A randomised controlled trial evaluating an alternative mouse and forearm support on upper body discomfort and musculoskeletal disorders among engineers.

OBJECTIVES: The aim of this intervention study was to determine the effects of an alternative mouse and/or a forearm support board on the change in upper body discomfort scores and the development of incident musculoskeletal disorders. METHODS: This randomised controlled intervention trial followed 206 engineers for one year. Participants were randomised to receive (1) a conventional mouse only, (2) an alternative mouse only, (3) a forearm support board, or (4) an alternative mouse plus forearm support board. Outcome measures included weekly upper body discomfort scores and incident musculoskeletal disorders. RESULTS: During the study, 42 participants were diagnosed with an incident musculoskeletal disorder. The group that received the forearm support board experienced a reduction in their right upper extremity discomfort (beta-coefficient -0.35, 95% CI -0.67 to -0.03) in comparison to those who did not receive a forearm board. The group that received the alternative mouse had a protective, but non-significant (p = 0.20), effect on incident cases of right upper extremity musculoskeletal disorders (HR 0.57, 95% CI 0.24 to 1.34) and a non-significant reduction in neck/shoulder discomfort (beta-coefficient -0.23, 95% CI -0.056 to 0.10) in comparison to those who received a conventional mouse. CONCLUSIONS: In engineers who use a computer for more than 20 h per week, a forearm support board may reduce right upper extremity discomfort attributed to computer use.

Work-organisational and personal factors associated with upper body musculoskeletal disorders among sewing machine operators.

OBJECTIVE: To assess the contribution of work-organisational and personal factors to the prevalence of work-related musculoskeletal disorders (WMSDs) among garment workers in Los Angeles. METHODS: This is a cross-sectional study of self-reported musculoskeletal symptoms among 520 sewing machine operators from 13 garment industry sewing shops. Detailed information on work-organisational factors, personal factors, and musculoskeletal symptoms were obtained in face-to-face interviews. The outcome of interest, upper body WMSD, was defined as a worker experiencing moderate or severe musculoskeletal pain. Unconditional logistic regression models were adopted to assess the association between both work-organisational factors and personal factors and the prevalence of musculoskeletal pain. RESULTS: The prevalence of moderate or severe musculoskeletal pain in the neck/shoulder region was 24% and for distal upper extremity it was 16%. Elevated prevalence of upper body pain was associated with age less than 30 years, female gender, Hispanic ethnicity, being single, having a diagnosis of a MSD or a systemic illness, working more than 10 years as a sewing machine operator, using a single sewing machine, work in large shops, higher work-rest ratios, high physical exertion, high physical isometric loads, high job demand, and low job satisfaction. CONCLUSION: Work-organisational and personal factors were associated with increased prevalence of moderate or severe upper body musculoskeletal pain among garment workers. Owners of sewing companies may be able to reduce or prevent WMSDs among employees by adopting rotations between different types of workstations thus increasing task variety; by either shortening work periods or increasing rest periods to reduce the work-rest ratio; and by improving the work-organisation to control psychosocial stressors. The findings may guide prevention efforts in the garment sector and have important public health implications for this workforce of largely immigrant labourers.

A randomised controlled trial evaluating the effects of two workstation interventions on upper body pain and incident musculoskeletal disorders among computer operators.

BACKGROUND: Call centre work with computers is associated with increased rates of upper body pain and musculoskeletal disorders. METHODS: This one year, randomised controlled intervention trial evaluated the effects of a wide forearm support surface and a trackball on upper body pain severity and incident musculoskeletal disorders among 182 call centre operators at a large healthcare company. Participants were randomised to receive (1) ergonomics training only, (2) training plus a trackball, (3) training plus a forearm support, or (4) training plus a trackball and forearm support. Outcome measures were weekly pain severity scores and diagnosis of incident musculoskeletal disorder in the upper extremities or the neck/shoulder region based on physical examination performed by a physician blinded to intervention. Analyses using Cox proportional hazard models and linear regression models adjusted for demographic factors, baseline pain levels, and psychosocial job factors. RESULTS: Post-intervention, 63 participants were diagnosed with one or more incident musculoskeletal disorders. Hazard rate ratios showed a protective effect of the armboard for neck/shoulder disorders (HR = 0.49, 95% CI 0.24 to 0.97) after adjusting for baseline pain levels and demographic and psychosocial factors. The armboard also significantly reduced neck/shoulder pain (p = 0.01) and right upper extremity pain (p = 0.002) in comparison to the control group. A return-on-investment model predicted a full return of armboard and installation costs within 10.6 months. CONCLUSION: Providing a large forearm support combined with ergonomic training is an effective intervention to prevent upper body musculoskeletal disorders and reduce upper body pain associated with computer work among call centre employees.

