Brief hourly exercise during night work can help maintain workers' performance.

Increased night work is an important issue because of its implications on workers' health, safety and performance. This study examined the effects of brief hourly exercise as a countermeasure against the adverse effects of night work, especially for workers requiring sustained attention while working in a prolonged sitting posture. During simulated night work (22:00-08:00), participants were required to follow an hourly schedule comprising a 30-min task, 15-min test and 15-min break. The study included 2 experimental conditions: (1) hourly exercise (HE; hourly exercise for 3 min during breaks) and (2) control (without exercise during breaks). Throughout the test period, work performance in the last 10 min of each 30-min task was better under the HE condition than under the control condition (p<0.01). During the second half of the test period, exercise showed an effect on sustained attention (p=0.02). Parasympathetic nerve activity under the HE condition was less than that under the control condition (p<0.01). However, exercise was not effective in reducing subjective fatigue and sleepiness. These results suggest that brief hourly exercise acts as a restraint on parasympathetic nerve activity and is capable of sustaining attention levels during the circadian rhythm nadir that occurs during early morning.

How do the timing and length of a night-shift nap affect sleep inertia?

Napping is one strategy that may assist night shiftworkers to cope with sleepiness and fatigue. However, one potential disadvantage of napping is that awakening from naps is disturbed by sleep inertia, which has also been found to impair performance and/or mood, transiently. The authors examined the effects of the timing and length of a night-shift nap on sleep inertia in a laboratory setting. Twelve male university students (mean +/- SD: 21.6 +/- 2.8 yrs) participated in this 3-day experiment, during which included a simulated night shift (22:00-08:00 h) and subsequent day (11:30-17:30 h) and night sleep (00:00-07:00 h). The simulated night shift was designed to include one of five (four nap/one no-nap) conditions. The napping conditions differed by their timing and duration: 00:00-01:00 h (Early 60 min; E60), 00:00-02:00 h (Early 120 min; E120), 04:00-05:00 h (Late 60 min; L60), 04:00-06:00 h (Late 120 min; L120). Participants completed all the experimental conditions in a counterbalanced order. Rectal temperature (R(T)) was recorded throughout the simulated shift and polysomnography (PSG) was recorded during the nap period. Immediately before and after each nap, participants were required to complete a visual analogue scale (VAS) to assess sleepiness and a visual vigilance test (VVT). During the simulated night shift, a set of tasks (an English transcription task, a performance test battery, and a break) was repeated hourly, except during the periods of napping. For each nap condition, the VAS and VVT (reaction time [RT]; lapses >5 s) results were analyzed by two-way, repeated-measures analysis of variance (ANOVA) (nap [nap versus no-nap] x time point [pre-nap versus post-nap]). PSG and R(T) data were analyzed with one-way repeated-measures ANOVA. Marginally significant interactions were observed for RTs and lapses in VVT for the L60 nap condition (p = .071 and p = .070, respectively). However, those effect sizes were moderate (partial eta(2) = 0.266, 0.268, respectively). Post hoc analyses showed significantly longer RTs (p < .05) and more lapses (p < .05) following the L60 nap compared with no nap. In contrast, there was no significant difference in sleepiness between the L60, or any of the other nap conditions, and the no-nap condition. Our findings suggest the effect of sleep inertia on VVT performance was profound in the L60 condition, although no significant effects on sleepiness were self-reported by VAS. The dissociation between performance and sleepiness might reflect an unstable state where participants cannot perceive decline in their performance. The present findings are significant in terms of occupational safety; the practical implication is that great care is needed when taking a 1-h nap between 04:00 and 05:00 h on the night shift.

Characterizing recovery of sleep after four successive night shifts.

The purpose of this study was to characterize the recovery pattern of sleep following simulated, four successive night shifts in ten healthy men (22.9 + or - 3.2 yr). Poor sleep was defined as sleep efficiency of 80% or lower as determined actigraphically. The results showed that four (rapid, slow, pseudo, and incomplete) patterns of sleep recovery were observed over three recovery sleep periods. The rapid and slow recovery pattern represented immediate and slow return to baseline level prior to the nightshifts, respectively. The pseudo recovery pattern demonstrated poor sleep at the 3rd recovery sleep period, despite transient recovery at the 2nd sleep period. The incomplete recovery pattern was characterized by consistently poorer sleep during the entire recovery period. The correlation analysis indicated that sleep habits (bed time and variation of wake time) prior to the experiment were significantly related to the recovery patterns, rather than performance and alertness during the night shifts.

