Hand Steadiness Research Articles

Practicing a Functional Task Improves Steadiness with Hand Muscles in Older Adults

Improvements in steadiness with practice have been associated with enhanced performance on a functional task in old adults. The aims of the study were to examine the specificity of the association between steadiness and a functional task and to assess the influence of practicing a functional task on force steadiness of hand muscles. Twenty-three older adults (≥70 yr) participated in the study and were assigned to either a practice group (n = 15) or a control group (n = 8). Subjects completed two testing sessions that were 2 wk apart. The practice group completed six additional sessions to practice a functional task (Grooved Pegboard). Tests included maximal voluntary contractions (MVC), force steadiness (precision pinch and index finger abduction) at three target forces (5%, 15%, and 25% MVC), and the Grooved Pegboard test. The associations between strength, steadiness, and the time needed to complete the Grooved Pegboard test were examined. In addition, MVC force, steadiness, and pegboard time were compared between the two testing sessions. The time needed to complete the Grooved Pegboard test was associated with index finger abduction steadiness for two of the three target forces (15% and 25% MVC) but was not associated with pinch steadiness. Practice significantly reduced the time needed to complete the Grooved Pegboard test and improved steadiness in both tasks. Force steadiness provides an appropriate index of hand function, especially when measured at low forces.

Gender differences in hand stability of normal young people assessed at low force levels

To examine gender differences in hand stability, finger position and force holding tasks at low force levels were conducted with 30 male and 30 female young adults. Total fluctuation was defined as the standard deviation of measured data and fluctuation and the 10-Hz component of the physiological tremor were compared between maleand female subjects. In all tasks, the total fluctuation and the 10-Hz tremor were significantly larger in male subjects than females. On average, the fluctuation was 1.3 times larger and the 10-Hz tremor was 1.6 times larger. The results of this study suggest that women have superior hand stability compared with men at low force levels. Finger length, maximal voluntary contraction and surface electromyography were also measured and factors related to gender differences in hand stability are discussed. Statement of Relevance: Hand stability is crucial for precise manual operations. This study demonstrated gender differences in hand steadiness at low force levels. Though hand dexterity cannot be explained only by hand stability, the results of thisstudy are useful not only for occupational aptitude tests but also for neuropsychological tests.

A Preliminary Evaluation of a Burr Hole Drilling Simulator for Craniotomy

A training transfer paradigm was used to evaluate a virtual reality (VR) simulator for performing the burr hole drilling portion of a craniotomy procedure. Participants used a VR simulator that had a physical drill handle interfaced with a haptic force/torque feedback system. They practiced until they met a priori performance criteria and then repeated the procedure with a genuine drill and foam model of a skull. The results showed some positive transfer related to hand steadiness, but not for drilling time. The drilling model incorporated in the simulator may require more effort to maintain the drill position and more revolutions of the drill bit to penetrate the model skull. Thus, practice on the VR simulator enabled the participants to maintain better drill position on the physical model. From a clinical perspective, the findings underscore the advantages of practicing a critical surgical procedure on a simulator prior to performing on a genuine patient.

Study of the Effect of Nortriptyline and Fluvoxamine on Psychomotor Functions in Healthy Volunteers

Background:Today, many antidepressants are available, but they often cause adverse effects, particularly psychomotor and cognitive. It leads to patient maladjustment and may impair psychomotor performance. Fluvoxamine is a newer antidepressant and hence the present study was planned to investigate its effect on psychomotor functions and compare with nortriptyline and record their adverse reactions.Materials and Methods:A total of 26 healthy volunteers were included in this double-blind, placebocontrolled, crossover study. Single oral doses of fluvoxamine 50 mg, nortriptyline 50 mg and placebo were administered following a Latin square design. The objective parameters-six digit cancellation test, digit symbol substitution test, critical flicker fusion test, arithmetic ability test, hand steadiness test and subjective parameters such as visual analogue scale 1, 2, 3 were tested at 0, 2 and 4 h. The side-effects were also investigated.Results:Nortriptyline impaired all subjective and objective psychomotor functions while fluvoxamine did not show any significant effect on objective tests. However, on subjective parameters, there was a significant effect. The side-effects observed were dryness of mouthwith the nortriptyline and nausea and headache with fluvoxamine.Conclusion:Fluvoxamine is a better antidepressant drug in comparison with nortriptyline as it causes a less impairment of psychomotor functions.

