Manual rolling load and low back pain among workers in Japan: a cross-sectional study.

OBJECTIVES: Manual rolling of heavy objects remains in the workplace. The Health and Safety Executive (HSE) in the United Kingdom recommends load weights of <400 kg in the rolling task. However, the association of rolling weights <400 kg with work-related low back pain (LBP) has not been sufficiently investigated. This study examined the effect of rolling loads weighing <400 kg on LBP among Japanese workers. METHODS: A web-based survey gathered information from 15 158 workers in 2022. Among them, 15 035 did not handle loads, whereas 123 handled rolling weights <400 kg. Load weight was categorized into 4 groups: no-handling (0 kg) and rolling weights of ≤20, 20-40, and >40 kg. Multiple logistic regression analysis examined the association between the subdivided rolling weight and LBP. RESULTS: No significant differences in odds ratio (OR) of LBP were found for workers handling ≤40 kg rolling weights compared with that for no-handling workers. However, workers handling >40 kg rolling weights had a significantly greater OR of LBP than those not handling loads. CONCLUSIONS: Rolling weights between 40 and 400 kg could place a high stress on the lower back. Implementation in Japan of the HSE recommendations regarding rolling load should be carefully considered.

Effect of occupational pushing and pulling combined with improper working posture on low back pain among workers.

This study aimed to investigate the impact of occupational pushing and pulling combined with improper working posture on work-related low back pain (LBP) among workers. A web-based survey was conducted in 2022 to collect data from 15,623 workers, who were categorized into proper and improper working posture groups. Multiple logistic regression analysis was used to analyze the association between pushing and pulling loads and LBP in each group. In the proper working posture group, the odds ratios (ORs) of LBP for workers who pushed and pulled were not significantly different compared with those of no-handling workers. However, in the improper working posture group, the ORs of LBP were significantly greater among workers who pushed and pulled compared with those of no-handling workers, and this association became stronger with increasing weights. Therefore, improper working posture combined with pushing and pulling were strongly associated with LBP among workers, particularly with heavier weights.

Effect of relative weight limit set as a body weight percentage on work-related low back pain among workers.

INTRODUCTION: A quarter of work-related low back pain (LBP) cases result from handling heavy loads in Japan. The maximum weight male/female workers can handle is 40%/24% of their body weight but has set a constant load weight in ISO 11228-1 and NIOSH lifting equation. The preventive effect of the relative weight limit on LBP has not been clarified. This study aimed to identify the effect of relative weight limits set as body weight percentages on LBP prevalence. METHODS: Data from 21924 workers were collected via a web-based survey in 2022. The workers were categorized into three groups: group A, "no handling," group B, "handling loads up to 40%/24% or less of body weight," and group C, "handling loads over 40%/24% of body weight." Moreover, they were categorized into eight groups: no handling, 1-5 kg, 5-10 kg, 10-15 kg, 15-20 kg, 20-25 kg, 25-30 kg, and ≥30 kg. Multiple logistic regression analysis was used to identify the effects of the limits set to body weight percentages and constant load weights on LBP. RESULTS: In groups A, B, and C, 25.5%, 39.2%, and 47.3% of males or 16.9%, 26.4%, and 38.0% of females had LBP, respectively. The odds ratio (OR) of LBP was significantly greater in group B than in group A and even greater in group C. The OR of LBP among workers handling loads under 10 kg was not significantly different compared to no-handling workers. CONCLUSIONS: LBP prevalence was greater in group B than in group A but lesser than in group C. Weight limits based on body weight percentages could not eliminate the factor of handling loads. However, handling loads under 10 kg suppressed LBP. Relative weight limits set as body weight percentages were inappropriate and ineffective for preventing LBP.

Relationship between using tables, chairs, and computers and improper postures when doing VDT work in work from home.

This study focused on everyday furniture and computers used in work from home and aimed to investigate how improper postures increase the risk of musculoskeletal disorders using different combinations of tables, chairs, and computers. Twenty-one healthy participants were asked to perform a visual display terminal task for 30 minutes in a laboratory modeled on the work from home concept. Seven experimental conditions were set up according to the different combinations of desks, chairs, and computers. Three-dimensional body posture was measured using a magnetic tracking device. The results showed that when using a low table, floor chair, and laptop computer, the body posture above the hip was similar to that when using a dining table, chair, and desktop computer. When using a sofa, and tablet computers, or laptop computer, severe neck flexion, which is stressful to the neck, was observed. Moreover, excessive low back flexion was observed when using a floor cushion and laptop computer. We suggest that computer work while sitting on a sofa or floor cushion without a backrest is harmful to the neck and low back.

