Prevalence and correlates of depression among veterans with multiple sclerosis.

OBJECTIVES: To establish the prevalence of major depressive episode (MDE) in a large sample of veterans with multiple sclerosis (MS); to identify demographic characteristics, aspects of disease presentation, and perceptions of disability associated with greater concurrent risk for MDE; and to examine the relationship between MDE, service utilization, and activity participation. METHODS: Veterans with MS (n = 1,032) were identified via computer database and surveyed by mail; 451 (43.7%) responded. RESULTS: Twenty-two percent of the sample met criteria for current MDE. Low income, unemployment, presence of falls, younger age, absence of a marital partner, and high levels of perceived disability due to bowel functioning were independently associated with MDE. Disease subtype, disease duration, use of disease modifying therapies, and perceived disability due to mobility or bladder problems were unrelated to MDE. Current MDE was in turn associated with increased primary care visits and increased impact of disease upon activity participation. Similar correlates were associated with minor depressive episode. CONCLUSIONS: Unlike the general population, rates of depression in this predominantly male sample were similar to those found in predominantly female samples of persons with multiple sclerosis. Specific aspects of disability were differentially associated with depression, and depression was independently associated with increased service utilization and increased participation limitations.

Botulinum toxin injection of spastic finger flexors in hemiplegic patients.

OBJECTIVE: To assess the outcomes of botulinum toxin injection of spastic finger flexors followed by intensive training of finger extensors. DESIGN: Fourteen subjects with chronic hemiplegia spasticity of the upper limb had electromyographic-guided botulinum toxin injection into the long finger flexors. All patients presented with minimal active finger extension with the wrist flexed, sustained clonus of the finger flexors, functional proximal arm function, and absence of fixed contracture. Cadaver dissections directed selection of two injection sites: the flexor digitorum sublimis and the flexor digitorum profundus. Fifty mouse units of botulinum toxin were injected into each muscle. After injection, the subjects were instructed in a home program of stretching the long finger flexors, upper limb weight bearing with a weight-bearing splint, and exercise to improve finger extension control. RESULTS: Compared with preinjection measures, assessment the first week after the initial injection showed significantly reduced tone, reduced clonus, and greater active finger extension with the wrist in the neutral position. Four months later, the Ashworth scale increased to preinjection levels in the six subjects with repeated injections but was again decreased postinjection. Active finger extension with the wrist in the neutral position and clonus showed a statistically nonsignificant trend toward cumulative improvement after the second injection. CONCLUSION: The greatest change in finger extension and spasticity reduction occurred after the first injection. Continued significant improvement in finger extension was not observed.

Neuromuscular and psychological characteristics in subjects with work-related forearm pain.

There are scant data available on the neuromuscular and psychological characteristics of patients with cumulative trauma disorders. We compared 16 subjects with work-related forearm and hand pain in the dominant upper limb with 9 age-matched control subjects. Pain subjects were divided into two groups based on nerve conduction studies: eight subjects were in the study group for median neuropathy at the wrist (MN, median transcarpal latency >2.3 ms), and eight were in the study group for electrodiagnostically negative pain (EN). Average pain, forearm muscle tenderness, grip strength, pinch strength, and wrist flexor and extensor strength were measured. The Health Status Questionnaire and the Beck Depression Inventory were used to measure health perception and depressive symptoms, respectively. Work satisfaction was determined by a newly devised scale. Statistical analysis was by analysis of variance and planned comparison analysis. The MN and EN groups did not significantly differ on any of the measures except median transcarpal latency. Both pain groups had significantly (P < 0.05) greater average pain, greater extensor muscle tenderness, higher Beck Depression Inventory scores, higher pain rating, and poorer physical functioning on the Health Status Questionnaire than did the normal control group. Grip strength and wrist extension force were diminished in both cumulative trauma groups compared with control subjects; however, only grip strength in the MN group and wrist extension force in the EN group differed significantly (P < 0.05) from control subjects. Only the EN group had significantly less work satisfaction than did the control group. Overall, both pain groups differed from control subjects and shared similar characteristics, with the exception of median neuropathy.

Physiologic assessment of botulinum toxin effects in the rat larynx.

