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Biomedical subjects

L S Krivickas

Publications and source records attributed to L S Krivickas.

At least 19 recordsLinked to original sources
PubMed2001

Contractile properties of adjacent segments of single human muscle fibers.

A comparison of the contractile properties of adjacent segments of single human muscle fibers may help to explain the interaction among nuclear domains within the myofiber. Biopsy samples were obtained from the vastus lateralis muscle of 20 healthy untrained women (age 18-79 years). Single fibers (n = 38) were dissected and cut into halves (segments A and B). Segment diameter and depth were measured using an image analysis system. Maximal force (Po) was recorded during activation with calcium (pCa 4.5). Maximal unloaded shortening velocity (Vo) was calculated using the slack test. Myosin heavy chain (MyHC) expression was determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). A significant difference ( approximately 7%) in Po was seen between adjacent segments expressing type I MyHC that could not be attributed to differences in fiber size. Significant differences were observed in Vo even after adjusting for fiber type. A positive correlation was seen in Po (concordance coefficient Rho_C = 0.803) and Vo (Rho_C = 0.690) between segments, but concordance was less than perfect in both cases. Possible explanations for nonuniformity of contractile properties include random variations in physiological systems or variability of protein expression among nuclear domains.

Adolescent↗
PubMed2001

Age- and gender-related differences in maximum shortening velocity of skeletal muscle fibers.

OBJECTIVE: To determine age- and gender-related differences in maximum unloaded shortening velocity (Vo) of Type I and IIA single muscle fibers. Muscle fibers must have a broad range of contractile velocities to generate the full range of power required for varied activities. DESIGN: Percutaneous needle biopsies of the vastus lateralis were obtained from 31 healthy subjects (n = 7 young men [YM], n = 7 young women [YW], n = 12 older men [OM], n = 12 older women [OW]). The slack test was used to determine Vo of individual fibers; 916 muscle fibers were chemically skinned. Fiber type was determined by myosin heavy chain isoform identification. RESULTS: Among men, Vo (fiber lengths/sec) was reduced with age in Type IIA fibers (OM vs. YM: 1.78 vs. 2.14; P < 0.05) but unchanged in Type I fibers. Among women, Vo was reduced with age in Type I fibers (OW vs. YW: 0.70 vs. 0.75; P < 0.05) but not IIA. OW had a lower Vo than did OM in both fiber types (Type I: OW = 0.70, OM = 0.77; Type IIA: OW = 1.51, OM = 1.78; P < 0.05). YW did not differ from YM. CONCLUSIONS: Both age and gender affect Vo. Age- and gender-related differences in Vo may partially explain the impairments in muscle function that occur with aging and the greater impairment in muscle function observed in OW compared with that observed in OM.

Adult↗
PubMed2001

Acquired inflammatory demyelinating neuropathies.

The acquired demyelinating neuropathies can be divided into those with an acute onset and course and those with a more chronic course. The acute neuropathies present as Guillain-Barré syndrome and include acute inflammatory demyelinating polyradiculoneuropathy (AIDP), Miller Fisher syndrome, acute motor axonal neuropathy (AMAN), acute motor and sensory axonal neuropathy (AMSAN), and acute pandysautonomia. The chronic neuropathies are collectively known as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and include MADSAM (multifocal acquired demyelinating sensory and motor neuropathy, also know as Lewis-Sumner syndrome) and DADS (distal acquired demyelinating symmetric neuropathy) as variants. The clinical features, pathology, pathogenesis, diagnosis, treatment, rehabilitation, and prognosis of these neuropathies are discussed.

Acute Disease↗
PubMed2000

Contractile properties of single muscle fibers in myotonic dystrophy.