Effects of a modified ambulance night shift system on fatigue and physiological function among ambulance paramedics.

OBJECTIVES: In the present study, we modified a night shift system for an ambulance service so that ambulance paramedics were assured of taking a nap, and examined the effects of this new system on the fatigue and physiological function of ambulance paramedics. METHODS: Ten ambulance paramedics at a fire station in the center of a large city in Japan voluntarily enrolled as subjects in this field study. They worked a 24-h shift system. There were two teams of 5 ambulance paramedics in the fire station. Three ambulance paramedics per shift usually provided the emergency services. In the traditional system, the ambulance paramedics had to deal with all emergency calls throughout a 24-h shift (T-shift). In the modified system, 2 ambulance paramedics were allotted time for naps in the 21:00-3:00 (C-shift) or 3:00-8:30 (B-shift) shift by the addition of another a firefighter (D-shift). RESULTS: There were fewer emergency dispatches and nap time was longer in the B- and C-shifts than in the T-shift. Parasympathetic nerve activities during naps in B- and C-shifts were higher than in the T-shift. The results of critical flicker fusion frequency and 3-choice reaction time in the B-shift at 7:30 tended to be higher and shorter than that in T-shift. CONCLUSIONS: The results of this study suggest that the modified night shift which ensured time for ambulance paramedics to take long, restful power naps alleviated subjective fatigue, and improved physiological functions which are often adversely affected by night workload.

Effects of adjustable sit-stand VDT workstations on workers' musculoskeletal discomfort, alertness and performance.

Adjustable sit-stand workstations, which are designed to allow workers to sit and stand autonomously while working, were examined to identify the effects on workers' musculoskeletal discomfort, alertness and performance. Twenty-four healthy subjects participated in the study. The subjects were required to do an English transcription task for 150 min under the following conditions: 1) sitting at standard workstations (Standard), 2) sitting on a chair with the work surface elevated to standing position (High-chair) and 3) a combination of 10-min sitting and 5-min standing with the same setting as that in the high-chair condition (Sit-stand). The subjective musculoskeletal discomfort scores indicated that High-chair and Sit-stand resulted in relatively higher discomfort levels than the Standard condition. Although the ratio between low-frequency (0.04-0.15 Hz) and high-frequency (0.15-0.4 Hz) components of heart rate variability (LF/HF ratio) in Sit-stand was higher than that in other conditions, there were no significant differences in subjective sleepiness among the three conditions. As for work performance, there was a tendency to be steadily high under the Sit-stand condition compared with other conditions, but not a significant difference. This study revealed that although the use of sit-stand workstations can contribute to keeping workers' arousal level steady, it has an adverse effect in light of musculoskeletal discomfort.

[Characteristic patterns of fatigue feelings on four simulated consecutive night shifts by "Jikaku-sho shirabe"].

The aim of the present study was to reveal characteristic patterns of fatigue feelings on consecutive night shifts by a questionnaire for work-related fatigue feelings "Jikaku-sho shirabe". Ten healthy males (Mean +/- SD: 22.9 +/- 3.2 years old) participated in the experiment. Participants were required to attend the laboratory for nine consecutive nights under the following conditions: adaptation sleep (0:00-7:00), simulated day shift (10:00-18:00), baseline sleep (0:00-7:00), directly followed by four simulated night shifts (22:00-9:00) and the subsequent daytime sleep (12:00-18:00), three recovery nights (0:00-7:00) and two simulated day shifts (10:00-18:00). During each simulated shift, participants were required to complete an English transcription task (30 min), a performance test battery (20 min) and break (10 min) every hour. Fatigue feelings were evaluated by "Jikaku-sho shirabe", which was proposed by the Industrial Fatigue Research Committee of the Japan Occupational Health in 2002. This questionnaire consists of 25 subjective fatigue symptom items that are categorized into 5 factors: feeling of drowsiness (Factor I), feeling of instability (Factor II), feeling of uneasiness (Factor III), feeling of local pain or dullness (Factor IV), and feeling of eyestrain (Factor V). For each item, respondents are requested to estimate the intensity of the feelings as "Disagree at all," "Agree scarcely," "Agree slightly," "Agree considerably," and "Agree strongly." These five intensities were assigned scores of 1 to 5 points, respectively. Hierarchical cluster analysis suggested that there might be at least three variation patterns of fatigue feelings on the consecutive night shifts (i.e. Clusters A, B and C). On the basis of subjective fatigue symptom items of each cluster, the patterns in Clusters A, B and C might reflect the loads of the reticular activating system, musculoskeletal and central nervous systems, and limbic system, respectively. For Clusters A and C, significant improvements were observed with the increase of the number of night shifts (F(11,99)=3.07, p<0.01, F(11,99)=3.37, p<0.01, respectively). On the other hand, Cluster B deteriorated with the progress of the simulated night shifts. Taken together, we suggest that the characteristic patterns of fatigue feelings on consecutive night shifts might represent dissociation among the feelings induced by several loads.