OBJECTIVE: Botulinum toxin (BT) is a currently used treatment for spasmodic dysphonia (SD) and other related focal dystonias. The goal of this study is to provide a basis for using the rat larynx to objectively assess physiological and histological effects of BT. STUDY DESIGN: Dosages and volumes of BT injection were varied and three physiological parameters were measured. These measures included: optical density of PAS-stained laryngeal muscle after electrical stimulation, which is an indirect measure of denervation, spontaneous laryngeal muscle activity, and laryngeal movement. METHODS: A new microlaryngoscopic technique was developed, which made it possible to observe and manipulate the rat larynx endoscopically. Laryngeal movement and electromyographic (EMG) measures were made prior to injection and 3 days following BT injections of various dosages and volumes. Optical density measures were made 3 days after injection. RESULTS: Significant reductions in vocal fold motion and spontaneous laryngeal muscle activity as a function of increased BT dosage were observed. In addition, the optical density of PAS-stained laryngeal muscle after electrical stimulation was increased following BT injection. Significant volume effects in optical density were observed in the lateral thyroarytenoid and lateral cricoarytenoid muscles on the contralateral side. CONCLUSIONS: The rat laryngeal model is suitable for assessing BT effects. In addition, the three physiological variables provided useful and reliable measures of laryngeal function. It is the authors' intention to use the rat laryngeal model to further examine the physiological and histological effects of BT with the goal of developing new methods for the treatment of patients with SD and other focal dystonias.

Subjective recovery time after exhausting muscular activity in postpolio and control subjects.

The purpose of this study was to determine whether the time to subjectively fully recover after the performance of exhausting muscular exercise was greater in unstable postpolio as compared with stable postpolio or control subjects. Twenty-five unstable (those complaining of declining muscle strength) postpolio, 16 stable (those denying declining muscle strength) postpolio, and 25 control subjects performed an isometric contraction of the knee extensor (quadriceps femoris) musculature at 40% of maximal torque until they were no longer able to do so. Five-second maximal effort contractions were made every 30 s through 2 min after the time of failure was reached and then at 1-min intervals through 10 min after failure was reached. Subjects reported the duration of time required to subjectively fully recover from this activity. Choices of "less than 1 day," "1 day," "2 days," etc., up to "greater than 2 wk" were given to the subjects for their response. Analysis was by nonparametric ANOVA and appropriate post hoc comparison procedures. Unstable postpolio subjects reported a greater recovery time than either the stable postpolio or control subjects (mean +/- SD of 2.6 +/- 3.0 days, 0.6 +/- 1.0 days, and 0.7 +/- 1.1 days, respectively, P < 0.05). Thus, the reported recovery time from exhausting isometric muscular exercise was found to be greater in unstable postpolio subjects than stable postpolio or control subjects. The cause for this finding is unknown and requires further investigation.

Transoral electromyographic recordings in botulinum toxin-injected rat larynges.

Objective assessment of muscle function following botulinum toxin injections in laryngeal muscles is difficult in human subjects. We developed a rat laryngeal model for the study of botulinum toxin injection. A new laryngoscopic technique has made it possible to observe the rat larynx endoscopically and to obtain electromyographic measurements during and after injection of toxin. The electromyographic interference pattern, fibrillation potentials, and vocal fold movement were used for analyzing dose and volume effects of injected toxin. We conclude that the lowest dosage able to produce the maximal duration of functional laryngeal impairment is 0.07 U in a volume of 0.4 microL. This model will enable us to obtain physiologic and histologic parameters that can be used to assess the selection of optimal treatment regimens with botulinum toxin for the treatment of patients with spasmodic dysphonia.

Electromyographic and neuromuscular variables in unstable postpolio subjects, stable postpolio subjects, and control subjects.

