Force steadiness in the lower extremities as an independent predictor of functional performance in older women

The relationship between isometric force control and functional performance is unknown. Submaximal steadiness and accuracy were measured during a constant force-matching task at 50% of maximal isometric voluntary contraction (MVC) of the knee extensors in 19 older women (70-89 years). Other variables included MVC, rate of torque development, and EMG activity. Functional performance was assessed during maximal performance of walking endurance, chair rising, and stair climbing. Isometric steadiness (but not accuracy) was found to independently predict chair-rise time and stair-climbing power and explained more variance in these tasks than any other variable. Walking endurance was related to muscle strength but not steadiness. These results suggest that steadiness is an independent predictor of brief, stressful functional-performance tasks in older women with mild functional impairment. Thus, improving steadiness might help reduce functional limitations or disability in older adults.     

Effects of a school based exercise program on children's resistance and flexibility

The aim of this study was to evaluate the short term effects of an exercise program on abdominal and back muscles resistance and hamstring flexibility among schoolchildren. Fifty eight healthy schoolchildren were divided into two groups: experimental (15 males and 14 females; mean age 12.2(1.8 years) and control (14 males and 15 females; mean age 11.9(2.1 years). The intervention was performed twice a week, on nonconsecutive days, during six weeks. The duration of each session was fifty minutes and they were composed by warming up aerobic exercises, isotonic and isometric abdominal and back muscle exercises and hamstring stretching. The intervention effects were evaluated through Kraus-Weber test (abdominal resistance), modified Biering-S?rensen test (back muscle resistance) and sit and reach test (hamstring flexibility). Data were analyzed by mixed-design two-way ANOVA, with one between-subjects and one within-subject (time) factors. The alpha level was set at P≤0.05. The experimental group improved back muscles resistance and hamstring flexibility, but not abdominal muscles resistance. There was a significant interaction between groups and time for back muscles resistance (P=0.018) and for hamstring flexibility (P=0.017). The 6-week training period showed positive results in improving back muscles resistance and hamstring flexibility of schoolchildren.     

Distal upper extremity musculoskeletal risk factors associated with colonoscopy

Gastroenterologists are at increased risk for developing recurrent thumb, hand, and elbow pain due to colonoscopy procedures. We evaluated forearm muscle loads and wrist postures during routine colonoscopy (N=12 gastroenterologists) to understand distal upper extremity musculoskeletal risk factors associated with the 4 different subtasks of colonoscopy. Bilateral forearm extensor carpiradialis (ECR) and flexor digitorum superficialis (FDS) surface electromyography and bilateral wrist postures were recorded continuously. The mean duration of colonoscopy was 24.2 (± 12.1) minutes and was dominated by the withdrawal subtask [13.7 (± 8.8) min] followed by right colon insertion [5.8 (± 4.8) min], left colon insertion [3.5 (± 3.1) min], and retroflexion [1.2 (± 2.1) min]. Median (APDF50) and peak (APDF90) left forearm muscle activity was significantly greater than right forearm muscle activity across all subtasks. Median and peak ECR muscle activity was significantly greater during the left and right colon insertion subtasks compared to retroflexion. Both wrists were predominantly in wrist extension during all phases of colonoscopy. The left forearm muscle activity was higher than right forearm activity due to differences in wrist posture and grip force. The risk factors for the left hand may be reduced with alternative designs and support mechanisms for the colonoscope head.     

Concurrent cognitive task may improve motor work performance and reduce muscle fatigue

Performance of certain cognitive tasks either during physical load or in rest pauses between boosts might lead to slowing of muscle fatigue and fatigue related decline in performance. Seventeen right-handed healthy volunteers (age 24 ± 1.4, 8 males) participated in this study, aiming to investigate the effect of the level of the cognitive information processing - 1) passive perception of audio stimuli, 2) active stimuli discrimination, 3) active stimuli discrimination following motor response - on motor task performance (handgrip test 30% and 7% of MVC) and muscle fatigue development. Cognitive tasks show the following effects on motor work: i) Perceived fatigue during 30 % MVC (fatiguing) condition developed slower if participant pressed button in response to deviant acoustic stimuli, as compared to passive listening. Counting task, an active task without motor component, took the intermediate position and did not differ significantly from two other cognitive tasks. ii) MVC after 30% MVC (fatiguing) condition tended to decrease stronger when accompanied with passive listening in comparison with both active tasks. iii) Motor task performance during 30% MVC (fatiguing) condition was better for active cognitive task with motor component than for passive task. Active task without motor component took the intermediate position and did not differ significantly from both the other cognitive tasks.     

