Trained humans can exercise safely in extreme dry heat when drinking water ad libitum.

Guidelines to establish safe environmental exercise conditions are partly based on thermal prescriptive zones. Yet there are reports of self-paced human athletic performances in extreme heat. Eighteen participants undertook a 25-km route march in a dry bulb temperature reaching 44.3°C. The mean (± s) age of the participants was 26.0 ± 3.7 years. Their mean ad libitum water intake was 1264 ± 229 mL · h(-1). Predicted sweat rate was 1789 ± 267 mL · h(-1). Despite an average body mass loss of 2.73 ± 0.98 kg, plasma osmolality and serum sodium concentration did not change significantly during exercise. Total body water fell 1.47 kg during exercise. However, change in body mass did not accurately predict changes in total body water as a 1:1 ratio. There was a significant relationship (negative slope) between post-exercise serum sodium concentration and changes in both body mass and percent total body water. There was no relationship between percent body mass loss and peak exercise core temperature (39 ± 0.9°C) or exercise time. We conclude that participants maintained plasma osmolality, serum sodium concentration, and safe core temperatures by (1) adopting a pacing strategy, (2) high rates of ad libitum water intake, and (3) by a small reduction in total body water to maintain serum sodium concentration. Our findings support the hypothesis that humans are the mammals with the greatest capacity for exercising in extreme heat.

Protection of total body water content and absence of hyperthermia despite 2% body mass loss ('voluntary dehydration') in soldiers drinking ad libitum during prolonged exercise in cool environmental conditions.

The extent to which humans need to replace fluid losses during exercise remains contentious despite years of focused research. The primary objective was to evaluate ad libitum drinking on hydration status to determine whether body mass loss can be used as an accurate surrogate for changes in total body water (TBW) during exercise. Data were collected during a 14.6-km route march (wet bulb globe temperature of 14.1°C ). 18 subjects with an average age of 26 ± 2.5 (SD) years participated. Their mean ad libitum total fluid intake was 2.1 ± 1.4 litres during the exercise. Predicted sweat rate was 1.289 ± 0.530 l/h. There were no significant changes (p>0.05) in TBW, urine specific gravity or urine osmolality despite an average body mass loss (p<0.05) of 1.3 ± 0.45 kg during the march. Core temperature rose as a function of marching speed and was unrelated to the % change in body mass. This suggests that changes in mass do not accurately predict changes in TBW (r=-0.16) because either the body mass loss during exercise includes losses other than water or there is an endogenous body water source that is released during exercise not requiring replacement during exercise, or both. Ad libitum water replacement between 65% and 70% of sweat losses maintained safe levels of hydration during the experiment. The finding that TBW was protected by ad libitum drinking despite approximately 2% body mass loss suggests that the concept of 'voluntary dehydration' may require revision.

Human serum albumin interference on plasmon-based immunokinetic assay for antibody screening in model blood sera.

The effect of human serum albumin (HSA) on an immunokinetic assay for an antibody to bovine serum albumin has been determined in model serum solutions with HSA concentrations in the range 0 to 450 microM (0-30 mgml(-1)). The assay is performed on two plasmon-based detection platforms: a continuous gold surface and a nanoparticle-based array reader. The assay has a minimum detection concentration of 760+/-160 pM (120+/-25 ngml(-1)) in phosphate-buffered saline, falling to 2.5+/-0.7 nM (380+/-100 ngml(-1)) in physiological HSA concentration. The concentration of HSA correlates with the refractive index of the solution, and this may be used to calibrate assay response. The addition of the charged chaotrope SCN(-) in 150 mM concentration improves the reproducibility and consistency of the assay, with a minimum detection concentration of 2.9+/-0.5 nM (440+/-80 ngml(-1)). The effect of high concentrations of HSA on the immunokinetic assay can be corrected with a measurement of bulk refractive index in a reference channel.

Ad libitum fluid replacement in military personnel during a 4-h route march.