OBJECTIVE: To compare strength and endurance variables obtained in the quadriceps muscles of postpolio and control subjects over a 7-year interval with macro and single fiber electromyography (EMG) variables. DESIGN: A controlled inception cohort study. SETTING: Neuromuscular research laboratory of a university hospital. SUBJECTS: A cohort of 23 postpolio and 14 control subjects. All postpolio subjects had a history, physical examination, and EMG consistent with previous poliomyelitis, and had greater than antigravity strength in the quadriceps muscle tested. Unstable postpolio subjects acknowledged new quadriceps weakness over the 7-year period of the study (n = 11), and stable postpolio subjects denied new weakness of the quadriceps over the same period (n = 12). MAIN OUTCOME MEASURES: All subjects had tests of neuromuscular function of the quadriceps muscles at the onset of this study and yearly over a 7-year period. EMG variables were determined on a separate day after the seventh year of neuromuscular measurements. Neuromuscular variables measured were isometric knee extension peak torque, isometric endurance (time to inability to maintain knee extensor contraction at 40% of maximal torque), tension time index (TTI) (product of isometric endurance time and 40% of maximal torque), and recovery of torque at 10 minutes after the endurance test. EMG variables were macro EMG and single fiber EMG (jitter, fiber density, and percent blocking). RESULTS AND CONCLUSIONS: Unstable postpolio subjects did not lose strength more rapidly than stable postpolio subjects or control subjects. Unstable postpolio subjects were significantly weaker, had decreased TTI, larger macro EMG amplitude, greater jitter, blocking, and fiber density in comparison with stable postpolio subjects (all p < .05). Strength was negatively correlated with macro EMG amplitude in the stable postpolio group (p < .05). The slope of the regression line of strength over 7 years did not correlate (p > .05) with neuromuscular or EMG variables in control, stable, or unstable postpolio subjects.

Strength, endurance, and work capacity after muscle strengthening exercise in postpolio subjects.

OBJECTIVE: To determine whether a 12-week home quadriceps muscle strengthening exercise program would increase muscle strength, isometric endurance, and tension time index (TTI) in postpolio syndrome subjects without adversely affecting the surviving motor units or the muscle. DESIGN: A longitudinal study to investigate the effect of a 12-week exercise program on neuromuscular function and electromyographic variables. SETTING: Neuromuscular laboratory of a university hospital. SUBJECTS: Seven subjects were recruited from a cohort of 12 subjects who had participated in a previous exercise study. All subjects had greater than antigravity strength of the quadriceps. Upon completion of a postpolio questionnaire, all acknowledged common postpolio syndrome symptoms such as new fatigue, pain, and weakness; 6 of the 7 acknowledged new strength decline. INTERVENTION: On Mondays and Thursdays subjects performed three sets of four maximal isometric contractions of the quadriceps held for 5 seconds each. On Tuesdays and Fridays subjects performed three sets of 12 dynamic knee extension exercises with ankle weights. MAIN OUTCOME MEASURES: Neuromuscular variables of the quadriceps muscles were measured at the beginning and completion of the exercise program and included: isokinetic peak torque (ISOKPT, at 60 degrees/sec angular velocity) and total work performed of four contractions (ISOKTW), isometric peak torque (MVC), endurance (EDUR, time subject could hold isometric contraction at 40% of the initial MVC), isometric tension time index (TTI, product of endurance time and torque at 40% of MVC), and initial and final ankle weight (WGT, kg) lifted. Electromyographic variables included: fiber density (FD), jitter (MCD), and blocking (BLK) from single fiber assessment and median macro amplitude (MACRO). Serum creatine kinase (CK) was also measured initially and at 4-week intervals throughout the study. RESULTS: The following variables significantly (p < .05) increased: WGT by 47%, ISOKPT, 15%, ISOKTW, 15%; MVC, 36%; EDUR, 21%; TTI, 18%. The following variables did not significantly (p > .05) change: FD, MCD, BLK, MACRO, and CK. CONCLUSIONS: This home exercise program significantly increased strength, endurance, and TTI without apparently adversely affecting the motor units or the muscle, as the EMG and CK variables did not change.

Muscular function in late polio and the role of exercise in post-polio patients.

Many post-polio individuals note new musculoskeletal and neuromuscular symptoms. In general, post-polio individuals are found to be weaker than non-postpolio individuals. Muscle weakness appears to play a role in functional limitations in post-polio individuals, especially for such activities as walking and stair climbing. Many post-polio individuals also have deficits in muscular work capacity and strength recovery following activity. Importantly, post-polio individuals are known to have normal perception of local muscle fatigue during activity. The perception of fatigue within the working muscle can be used to modify activity and to assist the individual in the avoidance of excessive local fatigue during exercise and performance of activities of daily living. Recent studies have shown that judicious exercise can improve muscle strength, range of motion, cardiorespiratory fitness, efficiency of ambulation as well as add to the patient's sense of well-being. These benefits appear to occur when activity and exercise are kept within reasonable limits in order to avoid excessive muscular fatigue and/or joint or muscle pain. It is suggested that post-polio patients be instructed to avoid activities that cause increasing muscle or joint pain or excessive fatigue, either during or after their exercise program as the performance of activity at too high a level may lead to overuse/overwork problems. The recent literature indicates that exercise within the constraints of fatigue and pain leads to a number of beneficial physiologic adaptations. Judicious exercise should be viewed as an adjuvant in the overall therapeutic program of the post-polio patient, when the individual has the physiologic capacity to exercise.

