Brian D. Lowe

Accuracy and validity of observational estimates of wrist and forearm posture.

Numerous observational methods for analysis of working posture of the wrist/forearm have been reported in the literature yet few of these methods have been validated for the accuracy of their posture classification. The present study evaluated the accuracy of estimates of working posture made by 28 experienced ergonomists using methods of scaling upper limb posture typical of those reported in the literature. Observational estimates of wrist/forearm posture of four jobs presented on video-recording were compared with posture levels measured directly with an electrogoniometer system. Ergonomists using a visual analogue scale tended to underestimate peak and average wrist extension with mean errors of − 29.4% and − 10.5% of the joint ROM, respectively (p < 0.05). While estimates of wrist flexion, pronation and supination resulted in less bias, variability in observer error was large for all wrist postures. The probability of an analyst misclassifying the most frequently occurring posture using a three- and a six-category scale was 54 and 70%, respectively. The probability of misclassifying peak posture was 22 and 61% using a three- and a six-category scale respectively. This suggests a trade-off between the degree of precision afforded by the categorical scale and the likelihood of posture misclassification. Estimates of the temporal distribution of posture among the categories appeared to be biased towards more neutral postures than were measured for the jobs. This indicated the possibility of a trend towards underestimation of posture duration severity by the ergonomists.

ORIGINAL RESEARCH—ERECTILE DYSFUNCTION: Cutting Off the Nose to Save the Penis

INTRODUCTION The average bicycle police officer spends 24 hours a week on his bicycle and previous studies have shown riding a bicycle with a traditional (nosed) saddle has been associated with urogenital paresthesia and sexual dysfunction. AIM The objective of this study was to assess the effectiveness of the no-nose bicycle saddle as an ergonomic intervention and their acceptance among male bicycle police officers. METHODS Bicycle police officers from five U.S. metropolitan areas were recruited for this study. Officers completed: (i) the International Index of Erectile Function Questionnaire (IIEF); (ii) computerized pressure measurements at the points of contact on the bicycle; the handlebars, the pedals, and the saddle; (iii) one night of nocturnal Rigiscan assessment; (iv) penile vibrotactile sensitivity threshold assessed by computerized biothesiometery. Officers selected a no-nose saddle for their bicycles and were asked to use the intervention saddle exclusively for 6 months, at which point they were retested. MAIN OUTCOME MEASURES Perineal pressure, urogenital numbness, penile vibrotactile sensitivity threshold, erectile function as measure by International Index of Erectile Function Questionnaire (IIEF) and Rigiscan. RESULTS After 6 months, 90 men were reassessed. Only three men had returned to a traditional saddle. The results are presented for those who used the no-nose saddle continuously for 6 months. There was a 66% reduction in saddle contact pressure in the perineal region (P < 0.001). There was a significant improvement in penis tactile sensation (P = 0.015). There was a significant improvement in erectile function assessed by IIEF (P = 0.015). There were no changes noted in the Rigiscan measures. The number of men indicating they had not experienced urogential paresthesia while cycling for the preceding 6 months, rose from 27% to 82% using no-nose saddles. CONCLUSIONS (i) With few exceptions, bicycle police officers were able to effectively use no-nose saddles in their police work. (ii) Use of no-nose saddles reduced most perineal pressure. (iii) Penile health improved after 6 month using no-nose saddles as measured by biothesiometry and IIEF. There was no improvement in Rigiscan(R) measure after 6 months of using no nose saddles, suggesting that a longer recovery time may be needed..

ORIGINAL RESEARCH—WOMEN’S SEXUAL HEALTH: Genital Sensation and Sexual Function in Women Bicyclists and Runners: Are Your Feet Safer than Your Seat?

