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Biomedical subjects

J C Agre

Publications and source records attributed to J C Agre.

At least 37 records · Page 2Linked to original sources
PubMed1993

Acoustic myography compared to electromyography during isometric fatigue and recovery.

This study compared the acoustic (RMS-AMG) to electromyographic (RMS-EMG) signal, median frequency of EMG power spectrum (Fm), and quadriceps torque during isometric fatiguing contraction (FC) and recovery. Seven subjects were tested for strength (MVC) and then, on separate days, maintained 20%, 40%, or 80% MVC to exhaustion followed by MVC testing at regular intervals. Throughout FC, RMS-EMG significantly (P < 0.05) increased and Fm significantly (P < 0.05) decreased during all trials; RMS-AMG significantly (P < 0.05) increased only during the 20% and 40% trials. During recovery, MVC and RMS-EMG recovered most slowly after the 20% trial and most rapidly after the 80% trial; Fm and RMS-AMG recovered by 90 seconds after all trials. RMS-AMG reflects RMS-EMG during low but not high levels of FC. Recovery of strength is most depressed following FC at lower relative levels of torque. We conclude that RMS-AMG behaves differently than RMS-EMG, torque, and Fm during FC and recovery.

Acoustics↗
PubMed1992

Therapeutic exercise in chronic neck and back pain.

Research regarding the effect of exercise on chronic benign axial pain is reviewed. Both chronic low back pain (LBP) and chronic neck pain are associated with weakness of the trunk and neck musculature; however, it is unknown whether weakness is a cause or effect. The relationship between incoordination of the neck or trunk musculature and chronic pain is unclear. Exercise is associated with improved strength and endurance and decreased pain in subjects with LBP but the literature is very sparse with respect to chronic neck pain. Range-of-motion is also diminished in those with LBP and improves with exercise, and is associated with abatement in symptoms. No evidence could be found regarding the effect of exercise on segmental motion. Exercise is also associated with improved function, however the mechanism whereby either pain report or function improves is unclear. A greater understanding of the role of exercise will require more specific studies of strength, coordination, motion, function, and pain.

Back Pain↗
PubMed1991

Correlation of motor units with strength and spectral characteristics in polio survivors and controls.

The purpose of this study was to determine whether quantitative motor unit analysis in postpolio individuals correlates with muscle strength, endurance, work capacity, or power spectral characteristics of surface EMG and to determine whether power spectrum differentiates postpolio from control subjects. This study was designed to compare these variables in 34 symptomatic postpolio, 16 asymptomatic postpolio, and 41 control subjects. Quantitative motor unit analysis of the quadriceps femoris muscle was performed using a concentric needle electrode. Isometric knee extension peak torque, endurance (time to exhaustion) at 40% of maximal torque, work capacity (tension time index), and recovery of force through 10 minutes post-exhaustion were determined. Median frequency of the surface power spectrum was determined during the above testing. Power spectrum histograms were compared at the onset and termination of endurance exercise. Motor unit action potential variables did not correlate with isometric peak torque, tension time index, endurance time, recovery of strength, or with median frequency. Surface power spectrum did not differentiate postpolio from control subjects.

Action Potentials↗
PubMed1991

Needle electromyographic evaluation of patients with myofascial or fibromyalgic pain.

Several past studies have evaluated the electromyographic activity of myofascial trigger points with conflicting results. This study was performed to determine whether spontaneous activity or motor unit activity was present in patients with focal myofascial pain or fibromyalgia. Using routine needle electromyographic techniques, we sampled reproducibly tender focal areas (tender points), similar tender areas with pain referral (trigger points), associated muscle bands and adjacent uninvolved musculature. Twenty-five subjects (14 females, 11 males, mean +/- SD age 43 +/- 14 years) were studied; twenty-one subjects with focal myofascial pain and four with fibromyalgia. Spontaneous fibrillatory or positive sharp wave potentials were not found in any muscle in the 25 subjects. There was no evidence of focal motor unit activity in the tender points, trigger points or associated muscle bands in either group. Motor unit recruitment was similar in all areas sampled. We conclude that no electrodiagnostic evidence of ongoing denervation or focal muscle spasm is found in association with focal myofascial pain or fibromyalgia.