Efficacy of repeated botulinum toxin injections as a function of timing.

This pilot study was designed to determine if the interval between repeated botulinum toxin injections influenced physiologic and histologic effects on laryngeal muscles in a rat model. The physiologic measurements included digitized videomicroscopic recording of vocal fold movement and electromyography. The histologic measurements included muscle fiber size and digitized optical density of laryngeal muscles after glycogen depletion by electrical stimulation. The results demonstrated that the effect of timing of the second injection was strongly correlated to laryngeal changes. Most notable were results in the subjects that underwent injections 6 weeks apart. We hypothesize that these findings might be related to terminal axonal sprouting with reinnervation. The results from this study help confirm and expand the validity of using the rat laryngeal model to understand the effect of botulinum toxin. Moreover, we believe that the data might be extrapolated to prove useful in predicting human responses to botulinum toxin treatment for functional dystonias such as spasmodic dysphonia.

Gait training efficacy using a home-based practice model in chronic hemiplegia.

OBJECTIVE: The efficacy of a home practice model for gait training was evaluated in 18 hemiplegic subjects 2.3 years (range, 1 to 5) after stroke. DESIGN: Uncontrolled case series. SETTING: Referral center. SUBJECTS: Patients at least 1 year poststroke referred to an outpatient rehabilitation program. INTERVENTION: Patients were taught home programs in two or more 2- to 5-day blocks averaging 35 physical therapy (PT) contact hours (range, 9.5 to 62.5); training extended over a mean of 22 months (range, 10 to 65). Training emphasized weight bearing, balance, segmental control, stretching, and bracing. MAIN OUTCOME MEASURES: Gait changes were measured using the newly developed Wisconsin Gait Scale (WGS). The patient-rated Falls Efficacy Scale (FES) was administered before and after training to 8 subjects, and the Health Status Questionnaire (HSQ) was retrospectively administered to all subjects to appraise subjective pretraining to posttraining changes and current psychological status. RESULTS: The average WGS score significantly improved (p < .05). Patients perceived that gait training increased the quality of their functional activities (p < .05). In a subset of patients, the FES showed that fear of falling was decreased (p < .05). Perception of well-being was comparable to a normative nonstroke reference population except for physical functioning. Compared to the only other published series (using traditional outpatient programming), the current model was of comparable cost. CONCLUSION: Despite the literature indicating a plateau in mobility function by 6 months after stroke, postacute training of gait in hemiplegic subjects using a home-based training model results in improved gait and the perception of improved function. Additionally, we provide validation for the newly developed Wisconsin Gait Scale, an instrument of gait measurement that may assist in comparing outcomes.

Low-intensity, alternate-day exercise improves muscle performance without apparent adverse effect in postpolio patients.

The purpose of this study was to examine the effect of a low-intensity, alternate-day, 12 wk quadriceps muscle-strengthening exercise program on muscle strength and muscle and motor unit integrity in 12 postpolio patients. Patients performed six to ten repetitions of a 5-s duration knee extension exercise with ankle weights. After completing six repetitions, patients rated the perceived exertion (RPE) in the exercised muscle. The patient continued repetitions until RPE was >/= 17 or ten repetitions were performed. The weight was increased the next exercise day whenever the RPE was < 17 after ten repetitions. Before and after the training program, median macroamplitude as well as jitter and blocking were determined electromyographically (EMG), serum creatine kinase (CK) was measured, and quadriceps muscle strength was assessed. The ankle weight lifted after 2 wk of training and at the end of the program were also recorded. Although the ankle weight lifted at the end of the program significantly (P < 0.05) increased from a mean +/- SD of 7.1 +/- 2.7 to 11.2 +/- 4.7 kg, the dynametrically determined muscle strength measures did not significantly (P > 0.05) increase. The EMG and the serum CK variables also did not significantly (P >0.05) change as a result of the exercise program. We conclude that performance was improved, as demonstrated by an increase in the amount of weight the patients lifted in the exercise program. No evidence was found to show that this program adversely affected the motor units or the muscle as the EMG and CK did not change.