Muscle fiber contractile dysfunction in myotonic dystrophy (MD) is poorly understood. We biopsied the tibialis anterior of two symptomatic and three asymptomatic subjects (aged 21-31 years) with the MD mutation. Biopsies were freeze dried. A total of 103 single muscle fibers were activated with Ca(++), allowing maximal force measurements and specific force (SF) estimates. The slack test was performed to calculate maximum unloaded shortening velocity (V(o)). The myosin heavy chain composition of each fiber was determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Type I and IIA fibers of all subjects had reduced SF when compared with healthy control subjects (P < 0.001). In addition, the type I fibers of symptomatic subjects generated less SF than those of asymptomatic subjects (P < 0.001). Type I fibers from asymptomatic and symptomatic subjects did not differ in V(o), but V(o) was lower than in control subjects (P < 0.001). There was no significant difference in V(o) of type IIA fibers from symptomatic, asymptomatic, and control subjects. These results indicate that the MD mutation leads to a diminished force-generating capacity of the myofilaments in both symptomatic and asymptomatic individuals. The results further suggest that reduction in force-generating capacity at the cellular level develops prior to clinical weakness.

Adenosine Triphosphatases↗
PubMed2000

Peripheral nerve injuries in athletes: a case series of over 200 injuries.

We retrospectively reviewed electrodiagnostic (EDX) studies performed on 346 athletes with sports injuries who were referred to our EDX laboratory from 1974 to 1997. These injuries included 216 nerve root, plexus, or peripheral nerve injuries sustained by 180 of the athletes. Eighty-six percent of the injuries were to the upper extremity. Athletes with nerve fiber injuries participated in 27 different sports, but over one third of injuries were sustained playing football. The most common symptomatic upper extremity injury was the "burner" (N=40). Forty-three athletes had median neuropathies, many of which were asymptomatic cases of carpal tunnel syndrome. Cervical radiculopathies (N=19) and axillary (N=22), ulnar (N=19), and suprascapular (N=14) mononeuropathies were also prevalent. The most common lower extremity injuries were peroneal neuropathies (N=17) and lumbosacral radiculopathies (N=7). This is the largest reported series of sports-related nerve injuries. The mechanisms of the most common nerve injuries are discussed.

Athletic Injuries↗
PubMed2000

Skeletal muscle fiber quality in older men and women.

Whole muscle strength and cross-sectional area (WMCSA), and contractile properties of chemically skinned segments from single fibers of the quadriceps were studied in 7 young men (YM, 36.5 +/- 3. 0 yr), 12 older men (OM, 74.4 +/- 5.9 yr), and 12 older women (OW, 72.1 +/- 4.3 yr). WMCSA was smaller in OM compared with YM (56.1 +/- 10.1 vs. 79.7 +/- 13.1 cm(2); P = 0.031) and in OW (44.9 +/- 7.5; P < 0.003) compared with OM. Age-related, but not sex-related, differences in strength were eliminated after adjusting for WMCSA. Maximal force was measured in 552 type I and 230 type IIA fibers. Fibers from YM (type I = 725 +/- 221; type IIA = 792 +/- 271 microN) were stronger (P < 0.001) than fibers from OM (I = 505 +/- 179; IIA = 577 +/- 262 microN) even after correcting for size. Type IIA fibers were stronger (P < 0.005) than type I fibers in YM and OM but not in OW (I = 472 +/- 154; IIA = 422 +/- 97 microN). Sex-related differences in type I and IIA fibers were dependent on fiber size. In conclusion, differences in WMCSA explain age-related differences in strength. An intrinsic defect in contractile proteins could explain weakness in single fibers from OM. Sex-related differences exist at the whole muscle and single fiber levels.

Adult↗
PubMed1999

Proximal neuropathies of the upper extremity.

This article provides a comprehensive review of the diagnosis and management of mononeuropathies of the long thoracic, suprascapular, axillary, and musculocutaneous nerves. Although these nerves are frequently injured in conjunction with other portions of the brachial plexus, this discussion focuses on isolated injury to each of these nerves. The anatomy, clinical presentation, differential diagnosis, findings on electrodiagnostic evaluation, origin, management, and prognosis of each mononeuropathy is discussed.

Arm↗
PubMed1998

Sports and peripheral nerve injuries: report of 190 injuries evaluated in a single electromyography laboratory.

We retrospectively reviewed electrodiagnostic studies performed on 169 athletes with 190 sports injuries to nerve fibers. Eighty-eight percent of the injuries were to the upper extremity. Athletes participated in 27 sports, but over one third of injuries were sustained playing football. The most common injuries were burners (n = 38) and cervical radiculopathies (n = 18), followed by median (n = 28), axillary (n = 22), ulnar (n = 19), suprascapular (n = 14), and peroneal (n = 11) mononeuropathies. This is the largest reported series of sports-related nerve injuries.