Action Potentials↗
PubMed1991

Motor unit firing rates in postpolio and control subjects during submaximal contraction.

Postpolio patients have a deficit in strength recovery after isometric activity. The cause for this is unknown, but may be the result of higher motor unit firing rates during the activity, which leads to excessive fatigue of the motor units. The purpose of this study was to determine whether postpolio subjects recruited motor units at higher firing rates than control subjects. Twelve control and seven postpolio subjects were tested for maximal voluntary contraction of the quadriceps isometrically. Randomly, subjects performed isometric contractions for five 10-s periods freely against gravity (threshold) and at 20% and 40% of maximal voluntary contraction. Decompositional motor unit electromyographic analysis was used to measure motor unit amplitude, motor unit firing rate and counted number of motor units identified. Analysis was by univariate analysis of variance. Motor unit firing rate was not significantly greater (P greater than 0.05) in postpolio subjects than control subjects at all three levels of contraction. Thus, it is unlikely that an increased motor unit firing rate leads to the deficit in recovery of strength in postpolio subjects.

Action Potentials↗
PubMed1991

Rate of decline in blood lactate after cycling exercise in endurance-trained and -untrained subjects.

The purpose of this study was to compare the rate of decline in blood lactate (La) levels in nine trained men [maximal O2 consumption (VO2max) 65.5 +/- 3.3 ml.kg-1.min-1] and eight untrained men (VO2max 42.2 +/- 2.8 ml.kg-1.min-1) during passive recovery from a 3-min exercise bout. Trained and untrained subjects cycled at 85 and 80% VO2max, respectively, to produce similar peak blood La concentrations. Twenty samples of arterialized venous blood were drawn from a heated hand vein during 60 min of recovery and analyzed in an automated La analyzer. The data were then fitted to a biexponential function, which closely described the observed data (r = 0.97-0.98). There was no difference in the coefficient expressing the rate of decline in blood La for trained and untrained groups (0.0587 +/- 0.0111 vs. 0.0579 +/- 0.0100, respectively). However, trained subjects demonstrated a faster time-to-peak La (P = 0.01), indicative of a faster efflux of La from muscle to blood. Thus the rate of decline in blood La after exercise does not appear to be affected by training. The faster decline previously reported for trained subjects may be due to the use of a linear rather than a biexponential curve fit.

Adolescent↗
PubMed1991

Neuromuscular function in polio survivors.

Although there is no documented, objective evidence that symptomatic post-polio subjects are rapidly losing strength, they have a number of neuromuscular deficits related to a more severe poliomyelitis illness that may explain why they complain of problems with strength, endurance, and local muscle fatigue. Symptomatic post-polio subjects were hospitalized longer during the acute poliomyelitis, recovered more slowly, and had electromyographic evidence of greater loss of anterior horn cells. Additionally, recent assessment demonstrated that they were weaker, had a reduced work capacity, and recovered strength less readily after activity in the quadriceps muscles as compared to asymptomatic subjects. Of great clinical importance, rating of perceived exertion in the muscle during exercise was the same in symptomatic and asymptomatic post-polio and control subjects, indicating that symptomatic subjects have a mechanism to monitor local muscle fatigue that could be used to avoid exhaustion. A study of pacing (interspersing activity with rest breaks) showed that symptomatic subjects had less local muscle fatigue and greater strength recovery when they paced their activity than when they worked at a constant rate to exhaustion. We recommend that post-polio individuals pace their daily activity to avoid excessive fatigue.

Electromyography↗
PubMed1991

Quantitative cervical flexor strength in healthy subjects and in subjects with mechanical neck pain.