Effects of short sleep duration on hemodynamic and psychological responses under long working hours in healthy middle-aged men: an experimental study.

This study examined the effects of short sleep duration (SSD) on hemodynamic and psychological responses under long working hours (LWH) in a laboratory experiment. Sixteen subjects participated in a crossover design experiment consisting of two conditions: normal (7-hours) sleep and short (5-hours) sleep. In each condition, participants engaged in simulated LWH (13 hours a day), comprising 12 task sessions. Hemodynamic and psychological responses were measured in each session. Results showed that there were significant main effects of condition and session but no interaction for hemodynamic and psychological responses. Systolic blood pressure and fatigue were higher in the later sessions than the first one. Stroke volume, sleepiness, fatigue, and stress were higher in the 5-hour than the 7-hour sleep condition (all p<0.05). These results suggest that although the combined effect of LWH and SSD was not significant, both LWH and SSD caused a hemodynamic and psychological burden.

Haemodynamic responses to simulated long working hours in different age groups.

OBJECTIVES: This study aimed to clarify haemodynamic responses of different age groups to simulated long working hours. METHODS: Men of three age groups participated in this study (16 in their 30s (mean 33.9±2.7 years old), 15 in their 40s (45.5±2.9) and 16 in their 50s (54.1±2.7)). All participants conducted 12 45-min personal computer-based tasks from 09:00 to 22:00. Nine 10-min to 15-min breaks between task periods, a 1-hour break at noon, and a 50-min break in the evening were provided. Haemodynamic responses were measured during task periods. All participants had normal resting systolic blood pressure (SBP <140 mm Hg) and diastolic blood pressure (DBP<90 mm Hg), which were measured before tasks started in the morning. Two-way repeated-measures analysis of variances and multiple comparisons (Bonferroni) were conducted. RESULTS: No haemodynamic indices were significantly different among groups at baseline. Compared with baseline, SBP was almost unchanged for the 30s group but increased for the 40s and 50s groups during task periods. The 50s group showed higher SBP compared with the 30s group especially in the latter half of the working hours (p<0.05). In addition, the 50s group also showed higher total peripheral resistance (TPR) than the 30s group (p<0.1). CONCLUSION: The 50s group showed higher SBP and TPR responses than the 30s group, especially in the latter half of working hours. These results suggest that older workers might suffer more cardiovascular damage related to long working hours.

Hemodynamic Responses to Simulated Long Working Hours with Short and Long Breaks in Healthy Men.

This study aimed to examine hemodynamic responses and the necessity of breaks under long working hours. Thirty-eight healthy males conducted PC-based work from 9:10 to 22:00. Nine 10-minute short breaks and two long breaks (a 1-hour break and a 50-minute break) were provided, and hemodynamic responses were measured regularly during this period. The results showed that systolic blood pressure increased during the working hours and cardiovascular burden increased under long working hours. Cardiac responses decreased, but vascular responses increased continually during work periods without long breaks. The long breaks, however, benefitted workers by preventing excessive decreases in cardiac responses and increases in vascular responses, but this effect may decrease with the extension of working hours. In conclusion, long working hours increase cardiovascular burden, and taking long breaks is important for reducing these burdens when long working hours cannot be avoided.

Comparison of hemodynamic responses between normotensive and untreated hypertensive men under simulated long working hours.

Objectives The present study examined hemodynamic responses of normotensive and untreated hypertensive participants under simulated long working hours (LWH) - 13 hours - in an experimental laboratory study. Methods Thirty-five men participated in this study. Twenty-two of these participants were categorized into the normotensive group (systolic blood pressure (SBP) ≤140 mmHg and diastolic blood pressure (DBP) ≤90 mmHg); one participant was excluded due to missing data, leaving twenty-one participants with a mean age of 49.2 years. Another thirteen participants were categorized into the high blood pressure group (SBP=140-160 mmHg or DBP=90-100 mmHg) with a mean age of 51.9 years. The hemodynamic responses at the resting state from 09:00-09:10 hours (baseline) and during LWH from 09:10-22:00 hours (12 sessions) were measured. In each session, participants performed mental tasks. Changes in the hemodynamic response (Δ) were calculated by subtracting the individual values at each session from the baseline values. Results The values for the ΔSBP, ΔDBP, and Δmean arterial pressure increased with work time. Additionally, we found a significant interaction between the group and sessions for the ΔSBP (P<0.05, partial η 2=0.086). Although ΔSBP values did not differ between the groups at first (09:10-14:30 hours), the values in later sessions (14:40-21:50 hours) were significantly higher in the high blood pressure compared to the normotensive group. Conclusions Our study found that LWH increases BP, with a larger increase in SBP in the later working hours among individuals with untreated hypertension, whereas other hemodynamic responses did not differ between groups as a function of the LWH.

