RESUMO
Objective: The purpose of this study was to investigate the utilization and perception of live blogged sessions of a physical therapy (PT) conference. Methods: Sessions at an international PT conference were covered in real time using a live-blogging platform. Session coverage could be viewed remotely using computers and mobile devices. Viewers could interact with the content by clicking on links and using the comment feature. Sessions could also be replayed following their conclusion. An online survey of user perceptions was made available the week following the conference. Results: Twenty-four sessions were live blogged with an average session length of 67 min (range: 27-120). On average, live sessions received 27 views (range: 2-65), 18 clicks (range: 2-36), and 2 comments (range: 0-10). The average time spent viewing a live session was 28 min (32% of viewers <1 min; 68% >1 min). Following the conference, session replays totaled 7206 views and 2910 clicks. The average survey respondent (n = 17) watched five live sessions (range: 1-17) and found the updates easy to read (4.5 on a scale of 5.0). When asked if they learned something from the coverage, 94% of respondents said yes and 94% said they would view if available for an upcoming conference. Discussion: Live blogging extended the viewing audience and facilitated viewer engagement. Survey respondents found the coverage educational, of high quality, and would participate again in the future.
Assuntos
Atitude do Pessoal de Saúde , Blogging , Educação Continuada/métodos , Educação a Distância/métodos , Fisioterapeutas , Especialidade de Fisioterapia/educação , Mídias Sociais , Congressos como Assunto , Humanos , Internacionalidade , Manipulações Musculoesqueléticas/educação , Modalidades de Fisioterapia/educação , Inquéritos e QuestionáriosRESUMO
The purpose of the study was to determine how long humans could sustain the discharge of single motor units during a voluntary contraction. The discharge of motor units in first dorsal interosseus of subjects (27.8 ± 8.1 years old) was recorded for as long as possible. The task was terminated when the isolated motor unit stopped discharging action potentials, despite the ability of the individual to sustain the abduction force. Twenty-three single motor units were recorded. Task duration was 21.4 ± 17.8 min. When analysed across discharge duration, mean discharge rate (10.6 ± 1.8 pulses s(-1)) and mean abduction force (5.5 ± 2.8% maximum) did not change significantly (discharge rate, P = 0.119; and abduction force, P = 0.235). In contrast, the coefficient of variation for interspike interval during the initial 30 s of the task was 22.2 ± 6.0% and increased to 31.9 ± 7.0% during the final 30 s (P < 0.001). All motor units were recruited again after 60 s of rest. Although subjects were able to sustain a relatively constant discharge rate, the cessation of discharge was preceded by a gradual increase in discharge variability. The findings also showed that the maximal duration of human motor unit discharge exceeds that previously reported for the discharge elicited in motor neurons by intracellular current injection in vitro.
Assuntos
Potenciais de Ação/fisiologia , Neurônios Motores/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Adolescente , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Anatomy with human dissection may help to develop respect for the human body and professionalism; however, dissection may worsen students' attitudes about body weight and adiposity. The purpose of this study was to measure weight bias among Doctor of Physical Therapy (DPT) students enrolled in gross anatomy and determine if, and how the experience of dissection impacts weight bias. Ninety-seven DPT students (70 University of Colorado [CU], 27 Moravian University [MU]) were invited to complete a survey during the first and final weeks of their anatomy course. The survey included demographic items, two measures of weight bias-the Modified Weight Bias Internalized Scale (M-WBIS) and the Attitudes Towards Obese Persons (ATOP) Scale-and open-ended questions for the students who participated in dissection (CU students) that explored attitudes about body weight and adiposity. At baseline, there were no significant differences (p > 0.202) in ATOP, M-WBIS, or BMI between the two universities. The mean scores on both the ATOP and M-WBIS indicated a moderate degree of both internalized and externalized weight bias. There were no significant changes in ATOP (p = 0.566) or M-WBIS scores (p = 0.428). BMI had a low correlation with initial M-WBIS scores (â´ = 0.294, p = 0.038) and a high correlation with change scores in CU students (â´ = 0.530, p = 0.011). Future studies should utilize the same measures of weight bias in other healthcare trainees to facilitate comparison and incorporate larger populations of DPT students.
