Measurement of angular wrist neutral zone and forearm muscle activity

OBJECTIVES: To determine the forearm muscles activity in different wrist deviated positions and wrist neutral zone, and to assess the self-selected resting position without visual feedback. BACKGROUND: Wrist deviation occurs in almost all industrial and office jobs. This has been deemed hazardous for carpal tunnel syndrome. Proper resting wrist position is likely to decrease the hazard for carpal tunnel pressure. METHODS: Twenty blindfolded subjects without history of hand/forearm musculoskeletal disorders participated in the study. The EMG of the forearm muscles (flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis and, extensor carpi ulnaris) in deviated and neutral wrist postures was recorded at a sampling rate of 1 kHz. Also, wrist neutral zone at rest was measured using a custom-made calibrated uniaxial electrogoniometer. One-way ANOVA with repeated measures was used in order to find the impact of wrist deviation on muscles activity. RESULTS: The participants positioned their wrist in rest at 7 degrees -9 degrees extension and 5 degrees -7 degrees ulnar deviation. Significantly higher EMG activity was recorded for each muscle in the wrist deviated postures when compared to neutral position (P < 0.001). CONCLUSIONS: Self selected wrist neutral posture decreased the muscle activity significantly. Placement of wrists in neutral zone is expected to reduce risk of injuries.     

Consequences of a cross slope on wheelchair handrim biomechanics

OBJECTIVE: To test the hypothesis that pushing on a cross slope leads to increased handrim loading compared with that found on a level surface. DESIGN: Case series. SETTING: Biomechanics laboratory. PARTICIPANTS: Twenty-six manual wheelchair users. INTERVENTION: Subjects pushed their own wheelchairs on a research treadmill set to level, 3 degrees , and 6 degrees cross slopes. Propulsion speed was self-selected for each cross-slope condition. Handrim biomechanics were measured for the downhill wheel, using an instrumented wheelchair wheel and a motion capture system. MAIN OUTCOME MEASURES: Speed, peak kinetics (force, rate of loading, torque), push angle, cadence, push distance, and power output were averaged over a 20-push set for each subject and each cross-slope condition. Outcomes were compared across cross slopes using a repeated-measures analysis of variance. RESULTS: Push angle and cadence were unaffected by cross slope. A trend of decreasing self-selected speeds with increasing cross slope was not significant. There were considerable increases in the peak kinetic measures, with the axial moment increasing by a factor of 1.8 on the 6 degrees cross slope (P=.000). More pushes were required to cover the same distance when on a cross slope (P<.034). The power required for propulsion increased by a factor of 2.3 on the 6 degrees cross slope (P=.000). CONCLUSIONS: Users must push harder when on a cross slope. This increased loading is borne by the users' arms, which are at risk for overuse injuries. Exposure to biomechanic loading can be reduced by avoiding cross slopes when possible.     

超声弹性成像在脑卒中后前臂屈肌痉挛定量评价中的应用

目的探讨应用超声弹性成像技术定量评价脑卒中后前臂屈肌痉挛的可行性及其特点。方法2019年1月至10月,脑卒中后屈腕和屈指肌痉挛的住院患者30例,采用超声弹性成像测量前臂屈肌群桡侧腕屈肌(FCR)、尺侧腕屈肌(FCU)、指浅屈肌(FDS)和指深屈肌(FDP)剪切波速度(SWV),采用改良Ashworth量表(MAS)评定屈腕和屈指肌张力。结果患侧和健侧各肌肉SWV在牵伸位时均显著高于放松位(|Z|>3.844,P<0.001);牵伸位时,患侧各肌肉SWV显著高于健侧(|Z|>3.593,P<0.001);牵伸位与放松位SWV差值比较,患侧各肌肉明显高于健侧(t>3.199,P<0.01);各肌肉牵伸位平均SWV与屈腕MAS评分显著相关(r=0.605,P<0.001);指浅屈肌和与指深屈肌牵伸位平均SWV与屈指MAS评分明显相关(r=0.540,P<0.01)。结论超声弹性成像可以定量评价脑卒中后前臂屈肌群内不同肌肉的痉挛程度。     

Smaller external notebook mice have different effects on posture and muscle activity