Cyclical articular joint loading leads to cartilage thinning and osteopontin production in a novel in vivo rabbit model of repetitive finger flexion.

OBJECTIVE: An in vivo rabbit model of repetitive joint flexion and loading was used to characterize the morphological effects of cyclical loading on articular cartilage. DESIGN: The forepaw digits of eight anesthetized New Zealand White adult female rabbits were repetitively flexed at 1 Hz with a mean peak digit load of 0.42 N for 2 h per day for 60 cumulative hours. Metacarpophalangeal joints were collected from loaded and contra-lateral control limbs, fixed, decalcified, embedded, and thin-sectioned. Serial sections were stained for histology or for immunohistochemistry. Morphometric data including the mean thicknesses of the uncalcified cartilage and of the calcified cartilage were collected from digital photomicrographs of safranin O-stained sections. The number of cells stained with anti-osteopontin antibody was counted. RESULTS: We observed a decrease in uncalcified cartilage mean thickness with no significant change in calcified cartilage thickness. We also observed a significant increase in the number of cells positive for osteopontin (OPN) in the uncalcified cartilage. These changes occurred without overt cartilage surface degeneration. CONCLUSIONS: Cyclical loading leads to changes at the tissue and cellular levels in articular cartilage. These changes are suggestive of tidemark advancement and may indicate a reactivation of cartilage mineralization steps analogous to endochondral ossification. This novel in vivo rabbit model of repetitive flexion and loading can be used to investigate the effects of cyclical loading on articular joints.

Ischemia causes muscle fatigue.

The purpose of this investigation was to determine whether ischemia, which reduces oxygenation in the extensor carpi radialis (ECR) muscle, causes a reduction in muscle force production. In eight subjects, muscle oxygenation (TO2) of the right ECR was measured noninvasively and continuously using near infrared spectroscopy (NIRS) while muscle twitch force was elicited by transcutaneous electrical stimulation (1 Hz, 0.1 ms). Baseline measurements of blood volume, muscle oxygenation and twitch force were recorded continuously, then a tourniquet on the upper arm was inflated to one of five different pressure levels: 20, 40, 60 mm Hg (randomized order) and diastolic (69 +/- 9.8 mm Hg) and systolic (106 +/- 12.8 mm Hg) blood pressures. Each pressure level was maintained for 3-5 min, and was followed by a recovery period sufficient to allow measurements to return to baseline. For each respective tourniquet pressure level, mean TO2 decreased from resting baseline (100% TO2) to 99 +/- 1.2% (SEM), 96 +/- 1.9%, 93 +/- 2.8%, 90 +/- 2.5%, and 86 +/- 2.7%, and mean twitch force decreased from resting baseline (100% force) to 99 +/- 0.7% (SEM), 96 +/- 2.7%, 93 +/- 3.1%, 88 +/- 3.2%, and 86 +/- 2.6%. Muscle oxygenation and twitch force at 60 mm Hg tourniquet compression and above were significantly lower (P < 0.05) than baseline value. Reduced twitch force was correlated in a dose-dependent manner with reduced muscle oxygenation (r = 0.78, P < 0.001). Although the correlation does not prove causation, the results indicate that ischemia leading to a 7% or greater reduction in muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TO2 causes muscle fatigue.

In vivo finger flexor tendon force while tapping on a keyswitch.