RESUMO
BACKGROUND: Identification of transthyretin cardiac amyloidosis (ATTR-CA) patients is largely based on pattern recognition by providers, and this can be automated through electronic medical systems (EMR). METHODS: All patients in a large academic hospital with ageâ¯>â¯60, ICD-10 code for chronic diastolic heart failure and no previous diagnosis of any amyloidosis were included. An Epic EMR scoring logic assigned risk scores to patients for ICD-10 and CPT codes associated with ATTR-CA, as follows: carpal tunnel syndrome (score 5), aortic stenosis/TAVR (5), neuropathy (4), bundle branch block (4), etc. The individual patients' scores were added, and patients were arranged in descending order of total scores- ranging from 50 to 0. Data is reported as median (interquartile range) and analyzed with non-parametric tests. RESULTS: Of the total 11,648 patients identified, 132 consecutive patients with highest risk scores (scoreâ¯≥â¯30) were enrolled as cases, while 132 patients with scores between 10 and 19 with available echocardiography data served as age-matched controls. Strain echocardiography is not routinely performed. Patients with high scores were more likely to have CA associated findings- African-American race, higher left ventricular (LV) mass index and left atrial volume and lower LV ejection fraction. High score patients had higher troponin and a trend towards high NT-proBNP. CONCLUSION: The modern EMR can be used to flag patients with high risk for ATTR-CA (scoreâ¯≥â¯30 using the proposed logic) through best practice advisory. This could encourage screening during echocardiography using strain or during unsuspected clinic visits.
RESUMO
The purpose of the study was to compare the discharge characteristics of biceps brachii motor units of young and old adults when they performed steady, submaximal contractions while the arm supported different inertial loads. Young (28 ± 4 yr; n = 16) and old (75 ± 4 yr; n = 14) adults performed steady contractions with the elbow flexors at target forces set at either small (11.7 ± 4.4% maximum) or large (17.8 ± 6.5% maximum) differences below the recruitment threshold force of the motor unit (n = 40). The task was to maintain an elbow angle at 1.57 rad until the motor unit was recruited and discharged action potentials for â¼120 s. Time to recruitment was longer for the larger target force difference (187 ± 227 s vs. 23 ± 46 s, P < 0.001). Once recruited, motor units discharged action potentials either repetitively or intermittently, with a greater proportion of motor units exhibiting the repetitive pattern for old adults. Discharge rate at recruitment and during the steady contraction was similar for the two target force differences for old adults but was greater for the small target force difference for young adults. Discharge variability was similar at recruitment for the two age groups but less for the old adults during the steady contraction. The greatest difference between the present results and those reported previously when the arm pulled against a rigid restraint was that old adults modulated discharge rate less than young adults across the two contraction intensities for both load types.
Assuntos
Braço/fisiologia , Contração Muscular , Músculo Esquelético/fisiologia , Potenciais de Ação , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Cotovelo/fisiologia , Feminino , Humanos , Masculino , Músculo Esquelético/inervação , Recrutamento NeurofisiológicoRESUMO
BACKGROUND: Emergency cricothyrotomy training for non-surgeons is important as rare "cannot intubate or oxygenate events" may occur multiple times in a provider's career when surgical expertise is not immediately available. However, such training is highly variable and often infrequent, therefore, enhancing these experiences is important. RESEARCH QUESTION: Is bronchoscopy-enhanced cricothyrotomy training in cadavers feasible, and what are the potential benefits provided by this innovation for trainees? METHODS: This study was performed during implementation of a new program to train non-surgeon providers on cadaveric donors on our campus. Standard training with an instructional video and live coaching was enhanced by bronchoscopic visualization of the trachea allowing participants to review their technique after performing scalpel and Seldinger-technique procedures, and to review their colleagues' technique on live video. Feasibility was measured through assessing helpfulness for trainees, cost, setup time, quality of images, and operator needs. Footage from the bronchoscopy recordings was analyzed to assess puncture-to-tube time, safety errors, and evidence for a training effect within groups. Participants submitted pre- and post-session surveys assessing their levels of experience and gauging their confidence and anxiety with cricothyrotomies. RESULTS: The training program met feasibility criteria for low costs (<200 USD/donor), setup time (<30 minutes/donor), and operator needs (1/donor). Furthermore, all participants rated the cadaveric session as helpful. Participants demonstrated efficient technique, with a median puncture-to-tube time of 48.5 seconds. Bronchoscopy recordings from 24 analyzed videos revealed eight instances of sharp instruments puncturing