Effects of acute insulin-induced hypoglycaemia on psychomotor function: people with type 1 diabetes are less affected than non-diabetic adults

We examined the effects of acute insulin-induced hypoglycaemia on psychomotor function in non-diabetic volunteers and in adults with type 1 diabetes. Non-diabetic adults (n = 20) and adults with type 1 diabetes mellitus (n = 16) each underwent a euglycaemic-hyperinsulinaemic glucose clamp on two separate occasions. Arterialised blood glucose was maintained for 1 h at either 4.5 mmol/l (euglycaemia) or 2.5 mmol/l (hypoglycaemia). During this time participants underwent neuropsychological tests to assess psychomotor function. During hypoglycaemia the non-diabetic participants showed a significant deterioration in the following: (1) four-choice reaction time (p = 0.008); (2) grooved pegboard (a test of manual dexterity; p = 0.004); (3) hand steadiness (p = 0.003); (4) pursuit rotor (a test of fine motor function, attention and coordination; p = 0.018); and (5) test of total body coordination (p = 0.004). No significant differences were observed between euglycaemia and hypoglycaemia in hand-grip (p = 0.897) and line tracing time (p = 0.480) tests. In type 1 diabetes mellitus patients, only four-choice reaction time (p = 0.023) and pursuit rotor (p = 0.045) were impaired significantly during hypoglycaemia. Although acute hypoglycaemia caused significant impairment of several psychomotor functions in non-diabetic adults, a lower magnitude of impairment was observed in those with type 1 diabetes. The mechanism underlying this discrepant effect of hypoglycaemia on psychomotor function remains unknown, but may be related to the difference in sympathoadrenal activation observed between the groups. People with type 1 diabetes may also have had a behavioural advantage of over non-diabetic participants derived from their previous exposure to hypoglycaemia or potentially the disparate results arose from hypoglycaemia-induced cerebral adaptation.

Hand Steadiness and Coherence Following Motor Learning Training in Older Adults

Motor learning training can improve hand steadiness. Motor unit coherence has been suggested to be related to force un-steadiness. It is possible that motor learning training may change motor unit coherence within and across synergistic muscles. PURPOSE: To compare force steadiness and motor unit coherence in the first dorsal interosseous (FDI) and adductor pollicis (AdP) muscles of older adults during a pinching task before and after a motor learning training program. METHODS: Pre and post tests consisted of 2-minute sustained contractions at 2, 4, 8, and 12 % maximal pinching force (MPF) with the non-dominant hand. Single motor units were recorded from the AdP and FDI muscles with intramuscular finewire electrodes. The training program consisted of 2 sessions per week for 4 weeks. Participants performed 5 contractions each at 2 and 4 % MPF for 20 seconds, as well as 10 slow ramp contractions up to 2 and 4% MPF at their own pace and at a designated velocity of 0.5% MPF/sec. 104 motor unit pairs before training and 95 motor unit pairs after training were analyzed to determine changes within and across muscles. RESULTS: Following motor learning training, the coefficient of variation in the force improved in the 2, 4, and 8 % MPF levels in the finger (0.08 ± 0.01 vs. 0.05 ± 0.005, p =0.009; 0.08 ± 0.01 vs. 0.06 ± 0.003, p< 0.001; and 0.05 ± 0.005 vs. 0.03 ± 0.003, p= 0.02, for the 2, 4, and 8 % levels, respectively) and the 2 and 4 % MPF in thumb ( 0.08 ± 0.01 vs. 0.06 ± 0.003, p= 0.01; and 0.08 ± 0.01 vs. 0.04 ± 0.003, p= 0.01, for the 2 and 4 % levels, respectively). Coherence indices pre-and post-training did not change at any level (p= 0.1, p= 0.5, p= 0.1, p= 0.4 for the 2, 4, 8, and 12 % MPF, respectively). CONCLUSIONS: Motor learning improved hand steadiness; however, it did not impact the incidence of coherence within or across the AdP and FDI muscles. Thus, motor unit coherence was not related to changes in hand steadiness with training. Supported by NIH Grant RO3 AR52883-01.