INTRODUCTION Bicycling is associated with neurological impairment and impotence in men. Similar deficits have not been confirmed in women. AIM To evaluate the effects of bicycling on genital sensation and sexual function in women. METHODS Healthy, premenopausal, competitive women bicyclists and runners (controls) were compared. MAIN OUTCOME MEASURES (1) Genital vibratory thresholds (VTs) were determined using the Medoc Vibratory Sensation Analyzer 3000. (2) Sexual function and sexually related distress were assessed by the Dennerstein Personal Experience Questionnaire (SPEQ) and the Female Sexual Distress Scale (FSDS). RESULTS Forty-eight bicyclists and 22 controls were enrolled. The median age was 33 years. The bicyclists were older, had higher body mass indices (BMIs), were more diverse in their sexual orientation, and were more likely to have a current partner. Bicyclists rode an average of 28.3 +/- 19.7 miles/day (range 4-100), 3.8 +/- 1.5 days/week, for an average of 2.1 +/- 1.8 hours/ride. The mean number of years riding was 7.9 +/- 7.1 years (range 0.5-30). Controls ran an average of 4.65 +/- 2.1 miles/day (range 1.5-8) and 5.0 +/- 1.2 days/week. On bivariate analysis, bicyclists had significantly higher VTs than runners, indicating worse neurological function at all sites (P < 0.05). Multivariate analysis found significant correlations between higher VTs and bicycling at the left and right perineum, posterior vagina, left and right labia. Increasing VTs at the clitoris, anterior vagina, and urethra were associated with age. In bicyclists, there were no correlations between VTs and miles biked per week, duration of riding, or BMI. Composite SPEQ scores indicated normal sexual function in all sexually active subjects. Neither group suffered from sexually related distress. CONCLUSION There is an association between bicycling and decreased genital sensation in competitive women bicyclists. Negative effects on sexual function and quality of life were not apparent in our young, healthy premenopausal cohort.

Evaluation of handle design characteristics in a maximum screwdriving torque task

The purpose of this study was to evaluate the effects of screwdriver handle shape, surface material and workpiece orientation on torque performance, finger force distribution and muscle activity in a maximum screwdriving torque task. Twelve male subjects performed maximum screw-tightening exertions using screwdriver handles with three longitudinal shapes (circular, hexagonal and triangular), four lateral shapes (cylindrical, double frustum, cone and reversed double frustum) and two surfaces (rubber and plastic). The average finger force contributions to the total hand force were 28.1%, 39.3%, 26.5% and 6.2%, in order from index to little fingers; the average phalangeal segment force contributions were 47.3%, 14.0%, 20.5% and 18.1% for distal, middle, proximal and metacarpal phalanges, respectively. The plastic surface handles were associated with 15% less torque output (4.86 Nm) than the rubber coated handles (5.73 Nm). In general, the vertical workpiece orientation was associated with higher torque output (5.9 Nm) than the horizontal orientation (4.69 Nm). Analysis of handle shapes indicates that screwdrivers designed with a circular or hexagonal cross-sectional shape result in greater torque outputs (5.49 Nm, 5.57 Nm), with less total finger force (95 N, 105 N). In terms of lateral shape, reversed double frustum handles were associated with less torque output (5.23 Nm) than the double frustum (5.44 Nm) and cone (5.37 Nm) handles. Screwdriver handles designed with combinations of circular or hexagonal cross-sectional shapes with double frustum and cone lateral shapes were optimal in this study.

ORIGINAL RESEARCHORIGINAL RESEARCH—ERECTILE DYSFUNCTION: Cutting Off the Nose to Save the Penis

INTRODUCTION The average bicycle police officer spends 24 hours a week on his bicycle and previous studies have shown riding a bicycle with a traditional (nosed) saddle has been associated with urogenital paresthesia and sexual dysfunction. AIM The objective of this study was to assess the effectiveness of the no-nose bicycle saddle as an ergonomic intervention and their acceptance among male bicycle police officers. METHODS Bicycle police officers from five U.S. metropolitan areas were recruited for this study. Officers completed: (i) the International Index of Erectile Function Questionnaire (IIEF); (ii) computerized pressure measurements at the points of contact on the bicycle; the handlebars, the pedals, and the saddle; (iii) one night of nocturnal Rigiscan assessment; (iv) penile vibrotactile sensitivity threshold assessed by computerized biothesiometery. Officers selected a no-nose saddle for their bicycles and were asked to use the intervention saddle exclusively for 6 months, at which point they were retested. MAIN OUTCOME MEASURES Perineal pressure, urogenital numbness, penile vibrotactile sensitivity threshold, erectile function as measure by International Index of Erectile Function Questionnaire (IIEF) and Rigiscan. RESULTS After 6 months, 90 men were reassessed. Only three men had returned to a traditional saddle. The results are presented for those who used the no-nose saddle continuously for 6 months. There was a 66% reduction in saddle contact pressure in the perineal region (P < 0.001). There was a significant improvement in penis tactile sensation (P = 0.015). There was a significant improvement in erectile function assessed by IIEF (P = 0.015). There were no changes noted in the Rigiscan measures. The number of men indicating they had not experienced urogential paresthesia while cycling for the preceding 6 months, rose from 27% to 82% using no-nose saddles. CONCLUSIONS (i) With few exceptions, bicycle police officers were able to effectively use no-nose saddles in their police work. (ii) Use of no-nose saddles reduced most perineal pressure. (iii) Penile health improved after 6 month using no-nose saddles as measured by biothesiometry and IIEF. There was no improvement in Rigiscan(R) measure after 6 months of using no nose saddles, suggesting that a longer recovery time may be needed..