the posterior tracheal wall (33% rate), and two instances of improper tube placement (8% rate). Sharp instruments reached potentially dangerous insertion depths beyond the midpoint of the anterior-posterior diameter of the trachea in 58.3% of videos. Bronchoscopic enhancement was rated as quite or extremely helpful for visualizing the trachea (83.3%) and to assess depth of instrumentation (91.7%). There was a significant average increase in confidence (64.4%, P<0.001) and average decrease in performance anxiety (-11.6%, P = 0.0328) after the session. A training effect was seem wherein the last trainee in each group had no posterior tracheal wall injuries. INTERPRETATION: Supplementing cadaveric emergent cricothyrotomy training programs with tracheal bronchoscopy is feasible, helpful to trainees, and meets prior documented times for efficient technique. Furthermore, it was successful in detecting technical errors that would have been missed in a standard training program. Bronchoscopic enhancement is a valuable addition to cricothyrotomy cadaveric training programs and may help avoid real-life complications.
Assuntos
Broncoscopia , Cartilagem Cricoide , Humanos , Cartilagem Cricoide/cirurgia , Currículo , Instrumentos Cirúrgicos , CadáverRESUMO
Anatomical knowledge is the foundation of the educational curricula in most healthcare programs. The varying scopes of practice between healthcare professions require anatomy educators to determine what content is essential to cover in a finite time with learners. When possible, the anatomy educator bases this decision on clinical experiences; this is a more significant challenge for the non-clinician educator teaching in a health profession curriculum. Although studies have determined essential anatomy content in many healthcare professions, no study has been undertaken in physical therapist education. This study was designed to determine what anatomical concepts are considered essential in physical therapist education in one doctor of physical therapy program. Faculty (n = 28), recent graduates (n = 134), and clinical instructors (n = 247) of a doctor of physical therapy program were invited to respond to a survey focused on rating the essential nature of 46 learning objectives. Consensus for learning objectives was determined using Lawshe's content validity method. One hundred forty-seven respondents completed the survey (36% response rate). Respondents represented a diversity in years of experience, highest physical therapist degree earned, specialty training, and setting of physical therapist practice. Of the 46 learning objectives presented, 10 were most frequently rated essential, 20 as useful but not essential, and 16 as not necessary. These results offer guidance for anatomy instructors at other institutions to make an informed decision on what anatomical content to focus on in their anatomy courses in order to increase time dedicated toward mastery of essential core anatomical knowledge for physical therapist practice. Supplementary Information: The online version contains supplementary material available at 10.1007/s40670-022-01574-1.
RESUMO
BACKGROUND: Preclinical medical learners are embedded in technology-rich environments, allowing them rapid access to a large volume of information. The anatomy laboratory is an environment in which faculty can assess the development of professional skills such as information literacy in preclinical medical learners. In the anatomy laboratory, many students use Google Images searches in addition to or in place of other course materials as a resource to locate and identify anatomical structures. However, the most frequent sources as well as the educational quality of these images are unknown. OBJECTIVE: This study was designed to assess the sources and educational value of Google Images search results for commonly searched anatomical structures. METHODS: The top 10 Google Images search results were collected for 39 anatomical structures. Image source websites were recorded and categorized based on the purpose and target audience of the site publishing the image. Educational value was determined through assessment of relevance (is the searched structure depicted in the image?), accuracy (does the image contain errors?), and usefulness (will the image assist a learner in locating the structure on an anatomical donor?). A reliable scoring rubric was developed to assess an image's usefulness. RESULTS: A total of 390 images were analyzed. Most often, images were sourced from websites targeting health care professionals and health care professions students (38% of images), while Wikipedia was the most frequent single source of image results (62/390 results). Of the 390 total images, 363 (93.1%) depicted the searched structure and were therefore considered relevant. However, only 43.0% (156/363) of relevant images met the threshold to be deemed useful in identifying the searched structure in an anatomical donor. The usefulness of images did not significantly differ across source categories. CONCLUSIONS: Anatomy faculty may use these results to develop interventions for gaps in information literacy in preclinical medical learners in the context of image searches in the anatomy laboratory.
