Sharon L. Kilbreath

Limited independent flexion of the thumb and fingers in human subjects.

1. We investigated whether human subjects can activate selectively flexor pollicis longus (FPL) and digital portions of flexor digitorum profundus (FDP). These muscles were selected because they are the only flexors of the distal phalanges. 2. Electromyographic activity (EMG) was recorded with intramuscular electrodes from one digital component of the deep flexors (‘test’) while subjects lifted weights by flexing the distal interphalangeal joint of the other digits in turn (‘lifting’ digits). Only recording sites at which single motor units were recruited selectively at low forces were used. The weights lifted represented 2.5‐50% of the maximal voluntary contraction (MVC). We measured the lowest weight lifted which produced phasic and tonic coactivation in the ‘test’ muscle. 3. The extent of coactivation varied with the ‘distance’ between the test and lifting digits although no significant difference occurred in the pattern of coactivation thresholds among the digital flexors. The extent of coactivation increased when angular displacement or velocity at the distal interphalangeal joint of the lifting digit increased but was not critically dependent on restraint of the hand. 4. Because mechanical ‘connections’ could interfere with the ability to move a distal phalanx independently, the arms of nine cadavers were studied. The separation of tendons between the thumb (FPL) and the index portion of FDP, and between the index and middle portions of FDP, usually extended more proximally in the forearm than separation between the tendons to the middle and ring fingers and between the ring and little fingers. Direct intertendinous links were also noted. 5. It is not possible to direct a sufficiently focal motor command to flex selectively the distal joint of the fingers and thumb when forces exceeding 2.5% MVC are generated. For the middle, ring and little fingers in particular, movement of adjacent digits may also involve ‘in‐series’ mechanical links between adjacent components of FDP.

Cardiorespiratory fitness and walking ability in subacute stroke patients.

OBJECTIVES To evaluate the cardiorespiratory fitness of subacute stroke patients and to determine whether reduced fitness is associated with gait performance. DESIGN Descriptive, cross-sectional study. SETTING Rehabilitation hospital. PARTICIPANTS Seventeen patients in an inpatient rehabilitation unit who had mild to moderate gait impairments after a recent (< or =7wk) stroke. All subjects could walk at least 3m alone or with an aid but with no standby assistance. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Peak and submaximal cardiorespiratory responses were measured during semirecumbent leg cycling exercise. Walking velocity and endurance were assessed with 10-m and 6-minute walk tests, respectively. RESULTS Peak oxygen uptake (Vo(2)peak) was 1.15+/-0.36L/min, which was only 50% of the Vo(2)peak reported in the literature for a healthy, age-matched group. Maximal walking velocity (1.02+/-0.28m/s) and endurance (294.1+/-120.2m) were also approximately 50% of an aged-matched healthy group. Pearson product-moment correlations revealed that 6-minute walking endurance was strongly associated with self-selected walking velocity (R=.91) and measures of peak cardiorespiratory fitness (R=.84). CONCLUSIONS Cardiorespiratory fitness was markedly impaired within 7 weeks after a stroke. Although muscle weakness and loss of coordination are the primary impairments that affect gait after a stroke, impaired cardiorespiratory fitness may secondarily affect gait performance by limiting walking endurance. To address this secondary impairment, current rehabilitation interventions can incorporate assessment of cardiorespiratory fitness status and aerobic exercise training for persons after stroke.

