Serum insulin-like growth factor-I (IGF-I) does not correlate positively with isometric strength, fatigue, and quality of life in post-polio syndrome.

OBJECTIVES AND BACKGROUND: To determine if serum insulin-like growth factor-I (IGF-I) levels are associated with strength, body mass index (BMI), fatigue, or quality of life in post-poliomyelitis syndrome (PPS). PPS is likely due to a distal disintegration of enlarged post-polio motor units as a result of terminal axonal sprouting. Age-related decline in growth hormone and IGF-I (which support terminal axonal sprouts) is proposed as a contributing factor. METHODS: As part of the North American Post-Poliomyelitis Pyridostigmine Study (NAPPS), baseline data on maximum voluntary isometric contraction (MVIC), BMI, subjective fatigue (fatigue severity scale, Hare fatigue symptom scale), health-related quality of life (short form health survey-36; SF-36), and serum IGF-I levels were gathered on 112 PPS patients. Pearson correlation coefficients were calculated to evaluate the association between serum IGF-I and MVIC in 12 muscles, BMI, two fatigue scales, and SF-36 scale scores. RESULTS: There is a significant inverse correlation of IGF-I levels with MVIC in left ankle dorsiflexors (r=-0.30, P<0.01), and left and right knee extensors (r=-0.22, -0.25, P=<0.01, 0.01), but no significant correlations in other muscles. When men and women were evaluated separately, inverse correlations of IGF-I levels with MVIC were found only in men. IGF-I correlated inversely with BMI (r=-0.32, P=0006) and age (r=-0.32, P=0.0005). IGF-I did not correlate with the fatigue or SF-36 scales. CONCLUSIONS: In this exploratory study, we found that contrary to our expectations, IGF-I did not correlate positively with strength. IGF-I correlated negatively with strength in several lower extremity muscles, BMI, and age. IGF-I is likely not an important factor in the pathogenesis of fatigue and in determining quality of life in PPS, but its role on strength should be studied further.

Neuromuscular rehabilitation and electrodiagnosis. 3. Generalized peripheral neuropathy.

This self-directed learning module provides an updated tool for establishing the differential diagnosis and subsequently designing a cost-effective workup for patients with peripheral neuropathy. It is part of the chapter on neuromuscular rehabilitation and electrodiagnosis in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. Medication intervention for neuropathic pain is reviewed by medication class with recommendations for starting doses and review of side-effect profiles. This article also reviews the current treatment standards for a patient with juvenile-onset diabetes, including recommendations for glucose control, management of nephropathy and retinopathy, and care of foot complications.

Neuromuscular rehabilitation and electrodiagnosis. 4. Specialized neuropathy.

This self-directed learning module briefly highlights the differential diagnosis for acute weakness in patients with acute respiratory failure requiring prolonged mechanical ventilation. It is part of the chapter on neuromuscular rehabilitation and electrodiagnosis in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article includes a discussion on the role of exercise in the treatment of patients with the late effects of poliomyelitis or with acute inflammatory demyelinating polyradiculoneuropathy.

A multicenter, randomized, double-blinded trial of pyridostigmine in postpolio syndrome.

BACKGROUND: Postpoliomyelitis syndrome (PPS) is likely due to degeneration and dysfunction of terminal axons of enlarged postpolio motor units. Age-related decline in growth hormone and insulin-like growth factor (IGF-I) may be a contributing factor. Neuromuscular junction abnormalities and decreased IGF-I levels may respond to the anticholinesterase pyridostigmine, with consequent improvement in strength, fatigue, and quality of life. OBJECTIVES: To determine the effect of pyridostigmine in PPS on health-related quality of life, isometric muscle strength, fatigue, and serum IGF-I levels; and to assess the safety of pyridostigmine in PPS. METHODS: The study was a multicenter, randomized, double-blinded, placebo-controlled trial of a 6-month course of pyridostigmine 60 mg three times per day in 126 PPS patients. The primary data analysis compared mean changes of outcomes between treatment and control groups at 6 months using an intention to treat approach. Secondary analyses included a comparison of outcomes at 6 and 10 weeks, and in compliant patients. RESULTS: The study showed no significant differences in pyridostigmine and placebo-treated patients with regard to changes in quality of life, isometric strength, fatigue, and IGF-I serum levels at 6 months in the primary analysis and in compliant patients. There were no differences in outcomes at 6 and 10 weeks between groups. However, very weak muscles (1 to 25% predicted normal at baseline) were somewhat stronger (p = 0.10, 95% CI of difference -9.5 to 73.3%), and in compliant patients IGF-I was somewhat increased (p = 0.15, 95% CI of difference -6.4 to 44.8 ng/mL) at 6 months with the medication. Pyridostigmine was generally well tolerated. CONCLUSIONS: This study showed no significant differences between pyridostigmine and placebo-treated PPS patients on measures of quality of life, isometric strength, fatigue, and serum IGF-I.