Impact of nap length, nap timing and sleep quality on sustaining early morning performance.

The study examined how nap length, nap timing and sleep quality affect early morning performance (6:00 to 8:00). Twelve students participated in a simulated nightshift schedule (22:00 to 8:00) where the length and timing of nocturnal naps were manipulated (0:00-1:00, 0:00-2:00, 4:00-5:00 and 4:00-6:00). A performance test battery was administered consisting of a psychomotor vigilance test, a logical reasoning test, and a visual analogue scale for subjective fatigue and sleepiness. The results showed that a 120-min nap sustained early morning performance better than a 60-min nap. Taking a nap earlier or later did not affect the neurobehavioral performance tests, although participants slept more efficiently during naps later in the night shift. A negative effect of a nocturnal nap during the night shift on subsequent daytime and nocturnal sleep was not observed in the sleep architecture. It still remains unclear whether slow wave sleep plays an important role in sustaining early morning performance. In terms of work safety and sleep health, the results suggest that a longer and later nap is beneficial during night shifts.

Impact of ISO/TS 20646-1 "Ergonomic procedures for the improvement of local muscular workloads" on work-related musculoskeletal disorders.

The International Organization for Standardization (ISO) published a new Technical Specification (TS), ISO/TS 20646-1 "Ergonomic procedures for the improvement of local muscular workloads (LMWL)--Part 1: Guidelines for reducing local muscular workloads" in 2004. However, little is known about whether the ISO/TS is really effective in taking action to improve the work conditions in real workplaces. This paper discussed the impact of preventive activities planned and carried out according to the ISO/TS in 17 enterprises. Results indicated that 61 improvements (96%) had already been implemented (63%) or in progress (33%) within 6 months of the start of the activities. Besides the initial improvements, new improvements added within one year reached 84 cases and 10 cases were in progress in 15 enterprises. Comprehensive risk analysis, which consisted of a series of applications of action oriented checklist and group discussions, contributed to the detection of widely diversified risks in each local workplace, and this seems to lead to sustainable activities for prevention of WMSDs. These results suggest that the ISO/TS 20646-1 help managers and workers to control multiple work-related musculoskeletal disorder (WMSD) risks on their own initiative and promote sustainable activities.

Evaluation of the effects of a health education program on the improvement of hypercholesterolemia.

This study examined the effects of a health education program based on the self- reliance and self-action philosophy and the use of group work methodology on hypercholesterolemia during and after the intervention period. Thirty-two people participated in the study. Measurement values were obtained at the commencement of the intervention (Baseline), during the 6-month intervention period, at the end of the 6-month intervention period (Middle Point) and 6 months after Middle Point (End Point). The average number of steps per day significantly increased during the 6-month intervention period. The energy intake and fat intake levels significantly decreased during the 6-month intervention period. Total cholesterol, triglyceride, and atherosclerosis-index levels significantly decreased between Baseline and End Point. The HDL cholesterol levels significantly increased between Baseline and End Point. Statistically significant decrease was also observed in total cholesterol and atherosclerosis-index levels between Baseline and Middle Point, and between Middle Point and End Point. It is concluded that the health education program based on self-reliance and self-action philosophy using a group work methodology is effective for improving hypercholesterolemia. Especially, the improvement in the serum total cholesterol and atherosclerosis-index levels was sustained even after the intervention period.