Although weakness of anterior cervical muscles is postulated to contribute to persistent neck pain in patients with mechanical neck pain, quantitation of weakness has never been reported. We compared anterior cervical muscle strength in 30 subjects with mechanical neck pain and in 30 asymptomatic control subjects. Testing was performed with the subject supine, chin retracted, and neck flexed. Assessment was made using a hand-held dynamometer with head held at the midline and with rotation left and right within a pain-free range. Analysis with Wilcoxon scores showed that patients with neck pain had significantly less (p less than .05) strength (N.Kg-1) in all three positions than controls (1.16 +/- 0.49 vs 1.71 +/- 0.42, sagittally; 1.01 +/- 0.52 vs 1.47 +/- 0.41, rotation left; .99 +/- 0.46 vs 1.43 +/- 0.43 rotation right; neck pain vs control, respectively.) This weakness and its role in persistent neck pain should be recognized. The efficiency and effect of cervical muscle strengthening in treatment of chronic neck pain should be further defined.

Adult↗
PubMed1991

Effect of training on VO2max, thigh strength, and muscle morphology in septuagenarian women.

The purpose of this study was to determine the effects of a long-term (50 wk) combined aerobic-resistance training program on maximal oxygen consumption (VO2max, thigh strength, and vastus lateralis fiber morphology in healthy septuagenarian women (mean age = 72 +/- 6 yr). Subjects volunteered to be in either an exercise (Ex; N = 17) or control (Con; N = 10) group. Con subjects were 34% less active in winter than in summer, Ex subjects maintained their summer activity level on exercise days in winter. Initial, intermediate (20 wk), and final (50 wk) measurements were made for isokinetic knee extension/flexion strength; VO2max and morphological measurements from a muscle biopsy were made at the initial and final times only. Both groups gained in leg strength (Ex = +6.5%; Con = +7.8%; P less than or equal to 0.05) during the summer; in the winter the Ex group maintained leg strength and the Con group declined 12.2% (P less than or equal to 0.05). The fast-twitch muscle fiber area (Type IIb) increased 29% (P less than or equal to 0.001) in the Ex group and declined 26% (P = 0.014) in the Con group. VO2max increased only in the Ex group (16%; P less than 0.001). We conclude that healthy septuagenarian women can increase aerobic capacity, leg strength, and Type IIb muscle fiber area with a long-duration, combined aerobic-resistance exercise program.

Aged↗
PubMed1991

Late effects of polio: critical review of the literature on neuromuscular function.

Many individuals who have had poliomyelitis are now complaining of several new problems attributed to their former illness including muscle atrophy; fatigue; progressive weakness; and muscle, back, and joint pain. This paper critically examines the literature regarding the neuromuscular effects of poliomyelitis. Weakness resulting from poliomyelitis was due to destruction of anterior horn cells. After the illness, muscle strength was partially recovered as a result of several physiologic adaptive mechanisms including terminal sprouting and reinnervation, myofiber hypertrophy, and, possibly, myofiber type transformation. Several pathophysiologic and functional etiologies have been proposed for late neuromuscular deterioration, but none has been proven. In fact, to date, there is no objective evidence documenting progressive loss of strength in polio survivors. Studies attempting to differentiate polio survivors with and without symptoms of deterioration have resulted in conflicting results; however, it appears reasonable to conclude that symptomatic postpolio subjects had a more severe illness with greater loss of neuromuscular function. Exercise may be helpful for many postpolio patients, but the prescription must be tailored to the individual to avoid problems of overuse or excessive fatigue.

Exercise↗
PubMed1991

Intermittent isometric activity: its effect on muscle fatigue in postpolio subjects.

