Volitional postures during maximal push/pull exertions in the sagittal plane

A set of push/pull experiments was performed by six men and women of varying anthropometry who were asked to exert maximal one-handed and two-handed push and pull forces on a load cell set at three different heights (67, 109, and 152 cm). They were each permitted to experiment with their postures to determine that which they sensed would permit the largest push or pull force, though no direct feedback was given as to their actual performance. Once they achieved what they believed to be their optimal posture, sagittal-plane photographs were taken. The angles of major body joints were then recorded along with the isometric force produced.

It is shown that foot placement, handle height, and body postures affect push and pull force capability in a manner that is reasonably logical, using biomechanical concepts. It is proposed that future biomechanical models of push an pull strengths and workplace layouts must be carefully assessed with reference to the postural variations reported.

Biomechanical stresses as related to motion trajectory of lifting

A laboratory study was conducted to assess the effects of lift angle on biomechanical stresses to the musculoskeletal system, and in particular, on the lower back. Male subjects were required to lift four different tote boxes from the floor to a height of 0.81 m using two different lifting techniques. Maximum acceptable weights were determined using a psychophysical method. The motion trajectory of lift was studied by means of stroboscopic photography. Moments and forces at various body joints were computed using a biomechanical strength model.

Maximum acceptable weights were 16% (range = 9 to 23%) greater for the free-style lifting technique as compared with the squat method of lifting. There were large differences between the maximum acceptable weights and the "maximum permissible limits" recommended by NIOSH. The results showed that the subjects pulled the load toward the body when lifting psychophysically determined maximum weights. The lift angle increased with an increase in box width. The lift angle was greater for the free-style lifting method as compared with the squat lifting technique for lifting compact loads. Lifting at an angle resulted in a decrease in moment at the elbow, shoulder, L5IS1 disc, and hips, and an increase in moment at the knees and ankles. The estimated compressive force on the lumbar spine was, on the average, 11% lower for lifting at an angle as compared with a straight vertical lift.

Role of radio-aerosol and perfusion lung imaging in early detection of chronic obstructive lung disease

The efficacy of radio-aerosol and perfusion lung imaging in the early detection of chronic obstructive lung disease was evaluated in 38 subjects. The subjects included 5 non-smokers, 21 smokers with minimal or no respiratory symptoms and 12 patients with chronic obstructive lung disease. Each subject consented to a respiratory questionnaire, detailed physical examination, chest X-ray examinations, detailed pulmonary function tests and 99mTc-radio aerosol-inhalation lung imaging. Perfusion lung imaging with 99mTc-labelled macroaggregated albumin was performed in 22 subjects. A significant correlation (P less than 0.001) was observed between the degree of abnormalities on radio-aerosol imaging and pulmonary function tests (PFTs) including forced expiratory volume in 1 s, maximum mid-expiratory flow rate and mean transit time analysis. Abnormal radio-aerosol patterns and deranged PFTs were observed in 21 subjects each. Of 21 subjects with abnormal radioaerosol pattern 8 had normal PFTs. Of 21 subjects with abnormal PFTs 8 had normal aerosol images. Aerosol lung images and PFTs were abnormal more frequently than perfusion lung images. The results suggest that radio-aerosol lung imaging is as sensitive an indicator as PFTs for early detection of chronic obstructive lung disease and can be usefully combined with PFTs for early detection of alteration in pulmonary physiology in smokers.

Endosulfan intoxication: Blood glucose, electrolytes, Ca levels, ascsorbic acid and glutathione in rats

Endosulfan-induced changes in blood glucose, plasma electrolytes, and blood and brain ascorbic acid, hexokinase and glutathione have been investigated following acute and subacute administration in 12 h fasted male rats. After a single oral dose of endosulfan (40 mg/kg) a significant increase in blood glucose, blood ascorbic acid, and blood and brain glutathione was observed. The maximum increase in blood was observed at 2 h (36%). Increase in blood and brain glutathione was highly significant at 4 h (50 and 43%, respectively). The blood ascorbic acid slowly increased by 19% over control during the treatment period. No significant change in brain hexokinase was observed. Repeated oral administration of endosulfan (0.625 to 20 mg/kg) for 7 weeks had no effect on plasma sodium and potassium. At the highest dose (20 mg/kg), blood glucose was slightly increased (16%). Plasma Ca was significantly decreased, the maximum fall (35%) being observed at 4 h.

Effects of lifting frequency and technique on physical fatigue with special reference to psychophysical methodology and metabolic rate

A laboratory study was conducted (1) to evaluate the effects of lifting frequency and technique on maximum acceptable work loads using psychophysical measurement technique, and (2) to compare the physiological fatigue criteria of 5 Kcal/min with the psychophysical fatigue criteria by measuring the metabolic rates at maximum acceptable work loads determined by subjective estimates of physical fatigue. Six male college students were required to lift from the floor to a 0.5 m height for 40 minutes. Four levels of lifting frequency (3, 6, 9 and 12 lifts/min) and three different lifting techniques (free sytle, stooped back and straight-back, bent-knee) were employed. Oxygen consumption rates were measured at maximum acceptable work loads (and were reduced to STPD). Statistical analysis showed that the maximum work loads acceptable to the workers were significantly affected by both lifting frequency and technique. Maximum acceptable work loads increased with an increase in lifting frequency. Both the subjective estimates of physical fatigue and the metabolic energy expenditure rate favored the free style lifting technique. The measured metabolic rates were in agreement with the physiological fatigue criteria of 5 Kcal/min only for six of the twelve combinations of lifting frequency and technique. Use of the physiological fatigue criteria will result in more liberal standards of work load at low work paces, especially for the stooped back and the free style lifting techniques.

Prediction of metabolic rates for manual materials handling jobs

A mew approach for estimating metabolic rates for manual materials handling jobs is presented. This approach was applied to 48 different jobs. The model validation showed a correlation coefficient of 0.95 between the measured and predicted metabolic rates. The coefficient of variation (standard error/sample mean) was 10.2 percent.

A method for evaluating the biomechanical stresses resulting from manual materials handling jobs

Manual materials handling tasks are inherent to many different jobs in industry today. The performance of such tasks exposes the worker to a variety of biomechanical hazards. This paper proposes a formalized algorithm for evaluating such hazards, and demonstrates the use of the algorithm in four different jobs. Medical data from these jobs are presented which serve to confirm the types of biomechanical stresses quantified by the biomechanical evaluations.