Chronic Ankle Instability: Evolution of the Model

CONTEXT The Hertel model of chronic ankle instability (CAI) is commonly used in research but may not be sufficiently comprehensive. Mechanical instability and functional instability are considered part of a continuum, and recurrent sprain occurs when both conditions are present. A modification of the Hertel model is proposed whereby these 3 components can exist independently or in combination. OBJECTIVE To examine the fit of data from people with CAI to 2 CAI models and to explore whether the different subgroups display impairments when compared with a control group. DESIGN Cross-sectional study. PATIENTS OR OTHER PARTICIPANTS Community-dwelling adults and adolescent dancers were recruited: 137 ankles with ankle sprain for objective 1 and 81 with CAI and 43 controls for objective 2. INTERVENTION(S) Two balance tasks and time to recover from an inversion perturbation were assessed to determine if the subgroups demonstrated impairments when compared with a control group (objective 2). MAIN OUTCOME MEASURE(S) For objective 1 (fit to the 2 models), outcomes were Cumberland Ankle Instability Tool score, anterior drawer test results, and number of sprains. For objective 2, outcomes were 2 balance tasks (number of foot lifts in 30 seconds, ability to balance on the ball of the foot) and time to recover from an inversion perturbation. The Cohen d was calculated to compare each subgroup with the control group. RESULTS A total of 56.5% of ankles (n = 61) fit the Hertel model, whereas all ankles (n = 108) fit the proposed model. In the proposed model, 42.6% of ankles were classified as perceived instability, 30.5% as recurrent sprain and perceived instability, and 26.9% as among the remaining groups. All CAI subgroups performed more poorly on the balance and inversion-perturbation tasks than the control group. Subgroups with perceived instability had greater impairment in single-leg stance, whereas participants with recurrent sprain performed more poorly than the other subgroups when balancing on the ball of the foot. Only individuals with hypomobility appeared unimpaired when recovering from an inversion perturbation. CONCLUSIONS The new model of CAI is supported by the available data. Perceived instability alone and in combination characterized the majority of participants. Several impairments distinguished the sprain groups from the control group.

The effect of recurrent ankle inversion sprain and taping on proprioception at the ankle.

PURPOSE A common explanation for the tendency for ankle inversion sprains to recur is that proprioception is impaired by the initial sprain. It is further hypothesized that the application of tape prevents further sprains by enhancing proprioceptive acuity. The purpose of this study was to determine whether proprioception was impaired in people with recurrent ankle inversion sprain, and whether taping the ankle provided enhanced proprioceptive ability. METHODS We compared the ability to perceive passive plantarflexion and dorsiflexion movements imposed at the relaxed ankle in 25 subjects with recurrent ankle inversion sprain, with a group of 18 healthy control subjects, matched for age, height, weight, and activity level. Subjects were tested with the ankle both taped and untaped. Detection thresholds were determined at three velocities, 0.1 degrees x s(-1), 0.5 degrees x s(-1), and 2.5 degrees x s(-1). Velocity of the imposed movements and testing of the taped and untaped conditions were randomized. RESULTS There was no significant difference in the ability to perceive ankle movements between subjects with sprains and healthy controls at any velocity of movement tested. In addition, there was no significant difference in movement perception between the taped and untaped conditions for either subject group at any velocity. CONCLUSION The ability to detect passive plantarflexion and dorsiflexion movements is not impaired in subjects with recurrent ankle inversion sprain. Furthermore, the protective effect of taping was shown not to arise from enhanced proprioception in the dorsiflexion-plantarflexion plane.

Assessment of breast cancer-related arm lymphedema--comparison of physical measurement methods and self-report.

ABSTRACT Purpose To determine the relationship between physical methods of measuring lymphedema and self-reported swelling, their reliability, and standard error of measurement. Method: Lymphedema in each arm of women with (n = 33) and without (n = 18) unilateral arm lymphedema, secondary to breast cancer was measured by self-report, bioimpedance spectroscopy (BIS), perometer, and the truncated cone method. Results: The physical measurement tools were highly reliable (ICC(2,1): 0.94 to 1.00) with high concordance (rc: 0.89 to 0.99). Selfreport correlatedmoderately with physical measurements (r = 0.65 to 0.71) and was moderately reliable (ICC(2,1): 0.70). Conclusions: Lymphedema assessment methods are concordant and reliable but not interchangeable.

Do voluntary strength, proprioception, range of motion, or postural sway predict occurrence of lateral ankle sprain?

Prevention of ankle sprain, the most common sporting injury, is only possible once risk factors have been identified. Voluntary strength, proprioception, postural sway, and range of motion are possible risk factors. A systematic review was carried out to investigate these possiblities. Eligible studies were those with longitudinal design investigating ankle sprain in subjects aged ⩾15 years. The studies had to have measured range of motion, voluntary strength, proprioception, or postural sway before monitoring incidence of lateral ankle sprain. Dorsiflexion range strongly predicted risk of ankle sprain. Postural sway and possibly proprioception were also predictors. Therefore the preliminary evidence suggests that people with reduced ankle dorsiflexion range may be at increased risk of ankle sprain.