INTRODUCTION: Opportunities to determine optimal rates of fluid ingestion could reduce the mass soldiers might need to carry on military missions. PURPOSE: The first objective was to evaluate the effects of an ad libitum fluid replacement strategy on total body water (TBW), core temperature, serum sodium concentrations [Na+], and plasma osmolality (POsm). The second objective was to determine if an ad libitum water intake was sufficient to maintain these variables during exercise. A third objective was to determine if changes in body mass are an accurate measure of changes in TBW. METHODS: A field study was conducted with 15 soldiers performing a 16.4-km route march. The average age of 15 subjects was 27 yr (SD = 4.6 yr). RESULTS: Their mean hourly ad libitum fluid intake was 383 mL (SD = 150 mL). Predicted sweat rate was 626 +/-122 mL.h-1. Despite an average body mass loss of 1.0 kg (SD = 0.50 kg) TBW, POsm and serum [Na+] did not change significantly during exercise. There was a significant (P < 0.05) linear relationship with a negative slope between postexercise serum [Na+] and changes in both body mass and percentage of TBW. Postexercise POsm and serum [Na+] were significantly related (P < 0.05). Higher postexercise percentage of TBW was associated with lower postexercise POsm and serum [Na+] levels. There was no relation between percent body mass loss and postexercise core temperature (38.1 degrees C +/- 0.6 degrees C). CONCLUSIONS: A mean ad libitum water intake of 383 mL.h-1, replacing approximately 61% of body mass losses during 4 h of exercise, maintained TBW, core temperature, POsm, and serum [Na+] despite a 1.4% body mass loss. A reduction in body mass of 1.4% (1.0 kg) was not associated with a reduction in TBW.

Work and family support systems and the prevalence of lower back problems in a South African steel industry.

INTRODUCTION: Back complaints are a common in society. METHODS: An analytical cross-sectional epidemiological study was carried out among 366 steel plant workers to examine the prevalence and association between lower back problems (LBP) and family and workplace related psychosocial risk factors. RESULTS: Using inclusive and stringent definitions for LBP, point prevalence was 35.8% and 15.3%, respectively. Logistic regression analyses indicated significant adjusted odd ratios (OR) for negative perceptions of workplace support (2.32; CI 1.09-4.92), unexpected events (2.58; CI 1.19-5.59) and working under time pressures and deadlines (2.83; CI 1.24-6.48). A significant protective association was found for control over the order and pace of working tasks (OR 0.30; CI 0.14-0.63). A significant univariate association was further found between LBP and negative perceptions of family (1.97; CI 1.06-3.68) support. CONCLUSION: These findings suggest that workers who feel more in control on the job and who have good family and workplace support systems in tact are less likely to experience LBP. Supervisors are therefore encouraged to develop appropriate support and organizational systems which may be an inexpensive, but potentially beneficial, means of reducing worker stress and LBP.

Lower back problems and work-related risks in a South African manganese factory.

An analytical cross-sectional epidemiological study carried out among 109 manganese plant workers aimed to examine the prevalence and association between lower back problems (LBP) and occupational risk factors. Outcome was defined using a guided questionnaire and a functional rating index. Exposure to occupational risk factors was determined using self-reported questionnaires and workstation analyses. Multivariate logistic regression analyses indicated significant adjusted odds ratios (OR) for prolonged 90 degrees trunk flexion (OR 2.16; CI 1.15-4.05); manual handling (1.89; 1.17-3.08); load carriage (1.54; 1.08-2.19); and lifting (4.61; 1.37-15.47). The findings illustrate regional and occupational specifics of risk for LBP, and indicate that self-selection or adaptation to task-specific demands could possibly lead to observations of ergonomically relevant risk factors, which do not necessarily yield statistically significant associations with LBP. The findings further support multi-modal preventative approaches.

Perceptions of work and family assistance and the prevalence of lower back problems in a South African manganese factory.