Moisture and mineral content of human feces--high fecal moisture is associated with increased sodium and decreased potassium content--.

BACKGROUND: The origin of moisture in diarrhea feces is unknown but may represent the unabsorbed part of intestinal contents or alternatively, body fluid excreted into the digestive canal. If the latter mechanism contributes to moisture in the feces, active transport of water (H2O) associated with ion exchange channels may be involved. OBJECTIVE: To investigate this possibility we measured the content of moisture and minerals (sodium [Na], potassium [K], calcium [Ca], magnesium [Mg], phosphorus [P], zinc [Zn], iron [Fe], copper [Cu] and manganese [Mn]) in feces collected during a 12-d metabolic study on 11 young Japanese female students. DESIGN: The study was carried out as part of a human mineral balance study. The same quantity of food was supplied to each of the subjects throughout the study without consideration of body weight. Fecal specimens were collected throughout the study and were separated into those originating from the diet during the balance period based on the appearance of the ingested colored marker in the feces. RESULTS: The moisture content of the feces ranged between 53 and 92%. Na content in the feces was low and stable when the moisture content was below 80%, whereas it increased up to serum levels when the moisture content increased above 80%. On the other hand, K content increased when compared to dry matter base. However, when comparing concentration/g moisture, K content increased when moisture was below 70%, but decreased when this rose above 70%.

Approaches to occupational health based on participatory methodology in small workplaces.

An intervention based on the methodology developed by the International Labour Office, the Work Improvement in Small Enterprises (WISE) was carried out to improve work condition of small-scale enterprises and the informal sector in the Philippines, Thailand and Japan. Through the evaluation of the efficacy of the approaches based on participatory methodology, it is concluded that the method is an efficient measure to improve work condition in small workplaces. It is also pointed out that the activities of supporting experts such as introduction of the methodology and evaluation of the activity are necessary. The important roles of the experts are 1) to encourage managers and workers to sustain the activities for work improvement, 2) to analyse the effectiveness and problems of the implemented improvements, 3) to give appropriate suggestions for the further improvement, and 4) to get materials for demonstrating the effectiveness of WISE activities on improving work conditions and productivity to other managers and workers who have not participated in the activity.

A case study on evaluations of improvements implemented by WISE projects in the Philippines.

The aim of this study is to evaluate the effects of work improvements in small enterprises (WISE) on workloads and productivity, and managers' satisfaction with those projects. Participating in this study from 1994 to 1996 were 9 small enterprises, 3 metal industries, 1 car parts manufacturing, 1 garment manufacturing, 1 food processing, and a few others. Upon visiting these worksites, we carried out interviews on the implemented WISE improvements and made objective evaluations of their effect on workloads and productivity. Reductions in physical workloads were found in 4 of 6 enterprises where that factor was estimated. Productivity in most of the enterprises increased after WISE improvements. Managers' subjective satisfaction with WISE activity ranged between 50-80% on each technical item. More than 50 percent of managers came to understand the necessity of workers' involvement and understanding of the activities in order to sustain activity for improvement. WISE activity can exert a beneficial influence on workload and productivity. Most of the managers were satisfied with the results. It is presumed that follow-up visits with objective estimation will provide both managers and workers with encouragement to maintain their efforts.

Achievement of the POSITIVE (Participation-Oriented Safety Improvement by Trade Union InitiatiVE) activities in the Philippines.

The POSITIVE (Participation-oriented safety improvement by trade union initiative) programme was introduced into the Philippines in 1995. The monitoring of activities was carried out in 2004 among core trainers who had been trained before. The results of the questionnaire survey showed that the core trainers evaluated their activities satisfactory in general, and particularly the training activities were considered excellent. Also, the union workers who had been trained by the POSITIVE programme implemented improvements at the rate of around 5 examples a year on average. It was of note that the installation ratio (the number of installations/that of plans) was higher in small- and medium-sized enterprises than in larger companies, although the numbers of plans and installations of improvements were greater in large enterprises. Together with the previous findings, the present results suggest that the POSITIVE-style participatory training program is effective and efficient for workers to take actions for the OSH in not only larger enterprises but also small enterprises.

Equilibrium intakes of calcium and magnesium within an adequate and limited range of sodium intake in human.