Motor Unit Coherence is Not Related to Un-steadiness in Hand

There is contradictory evidence as to whether motor unit coherence contributes to force un-steadiness. Little is known of the effect of coherence across synergistic muscle pairs during multi-digit hand tasks or of variation of motor unit coherence with force level. PURPOSE: To compare intra and across muscle motor unit coherence among pairs of simultaneously firing motor units in first dorsal interosseous (FDI) and adductor pollicis (AdP) muscles during a voluntary low-force pinch task with the non-dominant hand in older adults. METHODS: Seven (2 male, 5 female) healthy older adults (65 ± 3.6 yrs) performed 3 maximum pinching force (MPF) contractions followed by 2-minute pinch contractions at 2%, 4%, 8% and 12% of their respective MPF. Motor units were recorded from the FDI and the AdP muscles using intramuscular fine wire electrodes for a total of 118 motor unit pairs. The coefficient of variation (CV) of the force held was computed at each target level for the thumb and the finger as a measure of force steadiness. RESULTS: Force CV was not significantly different for thumb or finger (p= 0.96). Overall force CV at 2% MPF (0.08 ± 0.01) was greater than that at 8% MPF (0.05 ± 0.005, p= 0.04) and 12% MPF (0.03 ± 0.004, p 0.05). Overall motor unit coherence indices were higher within the FDI (0.13 ± 0.02) and AdP (0.11 ± 0.02) than across the two muscle groups (0.07 ± 0.009) with p= 0.02 and p= 0.09 respectively. CONCLUSION: In older adults, force steadiness was lower at lower target levels whereas, coherence indices did not change. Thus, decreased hand steadiness during low-force pinching tasks cannot be attributed to changes in motor unit coherence. Supported by NIH Grant RO3 AR52883-01.

Maximal manual stretcher carriage: performance and recovery of male and female ambulance workers

The effects of a maximal duration stretcher carriage on heart rate (HR), lactate concentration, hand steadiness and hand-grip strength were studied up to 72 h post-exercise in 17 male and 15 female military ambulance personnel. Using both hands for transport, the participants walked on a treadmill ergometer at a speed of 4.5 km/h. Force measurements at the handlebars yielded mean loads of 245 N (25 kg) on each side. Each step on the treadmill induced additional force oscillations with peak forces up to 470 N corresponding to 130% (women) and 98% (men) of maximal voluntary contraction (MVC). In the males the maximal transport time was about twice the time in women (mean ± SD: 184 ± 51 s vs. 98 ± 34 s). These differences had no significant effect on HR and lactate values. The same applies to hand steadiness, which showed only a transient deterioration immediately after exercise. In contrast to these parameters, substantial differences were seen in hand-grip strength recovery. Immediately after exercise, maximal hand-grip strength decreased by 150 N (25% MVC) in the males vs. 50 N (14%) in the females. Irrespective of gender, individuals with larger hand-grip strength and longer carriage durations (range 120 s–280 s) showed the slowest strength recoveries (up to 72 h) as compared to 1 h of recovery in participants with short transport durations (range 27 s–120 s). These findings suggest that the increasing number of eccentric strains during uninterrupted stretcher carriage induces cumulative muscle damages that may require some days for complete recovery.