Force may be a risk factor for musculoskeletal disorders of the upper extremity associated with typing and keying. However, the internal finger flexor tendon forces and their relationship to fingertip forces during rapid tapping on a keyswitch have not yet been measured in vivo. During the open carpal tunnel release surgery of five human subjects, a tendon-force transducer was inserted on the flexor digitorum superficialis of the long finger. During surgery, subjects tapped with the long finger on a computer keyswitch, instrumented with a keycap load cell. The average tendon maximum forces during a keystroke ranged from 8.3 to 16.6 N (mean = 12.9 N, SD = 3.3 N) for the subjects, four to seven times larger than the maximum forces observed at the fingertip. Tendon forces estimated from an isometric tendon-force model were only one to two times larger than tip force, significantly less than the observed tendon forces (p = 0.001). The force histories of the tendon during a keystroke were not proportional to fingertip force. First, the tendon-force histories did not contain the high-frequency fingertip force components observed as the tip impacts with the end of key travel. Instead, tendon tension during a keystroke continued to increase throughout the impact. Second, following the maximum keycap force, tendon tension during a keystroke decreased more slowly than fingertip force, remaining elevated approximately twice as long as the fingertip force. The prolonged elevation of tendon forces may be the result of residual eccentric muscle contraction or passive muscle forces, or both, which are additive to increasing extensor activity during the release phase of the keystroke.

The effects of keyswitch stiffness on typing force, finger electromyography, and subjective discomfort.

The effects of keyswitch stiffness and key action on typing force, electromyography (EMG), and subjective preference were examined. Each subject's own keyboard (with an audible key click and key activation force of 0.72 N) and three keyboards with no key click that were identical in design but had different key activation forces (0.28 N, 0.56 N, and 0.83 N) were used. Subjects (24 female transcriptionists) typed on each keyboard for 15 min while typing force and left hand surface EMG of the finger flexor and extensor muscles were monitored. Subjects then used one of the keyboards at their workstations for 7 workdays and were monitored again. This procedure was repeated for all four keyboards. Typing force and finger flexor and extensor EMG activity were highest for the 0.83 N keyboard. Lowest EMG values were for the 0.28 N and the 0.72 N audible key click keyboards. Baseline (10th percentile) and median (50th percentile) extensor EMG values were significantly higher than flexor EMG values. Peak (90th percentile) EMG values were comparable for flexors and extensors. Mean subjective discomfort was significantly higher for the 0.83 N keyboard at the fingers (36% higher), lower arm (40% higher), and overall (39% higher). Seventeen of 24 subjects preferred the 0.72 N keyboard, 4 the 0.28 N keyboard, and 3 preferred the 0.56 N keyboard. Results suggest that increasing make force causes typing force and EMG to increase but that the ratio of 90th centile typing force to make force decreases as make force increases. Subjective discomfort was significantly higher for the keyboard with 0.83 N make force. Buckling spring keyboards have better feedback characteristics, which may be responsible for a decrease in the amount of typing force and EMG produced.

Effects of finger posture on carpal tunnel pressure during wrist motion.

Persistent elevations in carpal tunnel pressure may aggravate carpal tunnel syndrome. This study examined the effects of finger posture on carpal tunnel pressure during wrist motion. Carpal tunnel hydrostatic pressure was measured using a saline-filled catheter inserted into the nondominant wrists of 14 healthy individuals. Range of motion tasks of wrist flexion-extension and radioulnar deviation were repeated with metacarpophalangeal (MCP) joint angles of 0 degrees, 45 degrees, and 90 degrees flexion. Pressures were significantly greater with the fingers straight (MCP = 0 degrees) than when the MCP joints were flexed to 45 degrees for all radioulnar deviation angles and from 10 degrees of wrist flexion to all angles of wrist extension tested. Pressures were also significantly higher with MCP joints at 0 degrees than at 90 degrees for wrist extension angles from 10 degrees to 40 degrees. Pressures increased to over 30 mm Hg (4.0 kPa) in some wrist extension and ulnar and radially deviated postures. Finger and wrist postures should be considered when designing splints or evaluating tasks for patients with carpal tunnel syndrome.

Control strategies for finger movement during touch-typing. The role of the extrinsic muscles during a keystroke.

A single keystroke during touch-typing is a rapid, goal-directed motion of the fingertip which consists of two single-direction movements. The neural control and the role of the finger extrinsic musculature during typing have not yet been explained. The fingertip motion and force, and the intramuscular electromyographic (EMG) activity (fine-wire) of the index finger extrinsic musculature were measured during touch-typing by ten experienced typists. The motions and forces were repeatable qualitatively across keystrokes. A three-burst EMG pattern was observed during a single keystroke. The three bursts were: (1) a burst of extensor activity lifted the finger before the keystroke; (2) a burst of flexor activity followed while the fingertip was moving downward; and (3) a second burst of extensor activity occurred as the fingertip reached the end of key travel. The timing of the third burst suggests the role of the extensors is to remove the fingertip from the keyswitch rather than stop the downward motion of the finger. The collision with the end of key travel stops the downward finger motion. The timing of the finger flexor EMG activity, burst 2, suggests that the flexor contraction principally overcomes the activation force of the keyswitch rather than accelerates the finger downward as expected.

