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Rhabdomyolysis is a recognized but uncommon side effect of statin therapy. Pravastatin is a commonly used statin after cardiac transplantation, with favorable outcome and acceptable side-effect profile. We report a case of localized rhabdomyolysis attributed to physical exertion in a cardiac transplant recipient taking pravastatin.
Spinal stability is related to the recruitment and control of active muscle stiffness. Stochastic system identification techniques were used to calculate the effective stiffness and dynamics of the trunk during active trunk extension exertions. Twenty-one healthy adult subjects (10 males, 11 females) wore a harness with a cable attached to a servomotor such that isotonic flexion preloads of 100, 135, and 170 N were applied at the T10 level of the trunk. A pseudorandom stochastic force sequence (bandwidth 0-10 Hz, amplitude +/-30 N) was superimposed on the preload causing small amplitude trunk movements. Nonparametric impulse response functions of trunk dynamics were computed and revealed that the system exhibited underdamped second-order behavior. Second-order trunk dynamics were determined by calculating the best least-squares fit to the IRF. The quality of the model was quantified by comparing estimated and observed displacement variance accounted for (VAF), and quality of the second-order fits was calculated as a percentage and referred to as fit accuracy. Mean VAF and fit accuracy were 87.8 +/- 4.0% and 96.0 +/- 4.3%, respectively, indicating that the model accurately represented active trunk kinematic response. The accuracy of the kinematic representation was not influenced by preload or gender. Mean effective stiffness was 2.78 +/- 0.96 N/mm and increased significantly with preload (p < 0.001), but did not vary with gender (p = 0.425). Mean effective damping was 314 +/- 72 Ns/m and effective trunk mass was 37.0 +/- 9.3 kg. We conclude that stochastic system identification techniques should be used to calculate effective trunk stiffness and dynamics.
A 40-year-old man sustained a circumferential crush injury to his right forearm. Four months after injury, he experienced the onset of numbness and tingling in the distribution of the median nerve after exercise. Elevated compartment pressures of the palmar forearm and slowing of median nerve conduction after exercise suggested chronic exertional compartment syndrome. A flexor fasciotomy led to complete relief of symptoms, which allowed the patient unrestricted activity.
A case of chronic exertional compartment syndrome of the forearm flexor muscles after routine, strenuous work activity is presented. Intramuscular pressure monitoring before and after operation documented the efficacy of decompressive fasciotomy. A higher index of suspicion of forearm chronic compartment syndrome might have led to earlier diagnosis and treatment.
The excretion of some acids in urine is subject to a circadian rhythm, if diversified nutrition is offered to the body sufficiently. The effect of physical exertion upon the excretion rates of acids in urine is very similar to that of a zero diet, resulting in an increase of final degradation products and a decrease of metabolic intermediates.
Exertional rhabdomyolysis (ER) is common in sled dogs, animals with high energy expenditures that consume high fat (60% of ingested calories) diets. Associations between pre-race plasma [vitamin E] and total antioxidant status (TAS) and risk of developing ER were examined in dogs competing in the 1998 Iditarod race. Pre-race blood samples were collected from 750 dogs and a second sample was collected from 158 dogs withdrawn from the race at various times. Plasma creatine kinase activity was used to identify withdrawn dogs with ER. There was no association between pre-race plasma [vitamin E] and risk of development of ER. Dogs that developed ER started the race with higher TAS, but when withdrawn, had lower TAS than unaffected dogs and had similar pre-race [vitamin E] but higher [vitamin E] at time of withdrawal. Hence, the risk of ER in sled dogs is not affected by plasma [vitamin E] before the race.