Shufa: Chinese calligraphic handwriting (CCH) for health and behavioural therapy

This paper presents an overview of psychological research on the Chinese art of calligraphy (Shufa). Using a theoretical framework, we have investigated the scientific nature of calligraphic brush handwriting as well as its treatment effects on behavioural and clinical disorders. The paper begins with an introduction to Chinese calligraphy, Chinese characters, and the character structures. This is followed by an account of a research‐based framework of the psychological characteristics of Chinese calligraphy handwriting (CCH). Our basic research includes measures of the writer's physiological changes associated with the brush‐writing act, and the results show that the practitioner experiences relaxation and emotional calmness evident in decelerated respiration, slower heart‐rate, decreased blood pressure, and reduced muscular tension. The cognitive effects of the CCH practice included quickened response time and improved performance in discrimination and figure identification, as well as enhanced visual spatial abilities, spatial relations, abstract reasoning, and aspects of memory and attention in the practitioners. Following these findings, our applied and clinical research has resulted in positive effects of the CCH treatment on behavioural changes in individuals with autism, Attention Deficit Disorder (ADD), and Attention Deficit Hyperactivity Disorder (ADHD); on cognitive improvements in reasoning, judgement, and cognitive facilitation; and on hand steadiness in children with mild retardation; as well as enhanced memory, concentration, spatial orientation, and motor coordination in Alzheimer's patients. Similarly, we have successfully applied the CCH treatment to patients with psychosomatic diseases of hypertension and diabetes, as well as mental diseases of schizophrenia, depression, and neurosis in terms of the patients' emotions, concentration, and hospital behaviours. This new system of CCH behavioural treatment has also been applied to users of other writing systems. In summary, the present CCH research has its roots in a Chinese art, has been scientifically investigated, and offers an alternative approach to improved health.

Recovery of hand grip strength and hand steadiness after exhausting manual stretcher carriage

Rescue activities frequently require not only substantial and sustained hand-grip forces but also a subtle coordination of hand and finger muscles, e.g. when manipulating injection syringes after manual stretcher carriage. We investigated the recovery kinetics of manual coordination and muscle strength after exhausting stretcher carriage (4.5 km/h, load at each handle bar: 25 kg). Hand steadiness (frequency and duration of wall contacts when holding a metal pin into a small bore) and parameters of hand-grip strength were determined in 15 male volunteers before and immediately after the stretcher carriage. Measurements were repeated after 0.5, 1, 4 and 24 h of recovery. Mean carrying time was 215+/-87 s (SD), mean transport distance amounted to 264+/-104 m. During the carriage test, forces at the stretcher handles oscillated in the order of +/-50 N within each gait cycle. Immediately after exhaustion, hand steadiness was significantly deteriorated (threefold increase in frequency and duration of wall contacts), maximum and mean hand-grip force over 15 s were reduced by almost 20%. While the recovery of hand steadiness was complete by minute 30 after stretcher carriage, a significant reduction in maximum and mean hand-grip force by 12% could still be observed after 24 h. The present findings demonstrate that hand steadiness recovers much faster than maximum hand-grip strength after exhaustive manual stretcher carriage (less than 30 min vs. more than 24 h). Probably, muscle damage induced in particular by the eccentric components during stretcher transport seems to affect only the generation of large forces. By contrast, the generation and coordination of the much lower forces required for hand-steadiness appears to be impaired only during the short transient of metabolic recovery.

The association between a genetic polymorphism of coproporphyrinogen oxidase, dental mercury exposure and neurobehavioral response in humans

