Steven L. Fischer

The effect of rest break schedule on acute low back pain development in pain and non-pain developers during seated work

A significant portion of the population (25-50%) is known to develop acute low back pain (LBP) within a bout of prolonged sitting. Previous research has supported the use of frequent rest breaks, from seated office work, in order to reduce self-reported LBP, however, there is limited consensus about the recommended frequency and duration of rest breaks. This may be due to the limited consideration of individual differences in acute LBP development. The purpose of this study was to examine the effect of three different standing rest-break conditions on a group of pain developers (PD) and non-pain developers (NPD) engaged in prolonged seated work. Twenty participants completed four one-hour-long bouts of seated typing: Condition A - no rest; Condition B - 5 min of standing rest every 30 min; Condition C - 2.5 min of standing rest every 15 min; Condition D - 50 s of standing rest every 5 min. Self-reported LBP, self-reported mental fatigue and 30-s samples of EMG were collected every 10 min throughout each session. Eight out of 20 participants (40%) reported LBP during Condition A (classified as PD). Only PD demonstrated clinically relevant increases in LBP across conditions where Conditions B, C, or D provided some relief, but did not restore pain scores to their original level, prior to sitting. PD and NPD developed mental fatigue equally, with Conditions B and D helping to reduce fatigue. No differences in productivity were observed between conditions or groups and no main effects were observed for muscle activity, median power frequency or co-contraction. These data suggests that frequent, short, standing rest breaks may help to reduce symptoms of LBP, however they are only a temporary solution as PD still developed clinically important LBP, even with frequent rest breaks.

Patient acuity as a determinant of paramedics' frequency of being exposed to physically demanding work activities.

BACKGROUNDnThe purpose of this investigation was to examine if paramedics frequency of being exposed to highly physically demanding activities, or their perception of physical, clinical, and emotional demands were altered by patients acuity level, operationalized using the Canadian Triage and Acuity Scale (CTAS).nnnMETHODSnPhysical demands descriptions (PDD) were compiled from thirteen services across Canada. The observation sessions took place during a minimum of two full-shift (12-h) ride-outs at each service. Data were obtained from 53 ride-outs, which included a total of 190 calls.nnnRESULTSnHigher urgency calls (CTAS level I or II) required significantly more stretcher handling, equipment handling, and intravenous (IV) work, also prompting higher ratings of perceived clinical, physical, and emotional demand. Independent of CTAS level, stretcher loading with patient (15.0%), horizontal patient transfer (13.7%), and pushing/pulling the stretcher with patient (13.1%) were identified as the most physically demanding tasks.nnnCONCLUSIONSnPatient acuity is an important determinant affecting the frequency for which paramedics are exposed to work tasks with inherent ergonomic hazards (e.g., handling a stretcher with a patient). Patient acuity also affects paramedics perceived clinical, physical, and emotional demands of a call.

Evaluating a prototype device designed to alleviate night vision goggle induced neck strain among military personnel

The purpose of this study was verify the design of a novel Helmet System Support Device (HSSD) that can be used by military aircrew to help intervene on and reduce the high prevalence of neck trouble. Twelve healthy participants repeated simulated helicopter aircrew tasks on 3 separate days. On each day they wore a different helmet configuration, where measures of performance, perceived demand/preference and muscular demand were recorded. The results showed that vigilance tasks were performed over 10% faster with the HSSD configuration compared to wearing the normal helmet configuration. Participants were able to maintain static (endurance) postures for 28% longer, and use of the HSSD helped to prevent neck muscle fatigue in the most demanding task. The results of this design verification study indicate that the HSSD may be a realistic, feasible near-term solution to intervene on the high prevalence of neck trouble among rotary-wing aircrew. Practitioner Summary: This paper verifies the effectiveness of the Helmet System Support Device (HSSD) as an on-body personal protective device to help control exposures associated with aircrew neck trouble. The HSSD reduced perceived demand, reduced cumulative muscle activity in select muscles and provided improved fatigue resistance, meeting its desired design objectives.

