groups and tasks and ellipse area was less reliable with low ICCs across groups and tasks. COP measures were less reliable during the arm raise than load drop post-stroke. Within session reliability was high for COP velocity and ML displacement requiring no more than six trials across tasks. CONCLUSIONS The COP velocity was the most reliable measure with high ICCs between sessions and the high reliability was achieved with fewer trials in both groups in a single session.

Retraining Postural Responses With Exercises Emphasizing Speed Poststroke

Background Postural responses are impaired after stroke, with reduced or delayed muscle activity in the paretic leg muscles. Objective The efficacy of exercises emphasizing speed of movement in modifying postural responses to perturbations that were not practiced was investigated. Design This was a dual cohort design. Methods A convenience sample of 32 individuals with hemiparesis poststroke (mean number of weeks poststroke=11.3, SD=4.1) who were recruited upon discharge from an inpatient rehabilitation hospital and a control group of age- and sex-matched individuals who were healthy (n=32) performed a single session of exercise emphasizing speed of movement. To assess postural responses to internal perturbation, unilateral arm raise and load drop tasks were performed before exercises (pre-exercise), immediately after exercises (post-exercise), and 15 minutes after exercises (retention). The time to burst peak and area of the biceps femoris muscle (BF) electromyographic (EMG) activity in the arm raise task was measured with the arm acceleration and velocity of the center of pressure (COP) excursion. For the load drop task, the anticipatory EMG deactivation area of the BF was calculated. In both tasks, the vertical ground reaction forces were recorded for each leg separately. Results Before exercise, EMG and force platform measures were smaller in the stroke group than in the control group. After exercise, the paretic BF time to burst peak decreased, the paretic BF EMG area increased, and the COP velocity increased in the arm raise task, as did the paretic BF anticipatory EMG deactivation area in the load drop task. The stroke group was weight bearing more symmetrically after exercises. Most changes were retained 15 minutes after the exercises. Limitations The retention period was short, and there was no control group of individuals with stroke. Conclusions The results of this efficacy study demonstrated that fast movement exercises improved postural responses to perturbations that were not practiced.

Morphological, electrophysiological, and metabolic characteristics of skeletal muscle in people with end-stage renal disease: a critical review.

PURPOSE Fatigue is one of the most frequent debilitating symptoms reported by people with end-stage renal disease (ESRD) on haemodialysis (HD) therapy. A wide range of underlying abnormalities, including skeletal muscle weakness, have been implicated as causes of this fatigue. Skeletal muscle weakness is well established in this population, and such muscle weakness is amenable to physical therapy treatment. The purpose of this review was to identify morphological, electrophysiological, and metabolic characteristics of skeletal muscles in people with ESRD/HD that may cause skeletal muscle weakness. METHOD Electronic databases were searched for relevant literature from inception to March 2010. Inclusion criteria were English language; adult subjects with ESRD/HD; and the use of muscle biopsy, electromyography, and nuclear magnetic spectroscopy ((31)P-NMRS) techniques to evaluate muscle characteristics. RESULTS In total, 38 studies were included. All studies of morphological characteristics reported type II fibre atrophy. Electrophysiological characteristics included both neuropathic and myopathic skeletal muscle changes. Studies of metabolic characteristics revealed higher cytosolic inorganic phosphate levels and reduced effective muscle mass. CONCLUSION The results indicate an array of changes in the morphological, electrophysiological, and metabolic characteristics of skeletal muscle structure in people with ESRD/HD that may lead to muscle weakness.

Test re-test reliability of centre of pressure measures during standing balance in individuals with knee osteoarthritis

Assessment of changes in standing balance following an intervention requires accurate measurement of balance parameters. The reliability of centre of pressure measures of balance during single-leg standing has not been reported in individuals with knee osteoarthritis. The purpose of this study was to assess the test re-test reliability of force platform centre of pressure measures during single-leg standing in older adults with knee osteoarthritis. Twenty-five adults with radiographic evidence of knee osteoarthritis performed single-leg standing balance trials on a laboratory-grade force platform on two occasions, no more than 14 days apart. Participants were asked to stand on their more symptomatic limb for three, ten second trials. Centre of pressure measures collected included: standard deviation in the mediolateral and anteroposterior directions, mean path length, velocity, and area. The mean of the three trials was calculated. Intraclass correlation coefficients, standard error of measurement, Bland and Altman plots and the minimum detectable change were calculated. Intraclass correlation coefficients ranged from 0.54 to 0.87, suggesting mixed reliability of measures. Reliability was lowest for the centre of pressure area (intraclass correlation coefficient=0.54), and highest for centre of pressure velocity and path length (intraclass correlation coefficient=0.87 for both). Standard error of measurement values were low for standard deviation in the mediolateral direction and high for centre of pressure area. These results suggest that centre of pressure values, in particular path length and velocity, are appropriate for assessment of standing balance in people with medial knee osteoarthritis.

Effects of Fast Functional Exercise on Muscle Activity After Stroke

Background. In stroke rehabilitation, considerable emphasis is placed on improving muscle strength with less focus on the speed of movement. Muscle power (product of force and velocity) is essential for balance and mobility but velocity of movement is impaired after stroke. Objective. The purpose of this efficacy study is to determine if a single session of fast functional movements can increase muscle activation and the speed of movement in participants with a subacute stroke. Methods. In total, 32 individuals poststroke and 32 age- and sex-matched controls performed a single session of 50 fast squats and steps. Electromyographic (EMG) activity was measured bilaterally in the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and soleus muscles. The average EMG area and the movement speed were calculated over 10 trials. The effect of exercise was determined as the change from the second set (Start) to the last set (End) of 10 trials. Results. The stroke group had significant increases in EMG area of the TA, BF, and RF during the squatting exercise. There was an increase in EMG area of the RF and BF when the paretic leg was stepping. Improvements in EMG area of the soleus and RF when the paretic leg was in stance accompanied increases in EMG area when the nonparetic leg was stepping. There was a trend for improved movement speed for both exercises. Conclusion. A single session of exercises emphasizing speed of movement can be used to improve muscle activation in persons with mild to moderately severe strokes.