Use of back belts in occupational settings.

Studies of the biomechanical and physiological mechanisms of action concerning the prophylactic use of back belts to prevent occupational low back injuries are limited in number and present conflicting findings. The epidemiological data concerning the efficacy of back belts in the prevention of occupational low back injuries are not sufficient to warrant general use of back belts in the occupational setting for uninjured workers. There is actually a potential for increasing the degree of low back injury with general application of back belts in occupational settings. In sum, there are insufficient data in the scientific literature to indicate that general use of back belts in occupational settings is appropriate for uninjured workers. Because the increase in use of soft canvas back belts has been fairly recent, physical and epidemiological studies pertaining specifically to soft canvas back belts are extremely limited. The sample size of many physical investigations also is extremely limited. In many instances, studies concerning the role of back belts in preventing occupational low back injuries have examined conditions that do not apply directly to the use of soft canvas back belts. For these reasons, further studies in both the physical and epidemiological realms are necessary before it is appropriate to use commonly constructed back belts as personal protective equipment in occupational settings.

Relationship of plantar-flexor peak torque and dorsiflexion range of motion to kinetic variables during walking.

BACKGROUND AND PURPOSE: Limited ankle plantar-flexor moments and power during walking have been documented in several patient populations and are believed to contribute to gait deviations. The primary purpose of this study was to determine the relationship of plantar-flexor peak torque (PFPT) and dorsiflexion range of motion (ROM) to peak ankle moments and power during walking in a group of subjects without diabetes mellitus (DM) and in a group of subjects with DM and associated peripheral neuropathies. SUBJECTS: Nineteen subjects, 9 with DM and associated peripheral neuropathies (mean age = 58 years, SD = 14, range = 35-75 years) and 10 without DM (mean age = 57 years, SD = 11, range = 37-68 years), were evaluated. METHODS: The following data were collected on all subjects: PFPT, dorsiflexion ROM, and ankle moments and power during walking (using a two-dimensional link-segment model). Hierarchical multiple regression was used for data analysis. RESULTS: Plantar-flexor peak torque made substantial contributions to the ankle moment (40%) and ankle plantar-flexor power (53%) during walking. There also was a high correlation between PFPT and dorsiflexion ROM (r = .78) and between dorsiflexion ROM and ankle power (r = .72). CONCLUSION AND DISCUSSION: Plantar-flexor peak torque and dorsiflexion ROM are interrelated and appear to be important factors that contribute to ankle plantar-flexor moments and power during walking. This finding suggests that increasing PFPT and dorsiflexion ROM may help decrease gait deviations such as decreased step length and walking speed. When increasing PFPT is not possible, the natural occurrence of limited dorsiflexion ROM may help to maximize ankle moments during walking. Further research is needed to test whether these proposed treatment strategies can have a clinically useful effect. [Mueller MJ, Minor SD, Schaaf JA, et al. Relationship of plantar-flexor peak torque and dorsiflexion range of motion to kinetic variables during walking.

Differences in the gait characteristics of patients with diabetes and peripheral neuropathy compared with age-matched controls.

BACKGROUND AND PURPOSE: Patients with diabetes and peripheral neuropathy have a high incidence of injuries while walking. Biomechanical analysis of their walking may lead to treatments to reduce these injuries. The purpose of this study was to compare (1) the gait characteristics, (2) the plantar-flexor peak torques, and (3) the ankle range of motion of subjects with diabetes mellitus (DM) and peripheral neuropathy with those of age-matched controls. SUBJECTS: Twenty subjects, 10 with DM and a history of peripheral neuropathy (DM group) (mean age = 58 years, SD = 15, range = 35-75) and 10 subjects without diabetes (NODM group) (mean age = 57 years, SD = 11, range = 37-68), were evaluated. METHODS: The following data were collected on all subjects: ankle joint mobility, plantar-flexor peak torque (ankle strength), kinematics of the trunk and lower extremity during normal walking, and ground reaction forces. Moments and power at the ankle, knee, and hip during walking were calculated using a two-dimensional link-segment model. RESULTS: The DM group subjects showed less ankle mobility, ankle moment, ankle power, velocity, and stride length during walking than the NODM group subjects. A significant decrease in ankle strength and mobility appeared to be the primary factor contributing to the altered walking patterns of the DM group. CONCLUSION AND DISCUSSION: The DM group subjects appeared to pull their legs forward using hip flexor muscles (hip strategy) rather than pushing the legs forward using plantar-flexor muscles (ankle strategy), as seen in the NODM group subjects. Implications for treatment are presented to attempt to reduce the number of injuries during walking in patients with DM and peripheral neuropathy.

