Orcadian Variation in Human Stature

Thyroxine (T₄) and triiodothyronine (T₃) plasma concentrations have been determined during 24-hr sampling periods in six mongrels (age 12-36 months), six beagles (age 35-37 months), three labradors (age 3.5 months) and three beagles (age 5 months). The mean T₄ levels of the labradors were significantly lower than the values found for mongrels or older beagles (P < 0.05), whereas T₃ was higher in the 5 month old beagles compared to the mongrels (P < 0.001), young beagles (P < 0.05) or labradors (P < 0.01).

Circadian and ultradian rhythmicities have been evaluated by cosinor and Fourier analysis. Mongrels and older beagles did have a 12-hr rhythmicity in plasma T₄ (P < 0.05), whereas 5 month old beagles had a circadian one (P < 0.01). A 12-hr rhythmicity was also found for T₃ in the older Beagles (P < 0.05). However, Fourier analysis indicated that the daily variation in T₄ and T₃ plasma levels was inadequately mathematically described by single sinusoidal rhythm and that more harmonic components are to be taken into account.

The obtained data during a 24-hr period indicate that T₄ and T₃ concentrations in plasma may vary according to breed, age and sampling hour.     

EMG median frequency changes in the neck–shoulder stabilizers of symptomatic office workers when challenged by different physical stressors

The problem of work-related neck and upper limb disorders among computer users has been reported extensively in the literature, and commonly cited risk factors include static posture, speed and force of keyboard operation. The present study examined changes in median frequency (MF) of the neck–shoulder muscles in symptomatic and asymptomatic office workers when they were exposed to these three physical stressors.

A quasi-experimental Case–Control design was used to examine MF changes in two groups of female office workers when they were subjected to controlled doses of computer work involving prolonged static posture, increased typing speed and increased typing force. The MF of four major neck–shoulder muscles were examined bilaterally and compared between groups.

The MF changes over time-at-task did not clearly illustrate any muscle fatigue mechanism. However, Case Group consistently showed trends for higher MF than the Control Group, and this pattern was observed in response to all three physical stressors. The consistent group differences in MF suggest different muscle recruitment strategies between symptomatic and asymptomatic office workers. These results implied that symptomatic individuals had altered motor control, which may have important implications in understanding the etiology of work-related musculoskeletal disorders.     

The use of surface electromyographic techniques in assessing musculoskeletal disorders in production operations

The use of surface electromyographic (SEMG) techniques in evaluating production line workstations is illustrated through the use of two case studies. Evaluation procedures are introduced. The results illustrate how SEMG can be used to document the strain upon muscles of the neck and shoulders and how workstations may be altered to comply with government regulations.     

Effects of visually demanding near work on trapezius muscle activity

Poor visual ergonomics is associated with visual and neck/shoulder discomfort, but the relation between visual demands and neck/shoulder muscle activity is unclear. The aims of this study were to investigate whether trapezius muscle activity was affected by: (i) eye-lens accommodation; (ii) incongruence between accommodation and convergence; and (iii) presence of neck/shoulder discomfort. Sixty-six participants (33 controls and 33 with neck pain) performed visually demanding near work under four different trial-lens conditions. Results showed that eye-lens accommodation per se did not affect trapezius muscle activity significantly. However, when incongruence between accommodation and convergence was present, a significant positive relationship between eye-lens accommodation and trapezius muscle activity was found. There were no significant group-differences. It was concluded that incongruence between accommodation and convergence is an important factor in the relation between visually demanding near work and trapezius muscle activity. The relatively low demands on accommodation and convergence in the present study imply that visually demanding near work may contribute to increased muscle activity, and over time to the development of near work related neck/shoulder discomfort.     

Special work-wear and protective clothing for Indian furnace workers

1. 1. In the present study two new, ergonomically designed, low-cost prototypes of protective work-wear for furnace workers of five hot metal and three glass factories in West Bengal were developed and evaluated on the basis of objective and subjective assessments.

2. 2. The objective assessments included the thermal data of the workplaces during summer and winter months, data on accidents and workers' physiological responses such as pulse rates, core and skin temperatures and sweat loss during work with the existing as well as work-wear. The subjective assessments were from questionnaires on the merits and demerits of the existing and new work-wear and the comfort votes.

3. 3. The study recommended the use of ergonomically designed, low-cost, washable, ventilated, vapour permeable, flame-retardant, radiant-heat-reflecting type special work clothing (Prototype No.II) by the workers to reduce the heat stress, accident risks and the physiological costs and to increase efficiency and productivity.

A mathematical musculoskeletal shoulder model for proactive ergonomic analysis

Occupational shoulder musculoskeletal injuries and disorders are common. Generally available shoulder work analysis tools do not offer insight into specific muscle load magnitudes that may indicate increased risk, nor do they address many concerns germane to job analysis. To address these issues, a biomechanical model of the shoulder was developed to include several critical components: the systematic inclusion of kinematic and kinetic effects, population scalability, geometric realism, an empirical glenohumeral constraint, and integration with digital ergonomics analysis software tools. This unique combination of features in a single model was explored through examination of both experimental and simulated data with the developed analysis tool. The utility of the model is discussed together with a review of its specific strengths and weaknesses, and the potential for its future use in proactive ergonomic analyses and workplace simulations.     

Behavioral flexibility in age castes of the antPheidole dentata

Division of labor among size and age classes in social insect colonies is a fundamental aspect of sociality, with such classes typically showing behavioral specialization and being associated with particular tasks for prolonged periods of time (i.e., forming castes). Theoretically, such specialization and division of labor enhance efficiency and, ultimately, reproductive success, and the ratios among members of those castes are hypothesized to be under selection and adaptive. However, our recent field study of the ant Pheidole dentatashowed no correlation between ecological factors which should affect colony growth and those caste ratios but implied flexibility in the association between minor worker age castes and their tasks. In laboratory experiments on behavioral flexibility in minor age castes of P. dentataold workers in colonies without young workers competently perform both old worker (castetypical) and young worker (atypical) tasks, and vice versa. The implications of these results for ergonomie theory are considered.     

The foraging ecology of the army ant Eciton rapax: an ergonomic enigma?

Abstract. 1. The army ant Eciton rapax (F. Smith) produces longer raid systems than any other member of its genus and it is a specialist predator of forest floor and understory ants such as species of Camponotus, Odontomachus and Pachycondyla.
2. Allometrical analysis confirms that E. rapax is the only member of its genus without distinct physical castes among its workers: its foraging population is entirely monomorphic and there are no majors.
3. The workers of E. rapax are distributed over a considerable size range, and there are distinct divisions of labour within these colonies: small workers tend to stay in the nests and among the larger foraging workers those retrieving prey items are significantly bigger than the rest.
4. An analysis of foraging efficiency and worker performance in E. rapax suggests that transport costs, resulting from the great distances that workers travel during raids and emigrations, are one of the selection pressures that have favoured the evolution of large monomorphic workers in this species.     

Cultural and health influences on building,housing, and community standards: Cost implications for the human habitat

International research and practices are reviewed with regard to cultural, social, economic, health, and physical-technological features of needs, standards, and codes regulating the residential environment. Housing and building codes, as well as zoning and subdivision ordinances, are influenced by nonscientific considerations that have significant cost and other policy implications. Noxious and promotive influences are examined for public health codes regulating potable water, waste disposal, and safety in the home, as well as density and congestion for cities, neighborhoods, and individual dwelling units. Density is distinguished from congestion, and the policy implications of both are examined. Cost-benefit ratios indicate that many standards can be appreciably lowered. Vague definitions of health, as adopted by WHO, also invite costinducing moral judgments.