James P. Dickey

DRY NEEDLE STIMULATION OF MYOFASCIAL TRIGGER POINTS EVOKES SEGMENTAL ANTI-NOCICEPTIVE EFFECTS

OBJECTIVE To test the hypothesis that dry needle stimulation of a myofascial trigger point (sensitive locus) evokes segmental anti-nociceptive effects. DESIGN Double-blind randomized controlled trial. SUBJECTS Forty subjects (21 males, 19 females). METHODS Test subjects received intramuscular dry needle puncture to a right supraspinatus trigger point (C4,5); controls received sham intramuscular dry needle puncture. Pain pressure threshold (PPT) readings were recorded from right infraspinatus (C5,6) and right gluteus medius (L4,5S1) trigger points at 0 (pre-needling baseline), 1, 3, 5, 10 and 15 min post-needling and normalized to baseline values. The supraspinatus and infraspinatus trigger points are neurologically linked at C5; the supraspinatus and gluteus medius are segmentally unrelated. The difference between the infraspinatus and gluteus medius PPT values (PPTseg) represents a direct measure of the segmental anti-nociceptive effects acting at the infraspinatus trigger point. RESULTS Significant increases in PPTseg were observed in test subjects at 3 (p = 0.002) and 5 (p = 0.015) min post-needling, compared with controls. CONCLUSION One intervention of dry needle stimulation to a single trigger point (sensitive locus) evokes short-term segmental anti-nociceptive effects. These results suggest that trigger point (sensitive locus) stimulation may evoke anti-nociceptive effects by modulating segmental mechanisms, which may be an important consideration in the management of myofascial pain.

Capsaicin-Induced Central Sensitization Evokes Segmental Increases in Trigger Point Sensitivity in Humans

UNLABELLED This study investigated whether inducing central sensitization evokes segmental increases in trigger point pressure sensitivity. We evoked central sensitization at the C(5) segment and validated its presence via mechanical cutaneous sensitivity (brush allodynia) testing. Trigger point pressure sensitivity was quantified using the pain pressure threshold (PPT) value. A 50 cm(2) area of the C(5) dermatome at the right lateral elbow was pretreated with 45 degrees heat for 10 minutes. Test subjects (n = 20) then received topical capsaicin cream (0.075%; Medicis, Toronto, Canada) to the C(5) dermatome, whereas control subjects (n = 20) received a topical placebo cream (Biotherm Massage, Montreal, Canada). PPT readings were recorded from the infraspinatus (C(5,6)) and gluteus medius (L(4,5)S(1)) trigger points at zero (pre-intervention), 10, 20, and 30 minutes after intervention; all PPT readings were normalized to pre-intervention (baseline) values. The difference between the PPT readings at the 2 trigger point sites represents the direct influence of segmental mechanisms on the trigger point sensitivity at the infraspinatus site (PPT(seg)). Test subjects demonstrated statistically significant increases in Total Allodynia scores and significant decreases in PPT(seg) at 10, 20, and 30 minutes after application, when compared with control subjects. These results demonstrate that increases in central sensitization evoke increases in trigger point pressure sensitivity in segmentally related muscles. PERSPECTIVE Myofascial pain is the most common form of musculoskeletal pain. Myofascial trigger points play an important role in the clinical manifestation of myofascial pain syndrome. Elucidating the role of central sensitization in the pathophysiology of trigger points is fundamental to developing optimal strategies in the management of myofascial pain syndrome.

Influence of Driving Speed, Terrain, Seat Performance and Ride Control on Predicted Health Risk Based on ISO 263I-I and EU Directive 2002/44/EC:

Operators of load-haul-dump (LHD) vehicles are commonly exposed to whole-body-vibration (WBV) levels above ISO 2631–1 and EU Directive 2002/44/EC guidelines. WBV was measured at the floor and seat while the same operator drove two LHDs on a controlled test track while driving speed, bucket load, ride control, terrain type, driving task, and seat optimization were varied. Frequency-weighted RMS acceleration was calculated and A(8) values were modeled for six driving scenarios. Vibration exposure was lowest when the LHD was driven at the lowest speed, forward, over smooth terrain, with ride control on and the bucket loaded (0.20 m/s2). The A(8) decreased from 0.84 m/s2 when driving with ride control off, over mixed terrain using all gears, to 0.53 m/s2 when driving with ride control on and an optimized seat. The estimated daily exposure decreased but remained just above the ISO 2631–1 and EU Directive 2002/44/EC guidelines.