Evaluating the Ergonomic Benefit of a Wrist Brace on Wrist Posture, Muscle Activity, Rotational Stiffness, and Peak Shovel-Ground Impact Force During a Simulated Tree-Planting Task:

Background Tree planters are at a high risk for wrist injury due to awkward postures and high wrist loads experienced during each planting cycle, specifically at shovel-ground impact. Wrist joint stiffness provides a measure that integrates postural and loading information. Objective The purpose of this study was to evaluate wrist joint stiffness requirements at the instant of shovel-ground impact during tree planting and determine if a wrist brace could alter muscular contributions to wrist joint stiffness. Method Planters simulated tree planting with and without wearing a brace on their planting arm. Surface electromyography (sEMG) from six forearm muscles and wrist kinematics were collected and used to calculate muscular contributions to joint rotational stiffness about the wrist. Results Wrist joint stiffness increased with brace use, an unanticipated and negative consequence of wearing a brace. As a potential benefit, planters achieved a more neutrally oriented wrist angle about the flexion/extension axis, although a less neutral wrist angle about the ulnar/radial axis was observed. Muscle activity did not change between conditions. Conclusion The joint stiffness analysis, combining kinematic and sEMG information in a biologically relevant manner, revealed clear limitations with the interface between the brace grip and shovel handle that jeopardized the prophylactic benefits of the current brace design. This limitation was not as evident when considering kinematics and sEMG data independently. Application A neuromechanical model (joint rotational stiffness) enhanced our ability to evaluate the brace design relative to kinematic and sEMG parameter-based metrics alone.

Investigating the Effect of Experience and Duration on Kinematics During 1 Hour of Sign Language Interpreting

OCCUPATIONAL APPLICATIONS Upper extremity injuries pose a considerable problem to sign language interpreters. Over 1 hour of interpretation, interpreters experienced a decrease in their mean rate of wrist flexion and extension, while novices also experienced decreases about other wrist and elbow axes as well. It is suspected that interpreters were beginning to fatigue over the 1-hour duration, more so among novices, and that this increasing fatigue may be reducing their ability to “keep-up” with the interpretation. While more research is needed to measure fatigue and the quality of sign output, 1 hour of signing can induce changes in a signers movements. In the near term, injury-prevention efforts could focus on helping interpreters (particularly novices) structure their workload to ensure they provide themselves with ample opportunities for recovery. Imposing stricter guidelines regarding the maximum length of a continuous interpretation session is one example of a practical, near-term intervention. TECHNICAL ABSTRACTu2003Background: Sign language interpreters frequently report pain, and many develop musculoskeletal disorders. Yet, there is limited research quantifying the mechanics of signing independently or how such factors as experience or duration might influence those mechanics. Purpose: The purpose of this study is to determine if duration (within a single session) or experience affected kinematics during a 1-hour simulated classroom interpreting session. Methods: Nine novice (<2 years of experience) and nine experienced (≥5 years of experience) sign language interpreters interpreted for a continuous 60-minute session. Kinematic measures of the left and right upper extremities were recorded and compared between groups (experience) and within participants (time). Results: Duration had a significant effect on the mean angular velocity of right wrist and elbow movements. Novices exhibited decreased velocities between the first and last 15-minute samples for all right limb velocity measures (interaction effect). However, experienced interpreters only exhibited this decrease at the right wrist about the flexion/extension axis (main effect). Additionally, the number of micro-breaks increased between the first and last 15-minute samples about the wrist flexion/extension axis in both groups (main effect) and about the right elbow flexion/extension axis only among novices (interaction effect). Conclusions: Despite anecdotal evidence suggesting that novice interpreters use a less effective signing approach, these data suggest that on the basis of kinematics, novice and experienced sign language interpreters sign using similar kinematics, at least during the initial 15 minutes of an interpreting session. However, over the course of a continuous 1-hour session, differences emerge. It is plausible that novices may be more fatigable than their experienced counterparts or that they have not yet learned strategies to slow the accumulation of fatigue while maintaining the similar signing kinematics.