An analytical cross-sectional epidemiological study was carried out among 109 manganese plant workers to examine the prevalence and association between lower back problems (LBP) and family and workplace related psychosocial risk factors. Outcome (LBP) was defined using a guided questionnaire and a functional rating index. Exposure to family and workplace related psychosocial risk was determined using the Occupational Risk Factor (ORFQ) and APGAR questionnaires for work and family support. Using inclusive and stringent definitions for perceived LBP, point prevalence was 37.6% and 29.4%, respectively. Only 8 cases of LBP were, however recorded officially over a 7-yr period (1996-2003). Multivariate analyses indicated a high, but non-significant odds ratio (OR) for negative perceptions of workplace support OR 3.29 (CI 0.95-11.30). A positive, non-significant, association for negative perceptions of family support (2.56; CI 0.69-9.52) and a protective, but non-significant, association for control over the order and pace of working tasks (OR 0.40; CI 0.12-1.35) was found. These findings together with the under-reporting, leads one to conclude that work hardening and a cultural ethos of non-complaining among manual labourers, moderates the association between LBP and the aetiological factors studied.

Fear-avoidance beliefs and pain coping strategies in relation to lower back problems in a South African steel industry.

The objective was to determine the association between the prevalence of lower back problems (LBP), fear-avoidance beliefs and pain coping strategies using an analytical cross-sectional epidemiological study among a group of 366 workers in a South African stainless steel industry. Outcome (LBP) was defined using a questionnaire and a functional rating index. Exposure to psychosocial risk was determined using the Fear-Avoidance Beliefs (FABQ) and Coping Strategies (CSQ) questionnaires. Multivariate logistic regression analyses for LBP indicated the following significant risk factors: work-related fear-avoidance beliefs (OR 3.40; 95% CI 2.20-5.25), catastrophizing (1.31; 1.01-1.7) and pain coping self statements (1.47; 1.16-1.87). Significant protective associations were found for increased activity levels (OR 0.57; 95% CI 0.42-0.78). These findings have utility in preventative screening procedures to identify workers with such beliefs and coping strategies who are at risk for prolonged work restrictions.

Lower back problems and occupational risk factors in a South African steel industry.

BACKGROUND: The etiology of work-related back disorders is often population specific. The objective of this study was to identify and establish the association of occupational risk factors with the prevalence of low back (LB) problems in a semi-automated South African Steel industry. METHODS: The design entailed an analytical cross-sectional epidemiological study among a group of 366 steel plant workers. Outcome of LB problems was defined using a guided questionnaire and a functional rating index. Exposure to occupational risk factors was determined using self-reported questionnaires. RESULTS: Multivariate logistic regression analyses indicated significant adjusted odds ratios (OR) for twisting and bending (OR 2.81; CI 1.02-7.73); bulky manual handling (5.58; 1.16-26.71); load carriage (7.20; 1.60-32.37); prolonged sitting (2.33; 1.01-5.37); kneeling and squatting (4.62; 1.28-16.60); and working on slippery and uneven surfaces (3.63; 1.20-10.90). CONCLUSIONS: This study supports the current view of a multifactorial etiology in idiopathic LB problems, and emphasizes the importance of multiple intervention strategies in industrial settings.

Psychosocial factors related to lower back problems in a South African manganese industry.

The purpose of this study was to determine the association between the prevalence of lower back problems, fear-avoidance beliefs, and pain-coping strategies in using an analytical cross-sectional epidemiological study among a group of 109 workers in a South African manganese industry. Outcome (LBP) was defined using a guided questionnaire and functional rating indexes. Exposure to psychosocial risk was determined using the Fear-Avoidance Beliefs (FABQ) and Coping Strategies (CSQ) questionnaires. Using inclusive and stringent definitions for perceived LBP, point prevalence was 37.6 and 29.4%, respectively. Only 8 cases of LBP were, however; recorded officially over a 7-year period reflecting a tendency of underreporting. Multivariate logistic regression analyses indicated significant adjusted relative risk ratios (RR) for work-related fear-avoidance beliefs (RR 2.35; 95% CI 1.39-3.95) as a singular psychosocial risk while no specific coping strategy could be isolated. In conclusion, work hardening and a contented ethos of the manual laborers under study moderates the association between the prevalence and etiology of LBP.