A polysaccharide storage myopathy is described in nine Quarterhorses, Quarterhorse crossbreds, American Paints and Appaloosa horses which had a history of recurrent exertional rhabdomyolysis. Muscle biopsies were characterized by high muscle glycogen concentrations with up to 5% of type 2 muscle fibers containing inclusions which stained positively with the periodic acid Schiff (PAS) stain. The inclusions were classified as an acid mucopolysaccharide, based on their histochemical staining characteristics. Ultrastructural studies revealed that the inclusions were composed of beta glycogen particles interspersed among arrays of filamentous material. In addition, many type 2 fibers contained multiple subsarcolemmal vacuoles. These vacuoles stained lightly with eosin and did not stain positively with PAS. Centrofascicular atrophy and necrosis of scattered type 2 fibers were present in biopsies from some horses. No glyco(geno)lytic enzyme deficiencies were identified using a biochemical screening test for anaerobic glycolysis. Attempts to measure branching enzyme activities in both affected and control samples were unsuccessful, employing methods developed for human muscle. The polysaccharide accumulation in these horses may represent a hereto yet undefined metabolic disorder of skeletal muscle.
We describe the presence of cylindrical spirals on muscle biopsy from a 31-year-old man who developed rhabodomyolysis following a long run. He had a prior history of exertional cramps and myoglobinuria. His maternal grandfather had similar symptoms. Transmission electron micrographs demonstrated continuity between the lamellae of the cylindrical spirals and native myofilaments. Whether these unusual structures confer a derangement in myofilament function is uncertain.
A review of compartment syndrome, both acute and chronic, is presented. The pathophysiology, anatomy, diagnosis, and treatment are presented in relation to a unique case report. The case is one of acute exertional compartment syndrome of the medial foot treated by fasciotomy. This condition is uncommon in both its nature and location.
Cold exposure facilitates body heat loss which can reduce body temperature, unless mitigated by enhanced heat conservation or increased heat production. When behavioral strategies inadequately defend body temperature, vasomotor and thermogenic responses are elicited, both of which are modulated if not mediated by sympathetic nervous activation. Both exercise and shivering increase metabolic heat production which helps offset body heat losses in the cold. However, exercise also increases peripheral blood flow, in turn facilitating heat loss, an effect that can persist for some time after exercise ceases. Whether exercise alleviates or exacerbates heat debt during cold exposure depends on the heat transfer coefficient of the environment, mode of activity and exercise intensity. Prolonged exhaustive exercise leading to energy substrate depletion could compromise maintenance of thermal balance in the cold simply by precluding continuation of further exercise and the associated thermogenesis. Hypoglycemia impairs shivering, but this appears to be centrally mediated, rather than a limitation to peripheral energy metabolism. Research is equivocal regarding the importance of muscle glycogen depletion in explaining shivering impairments. Recent research suggests that when acute exercise leads to fatigue without depleting energy stores, vasoconstrictor responses to cold are impaired, thus body heat conservation becomes degraded. Fatigue that was induced by chronic overexertion sustained over many weeks, appeared to delay the onset of shivering until body temperature fell lower than when subjects were rested, as well as impair vasoconstrictor responses. When heavy physical activity is coupled with underfeeding for prolonged periods, the resulting negative energy balance leads to loss of body mass, and the corresponding reduction in tissue insulation, in turn, compromises thermal balance by facilitating conductive transfer of body heat from core to shell. The possibility that impairments in thermoregulatory responses to cold associated with exertional fatigue are mediated by blunted sympathetic nervous responsiveness to cold is suggested by some experimental observations and merits further study.
Exertional hypotension is well described in quadraplegics, but there are few descriptions of this hemodynamic response in paraplegics or of treatment modalities to correct this condition. We describe a patient with a complete T3-4 spinal cord lesion who repeatedly demonstrated symptomatic hypotension with wheelchair sports and arm ergometry. We used gas exchange analysis and exercise echocardiography to delineate the mechanism for hypotension. These results enabled us to develop a simple treatment plan consisting of abdominal binding and elastic stockings to avoid recurrent symptoms.