A study of discomfort with electrical stimulation.

The primary purpose of this study was to investigate the influence of personality variables and contractile forces on magnitude estimates of pain unpleasantness and pain intensity during varying levels of neuromuscular electrical stimulation (NMES). Thirty volunteers, according to their scores on a preferred coping-style questionnaire, were assigned to one of two groups, one designated "monitors" (information seekers) and the other designated "blunters" (information avoiders). All subjects were administered varying levels of two types of NMES, one causing both afferent stimulation and muscle contraction and one causing only afferent stimulation. Subjects judged the intensity and unpleasantness of each current type using magnitude estimation. Data were analyzed using a 2 x 2 x 2 x 3 (coping style x current type x pain descriptor x current level) analysis of variance. The results indicated that the rate of increase of magnitude estimates for unpleasantness and pain intensity that corresponded to increases in current were dependent on (1) the preferred coping style of the subject, (2) whether the stimulus caused a muscle contraction, and (3) whether the subject was judging the intensity or the unpleasantness of the applied stimulus. Behavioral styles appear to affect how subjects characterize the discomfort associated with NMES, and involuntary muscle contractions contribute to the discomfort felt from NMES. These results suggest that interventions tailored to a preferred coping style may increase a subject's level of tolerance to NMES and thus provide a more beneficial treatment.

A comparison of motor unit behaviour in young and aged subjects.

We evaluated motor unit behaviour in young and aged subjects during ramped tension development and release to 10% maximum voluntary contraction requiring 10 seconds to complete. Six young and six elderly adults performed isometric abductor digiti minimi muscle contractions while motor units were recorded with implanted fine wire electrodes. Computer interactive programs yielded interspike interval (ISI) data for 16 units from the young and for 15 units from the aged subjects. Mean ISIs for young were 88.4 ms for shortening and 96.5 ms for lengthening contractions. Units from the aged had ISIs of 110.5 ms and 117.1 ms for shortening and lengthening contractions. Some evidence for between-group differences in firing pattern during ascending and descending ramps was also found.

Relationship of foot deformity to ulcer location in patients with diabetes mellitus.

The purpose of this study was to determine whether a relationship existed between type of foot deformity and the location of ulcers in patients with diabetes and insensitive feet. Forty-two ulcerated feet were examined in 40 patients. All patients had severely decreased or absent sensation. Foot deformities were classified according to operational definitions as 1) Charcot's foot, 2) a compensated forefoot varus, or 3) an uncompensated forefoot varus or forefoot valgus. The plantar surface of the midfoot and forefoot was divided into three regions. Six of the 7 patients with a Charcot's foot showed ulceration at the midfoot. Nine of 18 patients with a compensated forefoot varus showed ulceration at the second, third, or fourth metatarsal head. Fifteen of 17 patients with an uncompensated forefoot varus or forefoot valgus showed ulceration at the first or fifth metatarsal. A significant relationship was found between foot deformity and location of ulcer. These results support the hypotheses 1) that insensitivity, coupled with increased, repetitive pressure, is a primary cause of plantar ulcers and 2) that certain foot types are associated with characteristic patterns of pressure distribution and callus formation.

Electromyographic analysis of knee exercises in healthy subjects and in patients with knee pathologies.

Little information exists about the intensity of contraction required from knee and hip musculature during common therapeutic exercises used for patient populations. This study, therefore, was designed to compare electromyographic data obtained from the vastus medialis, rectus femoris, gluteus medius, and biceps femoris muscles during maximally resisted straight-leg-raising (SLR) exercises with EMG data obtained from the same muscles during quadriceps femoris muscle setting (QS) exercises in healthy subjects and in patients with knee pathologies. Of the 30 participants in the study, 16 had a history of knee injury or surgery. All participants performed randomly ordered trials of the SLR and QS exercises while the EMG data were recorded from surface electrodes and normalized to values derived from maximal effort isometric contraction trials. An analysis of variance demonstrated significantly greater activity (p less than .05) of the vastus medialis, biceps femoris, and gluteus medius muscles during QS exercises than during SLR exercises. The rectus femoris muscle was significantly more active (p less than .05) during SLR exercises than during QS exercises. The study demonstrated remarkably different degrees of muscle activation between the SLR and QS exercises, indicating that the exercise selected will affect the therapeutic intention.

Technique for EMG fine wire connections.

A fine wire electrode connector has been developed to incorporate the benefits of on-site pre-amplification, while concurrently providing the ease of repeatable quick connections for fine wires. Results show artifact-free electromyograms in studies of single motor unit action potentials or during functional activities.