Tensions of the flexor digitorum superficialis are higher than a current model predicts.

Existing isometric force models can be used to predict tension in the finger flexor tendon, however, they assume a specific distribution of forces across the tendons of the fingers. These assumptions have not been validated or explored by experimental methods. To determine if the force distributions repeatably follow one pattern the in vivo tension of the flexor digitorum superficialis (FDS) tendon of the long finger was measured in nine patients undergoing open carpal tunnel release surgery. Following the release, a tendon force transducer (Dennerlein et al. 1997 J. Biomechanics 30(4), 395-397) was mounted onto the FDS of the long finger. Tension in the tendon, contact force at the fingertip, and finger posture were recorded while the patient gradually increased the force applied by the fingertip from 0 to 10 N and then monotonically reduced it to 0 N. The average ratio of the tendon tension to the fingertip contact force ranged from 1.7 to 5.8 (mean = 3.3, s.d. = 1.4) for the nine subjects. These ratios are larger than ratios predicted by current isometric tendon force models (mean = 1.2, s. d. = 0.4). Subjects who used a pulp pinch posture (hyper-extended distal interphalangeal joint (DIP)) showed a significantly (p = 0.02) larger ratio (mean = 4.4, s.d. = 1.5) than the five subjects who flexed the DIP joint in a tip pinch posture (mean = 2.4, s.d. = 0.6). A new DIP constraint model, which selects different force distribution based on DIP joint posture, predicts force ratios that correlate well with the measured ratios (r2 = 0.85).

Fingertip loading and carpal tunnel pressure: differences between a pinching and a pressing task.

Carpal tunnel syndrome may be caused by repeated or sustained elevated carpal tunnel pressure. This study examined the relationship between carpal tunnel pressure, posture, and fingertip load. In 20 healthy individuals, carpal tunnel pressure was measured with a catheter inserted into the carpal tunnel of the dominant hand and connected to a pressure transducer. With the wrist in a pressure-neutral position, the subjects pressed on a force transducer with the index finger to levels of 0, 5, 10, and 15 N. They then pinched the transducer at the same levels of force. For both fingertip-loading postures, the carpal tunnel pressure increased with increasing fingertip load. Carpal tunnel pressures were significantly greater (p < 0.015) for the pinching task (14.2, 29.9, 41.9, and 49.7 mm Hg [1.89, 3.99, 5.59, and 6.63 kPa] for 0, 5, 10, and 15 N force levels, respectively) than for simple finger pressing (7.8, 14.1, 20.0, and 33.8 mm Hg [1.04, 1.88, 2.67, and 4.51 kPa]). This study indicates that although the external load on the finger remained constant between the two tasks, the internal loading, as measured by carpal tunnel pressure, experienced a near 2-fold increase by using a pinch grip. These findings should be given consideration in designing work tasks and tools because relatively low fingertip forces, especially in a pinch grip, elevate carpal tunnel pressures to levels that, if prolonged, may lead to the development or exacerbation of carpal tunnel syndrome.

Forearm muscle oxygenation decreases with low levels of voluntary contraction.

The purpose of our investigation was to determine if the near infrared spectroscopy technique was sensitive to changes in tissue oxygenation at low levels of isometric contraction in the extensor carpi radialis brevis muscle. Nine subjects were seated with the right arm abducted to 45 degrees, elbow flexed to 85 degrees, forearm pronated 45 degrees, and wrist and forearm supported on an armrest throughout the protocol. Altered tissue oxygenation was measured noninvasively with near infrared spectroscopy. The near infrared spectroscopy probe was placed over the extensor carpi radialis brevis of the subject's right forearm and secured with an elastic wrap. After 1 minute of baseline measurements taken with the muscle relaxed, four different loads were applied just proximal to the metacarpophalangeal joint such that the subjects isometrically contracted the extensor carpi radialis brevis at 5, 10, 15, and 50% of the maximum voluntary contraction for 1 minute each. A 3-minute recovery period followed each level of contraction. At the end of the protocol, with the probe still in place, a value for ischemic tissue oxygenation was obtained for each subject. This value was considered the physiological zero and hence 0% tissue oxygenation. Mean tissue oxygenation (+/-SE) decreased from resting baseline (100% tissue oxygenation) to 89 +/- 4, 81 +/- 8, 78 +/- 8, and 47 +/- 8% at 5, 10, 15, and 50% of the maximum voluntary contraction, respectively. Tissue oxygenation levels at 10, 15, and 50% of the maximum voluntary contraction were significantly lower (p < 0.05) than the baseline value. Our results indicate that tissue oxygenation significantly decreases during brief, low levels of static muscle contraction and that near infrared spectroscopy is a sensitive technique for detecting deoxygenation noninvasively at low levels of forearm muscle contraction. Our findings have important implications in occupational medicine because oxygen depletion induced by low levels of muscle contraction may be directly linked to muscle fatigue.