We previously described a polymorphism in exon 4 of the gene encoding the heme biosynthetic pathway enzyme, coproporphyrinogen oxidase (CPOX4), which significantly modifies the effect of mercury exposure on urinary porphyrin excretion in humans. Here, we examined potential consequences of this polymorphism (“CPOX4”) on performance within neurobehavioral domains, symptoms, and mood that are known to be affected by elemental mercury (Hg°) exposure in human subjects. A behavioral test battery was administered on the day of urine and buccal cell collections for 194 male dentists (DDs) and 233 female dental assistants (DAs) occupationally exposed to Hg° for an average of 19 and 10 years, respectively. Subjects had no history of health disorders and were employed for a minimum of 5 years in the dental profession. Respective mean urinary mercury (HgU) levels in DDs and DAs were 3.32 (4.87) μg/l and 1.98 (2.29) μg/l. Corresponding indices of chronic occupational Hg° exposure, weighted for historical exposure, were 27.1 (20.6) and 15.2 (12.3). The frequencies of the homogygous common (A/A), heterozygous (A/C), and homozygous polymorphic (C/C) genotypes were 75%, 23% and 2% for DDs and 73%, 25%, and 2% for DAs, respectively. DDs and DAs were evaluated separately. Regression analyses controlled for age, premorbid intelligence, alcohol consumption, and education. Statistically significant associations with HgU ( p < 0.05) were found for nine measures among DDs (BEES Digit Span Forward and Backward, WMS-R Visual Reproduction N Correct, BEES Symbol Digit Rate, BEES Finger Tapping Dom/Non-dom, and Alternate Partialed, Hand Steadiness Factor1, and BEES Tracking), and eight measures among DAs (BEES Digit Span Forward, BEES Symbol Digit Rate, BEES Pattern Discrimination Rate, BEES Trailmaking B, BEES Finger Tapping Dom/Non-dom, and Alternate Partialed, Hand Steadiness Factor1, and Vibration Sensitivity Hits). CPOX4 status was associated with four measures in DDs (BEES Spatial Span Forward, BEES Pattern Memory N Correct, BEES Symbol Digit Rate, and BEES Vigilance Hit) and five measures in DAs (BEES Digit Span Forward, WMS-R Visual Reproductions N Correct, BEES Symbol Digit Rate, BEES Simple and Choice Reaction Time Move. Both groups experienced an additive effect (no interaction term) for HgU and the CPOX4 polymorphisms on the Digit Rate whereas DAs also had additive effects for BEES Digit Span Forward and for Beck's Depression factor ‘Worthlessness’. These exploratory findings suggest that the CPOX4 polymorphism may affect susceptibility for specific neurobehavioral functions associated with mercury exposure in human subjects.

Chronic low-level mercury exposure, BDNF polymorphism, and associations with cognitive and motor function

Potential cognitive and motor effects from exposure to elemental mercury (Hg 0) were examined in the presence and absence of a polymorphism (Val66Met) in brain-derived neurotrophic factor (BDNF). A group of 194 male dentists (DDs) and 233 female dental assistants (DAs) were occupationally exposed to mercury and had no history of kidney or nervous system disorders. Acute exposure was measured using spot urinary Hg (HgU) concentrations (average 3.32 and 1.98 μg/l, respectively) and indices of chronic occupational exposure (26.3 and 14.9 years, respectively, weighted for historical exposures). The BDNF status was 68% and 66% wild type, 26% and 30% single substitution, and 5% and 4% full mutation for DDs and DAs, respectively. DDs and DAs were evaluated separately. Regression analyses controlled for age, premorbid intelligence, alcohol consumption, and education. Statistically significant adverse associations with HgU ( p < .05) were found for nine measures among DDs (Digit Span Forward, Digit and Spatial Span Backward, Visual Reproduction, Finger Tapping Dominant, Alternate, and Alternate Partialed, Hand Steadiness, and Tracking), and eight measures among DAs (Digit Span Forward, Visual Reproduction, Pattern Discrimination Rate, Symbol Digit Rate, Trailmaking B, Finger Tapping Dominant and Alternate Partialed, and Hand Steadiness). The BDNF status was associated with four measures in DDs and three measures in DAs. Joint effects were found for Finger Tapping Alternate and Alternate Partialed in DDs and Hand Steadiness and Trailmaking B in DAs. Joint effects were additive in all cases. Performance on verbal intelligence and reaction time were not associated with either HgU or BDNF status. A test of threshold effect for the association of Hand Steadiness with HgU demonstrated no lower boundary in both DDs and DAs. No associations were observed with estimates of chronic mercury exposure. Our findings are applicable to exposure levels of the general population and identify a potentially vulnerable group with a BDNF polymorphism.