Adolescent↗
PubMed1998

Is spectral analysis of the surface electromyographic signal a clinically useful tool for evaluation of skeletal muscle fatigue?

Normal values for initial median frequency (IMF) of the electromyographic (EMG) power-density spectrum must be determined before EMG spectral analysis can be used to evaluate clinically muscle fatigue. This study attempts to establish normal values in four muscles. Thirty-one healthy subjects performed isometric contractions of the biceps brachii, triceps, deltoid, and tibialis anterior muscles at 50% maximum voluntary contraction. Linear regression analysis was used to compute the IMF and the slope of the median frequency as it decayed with fatigue over 45 seconds. The IMF of the tibialis anterior (mean +/- standard deviation, 116 +/- 20 Hz) was significantly higher (p < 0.001) than that of the biceps (90 +/- 18 Hz), triceps (85 +/- 18 Hz), and deltoid (87 +/- 15 Hz). The deltoid and tibialis anterior had the steepest slopes. The IMF of all muscles was greater in men than in women, but gender did not affect the slope. This study attempted to establish normal values for IMF and slope in specific muscles. However, the range of normal values is so broad that it may preclude the clinical use of spectral analysis to evaluate muscle fatigue.

Adult↗
PubMed1998

The reliability of monopolar and bipolar fine-wire electromyographic measurement of muscle fatigue.

Bipolar intramuscular wire electrodes and spectral analysis of the electromyographic signal have been used to measure fatigue in muscles that cannot be studied with surface electrodes. Intramuscular electrodes can detect a greater range of frequencies from muscle, obtain a less distorted signal, and are therefore felt to be more sensitive to detecting fatigue. To determine the reliability and sensitivity of electrode placement (with a fixed distance) for assessing muscle fatigue, we placed three intramuscular electrodes in and two surface electrodes on the biceps brachii of 30 healthy male subjects. With these electrodes, we devised eight configurations that were analyzed separately for reliability. Subjects performed four, 30-s isometric fatiguing contractions divided between two testing sessions. Mean and median frequency of the power density spectrum were plotted against time. Linear regression was performed to obtain slopes, which were used as indicators of fatigue. The bipolar surface electrode configuration displayed mean and median frequency intrasession and mean frequency intersession reliability for slope. All four bipolar fine-wire configurations had mean and median frequency intrasession reliability (P < or 0.05). Only three of the four bipolar fine-wire configurations approached mean frequency intersession reliability, and none fo the four displayed median frequency intersession reliability. the configuration with distal bipolar intramuscular electrodes placed 1 cm apart was the most reliable intramuscular technique. The bipolar fine-wire configuration studied showed a trend toward better reliability than monopolar fine-wire configurations. No intramuscular technique, however, was reliable enough for clinical use in the study of fatigue.

Adolescent↗
PubMed1998

Electrodiagnosis in neuromuscular disease.

This article provides a general approach to the electrodiagnostic evaluation of the patient with neuromuscular disease. The electrodiagnostic findings in patients with various forms of peripheral neuropathy, motor neuron disease, neuromuscular junction disorders, and myopathy are presented. The pediatric electrodiagnostic evaluation is also discussed.

Adult↗
PubMed1997

Home care of patients with amyotrophic lateral sclerosis (ALS).

Optimal home care maximizes function and quality of life for patients with ALS. We designed a survey to study home care in the ALS population. Ninety-eight patients with ALS completed our survey. Of these, 24 receive non-hospice home care, nine hospice home care, and seven both hospice and non-hospice home care. Fifty-eight patients receive no outside help. Patients receiving hospice are older than those receiving non-hospice home care (68.9 vs. 57.7 years, P<0.05). Patients with home care assistance have a mean ALS Functional Rating Scale (ALS FRS) score of 13, and those without home care assistance have a mean score of 26 (P<0.0001). Patients receiving non-hospice home care assistance have a median of 16 h/week of care, while those with hospice receive 5.5 h/week (P=0.05). Patients on Medicaid receive more hours of home care than those with any other insurance (median 61 vs. 3.4 h/week with Medicare and 5 h/week with commercial insurance, P=0.008). Primary caregivers spend a median of 11 h/day caring for patients despite having home care assistance. Forty-two and 48% of primary caregivers feel physically and psychologically unwell, respectively. Home care received by patients with ALS often is inadequate and too late to relieve the burden placed on family caregivers.