In the previous analysis of our human mineral balance studies, we demonstrated positive correlations between the balances of calcium (Ca) and magnesium (Mg) and sodium (Na) intake in the range of 3.06 and 4.06 g/d or 43.71 and 96.40 mg/kg body weight (BW)/d, but there was no correlation between Na intake and Na balance. This suggested that the balances of Ca and Mg are affected by Na intake. Therefore, in the current study, we recalculated equilibrium intakes for Ca and Mg when balances of their intakes and outputs were equal to zero within the above Na range to reduce the effects of Na intake. From 1986 to 2000, 90 volunteers (10 male, 80 female; age 18 to 28 y) took part in 9 mineral balance studies. The balance periods ranged from 8 to 12 d, with adaptation periods of 2 to 4 d. The dietary intakes of Ca and Mg ranged from 294 to 719 and 154 to 334 mg/d, or from 4.83 to 15.07 and 2.44 to 6.42 mg/kg BW/d, respectively. Intake of Ca significantly correlated with Ca balance (r2 = 0.268; p < 0.0001). When the balance was equal to zero, the mean value and upper limit of the 95% confidence interval for the regression equation between intake vs. balance were 10.072 and 10.660 mg/kg BW/d, respectively. Mg intake correlated significantly with Mg balance (r2 = 0.141, p = 0.003). When the balance was equal to zero, the mean value and upper limit of the 95% confidence interval for the regression equation between intake and balance were 4.078 and 4.287 mg/kg BW/d, respectively.

Positive correlation between dietary intake of sodium and balances of calcium and magnesium in young Japanese adults--low sodium intake is a risk factor for loss of calcium and magnesium--.

The content of calcium (Ca) and magnesium (Mg) in sweat during exercise is considerably higher during a relatively low intake of sodium (Na) of 100 mmol/d than with an intake of 170 mmol/d. For this reason and also because Ca and Mg have a negative balance with a Na intake of 100 mmol/d, we analyzed the relationship between Na intake and balances of Ca and Mg in data from 11 balance studies. From 1986 to 2000, 109 volunteers (23 males, 86 females) with an age range of 18 to 28 y took part in mineral balance studies. The balance periods ranged from 5 to 12 d. In a given experiment, the diet of each subject contained the same quantity of food, although this varied between experiments, and was supplied during the balance period without consideration of body weight. In the data of all the studies (n= 109), the balances of Ca and Mg did not correlate positively with Na intake. However, when the data of the highest Na study were excluded, the balances of Ca and Mg correlated positively with Na intake. The mean value for the regression equation between Na intake and Ca and Mg balances when the respective balance was equal to zero were, 63.308 mg Na/kg BW/d (Ca: n=96, r2=0.134) and 60.977 mg Na/kg BW/d (Mg: n=96, r2=0.268), respectively. These values are considerably higher than Na requirements estimated by inevitable Na loss. Low dietary Na may therefore be a risk factor for maintaining positive balances of Ca and Mg.

Sodium and potassium balances in Japanese young adults.