A Checklist for the Ergonomic Evaluation of Nonpowered Hand Tools

A checklist was developed to evaluate nonpowered hand tools for basic features related to good ergonomic tool design. The checklist contains 16 items to which a yes/no response is required. The checklist is intended to be used by tradespersons and is written in clear, simple language. This column reports on a study conducted to examine the reliability of the checklist questions in identifying the presence or absence of the basic ergonomic design features that are believed to be important for nonpowered hand tools. Using the checklist, 14 ergonomists and 126 carpenters evaluated 18 typical hand tools. Agreement among the carpenters and ergonomists was high for most of the checklist items. A few checklist questions were associated with relatively low agreement among raters in terms of the presence or absence of a design feature. Lack of agreement between raters indicates that the criterion was not explicit or that users had difficulty identifying whether the tool satisfied the particular criterion. The majority of the 18 hand tools evaluated were deemed to be lacking in multiple highly important ergonomic design features. Additional studies are being conducted to make appropriate revisions to the checklist criteria based on quantitative measures of musculoskeletal loading.

Women's Bike Seats: A Pressing Matter for Competitive Female Cyclists

INTRODUCTION There are numerous genital complaints in women cyclists, including pain, numbness, and edema of pelvic floor structures. Debate ensues about the best saddle design for protection of the pelvic floor. AIM To investigate the relationships between saddle design, seat pressures, and genital nerve function in female, competitive cyclists. METHODS We previously compared genital sensation in healthy, premenopausal, competitive women bicyclists and runners. The 48 cyclists from our original study comprise the study group in this subanalysis. MAIN OUTCOME MEASURES Main outcome measures were: (i) genital vibratory thresholds (VTs) determined using the Medoc Vibratory Sensation Analyzer 3000 and (ii) saddle pressures as determined using a specially designed map sensor. RESULTS More than half of the participants (54.8%) used traditional saddles, and the remainder (45.2%) rode with cut-out saddles. On bivariate analysis, use of traditional saddles was associated with lower mean perineal saddle pressures (MPSP) than riding on cut-out saddles. Peak perineal saddle pressures (PPSP) were also lower; however, the difference did not reach statistical significance. Saddle design did not affect mean or peak total saddle pressures (MTSP, PTSP). Saddle width was significantly associated with PPSP, MTSP, and PTSP but not with MPSP. Women riding cut-out saddles had, on average, a 4 and 11 kPa increase in MPSP and PPSP, respectively, compared with women using traditional saddles (P = 0.008 and P = 0.010), after adjustment for other variables. Use of wider saddles was associated with lower PPSP and MTSP after adjustment. Although an inverse correlation was seen between saddle pressures and VTs on bivariate analysis, these differences were not significant after adjusting for age. CONCLUSION Cut-out and narrower saddles negatively affect saddle pressures in female cyclists. Effects of saddle design on pudendal nerve sensory function were not apparent in this cross-sectional analysis. Longitudinal studies evaluating the long-term effects of saddle pressure on the integrity of the pudendal nerve, pelvic floor, and sexual function are warranted.