Adult↗
PubMed1997

Anatomical factors associated with overuse sports injuries.

Overuse injuries develop when repetitive stress to bone and musculotendinous structures damages tissue at a greater rate than that at which the body can repair itself. A combination of extrinsic factors, such as training errors and environmental factors, and intrinsic or anatomical factors, such as bony alignment of the extremities, flexibility deficits and ligamentous laxity, predispose athletes to develop overuse injuries. Malalignant of the lower extremity, including excess femoral anteversion, increased Q angle, lateral tibial torsion, tibia vara, genu varum or valgum, subtalar varus and excessive pronation are frequently cited as predisposing to knee extensor mechanism overuse injuries. These and other forms of malalignment have also been implicated in iliotibial band syndrome, medial tibial stress syndrome, lower extremity stress fractures and plantar fasciitis. Muscle inflexibility aggravates and predisposes to the development of a variety of overuse injuries, especially those occurring in children and adolescents, including the traction apophysitises. Flexibility deficits may be improved by an appropriate stretching programme. Unfortunately, lower extremity malalignment is less amenable to intervention. Orthotics are often prescribed to improve lower extremity alignment. However, studies have not shown that orthotics have any effect on knee alignment and, while they can alter subtalar joint alignment, the clinical benefit of this remains unclear. Awareness of anatomical factors that may predispose to overuse injuries allows the clinician to develop individual prehabilitation programmes designed to decrease the risk of overuse injury. In addition, the clinician can advise the athlete on the importance of avoiding extrinsic factors that may also predispose to overuse injury.

Arm↗
PubMed1997

Peripheral nerve injuries in the athlete.

Peripheral nerves are susceptible to injury in the athlete because of the excessive physiological demands that are made on both the neurological structures and the soft tissues that protect them. The common mechanisms of injury are compression, traction, ischaemia and laceration. Seddon's original classification system for nerve injuries based on neurophysiological changes is the most widely used. Grade 1 nerve injury is a neuropraxic condition, grade 2 is axonal degeneration and grade 3 is nerve transection. Peripheral nerve injuries are more common in the upper extremities than the lower extremities, tend to be sport specific, and often have a biomechanical component. While the more acute and catastrophic neurological injuries are usually obvious, many remain subclinical and are not recognised before neurological damage is permanent. Early detection allows initiation of a proper rehabilitation programme and modification of biomechanics before the nerve injury becomes irreversible. Recognition of nerve injuries requires an understanding of peripheral neuroanatomy, knowledge of common sites of nerve injury and an awareness of the types of peripheral nerve injuries that are common and unique to each sport. The electrodiagnostic exam, usually referred to as the 'EMG', consists of nerve conduction studies and the needle electrode examination. It is used to determine the site and degree of neurological injury and to predict outcome. It should be performed by a neurologist or physiatrist (physician specialising in physical medicine and rehabilitation), trained and skilled in this procedure. Timing is essential if the study is to provide maximal information. Findings such as decreased recruitment after injury and conduction block at the site of injury may be apparent immediately after injury but other findings such as abnormal spontaneous activity may take several weeks to develop. The electrodiagnostic test assists with both diagnosis of the injury and in predicting outcome. Proximal nerve injuries have a poorer prognosis for neurological recovery. The most common peripheral nerve injury in the athlete is the burner syndrome. Though primarily a football injury, burners have been reported in wrestling, hockey, basketball and weight-lifting as a result of acute head, neck and/or shoulder trauma. Most burners are self-limiting, but they occasionally produce permanent neurological deficits. The axillary nerve is commonly injured with shoulder dislocations but is also susceptible to injury by direct compression. The sciatic and common peroneal nerves can be injured by trauma. The suprascapular, musculocutaneous, ulnar, median and tibial nerves are susceptible to entrapment. The long thoracic and femoral nerves can be injured by severe traction.