This study was conducted to estimate the requirements of sodium (Na) and potassium (K) in Japanese young adults. From 1986 to 2000, 109 volunteers (23 males, 86 females), ranging from 18 to 28 y old, took part in 11 mineral balance studies after written informed consent had been obtained. The duration of the study periods ranged from 5 to 12 d, with a 2-4 d adaptation period. Foodstuffs used in each study were selected from those commercially available. The Na and K content of the diet, feces, urine and sweat were measured by atomic absorption spectrophotometer. The results of a study in which Na intake was 6.87 g/d (ca. 300 mmol/d), the highest of all the studies, showed apparent positive Na balances. In contrast, another study in which Na intake was 2.21 g/d (ca. 100 mmol/d), the lowest of all the studies, showed apparent negative Na balances. These two studies seemed to differ from the other studies, as shown by regression equations calculated from either data of all the studies (n= 109) or data that did not include the two studies (n=90). The dietary intakes of Na and K ranged between 38.56-142.23 and 26.77-74.42 mg/kg body weight (BW)/d, or 2.21-6.87 and 1.83-3.61 g/d, respectively in the complete data, and 43.71-96.40 and 26.77-63.70 mg/kg BW/d, or 3.06-4.06 and 1.83-2.68 g/d, respectively in the data that did not include the two studies. The intakes of the two minerals were positively correlated. Na intake (Intake) was correlated positively with apparent absorption (AA) of Na, which was also correlated with Na urinary output (Urine). In the data that did not include the two studies, Na balance (Balance) was not correlated significantly with either Na Intake (r2=0.005) or AA of Na (r2=0.006). However, analysis of all the data showed a significant correlation between Na Balance and both Na Intake (r2=0.361) and AA of Na (r2=0.360). In the complete data, the mean value and upper and lower limits of the 95% confidence interval for the regression equation between Intake and Balance for Na, when balance was equal to zero (i.e mean, upper and lower limits), were 55.824, 60.787 and 50.862 mg/ kg BW/d, respectively. K Intake was correlated positively with AA of K, which was also correlated with both Urine K and K Balance. There was a significant correlation between K Intake and K Balance in both the complete data (r2=0.213) and the data that did not include the two studies (r2 = 0.116). In all the cases, mean, upper and lower limits for K were 39.161, 41.782 and 36.540 mg/kg BW/d, respectively. Intakes of Na and K did not correlate with their respective AA rates (%). Within the ranges of K Intake in this study, K Balance was affected markedly by K Intake itself as well as by Na Intake. However, in the case of Na, when the data of the highest and lowest Na intake studies were excluded from the analysis, Na Balance did not correlate with Na Intake, whereas the data of all the studies showed Na Balance was affected strongly by Na Intake. The data of this study allowed the estimated average requirements (EARs) for both minerals to be derived.

The nighttime nap strategies for improving night shift work in workplace.

Nighttime napping is an effective measure to prevent adverse effects due to night shift work. A characteristic of nighttime nap is that it can result in considerably deeper sleep. Several studies have shown that taking nighttime naps suppressed increasing sleepiness, decreasing alertness during the period following awaking from a nap, and prevented disturbance of circadian rhythm ("anchor sleep"). The length of daytime sleep after night shift, when combined with a nighttime nap, is shorter than that without nap. This finding might be interpreted as a beneficial effect rather than a negative feature because workers can then spend time engaged in other activities rather than sleeping. Nevertheless, the introduction of nighttime sleep break in the workplace has not been widely accepted. To promote nighttime napping strategy in the workplace, consensus building while acting on conflicting interest is essential. Recently, participatory method for improvement of working condition has expanded worldwide. A characteristic of the activity is using action checklist and group work, and heightening motivation to improvement working condition between worker and manager. Through the activities, nighttime napping strategy would be spread more in the workplaces and play a role as one of the effective tools for improving working conditions, work performance and safety in the future.

Effects of the length and timing of nighttime naps on task performance and physiological function.

OBJECTIVE: To examine the effects of the length and timing of nighttime naps on performance and physiological functions, an experimental study was carried out under simulated night shift schedules. METHODS: Six students were recruited for this study that was composed of 5 experiments. Each experiment involved 3 consecutive days with one night shift (22:00-8:00) followed by daytime sleep and night sleep. The experiments had 5 conditions in which the length and timing of naps were manipulated: 0:00-1:00 (E60), 0:00-2:00 (E120), 4:00-5:00 (L60), 4:00-6:00 (L120), and no nap (No-nap). During the night shifts, participants underwent performance tests. A questionnaire on subjective fatigue and a critical flicker fusion frequency test were administered after the performance tests. Heart rate variability and rectal temperature were recorded continuously during the experiments. Polysomnography was also recorded during the nap. RESULTS: Sleep latency was shorter and sleep efficiency was higher in the nap in L60 and L120 than that in E60 and E120. Slow wave sleep in the naps in E120 and L120 was longer than that in E60 and L60. The mean reaction time in L60 became longer after the nap, and faster in E60 and E120. Earlier naps serve to counteract the decrement in performance and physiological functions during night shifts. Performance was somewhat improved by taking a 2-hour nap later in the shift, but deteriorated after a one-hour nap. CONCLUSIONS: Naps in the latter half of the night shift were superior to earlier naps in terms of sleep quality. However performance declined after a 1-hour nap taken later in the night shift due to sleep inertia. This study suggests that appropriate timing of a short nap must be carefully considered, such as a 60-min nap during the night shift.

