Detecting submaximal grip exertions of variable effort by electromyography.

The purpose was to determine if the surface electromyogram (EMG) would allow detection of submaximal grip exertions of variable effort. Fifteen healthy subjects were instructed on different trials to give maximal 100% efforts, fixed 50% submaximal efforts, or submaximal efforts of variable amount (30, 40, 50 or 70%) with the right hand. The subjects were tested at each of the five handle positions of the Jamar dynamometer. Surface EMG was obtained for the right palmaris longus/flexor carpi radialis muscles. Consistent with previous research was the finding that the variable effort condition yielded a bell-shaped force curve, similar to that produced by patients with true injuries. The key finding was that 100% and 50% exertions yielded linear EMG amplitude curves whereas the variable-effort exertion yielded a bell-shaped or quadratic curve. Thus, the EMG did allow for detection of the variable submaximal effort. However, the 100% and 50% exertions could not be distinguished by the average sustained force/peak force ratio. The EMG has the potential of being a valuable adjunct for the clinician needing to determine if a patient is feigning loss of grip strength.

Consistency of sincere and feigned grip exertions with repeated testing.

Our purpose was to test the hypothesis that feigned exertions would show greater variability in both force and electromyograms than would sincere exertions over repeated testing sessions. Eleven normal subjects made sincere and feigned exertions while performing the five-handle position Jamar grip test. The subjects were tested 6 times in a 3- to 5-week period. Contrary to the hypothesis, feigned exertions did not show greater variability than sincere exertions. Both sincere and feigned exertions were highly consistent over the six sessions. However, the sincere and feigned exertions did differ in the patterns of force and electromyogram on the five-handle position test. These results and those of previous studies suggest that clinicians should use more than one type of test when testing suspected malingerers.

Electromyographic analysis of effort in grip strength assessment.

The purpose of the present research was to investigate the use of surface EMG in assessing effort while measuring grip strength with the Jamar dynamometer. We hypothesized that sincere, maximal grip contractions could be distinguished from feigned, submaximal contractions by differences in the amplitude and frequency content of the EMG, as well as by differences in force. Healthy subjects (seven men and ten women) were instructed on different trials to give a sincere (maximal, 100%) effort or a feigned (50% of maximal) effort with the right hand. The subjects were tested at each of the five handle positions of the Jamar dynamometer. Surface EMG was obtained for the right palmaris longus/flexor carpi radialis muscles. Consistent with previous research, we found that the 50% efforts, compared to 100% efforts, showed, (1) lower peak force; (2) a slower rise to peak force; and (3) a different pattern of force measurements as a function of handle position. Feigned and sincere efforts also differed in the EMG. As hypothesized, amplitude was lower for 50% than 100% efforts. The frequency spectra of the EMG were obtained by Fourier analysis. The 50% efforts showed a higher frequency EMG than did the 100%. The results supported the hypothesis that surface EMG may provide a measure of effort in a grip strength task. Analysis of the EMG, in conjunction with force analysis, has the potential of being a valuable tool for the clinician needing to determine whether a patient is giving a sincere, maximal effort or is feigning.

Effect of ibuprofen use on muscle soreness, damage, and performance: a preliminary investigation.

Twenty subjects were randomly assigned to: 1) prophylactic ibuprofen (N = 5) [400 mg TID initiated 4 h before collection of baseline data and strenuous eccentric exercise bout], 2) therapeutic ibuprofen (N = 5) [400 mg TID initiated 24 h after baseline], 3) placebo (N = 5), or 4) control (N = 5). Muscle soreness perception, plasma creatine kinase, knee extensor torque, and EMG of the quadriceps were evaluated at baseline, 24, and 48 h. The prophylactic ibuprofen group had between 40 and 50% less muscle soreness perception and significantly less decline in isometric, concentric, and eccentric torque at 24 h compared with the other three groups (P < 0.05). At 48 h both prophylactic and therapeutic ibuprofen had significantly less muscle soreness perception and decline in torque than the placebo and control groups (P < 0.05). There was no difference between the amount of muscle damage between the four groups at 24 and 48 h. Vastus medialis and lateralis EMG magnitude decreased across time. Vastus lateralis EMG magnitude had significantly less decline from baseline for prophylactic ibuprofen compared with the other three treatments at 24 h, while both prophylactic and therapeutic ibuprofen had significantly less decline at 48 h. These data indicate that a prophylactic dosage of ibuprofen does not prevent CK release from muscle, but does decrease muscle soreness perception and may assist in restoring muscle function.

Voluntary control of submaximal grip strength.