Electromyographic and neuromuscular variables in post-polio subjects.

OBJECTIVE: Post-polio subjects experience functional deterioration many years after developing acute poliomyelitis and have been shown previously to have a deficit in strength recovery after isometric activity. This study characterized the size and stability of the motor units in a group of post-polio subjects with macro and single fiber electromyography (EMG) and correlated these variables with isometric strength, endurance, "work capacity," and strength recovery after fatiguing isometric exercise. DESIGN: A cohort of 12 post-polio subjects was tested for neuromuscular function. Electromyographic variables were determined on a separate day. SETTING: Volunteers were recruited from the community and tested in our neuromuscular research laboratory. SUBJECTS: A volunteer sample was obtained from advertisements. All subjects acknowledged post-polio syndrome symptoms. MAIN OUTCOME MEASURES: Neuromuscular variables were isometric knee extension peak torque, endurance (time to exhaustion) at 40% of maximal torque, tension time index, and recovery of torque at 10 minutes. Electromyographic variables were macro EMG and single fiber EMG (percent blocking and jitter). RESULTS: Macro EMG amplitude was ninefold the control value, and both jitter and blocking were greatly increased in comparison to control values. Isometric strength significantly (p < .05) correlated negatively with macro EMG amplitude. CONCLUSIONS: The weakest subjects had the greatest number of muscle fibers within the motor unit (as measured by macro EMG amplitude). Jitter and blocking did not correlate with neuromuscular function.

A comparison of symptoms between Swedish and American post-polio individuals and assessment of lower limb strength--a four-year cohort study.

A cohort study with initial and 4-year follow-up evaluations was performed in 78 post-polio volunteers aged 34-65 years at the time of enrolment in the study, which was made to compare post-polio individuals living in Sweden and the United States, to determine whether lower limb musculature becomes weaker over time, and to determine whether individuals with complaints of post-polio syndrome, new weakness, fatigue, walking or stair climbing difficulty were weaker or lost more strength over a 4-year interval than those individuals without such complaints. Dynametrically-measured knee extensor and flexor strength and questionnaire data were obtained initially and 4 years later. The two cohorts were fairly similar, though they differed in weight gain. The Americans gained significantly (p < 0.05) more weight than the Swedish subjects. Both groups lost significant (p < 0.05) knee extensor strength (approximately 8%), but the loss was not significantly (p < 0.05) different between the groups. Knee flexor strength did not change significantly (p < 0.05) over time. Subjects acknowledging new strength loss were not significantly (p < 0.05) weaker than those denying strength loss; however, they lost significantly (p < 0.05) more isometric knee extensor strength than the other individuals. Subjects acknowledging new fatigue, walking or stair climbing difficulty were significantly (p < 0.05) weaker in both muscle groups than those without such complaints. Subjects acknowledging post-polio syndrome were significantly (p < 0.05) weaker than those denying this symptom, but the amount of loss of strength over time was not significantly (p < 0.05) different. We conclude that the two cohorts were quite similar. Knee extensor strength decreased during the study interval. Individuals acknowledging post-polio syndrome had weaker knee extensor musculature. Subjects with new fatigue, walking difficulty, or stair climbing difficulty were weaker in both the knee extensors and the knee flexors than the other subjects. Subjects reporting new muscle weakness also had a greater decline in isometric knee extensor strength during the study interval than those without such complaint.

Needle electromyographic evaluation of the diaphragm.

Needle electromyography of the diaphragm is a useful tool in diagnosis and prognosis of patients with diaphragmatic dysfunction. Spontaneous activity, polyphasic motor units and decreased recruitment can be found in phrenic nerve and spinal cord injury. We describe a safe technique for studying the diaphragm using needle electrodes.

Electromyographic assessment of spasmodic dysphonia patients prior to botulinum toxin injection.