A low profile human tendon force transducer: the influence of tendon thickness on calibration.

An in vitro calibration method for human tendon force transducers using tendon thickness to predict the calibration factor has been previously proposed (An et al., 1990, J. Biomechanics 23, 1269-1271). However, changes in the calibration factor due to changing tendon geometry during repeated tendon loading are unknown. A new, low-profile transducer design that measures tendon thickness in the transducer, in situ, is developed. An empirical model estimating the transducer's calibration factor is developed using data from in vitro tension testing of 12 fresh frozen human finger flexor tendons. Each tendon is preseated with ten loading cycles before data collection. Using tendon thickness, the model predicts the measured calibration factor to within 0-15% (average 6%). During repeated loading of an in vitro tendon, the calibration factor changes 15% over the first ten cycles (0-50 N) due to the observed changing tendon thickness. After the first ten loading cycles the variability of the calibration factor is reduced to less than 1% for the next three loading cycles. Hence this new, modified in vitro calibration procedure with tendon preseating reduces the cycle-to-cycle variability caused by the associated change in the tendon thickness.

Effects of psychological stress on human semen quality.

We investigated the relationship between psychological stress and sperm concentration, motility, and morphometry in a prospective study of 157 volunteers who were enrolled in a prepaid health plan. We measured psychological job stress and life-event stress by telephone interview. Sperm-kinematic and nuclear-morphometric variables were measured using computer-assisted image analyses. Sperm concentration, percent motility, and semen volume were determined by objective visual methods. We performed multiple linear regression for each semen variable to examine its relationship to stress, controlling for potential confounders. Stress at work and total number of life events were not related to differences in semen quality. However, the recent death of a close family member was associated with a reduction in straight-line velocity (P = 0.002) and percent of progressively motile sperm (P = 0.02); it was also marginally associated with an increase in the fraction of sperm with larger and more tapered nuclei. These findings suggest that the fecundity of men experiencing the stress of a family member's death might be temporarily diminished.

Smoking and low antioxidant levels increase oxidative damage to sperm DNA.

Our previous studies have shown that men with low ascorbate intake have markedly increased oxo8dG in the DNA of their sperm. Because cigarette smoke is high in oxidants and depletes plasma and tissue antioxidants, oxidative DNA damage in sperm and tocopherol and ascorbate levels in seminal plasma were determined in smokers and non-smokers. The level in sperm DNA of oxo8dG, an oxidative lesion of guanine, was 50% higher in smokers compared to nonsmokers (p = 0.005). The concentration of alpha-tocopherol in seminal plasma was decreased in smokers by 32% (p = 0.03). Smoking and low antioxidant levels increase oxidative damage to sperm DNA. We discuss the possibility that paternal smoking causes mutations in sperm that lead to cancer, birth defects, and genetic diseases in offspring.

Position of the wrist associated with the lowest carpal-tunnel pressure: implications for splint design.

Increased carpal-tunnel pressure has been implicated in the pathophysiology of carpal tunnel syndrome, but it is not known whether splints that immobilize the wrist in a functional position of extension minimize carpal tunnel pressure. To determine the position of the wrist that results in the lowest carpal-tunnel pressure, twenty control subjects and four patients who had carpal tunnel syndrome were evaluated with use of a new, dynamic method that continuously measures carpal tunnel pressure throughout the range of motion of the wrist. The pressure was measured by means of a pressure transducer connected to a flexible catheter that had been inserted into the carpal canal. The position of the wrist was measured simultaneously with use of a two-axis electrogoniometer. Aided by a computer monitor that displayed a moving line of real-time carpal-tunnel pressure, each subject was instructed to move the wrist throughout the range of motion and to adjust it to the position that corresponded to the lowest carpal-tunnel pressure. For the control subjects, the lowest carpal-tunnel pressure averaged 8 +/- 4 millimeters of mercury (1.07 +/- 0.53 kilopascals), and the average position of the wrist associated with the lowest pressure was 2 +/- 9 degrees of extension and 2 +/- 6 degrees of ulnar deviation.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of applied forces in alphanumeric keyboard work.