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.

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.

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.

The role of exercise in the patient with post-polio syndrome.

Recent studies have shown that judicious exercise can improve muscle strength, cardiorespiratory fitness, and the efficiency of ambulation in post-polio patients. It may also add to the patient's sense of well-being. These benefits appear to occur when the patients stay within reasonable bounds while exercising in order to avoid overuse problems. In particular, the patients should be instructed to avoid activities that cause increasing muscle or joint pain or excessive fatigue, either during or after their exercise program. The literature indicates that exercise within these constraints leads to a number of beneficial physiologic and psychologic adaptations in patients with post-polio syndrome. Judicious exercise should be viewed as important adjuvant in the overall therapeutic program of the patient. Patients seen in post-polio clinics frequently complain of new fatigue, weakness, muscle pain, and/or joint pain. The most frequent complaints involving activities of daily living include new difficulties with walking and stair climbing. The therapeutic benefit of exercise in these patients to minimize or reverse decline in function is an important question frequently asked by patients with post-polio syndrome. In the general population, physical activity is known to be an important adjunct to good health, bestowing both physiologic and psychologic benefits leading to a reduction in the risk to develop a number of serious ailments as well as leading to better psychological adjustment. On the other hand, limitation in physical activity results in a number of deleterious effects. Patients with post-polio syndrome have unique problems, however, which need to be considered when prescribing an exercise program for an individual patient. A number of functional etiologies for declining function have been hypothesized including disuse weakness, overuse weakness, weight gain, and chronic weakness. Because of the variability in which the motor neurons to different muscle groups may have been affected in a particular patient, both asymmetric and scattered weakness may be present. The challenge in prescribing exercise for the patient with post-polio syndrome comes in recognizing these unique factors in each patient and modifying the prescription accordingly. One must protect muscles and joints experiencing the adverse effects of overuse or body areas with very significant chronic weakness (in general, in areas where the muscles have less than antigravity strength on manual muscle testing) while exercising those body areas experiencing the deleterious effects of disuse. Weight gain is to be avoided if at all possible in this population, because increased weight only leads to further difficulty in the performance of daily activities.(ABSTRACT TRUNCATED AT 400 WORDS)

Compatibility of adaptive responses with combining strength and endurance training.

Impairment in strength development has been demonstrated with combined strength and endurance training as compared with strength training alone. The purpose of this study was to examine the effects of combining conventional 3 d.wk-1 strength and endurance training on the compatibility of improving both VO2peak and strength performance simultaneously. Sedentary adult males, randomly assigned to one of three groups (N = 10 each), completed 10 wk of training. A strength-only (S) group performed eight weight-training exercises (4 sets/exercise, 5-7 repetitions/set), an endurance-only (E) group performed continuous cycle exercise (50 min at 70% heart rate reserve), and a combined (C) group performed the same S and E exercise in a single session. S and C groups demonstrated similar increases (P < 0.0167) in 1RM squat (23% and 22%) and bench press (18% for both groups), in maximal isometric knee extension torque (12% and 7%), in maximal vertical jump (6% and 9%), and in fat-free mass (3% and 5%). E training did not induce changes in any of these variables. VO2peak (ml.kg-1.min-1) increased (P < 0.01) similarly in both E (18%) and C (16%) groups. Results indicate 3 d.wk-1 combined training can induce substantial concurrent and compatible increases in VO2peak and strength performance.

Human growth hormone effect on serum IGF-I and muscle function in poliomyelitis survivors.

Previous work showed low insulin-like growth factor I (IGF-I) in polio survivors compared with age-matched controls and it was hypothesized that the low IGF-I was caused by the lack of growth hormone (GH) secretion. The present study asked: Is the nocturnal release of GH subnormal in polio survivors? Can the low IGF-I level be raised to the range of healthy young men (240 to 460 ng/mL) by human growth hormone (hGH) treatment? If so, what dose of hGH is required? Does the hormone treatment affect muscle function? Eleven polio survivors with evidence of postpoliomyelitis syndrome, aged 50 to 65 years, and low IGF-I levels (average IGF-I value of 170 ng/mL) were studied. The serum level of GH was measured in the first 4 hours of sleep. The serum IGF-I level was determined before and during hGH treatment at 0.0075, 0.015 or 0.03 mg/kg of ideal body weight (IBW), three times a week for successive periods of 1 month. Before and after hGH treatment, strength was determined in knee extensor and flexor muscles and the elbow flexor and elbow extensor muscles. Nocturnal GH was low in the polio survivors compared with healthy young men. Serum IGF-I was raised into the target range by either 0.0075 or 0.015 mg hGH/kg three times a week. After 3 months of hGH treatment, no consistent changes in muscle strength were observed in the study group.(ABSTRACT TRUNCATED AT 250 WORDS)