Cognitive and psychomotor performance, mood, and pressor effects of caffeine after 4, 6 and 8�h caffeine abstinence

Many studies have found that caffeine consumed after overnight caffeine abstinence improves cognitive performance and mood. Much less is known, however, about the effects of caffeine after shorter periods of caffeine abstinence. The aim of this study was to measure the effects on psychomotor and cognitive performance, mood, hand steadiness, blood pressure and heart rate of caffeine administration after periods of 4, 6, and 8 h of caffeine abstinence. Participants (n = 49, 27 female) were moderate to moderate-high caffeine consumers (mean daily intake 370 mg/day). Following overnight caffeine abstinence, a 'pre-dose' of caffeine (1.2 mg/kg) was administered at 9 A.M, 11 A.M or 1 P.M. The participants started a baseline battery of measurements at 4 P.M.: before receiving caffeine (1.2 mg/kg) or placebo at 5 P.M.: They then performed the battery of tests again, starting at 5:30 P.M. This was a double-blind, placebo-controlled, randomised study. Performance and mood measurements confirmed a psychostimulant action of caffeine (versus placebo), but only after 8 h of caffeine abstinence. Caffeine also increased blood pressure after 8-h abstinence, whereas hand steadiness was decreased and perception of task demand was increased by caffeine after 4 h, but not after 6- and 8-h abstinence. A second cup-of-coffee equivalent dose of caffeine only reliably affected cognitive performance and mood after an 8-h interval between doses, but not after shorter intervals (when caffeine had some adverse effects). These results show that, apart from caffeine consumption soon after waking, the daily pattern of caffeine intake of many typical caffeine consumers is not well explained by the short-term psychostimulant effects of caffeine.

Manganese exposure and age: neurobehavioral performance among alloy production workers

Manganese (Mn) is associated with neurotoxic effects under certain conditions of exposure. A recent study on environmental Mn exposure showed an Mn × age interaction for several neurobehavioral functions. The objective of the present study was to examine the neurobehavioral test results in relation to age and Mn exposure, using an existing data set on 74 workers from an Mn alloy production plant and referents pair-matched for age (±3 years), educational level (±2 years), number of children, and smoking status. The pair differences between Mn-exposed workers and referents increased significantly with age for scores on Delayed Word Recall, Trail Making B, Cancellation H, Nine-Hole Hand Steadiness Test, and Vibratometer. These results suggest that for certain neurobehavioral functions, and in particular for information processing, Mn-related deficits increase with age. This outcome could not be explained by higher cumulative Mn exposure.

Effects of caffeine and caffeine withdrawal on mood and cognitive performance degraded by sleep restriction

It has been suggested that caffeine is most likely to benefit mood and performance when alertness is low. To measure the effects of caffeine on psychomotor and cognitive performance, mood, blood pressure and heart rate in sleep-restricted participants. To do this in a group of participants who had also been previously deprived of caffeine for 3 weeks, thereby potentially removing the confounding effects of acute caffeine withdrawal. Participants were moderate to moderate-high caffeine consumers who were provided with either decaffeinated tea and/or coffee for 3 weeks (LTW) or regular tea and/or coffee for 3 weeks (overnight caffeine-withdrawn participants, ONW). Then, following overnight caffeine abstinence, they were tested on a battery of tasks assessing mood, cognitive performance, etc. before and after receiving caffeine (1.2 mg/kg) or on another day after receiving placebo. Final analyses were based on 17 long-term caffeine-withdrawn participants (LTW) and 17 ONW participants whose salivary caffeine levels on each test day confirmed probable compliance with the instructions concerning restrictions on consumption of caffeine-containing drinks. Acute caffeine withdrawal (ONW) had a number of negative effects, including impairment of cognitive performance, increased headache, and reduced alertness and clear-headedness. Caffeine (versus placebo) did not significantly improve cognitive performance in LTW participants, although it prevented further deterioration of performance in ONW participants. Caffeine increased tapping speed (but tended to impair hand steadiness), increased blood pressure, and had some effects on mood in both groups. The findings provide strong support for the withdrawal reversal hypothesis. In particular, cognitive performance was found to be affected adversely by acute caffeine withdrawal and, even in the context of alertness lowered by sleep restriction, cognitive performance was not improved by caffeine in the absence of these withdrawal effects. Different patterns of effects (or lack of effects) of caffeine and caffeine withdrawal were found for other variables, but overall these results also suggest that there is little benefit to be gained from caffeine consumption.