Survey-based analysis of risk factors for injury among dogs participating in agility training and competition events

OBJECTIVE To identify potential risk factors for agility-related injuries among dogs. DESIGN Internet-based, retrospective, cross-sectional survey. ANIMALS 3,801 privately owned dogs participating in agility training or trials. PROCEDURES A retrospective electronic survey was used to investigate potential risk factors for injury among dogs participating in agility-related activities. Respondents were handlers recruited through member lists of large canine agility associations in Canada and the United Kingdom and through promotion on an agility blog site. Variables evaluated included demographic information for handlers and dogs, exposure variables (eg, frequency of agility practice and competition in the past year), and use of preventive measures intended to keep dogs fit for agility (warmup, cooldown, or conditioning exercises; alternative therapeutic treatments [eg, acupuncture, massage, or chiropractic care]; or dietary supplement products). RESULTS Data were collected from 1,669 handlers of 3,801 agility dogs internationally; 1,209 (32%) dogs incurred ≥ 1 injury. Previous injury (OR, 100.5), ≤ 4 years of agility experience for dogs (OR, 1.5), use of alternative therapeutic treatments (OR, 1.5), and Border Collie breed (OR, 1.7) were associated with increased odds of injury. Handlers having 5 to 10 or > 10 years of experience (OR, 0.8 and 0.6, respectively) and dogs having > 4 years of experience in the sport (OR, 0.6) were associated with decreased odds of injury. CONCLUSIONS AND CLINICAL RELEVANCE Specific factors were associated with agility-related injuries in dogs. Educational prevention strategies should target at-risk populations in an effort to reduce potential injuries. Future research should focus on the biomechanical factors associated with agility-related injuries.

Internet-based survey of the nature and perceived causes of injury to dogs participating in agility training and competition events.

OBJECTIVE To characterize injuries (on the basis of type and severity of injury and affected region of the body) among dogs participating in agility training and competition events and examine associations between injury characteristics and perceived causes of injury. DESIGN Internet-based, retrospective, cross-sectional survey. ANIMALS 3,801 privately owned dogs participating in agility training or trials. PROCEDURES A retrospective electronic survey was developed to investigate demographic factors for dogs and handlers, frequency of participation in agility training and competition, and perceived causes and characteristics of injuries acquired by dogs during agility-related activities. Respondents were handlers recruited through member lists of large canine agility associations in Canada and the United Kingdom and through promotion on an agility blog site. Associations between cause and anatomic site or type of injury and between injury severity (mild vs severe) and setting (competition vs practice) were investigated. RESULTS Surveys were received from 1,669 handlers of 3,801 agility dogs internationally. Handler-reported data indicated 1,209 of 3,801 (32%) dogs had ≥ 1 injury; of 1,523 analyzed injuries, the shoulder (349 injuries), back (282), and neck (189) regions and phalanges (202) were predominantly affected. Soft tissue injuries (eg, strain [muscle or tendon injury; 807], sprain [ligament injury; 312], and contusion [200]) were common. Injuries were most commonly incurred during interactions with bar jumps, A-frames, and dog walk obstacles (260, 235, and 177 of 1,602 injuries, respectively). Anatomic site and type of injury were significantly associated with perceived cause of injury. CONCLUSIONS AND CLINICAL RELEVANCE These findings provided a basis for further experimental studies to identify specific mechanisms of various types of injury in dogs that participate in agility activities.

Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631–1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s2 and 0.14 rad/s2. The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631–1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable. Statement of Relevance: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.

Trunk muscle contributions of to L4-5 joint rotational stiffness following sudden trunk lateral bend perturbations

The purpose of this research was to investigate the contributions of individual muscles to joint rotational stiffness and total joint rotational stiffness about the lumbar spines L(4-5) joint prior to, and following, sudden dynamic lateral perturbations to the trunk. Kinematic and surface EMG data were collected while subjects maintained a kneeling posture on a robotic platform, while restrained so that motions caused by the perturbation were transferred to the pelvis, causing motion of the trunk and head. The robotic platform caused sudden inertial trunk lateral perturbations to the right or left, with or without timing and direction knowledge. An EMG-driven model of the lumbar spine was used to calculate the muscle forces and contributions to joint rotational stiffness during the perturbations. Data showed 95% and 106% increases in total joint rotational stiffness, about the lateral bend and axial twist axes, when subjects had knowledge of the timing of the perturbation. Also, the contralateral muscles exhibited a significantly larger total joint rotational stiffness about the lateral bend axis, and earlier surface EMG responses, than the ipsilateral muscles. The results indicate that, when the timing of the perturbation was unknown, subjects relied more on delayed muscle forces following the perturbation to stiffen the L(4-5) joint.