Effects of the length and timing of nighttime naps on task performance and physiological function

OBJETIVO: Para investigar os efeitos da duração e horário de cochilos noturnos sobre o desempenho e as funções fisiológicas foi realizado um estudo experimental por meio do trabalho noturno simulado. MÉTODOS: Seis estudantes foram recrutados para o estudo que consistiu de cinco experimentos. Cada experimento consistia de três dias consecutivos com um turno noturno (22:00-8:00h) seguido por um período de sono diurno e noturno. Os experimentos compreendiam cinco condições em que a duração e o horário dos cochilos eram manipulados: 0:00-1:00 (E60), 0:00-2:00 (E120), 4:00-5:00 (L60), 4:00-6:00 (L120) e sem cochilo (N-nap). Durante os turnos noturnos, os participantes foram submetidos a testes de desempenho. Um questionário sobre cansaço subjetivo e um teste de freqüência crítica de luz foram aplicados depois dos testes de desempenho. A variabilidade da freqüência cardíaca e a temperatura retal foram registrados continuamente durante os experimentos. Polissonografia também foi realizada durante o cochilo. RESULTADOS: A latência de sono foi menor e a eficiência do sono maior no cochilo em L60 e L120 que em E60 e E120. O sono de ondas lentas nos cochilos em E120 e L120 foi mais longo que em E60 e L60. O tempo médio de reação em L60 ficou mais longo depois do cochilo e mais rápido em E60 e E120. Os cochilos em horário mais cedo serviram para neutralizar a queda no desempenho e funções fisiológicas durante o turno noturno. Houve uma ligeira melhora do desempenho ao se tirar um cochilo de duas horas num horário mais tarde durante o turno, mas houve piora depois de um cochilo de uma hora. CONCLUSÕES: Os cochilos na última metade do turno noturno foram melhores em termos de qualidade de sono do que os cochilos em um horário mais cedo. O desempenho, no entanto, piorou depois de um cochilo de uma hora em um horário mais tarde durante o turno por causa da inércia do sono. O estudo indica que o horário adequado de um cochilo curto deve ser cuidadosamente considerado, tal como um cochilo de 60 minutos durante o turno noturno.

Balances of calcium, magnesium and phosphorus in Japanese young adults.

This study was conducted to estimate the requirements of calcium (Ca), magnesium (Mg) and phosphorus (P) in Japanese young adults. From 1986 to 2000, 109 volunteers 123 males, 86 females), ranging from 18 to 28 y old, took part in mineral balance studies after written informed consent was obtained. The duration of the study periods ranged from 5 to 12 d, with 2-4 d of adaptation. Foodstuffs used in each study were selected from those commercially available. The minerals present in diet, feces, urine and sweat were measured by atomic absorption spectrophotometer (Ca, Mg) or spectrophotometer (P). The dietary intakes of Ca, Mg and P ranged from 4.83-23.58, 2.44-7.83 and 13.46-45.69 mg/ kg BW/d, respectively. Dietary intake (Intake) of Ca was positively correlated to apparent absorption (A.A.) (r2 = 0.425), which was also correlated with urine excretion (Urine) (r2 = 0.327) and balance (Bal) (r2 = 0.382). Intake of Ca was slightly but significantly correlated with Bal (r2 = 0.036, p = 0.048). The mean value and upper limit of the 95% confidence interval for the regression equation between Intake and Bal when balance is equal to zero (Mean and upper limit) for Ca were 11.752 and 12.555 mg/kg BW/d, respectively. Intake of Mg was positively correlated to A.A. (r2 = 0.451), which was also correlated with Urine (r2 = 0.486) and Bal (r2 = 0.349). However, Intake of Mg was not correlated with Bal. Intake of P was positively correlated with A.A. (r2 = (0.959), which was also correlated with both Urine (r2 = 0.908) and Bal (r2 = 0.135). Intake of P was slightly but significantly correlated with Bal (r2 = 0.103, p = 0.0013). Mean and upper limits for P were 22.584 and 24.059 mg/kg BW/d, respectively. Intakes of Mg and P correlated negatively with their respective A.A. rates (%) (r2 = 0.120 for Mg, r2 = 0.109 for P). However, there was not much of a correlation for Ca. Balance of Ca was positively correlated with that of Mg (r2 = 0.541), but not with that of P.