Previous reports have described significant limitations in the daily use of functional neuromuscular stimulation (FNS) ambulation systems by persons with spinal cord injuries (SCI). The potential application of these devices to provide physiological benefits as an exercise modality has prompted a reconsideration of the technology. However, the acute physiological effects related to the use of FNS systems have not been thoroughly examined. The purpose of this study was to investigate the relationships of oxygen consumption (VO2), heart rate (HR), and ratings of perceived exertion (RPE) during FNS ambulation by persons with SCI paraplegia. Eleven persons with thoracic level paraplegia, aged 21.5 to 38.0 years, participated in an incremental FNS ambulation test. Metabolic measures were collected continuously via open circuit spirometry as the subjects performed a series of ambulation passes of progressively increasing pace. At the end of each ambulation pass, HR and RPE measures were collected. The test was terminated when either the subjects judged the effort to be maximal or when the investigators deemed the effort to be maximal based on HR. A strong linear relationship was documented between the VO2 and HR measures of all subjects throughout subpeak levels of FNS ambulation. RPE did not vary proportionally with VO2 until relatively high levels of exercise intensity were reached. This study indicates that HR, but not RPE, is an appropriate indicator of exercise intensity for persons with SCI paraplegia using a FNS ambulation system.
OBJECTIVES: The purpose of this study was to compare the effects of a rehabilitation program on the perceived exertion (PE) and the cardioventilatory responses during exercise in healthy people and paraplegics. METHODS: A group of seven healthy persons (age 26.6 SD 6.2 years) and one of seven paraplegics (age 42 SD 15.9 years) participated in a rehabilitation program composed of Square Wave Exercise Tests (SWEET) during six weeks. The maximal oxygen uptake, the power output (PO), heart rate (HR) and measures of PE using the Borg CR 10 scale were investigated during a maximal graded test performed before and after the rehabilitation program. During the first SWEET session (SWEET 1) measures of PE and HR (base and peak) were also investigated and compared to the last session (SWEET 2) of the same absolute workload after the 6 weeks. RESULTS: Statistical analysis revealed no significant difference in both groups for PE between the two maximal graded tests. However, a significant decrease in the PE values (P<0.01) was observed in both groups during the SWEET 2. There was no significant difference in maximal HR between the two graded tests, but a significant decrease in HR (P<0.0001 for base HR and P<0.001 for peak HR) was observed in SWEET 2 compared to 1. The maximal tolerated power (MTP) and the peak oxygen uptake increased significantly in both healthy and paraplegic groups (P<0.0001 and P<0.05 respectively) after the 6 weeks of rehabilitation exercise. CONCLUSION: The results of the present study suggest that PE could be used to control the exercise intensity during a rehabilitation training program for paraplegics, similar to healthy subjects. The increase in the peak oxygen uptake and MTP demonstrates the positive effects of the rehabilitation program on the physical fitness of the subjects.
A 62-year-old man developed right frontal headache after mild exercise, relieved promptly by rest. Treadmill exercise (stress testing) demonstrated ST depression on the electrocardiogram as the headache appeared. The exertional headaches were cured by coronary bypass surgery. Possible mechanisms for this unusual pain referral pattern are discussed.
The purpose of the present investigation was i) to study the effect of sex on ratings of perceived exertion (RPE) and estimation of time limit (ETL) during runs to exhaustion at both absolute and relative physical and physiological reference criteria, ii) to propose some recommendations for exercise intensity prescription from both RPE and ETL according to sex. Eight male and eight female middle-distance endurance-trained runners performed two exercises until exhaustion on an outdoor track. The first test was a graded exercise to determine maximal aerobic velocity (vV.O2max), the velocity at the lactate threshold (vLT), and the velocity at delta 50 (vDelta50: the velocity halfway between vV.O2max and vLT). The second test was a constant all-out run at vDelta50 to determine the time to exhaustion at this intensity (tlim). The results of this study showed that the female runners perceived exercise as being harder, felt that they could endure less and had higher heart rate values than males for a given absolute velocity (km.h-1) whereas there were no difference between males and females for a given relative velocity (%vV.O2max). Moreover, the female runners perceived exercise as lighter and felt that they could endure more than the males for a given absolute time period (in s) whereas there was no difference between males and females for a given relative time period (%tlim). This result may be explained by the fact that the same exercise intensity or duration corresponded to higher %vV.O2max and lower %tlim for the females compared to the males. Consequently, physical trainers can prescribe the same perceived ratings for a given percentage of vV.O2max or tlim both in male and female athletes.
