Richard A. Mostardi

Isokinetic lifting strength and occupational injury : a prospective study

One hundred seventy–one nurses had their back strength evaluated on an isokinetic lifting device and filled out an epidemiologic questionnaire. They were then followed prospectively for 2 years to determine the incidence of job–related low–back injuries. The data were analyzed to determine if the injury incidence correlated with any of the strength or epidemiologic variables collected during the original evaluation. Average peak force measured during the isokinetic lift was 63.8 kg + 13.6 kg at a lift speed of 30.5 cm/sec and 59.1 kg + 14.9 kg at a lift speed of 45.7 cm/sec. Sixteen nurses reported an occurrence of job–related low–back pain or injury during the 2–year prospective period. Discriminate statistical techniques showed that none of the strength or epidemiologic variables correlated with the incidence of pain or injury or explained significant amounts of variance when the variables were regressed on strength or work calculated from the lift force/lift height data. It was concluded that in this high risk population, in which loads are heavy and lifting postures are variable, the use of low–back strength or prior history of pain or injury are poor predictors as to subsequent low–back pain or injury.

Myoelectric activity and sequencing of selected trunk muscles during isokinetic lifting.

Trained weight lifters lift heavy loads without a concomitant degree of acute low–back injuries. To study the process by which large loads are lifted with minimal injury, integrated electromyographic signals were recorded from four large muscle groups: gluteus maximus, quadriceps, latissimus dorsi, and erector spinae in 4 weight lifters and 11 asymptomatic control subjects. These signals were recorded during a floor–to–knuckleheight isokinetic lift (dead lift) at 30.5 and 45.7 cm/sec. The signals were normalized for the height of the lift and the maximal isokinetic integrated electromyographic activity. The weight lifters achieved maximal force at 50% of maximal lift height, whereas the control subjects achieved it at 67%. Although not statistically significant, the weight lifters used the gluteus maximus more during the early stages of the lift, perhaps contributing to earlier development of force. This process would stabilize the pelvis and permit the erector spinae to extend the trunk more efficiently. The weight lifter then completed the lift with prolonged and increasing activity in the quadriceps. This technique may minimize the required force in the erector spinae and the forces on the low–back structures. Clinical implications include more effective strength training of lifting muscle groups other than spinal extensors and the teaching of lifting strategies employed by weight lifters in low–back rehabilitation and work–hardening programs.

In vitro response of human fibroblasts to commercially pure titanium.

The generation of metal particles through surface wear of prosthetic joints has been associated with biological reactions that may lead to prosthetic component loosening. The role of the macrophage in these reactions has been studied extensively, but that of the fibroblast has not. The few fibroblast studies that there have been have shown that particles of several metals, with sizes over a wide range, can promote cytokine release and may cause cell necrosis. The intent of this study was to determine if there are metal particle exposure threshold levels that result in morphological changes and cell necrosis of fibroblasts in peri-articular tissues. Retrieved human fibroblasts (superior medial plica) were cultured in standard fashion and then were exposed to various particle dosages of commercially pure Titanium (cpTi). Cell morphological changes and necrosis were observed to occur when the total mass of the particle dosage exceeded a threshold level. These data imply that these cell responses occur at threshold levels of wear particle exposure.

Aerometric and hair trace metal content in learning-disabled children

Abstract Children in the fourth to sixth grades at two schools were studied and divided in a control group ( n = 323) and a learning disability (LD) group ( n = 77). The following trace metals were analyzed in the air (7 months) at the two schools and in the childrens hair: cadmium, selenium, arsenic, mercury, and lead. Discriminant analysis showed that selenium, mercury, cadmium, diastolic blood pressure, arsenic, and sex (all P P P P P P P 3 , Hg = 1.5 ng/m 3 , Se = 1.75 ng/m 3 ). The data suggest that there is a significant difference between LD and control trace metal hair content and blood pressure, but that the air is not a major source of this effect although it does add to the cumulative trace metal hair content.

Carboxyhemoglobin and methemoglobin levels in residents living in industrial and nonindustrial communities

Abstract Carboxyhemoglobin and methemoglobin concentrations were compared in residents living in an industrial (Cleveland, Ohio) and a nonindustrial community (Elyria, Ohio). Carboxyhemoglobin levels were significantly higher among both male and female smokers and nonsmokers in Cleveland as compared to their counterparts in Elyria. Male smokers at both sites had significantly higher carboxyhemoglobin values than did the females. Methemoglobin levels were significantly higher in the nonindustrial site for all breakdowns even though ambient NO 2 and NO 3 levels were higher in the industrial site. The high methemoglobin levels are attributed to the higher nitrate levels in the drinking water in the nonindustrial city. In the industrial city, both male and female smokers had significantly higher methemoglobin values than nonsmokers. These differences were not found in the nonindustrial site. It is suggested that methemoglobin has physiological importance and in combination with carboxyhemoglobin elevated values could be a health factor.

Air Pollution and Cardiopulmonary Functions

To determine the long-term effects of air pollutants on adolescents, 42 high school students from an urban industrialized area (Barberton, Ohio) were compared with 50 from a rural area (Revere, Ohio). The comparative measures were vital capacity (VC), forced expiratory volume (FEV1.0), maximal midexpiratory flow (MMF), and maximal indirect oxygen consumption ([Vdot]o2 max). The subjects were all males and were drawn from original populations that were studied three years ago with VC and FEV0.75 being the tests of pulmonary function used. The results of this study were similar to those of the first. The Barberton group had a mean VC that was lower than the mean of the Revere group (P < .01). Neither FEV1.0 nor MMF were significantly different but [vdot]o2 max was P < .01). Since values for air pollutants are consistantly higher in Barberton, it is concluded that such pollutants should be considered important contributory factors in the impairment of cardiopulmonary functions.