BACKGROUND: Extensive computer mouse use is an identified risk factor for computer work-related musculoskeletal disorders; however, notebook computer mouse designs of varying sizes have not been formally evaluated but may affect biomechanical risk factors. METHODS: Thirty adults performed a set of mouse tasks with five notebook mice, ranging in length from 75 to 105 mm and in width from 35 to 65 mm, and a reference desktop mouse. An electro-magnetic motion analysis system measured index finger (metacarpophalangeal joint), wrist and forearm postures, and surface electromyography measured muscle activity of three extensor muscles in the forearm and the first dorsal interosseus. FINDINGS: The smallest notebook mice were found to promote less neutral postures (up to 3.2 degrees higher metacarpophalangeal joint adduction; 6.5 degrees higher metacarpophalangeal joint flexion, 2.3 degrees higher wrist extension) and higher muscle activity (up to 4.1% of maximum voluntary contraction higher wrist extensor muscle activity). Participants with smaller hands had overall more non-neutral postures than participants with larger hands (up to 5.6 degrees higher wrist extension and 5.9 degrees higher pronation); while participants with larger hands were more influenced by the smallest notebook mice (up to 3.6 degrees higher wrist extension and 5.5% of maximum voluntary contraction higher wrist extensor values). Self-reported ratings showed that while participants preferred smaller mice for portability; larger mice scored higher on comfort and usability. INTERPRETATION: The smallest notebook mice increased the intensity of biomechanical exposures. Longer term mouse use could enhance these differences, having a potential impact on the prevention of work-related musculoskeletal disorders.     

一种新型腕手矫形器的结构特点及其使用

目的:介绍一种新型腕手矫形器.方法:该腕手矫形器由腕背护板和腕托架构成的主架,主架的前侧固定安装一U形前支架;食指套圈、中指套圈、无名指套圈和小指套圈分别通过弹力带连接在主架的腕背护扳上;拇指套圈通过钢丝安装在腕背护板的食指套圈一侧;一外展弹力套通过钢丝设置在小指套圈外侧的腕背护板上.使用时可根据矫形需要,将手腕以手心朝上或朝下之方式伸入腕背护板和腕托架构成的主架内,手位于其前方,指套置于滚动套管上的前方,手指伸至滚动套管下的前方,指套圈分别套在食指、中指、无名指和小指上,拇指套圈套在拇指上.然后根据矫形需要活动手腕,实现其各种矫形功能.结果:该新型腕手矫形器可用于伸指肌腱损伤术后保持手指呈伸直状态,以限制手指的活动范围,促进断端的愈合;用于屈指肌腱损伤损伤术后保持腕关节和指关节处于屈曲状态;改善腕关节屈、伸,增加腕关节屈曲的活动范围;增加腕关节桡侧偏移的活动范围;增加桡侧腕屈肌和尺侧腕屈肌肌力、桡侧腕伸肌和尺侧腕伸肌肌力、尺侧伸腕肌和尺侧屈腕肌肌力、指总伸肌肌力、指浅屈肌及指深屈肌肌力.结论:该种型腕手矫形器适用于腕及手的神经、肌腱、肌肉、血管损伤术后保护,腕及手骨折所致的腕关节、指关节运动功能障碍恢复,可改善腕关节活动范围,增加肌力.     

前臂腕掌指矫形器

自行设计一种适合矫正前臂、腕、掌、指功能障碍的矫形器,有利于前臂外伤、手外伤后的保护和功能训练。该矫形器由主架、掌指关节背杆架、前支架、各指的手指套圈和弹力带及钢丝结构组成。由掌背护板和腕托架构成主架,主架的前侧固定安装一U形前支架;食指套圈、中指套圈、无名指套圈和小指套圈分别通过弹力带连接在主架的掌背护板上;拇指套圈通过钢丝安装在掌背护板的食指套圈外侧;一用于腕臂套置的腕臂套圈通过弹力带连接在U形前支架的横杆上。根据训练方式不同,起到了保护神经、肌腱、血管吻合端和防止骨折端错位的作用;起到了改善腕关节、掌指关节、指间关节活动度的作用;起到了增强旋前圆肌、旋前方肌、旋后肌、腕伸肌、腕曲肌、指总伸肌、指深屈肌和指浅屈肌肌力的作用。该矫形器可用于前臂、腕、手损伤术后,能较好地促进该部位功能的恢复。     

Flexor muscle incursion into the carpal tunnel: a mechanism for increased carpal tunnel pressure?