RESUMO
The purpose of this study was to compare the discharge characteristics of motor units recruited during an isometric contraction that was sustained with the elbow flexor muscles by older adults at target forces that were less than the recruitment threshold force of each isolated motor unit. The discharge times of 27 single motor units were recorded from the biceps brachii in 11 old adults (78.8 ± 5.9 yr). The target force was set at either a relatively small (6.6 ± 3.7% maximum) or large (11.4 ± 4.5% maximum) difference below the recruitment threshold force and the contraction was sustained until the motor unit was recruited and discharged action potentials for about 60 s. The time to recruitment was longer for the large target-force difference (P = 0.001). At recruitment, the motor units discharged repetitively for both target-force differences, which contrasts with data from young adults when motor units discharged intermittently at recruitment for the large difference between recruitment threshold force and target force. The coefficient of variation (CV) for the first five interspike intervals (ISIs) increased from the small (18.7 ± 7.9) to large difference (35.0 ± 10.2%, P = 0.008) for the young adults, but did not differ for the two target force differences for the old adults (26.3 ± 14.7 to 24.0 ± 13.1%, P = 0.610). When analyzed across the discharge duration, the average CV for the ISI decreased similarly for the two target-force differences (P = 0.618) in old adults. These findings contrast with those of young adults and indicate that the integration of synaptic input during sustained contractions differs between young and old adults.
Assuntos
Contração Isométrica/fisiologia , Neurônios Motores/fisiologia , Músculo Esquelético/fisiologia , Recrutamento Neurofisiológico/fisiologia , Adulto , Idoso , Feminino , Humanos , MasculinoRESUMO
Biomedical educators have turned to technologies, like social media, to supplement progressive reductions in time spent in class. Many studies of social media have been limited to quantifying learner satisfaction and studies on the effects on learning outcomes are sparse. The purpose of this study was to examine the effects of using Snapchat on learner satisfaction and learning outcomes. A Snapchat account was used to share blood flow diagrams during the anatomy course of a physical therapist education program. Viewing statistics were recorded, a survey was distributed, and learning outcomes quantified at the end of the course and 12 months later were compared with a control group that did not have access to the account. Eighty-two percent of the class subscribed to the Snapchat account and 86.7% of the subscribers completed viewing of the five drawings posted. Learners rated the account as extremely accurate, were quite interested in more content presented, and felt quite confident in the diagrams. Performance on blood flow questions on the end of course examinations were similar between experimental and control groups. Assessments administered 12 months later revealed greater scores for the Snapchat group (90.7% correct) compared with the control group (86.7% correct, p = 0.04). These findings suggest that Snapchat is an effective way to deliver educational content and that learners found the content useful, accurate, and helpful in preparing them for the assessment. The ephemeral nature of disappearing content has potential to garner greater student attention and can be leveraged to improve knowledge retention.
RESUMO
Personal computer use for educational purposes by the healthcare professions students has become ubiquitous. Although the effect of computer-based dissection instructions has been studied, there is a paucity of information regarding student browsing habits of information available on the Internet. Although current students have favorable attitudes toward accessing anatomical information online, web browsing habits have not yet been investigated specifically in the dissection laboratory setting. The purpose of this study was to describe the browsing habits of the healthcare professions students in the gross anatomy setting using a retrospective analysis. Files containing web browser history were retrieved from desktop computers in the gross anatomy laboratory and custom code was written to parse them into comma separated value files. Each web address was categorized and descriptive statistics was calculated. Browser history for 24 computers was analyzed from June 2013 to January 2015. During this period, students accumulated 100,857 webpage visits. Most often, students performed a Google search for anatomy (22.0% of all visits) and non-anatomy related (20.6% of all visits) information. Students also used the web browser to access various entertainment (16.4% of all visits) and productivity related services (15.9% of all visits). This analysis revealed a large volume of webpage visits by the healthcare professions students in the gross anatomy laboratory. A wide diversity of anatomy and non-anatomy related webpages were visited. Future analyses could be directed at examination of when in relation to class time students accessed the information, how browsing habits change over time, and what anatomical structures were most commonly searched for.