Tremor in otosurgery: influence of physical strain on hand steadiness.

The microscopically small middle ear structures require the otosurgeon to have a steady hand because instrument stability is a critical factor for a successful microsurgical procedure. Hand steadiness is mainly influenced by the tremor movements of the hand. The aim of this study was to measure hand tremor under simulated microsurgical conditions and to estimate the influence of different kinds of physical strain (e.g., physical exertion and hand exercise), as well as food abstinence and coffee consumption. Further, the effect of one-or two-handed manipulation and microsurgical experience was investigated. The hand movements of 16 adult subjects were assessed during a defined manual manipulation using a stapes model to simulate microsurgical procedures. A laserinterferometric-based displacement technique was developed to measure tremor amplitude and frequency, as well as maximum displacement, to evaluate the subjects' fine motor skills. The mean tremor frequency across all measurements was 8.1 Hz and did not show any dependence on different kinds of physical strain. Two-handed manipulations showed significantly lower tremor amplitudes than one-handed performances. Tremor amplitude and maximum displacement did not change after hand exercise, food abstinence, and coffee consumption. However, after physical exertion, a significant increase in the tremor amplitude was found. Subjects with advanced microsurgical experience showed smaller tremor amplitudes for one-handed runs. The tremor data are interpreted as a recommendation to avoid physical exertion before microsurgery. In cases of absolute necessity for hand steadiness, two-handed manipulations are preferable. Further, hand steadiness might be improved by microsurgical training and experience.

THE EFFECT OF VARIED EXERCISE INTENSITIES ON REACTION TIME AND COORDINATION IN OLDER ADULTS INVOLVED IN A 10 WEEK EXERCISE TRAINING PROGRAM

The loss of reaction time and hand-eye coordination with aging has been well documented in the literature. However, its responsiveness to an exercise training program is the subject of much debate. Several studies have shown a favorable response, while others have shown no effect. These studies differed in many programming parameters. It was the purpose of this study to assess the change in reaction time, hand-eye coordination and hand steadiness in response to three exercise programs of differing intensities. Program 1 Light Exercise, n = 12, mean age-83 years. Exercise intensity: heart rate near resting levels (stretching program). Program 2 Moderate Exercise, n = 18, mean age-87 years. Exercise intensity: heart rate between 85–100 bpm (low intensity aerobic program). Program 3 Heavy Exercise, n = 12, mean age-85 years. Exercise intensity: heart rate between 110–120 bpm (moderate intensity aerobic program). The total duration of all programs was 10 weeks, 3 sessions per week. Data were collected and analyzed using analysis of variance techniques. Results indicated a small but nonsignificant improvement in reaction time in the light and heavy exercise groups, while the moderate exercise group remained the same. Hand steadiness improved significantly in the light and heavy exercise group (p < .05), while the moderate exercise group remained the same. Hand-eye coordination improved significantly in all three groups. These results suggest that a 10 week exercise program can elicit improvements in hand-eye coordination and hand steadiness. However, this study did not support the improvement of reaction time through exercise of any intensity.