Comparison between static maximal force and handbrake pulling force

The measurement of maximum pulling force is important not only for specifying force limit of industrial workers but also for designing controls requiring high force. This paper presents a comparison between maximal static handbrake pulling force (FST) and force exerted during normal handbrake pulling task (FDY). These forces were measured for different handle locations and subject characteristics. Participants were asked to pull a handbrake on an adjustable car mock-up as they would do when parking their own car, then to exert a force as high as possible on the pulled handbrake. Hand pulling forces were measured using a six-axes force sensor. 5 fixed handbrake positions were tested as well as a neutral handbrake position defined by the subject. FST and FDY were significantly correlated. Both were found to be dependent on handbrake position, age and gender. As expected, women and older subjects exerted lower forces. FST was significantly higher than FDY. The ratio FmR (FDY divided by FST) was also analyzed. Women showed higher FmR than men meaning that the task required a higher amount of muscle capability for women. FmR was also influenced by handbrake location. These data will be useful for handbrake design.     

Perineal Neurophysiological Assessment in 23 Patients Suffering from Persistent Genital Arousal Disorders: Evidence of Pudendal Neuropathy?

ABSTRACT

Objectives: Persistent genital arousal disorder (PGAD) is a rare condition. Our aim was to study whether or not the pudendal nerve is involved in PGAD, by means of electromyographic (EMG) testing. Methods: Twenty-three women who fulfilled the five criteria of PGAD were included in this study. After an in-depth interview and routine investigations, a perineal EMG assessment was performed. Concentric needle electromyography (EMG) testing with motor unit potential analysis of the pelvic floor muscles (bulbocavernosus muscle and striated external anal sphincter), study of the sacral reflex latency (SRL), and measurement of pudendal nerve terminal motor latency (PNTML) were performed. Results: Perineal ENMG demonstrated neurogenic changes in 14 (60.8%) of the patients. Denervation was found in all 14 patients with abnormal electrophysiological findings. Among them, 12 (85.7%) had altered PTNML and/or SRL. PTNML was delayed on the anal branch in 9 out of 14 (bilateral in 5 cases) and on the perineal branch in 9 out of 14 (bilateral in 6 cases). Conclusions: This study shows that pudendal neuropathy is frequent among women suffering from PGAD. However, due to the lack of a control group, involvement of pudendal neuropathy in the pathogenesis of PGAD remains unclear.     

Co-variation in time between near-far accommodation of the lens and trapezius muscle activity

Visual strain and discomfort may contribute to the generation of work-related musculoskeletal disorders among e.g. computer workers. A positive correlation on a group level between eye-lens accommodation and trapezius muscle activity has been reported. In this study we investigated the possibility of a direct, fast, connection between lens accommodation and trapezius muscles activity. The subjects focused alternately on Near and Far targets, with a mean switch time of 5 s, through four different lenses. The cross-correlation, R(tau) was computed, between the time signals of accommodation and electromyography (EMG) from 23 subjects. In the overall mean R(tau) of 736 curves, a small but significant correlation peak (0.019) with a delay (of the EMG signal) of about 0.3 s, revealed a small common component in the two signals. Among the lenses, the positive lens (3.5 D), showed the highest correlation peak (0.040). The correlation may be caused by a direct "hard-wired" connection between the ciliary and trapezius muscles. But it could also be caused indirectly by the subject's need for a more stable head in a more demanding visual task. The latter is supported by the result that the correlation was the highest in the positive lens condition. The present correlation is however weak and it has probably a low practical importance.     

Endurance training for cancer patients during and shortly after completion of the anti-cancer treatment

Cardiorespiratory fitness is one of the most important indicators of health and improves length of life. The attention and acceptance for endurance training in patients with several cancer diagnoses increased during the last decade. This review highlight’s the effect of endurance training in cancer patients by summarizing exemplary randomized clinical trials and systematic reviews both within the acute hospital treatment context, as in a rehabilitation setting. To date, most studies focus on endurance training in patient groups with moderate to good prognosis. The studies within these patient groups evaluate the endurance training in cancer patients using a moderate training intensity between 50 and 75 % of the VO₂ peak with an exercise time varying from 20 min (five times per week) in hospital up to 45 min (two to three times per week) in an ambulatory setting. Recently, the American College of Sports Medicine indicated that cancer survivors should follow the Physical Activity Guidelines for Americans, which represents ≥150 min per week of moderate intensity, ≥75 min per week of vigorous intensity aerobic exercise, or an equivalent combination of moderate and vigorous intensity aerobic exercises. To date, fewer studies evaluate the effects of endurance training in a palliative setting to maintain physical function of the patient. Future studies should investigate the effect of endurance training by evaluating different types of intensity training (moderate vs. high intensity training), the use of high-tech devices to improve physical activity, and to evaluate the effect of endurance training in patients with a palliative intention.     