Electromyographic (EMG) evidence of inappropriate muscle activity (IMA) in the cricothyroid (CT) and vocalis (V) (thyroarytenoid) muscles was correlated with clinical voice measures in 32 patients with spasmodic dysphonia (SD). Subjective voice rating and quantified fluency and laryngeal diadochokinesis measures were obtained prior to botulinum toxin (Botox) injection into the V muscles. Pre-Botox EMG was performed using a monopolar needle electrode. Each muscle was sequentially examined at rest, during vocal click, scale, sustained "E" at different pitches, and repeated "E" voicings for brief periods. A three point EMG severity scale was used to grade the amount of IMA seen in each muscle. EMG evaluation showed no evidence of lower motor neuron involvement but did reveal IMA in 81.3% of the subjects. There were no significant correlations for the patients between different EMG-based IMA severity scales and the measures of voice quality and sound production. EMG did discriminate between predominantly adductor and abductor SD pattern types, but could not correctly differentiate a mixed SD group. Those patients with adductor SD displayed IMA in the V and CT muscles, while those with abductor SD displayed more IMA in the CT than the V muscles. Sequential EMG assessment of CT and V IMA in SD did not predict clinical severity or outcome following Botox injection into the V muscles.

Close-proximity concentric and modified single fiber electromyographic recordings using revised techniques with a paired wire electrode.

Using a combined concentric (CN) and modified single fiber (MSF) electromyographic needle electrode with both recording surfaces at the tip approximately 25 microns apart, 24 motor unit potentials (MUPs) were recorded from one extensor digitorum communis muscle, triggering from either the CN or MSF channel in equal numbers and averaging both CN and MSF recordings. Filter settings were 20-10,000 Hz. Correlations of MUP amplitude, phases, turns, negative turns (NTs), and main spike duration, but not rise time or duration, between the CN and MSF recordings were statistically significant (P < 0.05). Mean +/- SD numbers of estimated single fiber potentials (ESFPs) and NTs for the MSF recordings were 1.17 +/- 0.38 and 1.54 +/- 0.72. Correlations between numbers of ESFPs and turns, NTs and phases, NTs and turns, and NT and main spike duration for the MSF and CN MUP recordings, respectively, were statistically significant (P < 0.05). The study findings using these techniques continue to support evidence that one or a few muscle fibers contribute to the main spike component of the MUP.

Functional psychomotor deficits associated with carpal tunnel syndrome.

A reliable task was developed for investigating functional deficits associated with carpal tunnel syndrome (CTS). A rapid pinch and release psychomotor task utilizing muscles of the hand innervated by the median nerve was administered using a strain gauge dynamometer and providing limited force feedback. The motor performance characteristics studied were speed and force control. An experiment was conducted for studying the effects of force level, hand dominance, test-retest reliability, learning, and inter-subject variability using 13 subjects free from any hand disabilities or symptoms. A companion study was also conducted using 17 normal subjects and ten subjects diagnosed having CTS to investigate differences between CTS and control subjects. Dominant hands performed 4% to 8% better than the non-dominant hands by having a greater pinch rate, a smaller overshoot force, and less time above the upper force level and below the lower force level. Control subjects performed 25% to 82% better than CTS subjects. Age contributed 6% of the total variance for pinch rate and 7% of the total variance for the time below the lower force level. The results suggest that people suffering from CTS may experience similar functional psychomotor deficits in daily living and manual work activities.

Median nerve electrophysiologic parameters and psychomotor performance in carpal tunnel syndrome.

Psychomotor performance (PMP) involving a repeated, rapid pinch and release task was correlated with median nerve electrophysiologic parameters for control subjects (16 hands) and subjects with carpal tunnel syndrome (CTS) (14 hands). The psychomotor task was used because of its functional resemblance to many work related activities. A strain gauge dynamometer was repeatedly pinched to a predetermined force level using the index finger and thumb and then released as rapidly as possible, while measuring the actual isometric force exerted. Discrete visual and auditory feedback was provided. Median and ulnar nerve motor latencies and amplitudes, as well as median antidromic sensory latencies and amplitudes, and transcarpal latencies and amplitudes were obtained. CTS subjects had longer median motor and sensory latencies and were weaker than controls, however median motor and sensory amplitudes were not statistically different. A strong relationship was observed between electrophysiologic variables and PMP, which could not be accounted for by age differences alone. It is unclear whether the measured differences in PMP are related to sensory or motor deficits.

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.