Symptomatic postpolio patients report improved function when they pace their activities, but this has never been objectively assessed. The purpose of this study was to determine whether seven symptomatic postpolio subjects would (1) have less evidence of local muscle fatigue and recover strength more readily when they pace their activity (via work-rest intervals) than when they work at a constant rate to exhaustion, and (2) be able to perform more work with less fatigue by pacing. Subjects were evaluated on three separate days with at least one week between tests. On the first test day (constant exercise), isometric peak torque (MVC) of the quadriceps was determined and an isometric endurance test was performed to exhaustion at 40% of MVC. Thirty seconds after exhaustion the subject performed an MVC. One psychophysiologic and two electrophysiologic variables associated with fatigue were measured during the testing procedure. Work capacity (TTI) was determined as torque x time. In test 2 (quartile exercise), the same TTI was performed at 40% of MVC, but in this instance the work was performed in quartiles with two-minute rest breaks between work quartiles rather than continuously to exhaustion. In test 3 (interval exercise), exercise was performed at 40% of MVC in 20-second bouts with two-minute rest breaks until rating of perceived exertion exceeded 17 (very hard), or until six-minutes of work were performed. Analyses demonstrated that both work-rest interval programs resulted in less evidence of local muscle fatigue, increased capacity to perform work, and increased ability to recover strength after activity in symptomatic postpolio patients.

Adult↗
PubMed1991

Electrophysiologic study of the quadriceps muscles during fatiguing exercise and recovery: a comparison of symptomatic and asymptomatic postpolio patients and controls.

This study was performed to determine whether deficits in muscle strength, work capacity, and ability to recover strength after exhaustion in symptomatic postpolio subjects were due to central inhibition (lassitude) or other physiologic differences. We studied 34 symptomatic polio subjects, 16 asymptomatic polio subjects, and 41 control subjects. Root mean squared electromyography (RMS-EMG) and the median frequency (Fm) of the power spectrum of the quadriceps muscle was determined with surface electrodes during maximal volitional contraction (MVC) of isometric knee extension, an endurance test to exhaustion at 40% of maximal torque, and strength recovery testing that was performed at regular intervals for 10 minutes postexhaustion. Initial Fm during MVC and during the 40% MVC endurance test were similar in all three groups. The Fm decreased during the endurance test and increased during recovery similarly in all three groups. The RMS-EMG also changed in parallel fashion in all three groups during the same procedures. During recovery, a similar degree of RMS-EMG facilitation was seen in all three groups. Thus, reduction in strength, work capacity, and ability to recover from fatiguing exercise do not appear to be related to central factors (lassitude); they are probably related to other factors, such as local muscle fatigue. Each group appears to fatigue and recover in a similar manner electrophysiologically, although symptomatic polio subjects have a deficit in strength recovery, apparently due to local muscular fatigue.

Electrophysiology↗
PubMed1991

Neuromuscular function in polio survivors at one-year follow-up.

Many polio survivors complain of progressive loss of strength, work capacity, endurance, and ability to recover from fatiguing activity. These variables were measured initially and one year later in the quadriceps muscles of 28 symptomatic and 16 asymptomatic persons who had polio and 38 control individuals. Peak knee extension torque was measured isokinetically and isometrically. Endurance, or the amount of time the subject could maintain isometric torque at 40% of maximal torque, was measured. Work capacity was determined as the product of isometric torque and endurance time. Recovery of strength was measured at regular intervals for ten minutes after the endurance test. Statistical analysis was done by repeated measures ANOVA. Although the initial measures showed significant deficits in mean peak torque, work capacity, and recovery of strength in symptomatic postpolio subjects, no significant changes were found one year later in any of the variables. We conclude that symptomatic postpolio subjects do not lose significant neuromuscular function in one year.

Adult↗
PubMed1991

Physiologic parameters and perceived exertion with local muscle fatigue in postpolio subjects.

Fifty postpolio patients, 34 with and 16 without complaints of progressive loss of muscle strength, and 41 control subjects were studied to compare physiologic measures of the fatiguing process and to determine whether there is a significant interaction between the rating of perceived exertion (RPE) and physiologic measures. Statistical analyses were by ANOVA and repeated-measures ANOVA. The RPE was obtained every 20 seconds during an isometric contraction of the quadriceps at 40% of maximal torque; median frequency (Fm) of the power spectrum of the surface electromyographic signal and neuromuscular efficiency (NME) were constantly monitored. The RPE increased similarly (p greater than .05), whereas Fm and NME decreased similarly (p greater than .05) during endurance exercise at 40% of maximal torque in all three groups. A significant (p less than .05) interaction was found between RPE and both Fm and NME. We conclude that physiologic measures of the fatiguing process (Fm and NME) occur in a similar manner in postpolio and control subjects and that there is a significant interaction between subjective RPE and physiologic measures of the fatiguing process.