Cut-points to prevent low back injury due to force exertion at work

Force exertion is related to low back injuries (LBI). This paper critically reviews the literature concerning cut-points for back force exertion, presents available guidelines in a concise manner, and identifies areas that need further research. The studies reviewed were grouped according to the criteria used to set the cut-point values. Most often cut-points differ than concur. The approach considering physiological, psychophysical, epidemiological, and biomechanical aspects of back force exertion meets the most known criteria and presents the lowest common denominator of instantaneous load for lifting tasks. Further experimental and epidemiological studies in peak load and cumulative exposure are necessary. Compound indices should also be developed for pushing, pulling, and carrying. Future indices should consider electromyographically determined fatigue, differential viscoelastic properties of tissues, aging, and the cross sectional area of back muscles. We hope that this paper contributes to a more systematic appraisal of back force exertion at work.     

Self-regulatory strength depletion and muscle-endurance performance: a test of the limited-strength model in older adults

Self-regulation consumes a form of strength or energy. The authors investigated aftereffects of self-regulation depletion on muscle-endurance performance in older adults. Participants (N = 61, mean age = 71) were randomized to a self-regulation-depletion or control group and completed 2 muscle-endurance performance tasks involving isometric handgrip squeezing that were separated by a cognitive-depletion task. The depletion group showed greater deterioration of muscle-endurance performance than controls, F(1, 59) = 7.31, p = .009. Results are comparable to those of younger adults in a similar study and support Baumeister et al.'s limited-strength model. Self-regulation may contribute to central-nervous-system fatigue; however, biological processes may allow aging muscle to offset depletion of self-regulatory resources affecting muscle-endurance performance.     

Cervico‐motor reflex: Description of the reflex and role in sexual acts

A recently identified reflex, termed the “cervico‐motor reflex,” was studied in 15 healthy women (mean age 36.6 years). The response of levator ani (LA) and puborectalis (PR) muscles to electrical and mechanical stimulation of the cervix uteri (CU) was determined. One concentric needle electrode was inserted into the CU (stimulating), a second into the LA (recording), and a third into the PR (recording). The vaginal pressure was measured at rest and on cervical stimulation by balloon‐tipped catheters. Electrical stimulation of the CU led to a reduction in pressure in the upper portion of the vagina (p < .05) and an increase in pressure in the middle and lower portions (p < .001). Stimulation also caused an increase in the electromyographic (EMG) activity of the LA and PR muscles (p < .01). Mechanical stimulation induced the same effects but to a lesser degree. Stimulation of the anesthetized CU, LA, or PR did not evoke the response. The data suggested the presence of a reproducible reflex relationship between the CU and both the LA and PR. During the sexual act and penile buffeting of the CU, levator contraction “balloons” the upper vagina, which acts as a “receptacle” for the semen. Meanwhile, PR contraction narrows the lower vagina, which may effect an increase of penile erection and rigidity. The cervico‐motor reflex may be incorporated as an investigative tool in sexual act disorders.     

Static load in the nursing profession; the silent killer?

Traditionally back pain in the nursing profession is associated with heavy lifting of patients. Although there is a strong relationship between heavy loads on the spine and lifting patients, literature indicates that there is a major factor that should not be underestimated: static load. Static load can be defined as the result of static, not moving, not dynamic, working positions. For example when a caregiver is washing a patient on a bed which is too low, her back is in a static (bended) stooped position up to several minutes. Exposure to static load is an underestimated silent killer of nurses musculoskeletal system . There is evidence from this cross-sectional study that static load can be reduced by a combination of introducing the right equipment, creating awareness and education.     

Ergonomics of novices and experts during simulated endotracheal intubation

Endotracheal Intubation (ETI) is an airway procedure commonly used to secure the airway for a variety of medical conditions. Proficiency in ETI procedures requires significant clinical experience and insufficient data currently exists describing the physical ergonomics of successful direct laryngoscopy. The research objectives of this study were to examine how ETI time, error and practitioner biomechanics varied among clinical experience levels and hospital bed heights. The participant population included novice and expert personnel, differentiated by their exposure to ETI procedures. Participants used a standard laryngoscope and blade to perform ETI trials on an airway manikin trainer at predesigned hospital bed heights. Participants were evaluated based on ETI time and accuracy, as well as wrist postures and muscle utilization. Hospital bed height did not affect task completion time, error rates or muscle utilization. Expert participants exhibited less ulnar deviation and forearm supination during task trials, as well as a higher utilization of the bicep brachii and anterior deltoid muscles. Expert grasped instrumentation differently, requiring less wrist manipulation required to achieve ideal instrument positions. By encouraging ergonomic best-practices in hand and arm postures during ETI training, the opportunity exists to improve patient safety and reduce the learning curve associated with ETI procedures.     