Athletic Injuries↗
PubMed1996

Lower extremity injuries in college athletes: relation between ligamentous laxity and lower extremity muscle tightness.

OBJECTIVE: Two components of flexibility, muscle tightness, and ligamentous laxity in college athletes were studied to determine whether these factors were associated with the incidence of lower extremity injuries. DESIGN: Prospective cohort study. SETTING: College athletic department. PARTICIPANTS: 201 college athletes. OUTCOME MEASURES: College men and women athletes were tested for ligamentous laxity with the Beighton scale and for muscle tightness with a new scale based on the tightness of the iliopsoas, iliotibial band, hamstring, rectus femoris, and gastrocsoleus muscles. Lower extremity injuries incurred during practice and play were recorded during the following year. RESULTS: Of the 201 athletes tested, 71 sustained 115 injuries. For each additional point on the 9-point ligamentous laxity scale (9 = hyperlax), the risk of injury decreased 16%. For each additional point on the 10-point muscle-tightness scale (10 = all muscles tight), the risk of injury increased 23%. The two scores were moderately inversely correlated (Spearman's rho = -0.3; p < .001). Women had greater mean (+/- SD) laxity scores than men (3.3 +/- 2.2 vs. 1.8 +/- 2.0; p < .001) and lower mean overall muscle tightness scores (1.5 +/- 1.6 vs. 3.5 +/- 2.1; p < .001). Among Women athletes, the rate of lower extremity injury was unrelated to ligamentous laxity or to flexibility. Among men, lower extremity injuries were associated with lower ligamentous laxity scores (p = .008) and greater muscle tightness (p = .04). CONCLUSIONS: This study introduces a new scale for lower extremity muscle tightness. Tight ligaments and muscles are related to injury in men, but not women, college athletes. A preseason flexibility program may decrease injuries in college men athletes.

Adult↗
PubMedDate not supplied

Correlation of flexion contractures with upper extremity function and pain for spinal muscular atrophy and congenital myopathy patients.

To ascertain the patients' perception of the consequences of elbow flexion contractures and better understand the circumstances at their inception, we surveyed 405 spinal muscular atrophy and congenital myopathy patients. Diagrams of various elbow angles and questions concerning the effect of elbow contractures on daily activities were part of the survey. Of 108 completed responses, effectively a 24% response rate, 49 reported elbow flexion contractures. Thirteen of the 49 patients reported first noting them during extended periods of inactivity. Elbow flexion contractures greater than 25 degrees were intractable and were reported to hamper 17% (77 of 410) of specifically considered daily activities for the 49 subjects. Twenty-nine of the 49 (59%) subjects with contractures complained of contracture-associated hindrance of at least one daily function. Perceived contracture-associated difficulties increased significantly as a function of contracture severity. Elbow contractures were perceived to be useful by 12% of the respondents. The correlation between contracture severity and upper limb discomfort was also striking. We conclude that elbow flexion contractures are common and perceived to be associated with disability and discomfort for about one-half of spinal muscular atrophy and congenital myopathy patients.

Activities of Daily Living↗
PubMedDate not supplied

Spectral analysis during fatigue. Surface and fine wire electrode comparison.

Fine wire (FW) intramuscular electrodes and spectral analysis have not previously been used to quantify metabolic muscle fatigue in deep muscles not accessible with surface electrodes. This study compares initial median frequency (IMF) and decline in median frequency with fatigue (SLOPE) using surface and FW electrodes. Eighteen men performed isometric biceps contractions for 100 s. Electromyographic signals were collected using FW and surface electrodes. The recordings of SLOPE was greater with FW (-0.44 v -0.23 %IMF/s) and IMF was higher (195 v 69 Hz). Intrasession reliability for slope was better with FW electrode (intraclass correlation coefficient (ICC) = 0.74; P<0.0001) than with the surface electrode (ICC = 0.43; P = 0.006), but intersession reliability was best with the surface electrode (ICC = 0.50; P = 0.03). Spectral analysis using FW electrodes provides earlier detection of muscle fatigue and can be used in deep muscles, but the reliability must be improved before clinical application.

Adult↗