This paper considers one way that occupational health professionals can assess the force exerted by keyboard users and the possible relationship between that force and the key force-displacement relationship. First, three personal-computer keyboards with the standard QWERTY layouts were tested as described by the American National Standard for Human Factors Engineering of Visual Display workstations (ANSI/HFS 100-1988) to determine the peak forces, 0.47-0.89N; displacements prior to the "breakaway" force that acknowledges key registration, 2.0-2.5 mm; and total key travel, 3.3-4.3 mm. Second, keyboard reaction forces were recorded while 10 subjects typed 4 alphanumeric sentences on the keyboards. It was found that the peak forces corresponding to each keystroke were 2.5 to 3.9 times the required activation forces, indicating that the subjects consistently displaced the keys to their limits. The average of the peak forces for all keystrokes was lowest for the keyboard with the lowest required activation force. It was concluded that keyboard reaction forces can be used as an index of finger forces for keying tasks. Further studies are necessary to evaluate the relationship between keyboard reaction forces, fatigue, and chronic muscle, tendon, and nerve disorders.

Work-related cumulative trauma disorders of the upper extremity.

Cumulative trauma disorders due to performance of repetitive tasks account for more than 50% of all occupational illnesses in the United States today. Employees affected by these disorders frequently experience substantial pain and functional impairment that may require a change in occupation. For the employer, these injuries result in loss of productivity and increased costs in the form of higher medical expenses and disability payments for injured workers. Successful treatment of work-related repetitive tissue injuries depends on early diagnosis and appropriate therapy. Prevention requires identifying sites and tasks that place employees at risk of injury and supporting efforts to develop safer work environments.

A study of the effect of perchloroethylene exposure on the reproductive outcomes of wives of dry-cleaning workers.

The purpose of this investigation was to compare the reproductive outcomes of wives of men exposed to perchloroethylene in the dry-cleaning industry compared to those of wives of laundry workers. Seventeen female partners of dry cleaners and 32 partners of laundry workers were interviewed. The number of pregnancies and the standardized fertility ratios were similar between the two groups. Wives of dry cleaners did not have higher rates of spontaneous abortions. However, wives of dry cleaners were more than twice as likely to have a history of attempting to become pregnant for more than 12 months or to have sought care for an infertility problem. Cox proportional hazards models indicated that dry-cleaners' wives had half of the per-cycle pregnancy rate of wives of laundry workers, when controlling for other potential confounders (estimated rate ratio of 0.54, 95% C.I. = 0.23, 1.27).

A study of the effect of perchloroethylene exposure on semen quality in dry cleaning workers.

The purpose of this investigation was to determine the effects of perchloroethylene (PCE) exposure on human semen quality. We compared the semen quality of 34 dry cleaners with that of 48 laundry workers. We examined the relationships of 17 semen parameters to expired air levels of PCE and to an index of exposure based on job tasks in the last three months. The average sperm concentration was over 80 million for both dry cleaners and laundry workers, but approximately one-quarter of each group was oligospermic. The overall percentage of abnormal forms was similar for the two groups; however, sperm of dry cleaners were significantly more likely to be round (t = -3.29, p = 0.002) and less likely to be narrow (t = 2.35, p = 0.02) than the sperm of laundry workers. These effects were dose-related to expired air levels and to the exposure index after controlling for potential confounders (e.g., heat exposure). The average percent motile sperm for both groups was slightly over 60%; however, sperm of dry cleaners tended to swim with greater amplitude of lateral head displacement (ALH) than those of laundry workers (t = -1.73, p = 0.09), and level of PCE in expired air was a significant predictor of ALH in the multiple regression model (t = 2.00, p = 0.05). In addition, exposure index was a significant negative predictor of the sperm linearity parameter (t = -2.57, p = 0.01). These results suggest that occupational exposures to PCE can have subtle effects on sperm quality. Additional analyses are required to determine whether these effects are associated with changes in fertility.