Psychosocial indicators among aircraft maintenance workers with and without neck and shoulder musculoskeletal symptoms

In the aircraft maintenance industry, most of workers performs manual handling tasks of different materials, varying from small objects up to large pieces of the aircraft. It can increase the occurrence of work-related musculoskeletal disorders (WMSDs), which are strongly associated with high physical demands required by the task. Moreover, psychosocial demands are considered as risk factors for musculoskeletal disorders in both the upper limbs and lumbar spine. Thus, the objective of this study was to assess psychosocial indicators among aircraft maintenance workers according to the presence of neck and shoulder musculoskeletal symptoms. Eighty workers of an aircraft maintenance company were evaluated (32.69 ± 8.25 years, 79.8 ± 13.4 kg, 175 ± 7 cm). According to physical examination, 50 workers were classified as asymptomatic (AS - 4.1 ± 3.17 positive signs) whilst 30 workers were classified as symptomatic (SS - 26.72 ± 11.44 positive signs). AS and SS have shown similar profile of demand (p = 0.62), control (p = 0.66) and social support (p = 0.74) according to the Job Content Questionnaire. However, the groups are different when considering work engagement variables. In general, SS have higher scores than AS (p < 0.05).     

Endurance performance in masters athletes

Masters athletes are typically older than 35 years of age and systematically train for, and compete in, organized forms of sport specifically designed for older adults. They are motivated to participate in masters sport for a wide variety of reasons. Age-related declines in endurance performance are observed across the endurance sports of running, orienteering, rowing, and swimming. These declines are curvilinear from age 35 years until approximately age 60–70 years and exponential thereafter. The decline in endurance performance appears primarily due to an age-related decrease in VO_2max secondary to an age-related decrease in HR_max and possible age-related declines in stroke volume and arteriovenous oxygen difference. While performance velocity at lactate threshold decreases with age in masters endurance athletes, it appears to increase relative to VO_2max while exercise economy is maintained. There also appears an age-related decrease in active muscle mass, type II muscle fiber size, and blood volume that contribute to decreased endurance performance. However, research suggests that maintenance of training intensity and volume into older age may mediate the rate of age-related decline in VO_2max, stroke volume, arteriovenous oxygen difference, blood volume, and muscle mass in masters endurance athletes.     

Effects of physical and mental demands on shoulder muscle fatigue

Mental demands have been associated with increased risk of injuries; however, its influence on muscle fatigability remains unclear. The aim of this study was to investigate the interaction of mental workload and physical workload on muscle fatigability during repetitive shoulder work. Twelve young participants, balanced by gender, performed shoulder abduction exercises until exhaustions at three levels of physical workload (low (5% maximum voluntary contraction (MVC)), moderate (35% MVC), and high (55% MVC)) in the absence and presence of a mental arithmetic test. Endurance time and rate of strength decline were employed as indicators of muscle fatigue. Concurrent physical and mental processing was found to adversely decrease muscle endurance by ~25% at the moderate intensity level. Furthermore, concurrent demands were associated with faster rate of strength decline compared to the control, irrespective of the physical intensity level. Findings from the current study provide evidence of the adverse effects of mental workload on muscle capacity (i.e., endurance and fatigue). It is therefore important to consider potential changes in worker capacity with concurrent physical and cognitive demands before designing work tasks/products.     

Fitness profiles and activity patterns of entering college students.

Fitness levels of American youth have shown a marked decline in the last decade, according to recent studies. To determine whether such a tendency persists for entering college students, the authors evaluated 115 male and 143 female students for performance on the following fitness-related variables: (1) maximal oxygen consumption (estimated from Astrand cycling protocol), (2) body composition (skin-fold techniques), (3) muscle endurance (sit-up protocol), (4) muscle strength (bench-press protocol), and (5) joint flexibility (upper and lower body protocols). Although neither men nor women exhibited high levels of cardiorespiratory fitness, the women in the study showed higher relative levels than their male counterparts. Both groups showed excellent levels of muscle strength (compared with normative standards), but they achieved only an average standard for muscle endurance. Findings of relatively low levels of cardiovascular fitness compared with levels of muscle strength, particularly in men, seem to be a reflection of an inappropriate concentration of physical activity.     

A polynomial equation to predict low back compression force: accounting for the effects of load height on instability

The purpose of this study was to develop a regression equation that, incorporating the potential energy of the load in the hands, was capable of improved predictions of spinal compression forces. A stepwise polynomial equation was developed from EMG profiles of 15 muscles, and its spinal joint loading predictions at L4/L5 were compared to current methods of calculating spinal compression. Absolute muscle activation was shown to increase with increased loading height, indicating that the central nervous system responds to changes in spinal stability. The inclusion of potential energy into the calculation of spinal disc compression at L4/L5 improved estimates of the compressive forces acting on the spine. This is the first model to incorporate potential energy into a predictive model for lumbar spine compression without the use of electromyography. It was concluded that potential energy plays a vital role in dictating the recruitment patterns of the trunk.