Assuntos
Anatomia/educação , Instrução por Computador/estatística & dados numéricos , Comportamento de Busca de Informação , Estudantes de Ciências da Saúde/estatística & dados numéricos , Navegador/estatística & dados numéricos , Adulto , Feminino , Ocupações em Saúde/educação , Humanos , Laboratórios/estatística & dados numéricos , Masculino , Estudos Retrospectivos , Estudantes de Ciências da Saúde/psicologia , Adulto JovemRESUMO
Anatomical knowledge is requisite for effective physical therapy (PT) practice. Cadaver dissection is a popular teaching method employed in PT anatomy courses. Limited time in the laboratory requires effective dissection instructions. Several limitations of a printed, non-discipline specific dissection guide have been identified by students and instructors in anatomy curricula. The objective of this project was to evaluate the effect of using a digital, PT specific dissection guide on examination performance and student satisfaction. A digital guide was developed that incorporated improvements based on observations of student experiences using a printed guide. The digital guide covered two lower extremity regional dissections and was distributed for use during the summer 2017 course. Enhancements included clarification of dissection procedures, formative quizzes, image galleries, embedded videos, and a glossary of terms. Students used a printed guide for all other dissections in the course. The percentage of correct answers from practical examinations was calculated and compared between summer of 2015 (print) and 2017 (digital) courses. A survey consisting of nineteen five-point Likert items was distributed. The percentage of correct answers was significantly higher for the digital guide (91.7 ± 7.11%) compared with the print guide (84.2 ± 9.51%, P < 0.0001). On the survey, the median item rating was strongly agree for two, agree for fifteen, and neither agree or disagree for two. These results suggest that developing a curriculum specific, digital guide was effective in improving student knowledge and satisfaction. These results encourage development of additional content specific guides in a digital format.
RESUMO
The purpose of the experiment was to compare the level of synchronization exhibited by pairs of motor units located within and between functionally distinct regions of the biceps brachii muscle. Pairs of single motor units were recorded from seven subjects using separate electrodes located in the lateral and medial aspects of the long head of biceps brachii. Participants were required to exert a combination of flexion and supination torques so that both motor units discharged at approximately 10 pps for >/=200 s and the level of motor unit synchronization could be quantified. When motor unit recordings were sufficiently stable at the completion of this synchrony task, a series of ramp contractions with multiple combinations of flexion and supination torques were performed to characterize the recruitment thresholds of the motor units. Common input strength (CIS) was significantly greater (P < 0.01) for the within-region pairs of motor units (0.28 extra sync. imps/s, n = 26) than for the between-region pairs (0.13 extra sync. imps/s, n = 18), but did not differ significantly for the 12 within-region pairs from the lateral head and 14 from the medial head (0.27 vs. 0.29 extra sync. imps/s; P = 0.83). Recruitment thresholds were measured for 33 motor units, but there was only a weak association between CIS and the respective recruitment patterns for motor unit pairs (n = 9). The present investigation provides evidence of a differential distribution of synaptic input across the biceps brachii motor neuron pool, but this appears to have minimal association with the recruitment patterns for individual motor units.