Perceptual ratings given on the Visual Analogue Scale (VAS) and the Category Ratio Scale (CR-10) were compared in 24 healthy male volunteers (18-39 years) subjected to an exercise test using a bicycle ergometer. Ratings of leg exertion were made by means of the CR-10, the VAS and, as a complementary measure, the method of free magnitude estimation (ME). Blood lactate levels (BL) and heart rates (HR) were used as correlates to sensory perception. The correlation between the CR-10 ratings and BL at 180 W were .59 (p less than .01), and between VAS ratings and BL .45 (p less than .05). The corresponding correlations with HR were .64 (p less than 0.01) and .58 (p less than 0.01), respectively. No significant correlation was found for ME. It was concluded that both the CR-10 and the VAS scales were found to be useful for the psychophysical estimation of perceptual intensities. The CR-10 scale appeared to be slightly more efficient than the VAS and both these methods much better than ME. The advantage of the CR-10 scale might be due to a greater ability to discriminate at high intensity levels.
We examined the effects of intensity of training on ratings of perceived exertion (RPE) at the lactate threshold (LT), fixed blood lactate concentrations (FBLC) of 2.0, 2.5 and 4.0 mM and peak in 25 untrained eumenorrheic women (mean +/- SD: age = 30.9 +/- 4.1 yrs; height = 165.7 +/- 5.9 cm; weight = 65.5 +/- 7.6 kg) who completed one year of run training. Subjects were recruited as sedentary controls or were randomly assigned to one of two training groups: 1) at the lactate threshold (at LT) or 2) above the lactate threshold (greater than LT). The at LT group trained at velocity LT and the greater than LT group trained at the velocity midway between velocity LT and peak velocity. Training subjects were reevaluated every fourth menstrual cycle and training intensity was adjusted. The control group was reassessed at menstrual cycle 12. Before training no among group differences were observed for VO2 or velocity at LT, FBLC and peak. Both training groups increased VO2 at LT, FBLC and peak as a result of training (p less than 0.05), with the greater than LT group exhibiting greater improvement than the at LT group (VO2 at LT, FBLC of 2.0, 2.5 and 4.0 mM and peak increased by 6.4, 5.3, 5.1, 4.0 and 4.7 ml/kg.min-1 for at LT and by 10.4, 9.2, 8.6, 5.1 and 5.9 ml/kg.min-1 for greater than LT; p less than 0.05). Similar findings were observed for the velocity associated with these lactate concentrations. No pre/post differences were observed in VO2 or velocity for the control group.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of this study was to examine the reliability of the rating of perceived exertion (RPE), using the Borg 6-20 scale, at ventilatory threshold (VT) in children. Thirty children (19 male, 11 female) with a mean +/- SD age of 10.4 +/- 1.1 yrs performed two graded exercise tests for the assessment of VT and VO2max. RPE was recorded throughout each exercise test. There were no significant (p > 0.05) differences between the mean VO2max (50.9 +/- 6.0 vs 51.0 +/- 5.7 ml.kg-1.min-1; r = 0.95) or the mean VO2 at VT (36.2 +/- 4.4 vs 36.7 +/- 4.5 ml.kg-1.min-1; r = 0.87) between trials. The mean RPE at VT during trial 1 (12.4 +/- 2.7) was significantly higher than during trial 2 (11.4 +/- 3.3; p < 0.05). The test-retest reliability correlation for the RPE at VT was r = 0.78. The lower RPE in the second trial may have been due to a greater comfort and familiarity with the testing procedures. The reliability analysis indicates that the RPE at VT within a given child is fairly consistent from trial to trial. However, large inter-individual variability in the RPE at VT (range = 6 to 19) was noted and was not related to variations in the onset of VT. This raises some concern over the use of a given RPE value or range of RPE values in the regulation of exercise intensity for this age group. The test-retest reliability of VT and VO2max in this age group is similar to previous reports.