Electromyography↗
PubMed1990

Plasma lipid and lipoprotein concentrations in symptomatic postpolio patients.

This study reports lipid and lipoprotein concentrations in postpolio patients seen in our postpolio clinic who were evaluated for complaints of progressive weakness, fatigue, and/or pain. Concentrations of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) were determined after an overnight fast. Sixty-four patients (24 men and 40 women) with a mean age of 48 +/- 10 years were studied. Mean (+/- SD) lipid concentrations (mg/dL) for men and women, respectively, were 220 +/- 46 and 213 +/- 43 for TC; 38.5 +/- 8.6 and 59.1 +/- 18.1 for HDL-C; 148 +/- 46 and 129 +/- 36 for LDL-C; and 205 +/- 107 and 105 +/- 55 for TG. Hyperlipidemia was found in 16 of 24 men and 10 of 40 women. In the men, mean HDL-C concentration was in the lowest decile of our hospital laboratory's reference range, whereas mean TC/HDL-C ratio was elevated above the recommended value. It is suggested that lipid and lipoprotein concentrations be evaluated in postpolio patients because a high prevalence of lipid/lipoprotein disorders was found in our subjects. Further research is needed on this topic.

Adult↗
PubMed1990

Neuromuscular function: comparison of symptomatic and asymptomatic polio subjects to control subjects.

The purpose of this study was to determine if there were any differences between symptomatic and asymptomatic polio survivors by history of acute poliomyelitis illness, electromyographic evidence of terminal motor unit reorganization, and neuromuscular function of the quadriceps femoris muscle. Thirty-four symptomatic postpolio subjects, 16 asymptomatic postpolio subjects, and 41 controls were studied. A questionnaire assessed polio history. Peak knee extension torque was measured isokinetically and isometrically. Endurance (time to exhaustion) was measured at 40% of maximal isometric torque. Work capacity was determined as the product of torque and duration. Recovery of isometric strength was measured at regular intervals for ten minutes after exhaustion. Quantitative electromyography was also performed on the quadriceps to determine motor unit action potential duration and amplitude. It was found that symptomatic subjects had evidence of more severe original polio involvement by history (documented electromyographically), were weaker and capable of performing less work than asymptomatic subjects, and recovered strength less readily than controls.

Adult↗
PubMed1989

Psychologic characteristics of polio survivors: a preliminary report.

Ninety-three men and women with histories of polio were administered the Symptom Check List-90 Revised (SCL-90R), Psychosocial Adjustment to Illness Scale-Self Report (PAIS-SR), and a questionnaire about their polio histories. The SCL-90R and PAIS-SR are measures of emotional and psychosocial functioning. Two samples were used: a clinic sample (n = 71) and a postpolio support group sample (n = 22). Initial results for both on the SCL-90R and PAIS-SR indicated elevated scores on a number of subscales. SCL-90R subscale elevated scores for men included those for somatization, depression, anxiety, hostility, and phobia, whereas for women there were elevations on measures of somatization, depression, anxiety, and psychoticism. Elevations were found in the following subscales on the PAIS-SR (pooling men and women): health care orientation, social environment, and extended family relationships. Men scored slightly, but not significantly, higher than women in the SCL-90R except for the hostility subscale, in which the difference was significant (p less than 0.05). Symptom profiles indicated psychologic distress. Comparisons with variables associated with polio and its late effects (such as severity of initial polio, use of an iron lung during initial illness, number of involved limbs, etc) were not statistically significant.

Attitude to Health↗