Evaluation of Various Handle Grip Spans for Optimizing Finger Specific Force Based on the Users' Hand Sizes

This study evaluated the effects of handle grip span and users hand size on maximum grip strength and individual finger force using a computerized digital dynamometer with five various grip spans (45, 50, 55, 60, and 65mm). Forty-six males participated and were assigned into three hand size groups (small, middle, large) according to their hand lengths. Results showed that generally 55 and 50mm grip spans had the highest grip strength (433.6N and 430.8N, respectively), whereas 65mm grip span had the least grip strength. With respect to the interaction effect of grip span and hand size, small hand sized participants produced the highest grip forces at the 45mm grip span, followed by 50 and 55mm, middle hand size participants provided the highest grip force at the 55mm followed by 50 and 45mm, whereas large hand size participants exerted the highest grip force at the 55mm followed by 60mm. In the analysis of individual finger force, the middle finger force was the strongest and the highest contribution (37.5%) to the total finger force, followed by ring (28.7%), index (20.2%) and little (13.6%) fingers. In addition, it was noted that each finger had a different optimal grip span for exerting maximum force, resulting in a bowed contoured shaped handle (i.e., the grip span of the handle at the center is larger than that of the handle at the end) for two-handle hand tools.

Finger Tendon Travel Associated with Sequential Trigger Nail Gun Use.

OCCUPATIONAL APPLICATIONS This article reports a method for assessing finger tendon motion associated with the use of a sequential actuation trigger pneumatic nail gun. The two-stage actuation process of the sequential actuation trigger reduces risk of nail puncture injury from unintended nail discharge (relative to the higher risk of the contact actuation trigger). However, widespread adoption of the sequential actuation trigger nail gun throughout the construction industry has been hindered by beliefs about productivity and musculoskeletal concerns about the repetitive trigger actuation and finger motion for each nail fired. Though existing guidelines for finger tendon travel exposure are not well established, predictions derived with the present method combined with productivity standards suggest insufficient evidence to contradict the safety-based recommendation to adopt the sequential actuation trigger trigger. TECHNICAL ABSTRACT Background: Pneumatic nail guns used in wood framing are equipped with one of two triggering mechanisms. Sequential actuation triggers have been shown to be a safer alternative to contact actuation triggers because they reduce traumatic injury risk. However, the sequential actuation trigger must be depressed for each individual nail fired as opposed to the contact actuation trigger, which allows the trigger to be held depressed as nails are fired repeatedly by bumping the safety tip against the workpiece. As such, concerns have been raised about risks for cumulative trauma injury, and reduced productivity, due to repetitive finger motion with the sequential actuation trigger. Purpose: This study developed a method to predict cumulative finger flexor tendon travel associated with the sequential actuation trigger nail gun from finger joint kinematics measured in the trigger actuation and productivity standards for wood-frame construction tasks. Methods: Finger motions were measured from six users wearing an instrumented electrogoniometer glove in a simulation of two common framing tasks—wall building and flat nailing of material. Flexor tendon travel was calculated from the ensemble average kinematics for an individual nail fired. Results: Finger flexor tendon travel was attributable mostly to proximal interphalangeal and distal interphalangeal joint motion. Tendon travel per nail fired appeared to be slightly greater for a wall-building task than a flat nailing task. The present study data, in combination with construction industry productivity standards, suggest that a high-production workday would be associated with less than 60 m/day cumulative tendon travel per worker (based on 1700 trigger presses/day). Conclusion and Applications: These results suggest that exposure to finger tendon travel from sequential actuation trigger nail gun use may be below levels that have been previously associated with high musculoskeletal disorder risk.

Muscular activity of lower limb muscles associated with working on inclined surfaces

This study investigated the effects of visual cues, muscular fatigue, task performance and experience of working on inclined surfaces on activity of postural muscles in the lower limbs associated with maintaining balance on three inclined surfaces – 0°, 14° and 26°. Normalised electromyographic (NEMG) data were collected in 44 professional roofers bilaterally from the rectus femoris, biceps femoris, tibialii anterior and gastrocnemii medial muscle groups. The 50th and 95th percentile NEMG amplitudes were used as EMG variables. Results showed that inclination angle and task performance caused a significant increase in the NEMG amplitudes of all postural muscles. Visual cues were significantly associated with a decrease in the 95th percentile EMG amplitude for the right gastrocnemius medial and tibialis anterior. Fatigue was related to a significant decrease in the NEMG amplitude for the rectus femoris. Experience of working on inclined surfaces did not have a significant effect on the NEMG amplitude. Practitioner Summary: Increasing angle of the working surface and task performance are two main factors contributing to muscular loading in the lower limb muscles. Input of visual cues while working on inclined surfaces may provide beneficial effects on reducing muscular loading to prevent occupational falls.