Assuntos
Braço/fisiologia , Atividade Motora/fisiologia , Neurônios Motores/fisiologia , Músculo Esquelético/fisiologia , Adulto , Braço/anatomia & histologia , Eletromiografia , Humanos , Masculino , Força Muscular , Músculo Esquelético/anatomia & histologiaRESUMO
Electrical stimulation of the brachioradialis branch of the radial nerve has been shown to inhibit the discharge of voluntarily activated motor units in biceps brachii during weak contractions with the elbow flexor muscles. The purpose of the present study was to characterise the inhibitory reflex by comparing its strength in the short and long heads of the biceps brachii and examining the influence of forearm position on the strength of the reflex. Spike-triggered stimulation was used to assess the influence of radial nerve stimulation on the discharge of single motor units in the biceps brachii of 15 subjects. Stimulation of the radial nerve prolonged the interspike interval (P < 0.001) of motor units in the long (n = 31, 4.8 +/- 5.6 ms) and short heads (n = 26, 8.1 +/- 12.3 ms) of biceps brachii with no difference between the two heads (P = 0.11). The strength of inhibition varied with forearm position for motor units in both heads (n = 18, P < 0.05). The amount of inhibition was greatest in pronation (7.9 +/- 8.9 ms), intermediate in neutral (5.8 +/- 7.1 ms), and least in supination (2.8 +/- 3.4 ms). These findings indicate that the inhibition evoked by afferent feedback from brachioradialis to low-threshold motor units (mean force 3-5% MVC) in biceps brachii varied with forearm posture yet was similar for the two heads of biceps brachii. This reflex pathway provides a mechanism to adjust the activation of biceps brachii with changes in forearm position, and represents a spinal basis for a muscle synergy in humans.
Assuntos
Articulação do Cotovelo/fisiologia , Movimento/fisiologia , Músculo Esquelético/fisiologia , Nervo Radial/fisiologia , Medula Espinal/fisiologia , Adulto , Vias Eferentes/fisiologia , Articulação do Cotovelo/inervação , Estimulação Elétrica , Eletromiografia , Feminino , Humanos , Masculino , Contração Muscular/fisiologia , Músculo Esquelético/inervação , Inibição Neural/fisiologia , Reflexo/fisiologia , Tendões/inervação , Tendões/fisiologia , Volição/fisiologiaAssuntos
Anatomia , Médicos , Humanos , Autonomia Pessoal , Profissionalismo , Anatomia/educação , Atitude do Pessoal de SaúdeRESUMO
The purpose of this study was to compare the influence of prolonged vibration of a hand muscle on the amplitude of the stretch reflex, motor unit discharge rate, and force fluctuations during steady, submaximal contractions. Thirty-two young adults performed 10 isometric contractions at a constant force (5.0 +/- 2.3% of maximal force) with the first dorsal interosseus muscle. Each contraction was held steady for 10 s, and then stretch reflexes were evoked. Subsequently, 20 subjects had vibration applied to the relaxed muscle for 30 min, and 12 subjects received no vibration. The muscle vibration induced a tonic vibration reflex. The intervention (vibration or no vibration) was followed by 2 sets of 10 constant-force contractions with applied stretches (After and Recovery trials). The mean electromyogram amplitude of the short-latency component of the stretch reflex increased by 33% during the After trials (P < 0.01) and by 38% during the Recovery trials (P < 0.01). The standard deviation of force during the steady contractions increased by 21% during the After trials (P < 0.05) and by 28% during the Recovery trials (P < 0.01). The discharge rate of motor units increased from 10.3 +/- 2.7 pulses/s (pps) before vibration to 12.2 +/- 3.1 pps (P < 0.01) during the After trials and to 11.9 +/- 2.6 pps during the Recovery trials (P < 0.01). There was no change in force fluctuations or stretch reflex magnitude for the subjects in the Control group. The results indicate that prolonged vibration increased the short-latency component of the stretch reflex, the discharge rate of motor units, and the fluctuations in force during contractions by a hand muscle. These adjustments were necessary to achieve the target force due to the vibration-induced decrease in the force capacity of the muscle.