Cathodal transcranial direct-current stimulation over right posterior parietal cortex enhances human temporal discrimination ability.

BACKGROUND: Time perception associated with durations from 1 s to several minutes involves activity in the right posterior parietal cortex (rPPC). It is unclear whether altering the activity of the rPPC affects an individual's timing performance. Here, we investigated the human timing performance under the application of transcranial direct-current stimulation (tDCS) that altered the neural activities of the rPPC. METHODS: We measured the participants' duration-discrimination threshold by administering a behavioral task during the tDCS application. The tDCS conditions consisted of anodal, cathodal, and sham conditions. The electrodes were placed over the P4 position (10-20 system) and on the left supraorbital forehead. On each task trial, the participant observed two visual stimuli and indicated which was longer. The amount of difference between the two stimulus durations was varied repeatedly throughout the trials according to the participant's responses. The correct answer rate of the trials was calculated for each amount of difference, and the minimum amount with the correct answer rate exceeding 75% was selected as the threshold. The data were analyzed by a linear mixed-effects models procedure. RESULTS: Nineteen volunteers participated in the experiment. We excluded three participants from the analysis: two who reported extreme sleepiness while performing the task and one who could recognize the sham condition correctly with confidence. Our analysis of the 16 participants' data showed that the average value of the thresholds observed under the cathodal condition was lower than that of the sham condition. This suggests that inhibition of the rPPC leads to an improvement in temporal discrimination performance, resulting in improved timing performance. CONCLUSIONS: In the present study, we found a new effect that cathodal tDCS over the rPPC enhances temporal discrimination performance. In terms of the existence of anodal/cathodal tDCS effects on human timing performance, the results were consistent with a previous study that investigated temporal reproduction performance during tDCS application. However, the results of the current study further indicated that cathodal tDCS over the rPPC increases accuracy of observed time duration rather than inducing an overestimation as a previous study reported.

Additive Effects of Sinusoidal Lower Body Negative Pressure on Cardiovascular Responses.

BACKGROUND: Sinusoidal lower body negative pressure (SLBNP) has been used to investigate the cardiovascular response to slow periodic changes in blood shifts, but measurements of slow fluctuations take a long time if measured for each period of SLBNP separately. Our study aimed to investigate whether the cardiovascular responses to superimposed SLBNP (S-SLBNP), which is expected to reduce the measurement time, are different from responses measured individually. METHODS: S-SLBNP was configured by superimposing two conventional SLBNPs (C-SLBNP) at 180-s and 30-s periods in the pressure range from 0 to -25 mmHg. As the S-SLBNP has double the static load of C-SLBNP, we also used offset SLBNP (O-SLBNP), which has the same static load level as S-SLBNP. Heart rate (HR), thoracic impedance (Z0), and mean arterial pressure (MAP) were measured from 11 male subjects. The transfer functions of gains from MAP to HR (Gain-HR/MAP) and from Z0 to HR (Gain-HR/Z0) were calculated as indexes of arterial baroreflex and cardiopulmonary baroreflex regulation of HR, respectively. RESULTS: The Gain-HR/MAP in the 180-s period (2.11 ± 0.17 bpm/mmHg; mean ± SEM) was larger than that of the 30-s period (1.04 ± 0.09 bpm/mmHg); however, there was no significant difference between the SLBNP conditions. The Gain-HR/Z0 in C-SLBNP (9.37 ± 1.47 bpm/ohm) was smaller than that of the other conditions [18.46 ± 2.45 bpm/ohm (O-SLBNP); 16.09 ± 2.29 bpm/ohm (S-SLBNP)]. DISCUSSION: Using S-SLBNP could reduce the measurement time needed to examine the arterial baroreflex. However, the cardiopulmonary baroreflex was modified by the static load of SLBNP.Ishibashi K, Oyama F, Yoshida H, Iwanaga K. Additive effects of sinusoidal lower body negative pressure on cardiovascular responses. Aerosp Med Hum Perform. 2017; 88(2):137-141.