Stokes (J Occup Med; 1983;25:683-684) proposed that feigned weak hand grip can be distinguished from sincere efforts by examining force measurements for the different handle positions of the Jamar hand dynamometer. Sincere efforts yield a curvilinear relationship between grip force and handle position; feigned efforts yield a horizontal, linear relationship. The purpose of the present set of three experiments was to investigate the degree of control normal subjects have over submaximal effort and their ability to feign weakened grip. In Experiment 1 we found that subjects instructed to exert a specific amount of submaximal effort (50%) did not produce a response pattern of grip force consistent with Stokes' hypothesis. In Experiment 2 we found a linear relationship between the degree of submaximal effort and grip force for efforts of 30, 50, 70, and 90% of maximal effort. In Experiment 3 we found that subjects, with proper instruction as to the amount of effort to exert, can produce feigned submaximal efforts similar to the sincere, maximal efforts of injured people. Simple maximal grip force measurements are insensitive to the different motor strategies used in maximal and submaximal efforts and may provide little evidence for the detection of feigning.

Short-term memory constraints upon the generation of diagnosis hypotheses by novice clinicians.

The structure and function of memory affect medical problem solving. The purpose of this 1982 study was to test the assertion that the number of diagnoses actively entertained by novice clinicians during a simulated case would not be greater than seven, the average maximum storage capacity of short-term memory. A total of 24 junior physician's assistant students took mock medical histories and gave mock physical examinations using simulated patients. Each of the eight cases investigated by each group included a primary problem with various numbers of secondary problems. Three successive time periods, called interludes, were provided in which each student had three minutes to list all the hypotheses he or she was actively considering concerning the diagnosis of the patient's problem. Each interlude was scheduled at a progressively more complete point in the student's knowledge of the case. The results supported the assertion that was tested.

Detecting sincerity of effort when measuring grip strength.

The purpose of the present study was to determine whether sincere and faked grip strength measurements could be distinguished from one another by the patterns of measurements obtained for the five handle (hand size) positions of the Jamar dynamometer. Healthy subjects were instructed on different trials to give a sincere, maximal effort or to fake weakness of grip. Results were that the patterns did differ for sincere and fake trials, but not as strongly as expected. The recommendation is made that further research be done using patients with upper extremity injury.

The redundancy of student comments and numerical ratings in evaluations of teaching.

Student evaluation of teaching effectiveness is widely used in undergraduate institutions as one element of determining overall faculty effectiveness. The evaluation format typically consists of (1) a number of questions the student answers by indicating a numerical rating and (2) an open-ended section for written comments. Some faculty members believe that the numerical ratings are not taken seriously by the students, and that the written comments impose greater accountability on the part of students. On the other hand, numerical ratings are necessary to minimize the fear that unfavorable written comments will be taken out of context in promotion decisions. Tabulation of numerical ratings is essential if a computerized data base for faculty evaluation is to be established. This study was designed to examine the relationship between student's numerically based ratings and written comments by evaluating allied health instructors using a standard, schoolwide evaluation form. Written comments were categorized according to a five-point scale and compared to mean values obtained from numerical ratings. Twenty-two faculty and 1,311 student evaluations were included. Significant positive correlations were found between the numerical student ratings and the written comments. The highest correlations were between student comments and two items related to overall teaching effectiveness. Students who evaluated instructors at either extreme on the spectrum of effectiveness were most likely to include written comments. Based on the consistency of numerical ratings and written comments we recommend that only the numerical ratings be used as part of the promotion and tenure decision-making process.(ABSTRACT TRUNCATED AT 250 WORDS)

Professional performance of physician's assistants: a comparison of physician's assistant and physician ratings.

Physician's assistant educational programs have used surveys of their graduates as one method of evaluating educational objectives and curricula. A concern is the validity of physician's assistant self-ratings as measures of job performance. Ratings by supervising physicians have been suggested as more valid measures. In the present study ratings of physician's assistants and their supervising physicians were compared. Physician's assistants and their supervising physicians were interviewed using an interview instrument developed to cover the performance of the physician's assistant in the major activities of primary care practice. While the physicians and physician's assistants disagreed on several measures, in all cases the ratings of the physician's assistants were more conservative. Thus, the physician's assistants did not show any tendency to inflate ratings of their own performance.

Additive and suppressive response summation with a chain schedule.

Rats responded in a two-segment (variable-interval variable-interval) chain schedule. In one experiment, three subjects had either clicker, light, or clicker plus light as terminal-segment stimuli. All three responded at the highest rate when clicker plus light were present, thus showing additive summation. For three other subjects, initial-segment stimuli were either clicker, light, or clicker plus light. Two subjects responded at the lowest rate when clicker plus light were present, thus showing suppressive summation. In a second experiment, three subjects had either clicker, light, or neither clicker nor light as terminal-segment stimuli. None of these subjects showed reliable additive summation. Three other subjects had clicker, light, or neither as the initial-segment stimulus, and all three showed suppressive summation. Additive and suppressive summation both can be demonstrated with chain schedules, but stimulus parameters may be major variables in producing the effect.