Assuntos
Neurônios Motores/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/inervação , Músculo Esquelético/fisiologia , Reflexo de Estiramento/fisiologia , Adolescente , Adulto , Eletromiografia , Feminino , Mãos/fisiologia , Humanos , Masculino , Neurônios Aferentes/fisiologia , VibraçãoRESUMO
INTRODUCTION: Age-related differences in force steadiness have been extensively examined and used as an index of motor function. However, the functional relevance of steadiness remains unclear. PURPOSE: The aim here was to evaluate the relations among hand strength, steadiness, and function across the adult life span. METHODS: Seventy-five adults (45 women; 18-89 yr) performed three strength, two steadiness, and four functional tests with both hands. Strength was measured during index finger abduction, precision pinch, and handgrip, and steadiness was measured during index finger abduction and precision pinch. Functional tests included the Grooved Pegboard test, the game Operation™, a scissor task, and a tracing task. RESULTS: Moderate correlations were observed between both steadiness tasks and performance on the Grooved Pegboard test (R(2) = 0.57 and R(2) = 0.46, respectively) and Operation™ (R(2) = -0.47 and R(2) = -0.57, respectively). CONCLUSIONS: The relation between measures of steadiness and hand function suggests that the physiological mechanisms responsible for differences in steadiness also contribute to differences in the performance of fine motor tasks with the hand.
Assuntos
Envelhecimento , Força da Mão/fisiologia , Mãos/fisiologia , Desempenho Psicomotor/fisiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Contração Isométrica/fisiologia , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
The discharge of single motor units (n = 34) in the first dorsal interosseus muscle and the fluctuations in force during steady contractions were measured across a range of index finger abduction forces in old adults (77.1 +/- 6.9 yr, n = 20). These results were compared with previously reported data on 38 motor units from young adults (25.7 +/- 5.7 yr). Both minimal and peak discharge rates increased with recruitment threshold, but the strength of these relations was notably weaker for the old adults. Minimal discharge rates were similar for young and old adults (P = 0.77), whereas peak discharge rates were lower for old adults (P < 0.01). Consequently, the range of rate coding for each motor unit was substantially less for the old adults (7.1 pps) compared with the young adults (12.1 pps, P < 0.01). However, the variability in motor-unit discharge was similar for young and old adults; the coefficient of variation of the interspike intervals was similar at recruitment (old: 25.4%, young: 27.1%, P = 0.39) and declined with an increase in discharge rate (old: 13.2%, young: 14.2%, P = 0.21). Furthermore, the fluctuations in force during steady isometric contractions (2-95% of maximal force) were similar for young and old adults, except that the relative variability at the lowest force was greater for the old adults. A computational model of motor-unit recruitment and rate coding incorporated the experimental observations and was able to match the measured and simulated values for force steadiness across the operating range of the muscle.
Assuntos
Mãos , Neurônios Motores/fisiologia , Músculo Esquelético/citologia , Potenciais de Ação/fisiologia , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Eletromiografia/métodos , Feminino , Força da Mão/fisiologia , Humanos , Masculino , Modelos Neurológicos , Contração Muscular/fisiologiaRESUMO
The goal of this study was to improve the ability of a motor unit model to predict experimentally measured force variability across a wide range of forces. Motor unit discharge characteristics were obtained from 38 motor units of the first dorsal interosseus muscle. Motor unit discharges were recorded in separate isometric contractions that ranged from 4 to 85% of the maximal voluntary contraction (MVC) force above recruitment threshold. High-threshold motor units exhibited both greater minimal and peak discharge rates compared with low-threshold units (P < 0.01). Minimal discharge rate increased from 7 to 23 pps, and peak discharge rate increased from 14 to 38 pps with an increase in recruitment threshold. Relative discharge rate variability (CV) decreased exponentially for each motor unit from an average of 30 to 13% as index finger force increased above recruitment threshold. In separate experiments, force variability was assessed at eight force levels from 2 to 95% MVC. The CV for force decreased from 4.9 to 1.4% as force increased from 2 to 15% MVC (P < 0.01) and remained constant at higher forces (1.2-1.9%; P = 0.14). When the motor unit model was revised using these experimental findings, discharge rate variability was the critical factor that resulted in no significant difference between simulated and experimental force variability (P = 0.22) at all force levels. These results support the hypothesis that discharge rate variability is a major determinant of the trends in isometric force variability across the working range of a muscle.