Effects of workload level and 8- versus 12-h workday duration on test battery performance

It is generally agreed that workday durations of 12 h or more are not advisable where workload levels are very high. However, there is no clear research basis for the identification of workload levels which should preclude the introduction of extended shifts. In the present study, the effects of varying workload levels and shift durations were investigated both in the laboratory and in a workplace. In the laboratory study subjects performed either cognitive work (two workload levels) or physically demanding work (heart rate maintained at 35 beats/min above resting), and there were significant effects of both shift duration and workload level on various performance tests, bodily discomfort, hand steadiness and alertness. In the physically demanding condition, perceived workload was higher on 12 h days despite heart rate being unchanged. In a field study, 34 workers participating for three days each, half of them on 8 h days and half on 12-h days; workload data were obtained for each subject at each half-day data collection point. The combination of higher workload and 12-h workdays produced greater fatigue, as manifested in increased bodily discomfort, decreased alertness, decreased hand steadiness and increased errors on the grammatical reasoning task. In addition to these interacting effects of workload and work duration, there were main effects of both workload and work duration on bodily discomfort, and of workload on hand steadiness. Relevance to industry The results have relevance for managers and employees regarding the adoption of extended shift systems, particularly in relation to the nature of job demands, overall workload levels, and the criticality of human performance for system safety and efficiency.

Neurobehavioral performance in aluminum welders.

Twenty aluminum welders (mean age 33 years; range 21-52), who had been exposed to aluminum for an average of 8.1 years (range 2-21), were tested for tremor and reaction time and screened for neuropsychiatric symptoms in a cross-sectional study. The welders' median urinary aluminum concentration was 1.5 micromol/L (range 0. 7-4.8). Aluminum in air, measured inside the respiratory protection, was 0.9 mg/m(3) (range 0.6-3.8). The welders were compared with twenty construction workers matched for age. Welders reported more symptoms than referents did (median 2 vs. 1; P=0.047). Although the welders as a group performed better than the referents on a tremor test, years of exposure, but not age, was predictive of poorer performance. The welders' reaction times were rapid by clinical standards (mean simple reaction time (SRT): 221 milliseconds; mean continuous performance test (CPT): 364 milliseconds). Although, as a group, they performed better than the referents, there was a statistically significant relation between longer reaction times and aluminum in air (air-Al). The relations between hand steadiness and years exposed, and between reaction time and air-Al, could indicate slight effects from exposure to aluminum. The possibility of selection of workers with high manual skills into welding work and a possible job-related training effect, might partly serve to explain the good performance among the welders.

THE EFFECT OF CAFFEINE ON REACTION TIME, HAND STEADINESS, AND SPECIFIC PHYSIOLOGICAL VARIABLES

450 The problem of this study was to analyze the effect of caffeine on heart rate, blood pressure, reaction time, and hand steadiness. Subjects (N = 20) were classified as high-caffeine users or low-caffeine users. Heart rate, blood pressure, reaction time, and hand steadiness were measured. Subjects then consumed 24 oz of coffee containing 345 mg of caffeine in a 5-min period. Dependent variables were measured again at 30, 60, and 90 min after caffeine administration. No significant differences (p > .05) were found between the groups, high- and low-caffeine users, for heart rate, systolic blood pressure, diastolic blood pressure, reaction time, or hand steadiness. Significant differences (p < .05) were found among test time means for all variables. A significant (p < .05) first order interaction effect, groups by test times, occurred for reaction time. The researchers concluded that caffeine (a) did not increase heart rate, (b) increased systolic blood pressure 60 min after caffeine intake, (c) increased diastolic blood pressure at 30 and 60 min after caffeine intake, (d) decreased reaction time for the high-caffeine-use group, and (e) had no effect on hand steadiness. Recommendations for further study included designing the study to measure baseline heart rate and blood pressure prior to caffeine administration and using a balanced placebo design to see if regular caffeine users respond due to caffeine or to expectancy.