Cervical spine rotation and range of motion: pilot measurements during driving

Objective: Previous studies have evaluated the cervical range of axial rotation during simulated driving conditions. The goals of this pilot study were to describe cervical spine rotation during in-car driving and determine the percentage of time outside neutral neck rotation and peak cervical axial rotation angles that the subjects adopted during various driving conditions. Methods: Subjects drove around a specified route through the city of Guelph, Ontario, which included residential, thruway, and highway driving; additional minor driving tasks, such as lane changes, were also included. The cervical range of motion was measured continuously throughout the drive using an electromagnetic sensor; we also used videotape to document the specific driving tasks. Results: The subjects spent 87.0 percent (SD = 8.8) of time with their cervical spine in the neutral axial rotation position (±15 degrees). The percentage of time that the subjects spent outside of the neutral range of cervical axial rotation depended upon the driving section (including residential, thruway, and highway), and driving task being performed (starts, stops, and lane changes). The subjects spent a significantly greater proportion of time with their necks rotated beyond neutral during residential driving compared to thruway and highway driving (19.1% SD = 8.3 vs. 10.7% SD = 9.5 and 9.3% SD = 8.7, respectively; p < .001). During driving, the peak angles of cervical axial rotation were an average of 35.7 degrees (SD = 14.2) left and 42.5 degrees (SD = 18.0) right. Conclusions: We observed a large degree of variability in cervical axial rotation during driving. We observed that most of the driving tasks related to stopping had increased proportion of time out of neutral rotation. Also, right-hand lane changes increased time out of neutral rotation more than left-hand lane changes. Drivers routinely adopt nonneutral head positions (on average 13% of the time); this is likely not enough to lead to injury.

A systematic approach to simulating field-based occupational whole-body vibration exposure in the lab using a 6df robot

BACKGROUND Whole-body vibration is a significant workplace risk factor for discomfort and injury in many work sectors. The current approach for evaluating vibration exposures typically involves field studies of seatpan acceleration while the operators perform typical workplace activities. These vibration exposures are then compared to international standards to evaluate the risk of discomfort or injury. This approach does not enable systematic and controlled study of specific workplace factors such as the effect of seating, and it is difficult and expensive to perform. APPROACH TO PAPER: We have developed a systematic approach for studying whole-body vibration in the laboratory setting. This approach involves field studies of occupational exposures measuring the 6 degree of freedom chassis accelerations (translational and rotational) and replication of these exposures in the laboratory. FINDINGS To date, as a research team, we have collected chassis vibration data from specific vehicles in the forestry (skidders), mining (load-haul-dump vehicles), and construction (scrapers) sectors. We have processed these exposures to develop a library of representative vibration motions, and have replicated these motions in the laboratory using a robotic platform. CONCLUSIONS This systematic approach of combining field- and laboratory-based measures has facilitated research into specific relevant questions such as the effects of multi axis vibrations on the physical risks to operator health and direct evaluation of the vibration attenuation properties of industrial seats.

Wrist rotations about one or two axes affect maximum wrist strength

Most wrist strength studies evaluate strength about one axis, and postural deviations about that same axis. The purpose of this study was to determine if wrist posture deviations about one axis (e.g. flexion/extension), or two axes (e.g. flexion/extension and pronation/supination), affect the strength about another axis (e.g. ulnar deviation). A custom-built instrumented handle was used to measure maximum static isometric torque exertions at 18 wrist postures (combinations of flexion/extension, radial/ulnar deviation, and pronation/supination). Ulnar deviation torques were highest when the wrist was in neutral. This pattern was not maintained for the other torque directions; the generated torque tended to be highest when the wrist posture was not neutral. The effects were similar for male and female subjects, although male subjects exerted significantly larger torques in all directions. This study illustrates that there is a complex relationship between wrist posture and maximal wrist torques.