Comparison of Effect of Aerobic Cycle Training and Progressive Resistance Training on Walking Ability After Stroke: A Randomized Sham Exercise–Controlled Study

OBJECTIVES: To determine whether changes in strength or cardiorespiratory fitness after exercise training improve walking ability in individuals who have had a stroke.

Frequency of hand use in healthy older persons

The aim of this study was to describe the type and frequency of hand use in healthy older adults. Observational studies were conducted involving structured observations at five-minute intervals on 15 healthy older adults as they went about their normal daily routine between 10.00 am and 2.00 pm. Overall, the dominant hand was used more frequently than the non-dominant hand. Subjects used their hands predominantly to hold and manipulate objects, and not for balance. There was no significant difference between the frequency of manipulating objects with the fingers and the frequency of use of the whole hand. Subjects used their hands significantly more often in bimanual activities than in unimanual activities or in no activity. Although subjects usually stood while they held or manipulated objects, they also sat or walked while manipulating them. The present study provides insights into how healthy older adults naturally use their hands in performing everyday activities. While the dominant hand is used more than the non-dominant hand, the hands are used predominantly together to perform bimanual tasks.

Accuracy of weight estimation for weights lifted by proximal and distal muscles of the human upper limb.

1. It is well established that tactile acuity is greater over digits than over the proximal parts of the upper limb and that the corticospinal projection is especially dense for distal muscles. To determine whether the acuity for judgements of forces exerted by distal muscles differed from that for proximal muscles, a weight‐matching task was used with first dorsal interosseous, flexor pollicus longus and elbow flexors. 2. Reference weights equivalent to approximately 3% (light) and 15% (heavy) of the maximal voluntary contraction were lifted by one muscle group on the left. They were matched with a variable weight, lifted by the same group, on the right. 3. In naive subjects, the coefficient of variation for repeated estimates of perceived heaviness was significantly lower for proximal than distal muscles. Measured in this way, ‘accuracy’ (i.e. reproducibility of the estimates) was not greater for the intrinsic muscles of the hand. This result could not be explained by the way in which the weights were supported by the index finger. When the data were expressed as the relative difference between the reference and the matched weight, each muscle group behaved similarly. 4. For a particular muscle, accuracy was greater when the heavy rather than the light weights were lifted. 5. Given that estimates of forces and heaviness are biased by signals of central motor command (McCloskey, 1981; Gandevia, 1987; Cafarelli, 1988; Jones, 1988). these signals could be graded no more finely for distal than proximal muscles. Furthermore, relative accuracy was greater for forces at the high rather than the low end of the comfortable ‘matching’ range of force for a particular muscle.

Intrinsic Predictors of Lateral Ankle Sprain in Adolescent Dancers: A Prospective Cohort Study

Objective:To identify intrinsic predictors of lateral ankle sprain. Design:Prospective cohort study. Setting:A performing arts secondary school and a dance school. Participants:One hundred fifteen adolescent dancers (94 female and 21 male) entered the study. One ankle of each dancer was randomly assigned to a test group (n = 114), and the other was assigned to a validation group (n = 112). Predictors:Eighteen measures, including age, dance history, previous ankle sprain, ankle and foot laxity and range of motion, and balance from test ankles were entered into a backwards stepwise Cox regression model. The model generated with the test group was used to predict ankle sprains in the validation group. Main Outcome Measure:Time to first lateral ankle sprain. Results:An increased risk of sprain in the test group was predicted by younger age [hazard ratio (HR) = 0.65, 95% CI 0.45-0.94], previous sprain of the contralateral ankle (HR = 3.76, CI 1.24-11.40), increased passive inversion range (HR = 1.06, CI 1.00-1.12), and inability to balance on demipointe (HR = 3.75, CI 1.02-13.73). Of these predictors, only previous sprain of the contralateral ankle significantly predicted ankle sprain in the validation group (HR = 3.90, CI 1.49-10.22). The predictive accuracy of this variable was not strong (positive likelihood ratio of 2.01 and negative likelihood ratio of 0.45). Conclusion:A history of previous lateral ankle sprain is associated with an increase in the risk of future sprain of the contralateral ankle.