PURPOSE: To explore the hypothesis that the extrinsic finger flexor muscles have the potential to move into the proximal end of the carpal tunnel with wrist extension. METHODS: The most distal muscle fibres from the deep and superficial finger flexors were measured relative to the pisiform bone in 18 cadaveric specimens. Muscle excursions during wrist extension were calculated using regression equations previously reported in the literature. RESULTS: The mean distances from the pisiform were 9.3 and 4.9 mm for the deep and superficial flexors, respectively. Ten flexor muscle bellies were at the level of or distal to the pisiform bone in the anatomical position, while 17 of 36 were within 5 mm. DISCUSSION: The excursions expected with wrist extension indicate that many muscles have the potential to enter the carpal tunnel, especially those within 5 mm of the pisiform bone. Comparing the expected excursions to recent pressure data, corroborating support for the pressure increase is found. CONCLUSION: Although not directly measured, the results of this study indicate incursion of the flexor muscles into the carpal tunnel space, particularly with wrist extension, is a plausible mechanism for increased carpal tunnel pressure. RELEVANCE: Proposing a mechanism by which carpal tunnel pressure is elevated during wrist and finger extension is a stepping stone to determining the etiology of the disease itself. Finding that the flexor muscle bellies appear to enter the carpal tunnel with wrist extension indicates that use of the flexor muscles should be avoided when the wrist and fingers are extended.     

Movement of finger joints induced by synergistic wrist motion

BACKGROUND: An experiment has recently been conducted to evaluate and compare the differences in tendon excursions between the flexor digitorum profundus and superficialis using three mobilization techniques. No previous studies deal with the total joint excursions with constant tendon length. The purpose of this study was to investigate the coordinated motion between the finger and wrist joints resulting from passive tension of the muscles while performing synergistic wrist motion. METHODS: The relative joint positions of the hand and wrist were measured using a three-dimensional motion analysis system with external retroreflective markers 2 mm in diameter placed on the dorsal surface of the hand. Fifty normal subjects, with a 1:1 gender ration, ranging in age from 20 to 40 years, and with no previous history of upper extremity injury, were recruited for the experiment. FINDINGS: The relationships of synergistic motion between the wrist and finger joints due to passive tension in the muscles were approximately linear. The ranges of wrist motion averaged 60 degrees extension and 60 degrees flexion. Moving the wrist from flexion into extension induced synergistic finger joint motion as follows: the distal interphalangeal joint angles changed from an average of 12 degrees of flexion to 31 degrees; proximal-interphalangeal joint angles changed from 19 degrees to 70 degrees; and metacarpal phalangeal joints changed from 27 degrees to 63 degrees of flexion. INTERPRETATION: The relationships of synergistic motion between the wrist and finger joints were systematically documented. Such a relationship could be considered in optimizing the design of dynamic splints used for rehabilitation in post-surgical tendon repair, as well as providing useful information about potential diagnoses of problems with the integrity of the flexor and extensor mechanisms.     

Joint-angle-dependent neuromuscular dysfunctions at the wrist in persons after stroke

OBJECTIVE: To evaluate the joint-angle-dependent neuromuscular functions at the affected wrist in hemiplegic subjects after stroke while doing isometric maximal voluntary wrist flexion and extension across different wrist angles. DESIGN: We investigated torques during isometric maximal voluntary wrist flexions and extensions at 8 different wrist angles, ranging from -45 degrees to 60 degrees. We used the associated electromyographic activities of 2 agonist and antagonist muscle pairs related to wrist and elbow joints for the analysis of muscular coactivations. We compared the data obtained from poststroke subjects' affected and unaffected sides. SETTING: A research laboratory in a rehabilitation center. PARTICIPANTS: Eleven subjects with hemiplegia after stroke with passive range of motion (ROM) in the wrist from -45 degrees to 60 degrees. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Directly measured torques, torques after normalization during maximal isometric wrist contractions, and normalized moving average electromyographic signals of each muscle at the tested positions. RESULTS: The measured torques of the affected wrists were significantly lower than those of the unaffected wrists at all tested angles during wrist flexion and extension (P<.05). The angle-dependent patterns of the normalized torque across the tested wrist angles varied from those of the unaffected wrists (2-way analysis of variance, P<.05). There were decreases in normalized torques during both flexion and extension at the extended positions in the affected group (P<.05). Abnormal cocontractions were found in agonist and antagonist muscle pairs related to wrist and elbow joints, and between the elbow flexor and wrist extensor when subjects did the wrist contractions on the paretic side, especially at the wrist extended positions. CONCLUSIONS: Wrist muscle weakness was distributed unevenly across the selected wrist ROM on the affected side, as represented by the varied patterns of the normalized torque-angle relationship, compared with the unaffected wrists. There were reductions in the selective control of muscle coactivating synergies both single-jointly and cross-jointly in the impaired nervous system during wrist contractions; the extent of these reductions was also related to the wrist angle configuration.     

Effects of the Different Screwdriver Handle Sizes on the Forearm Muscles Activities and Wrist Motion during Screw-driving Work

[Purpose] This study investigated the difference screwdriver handle size has on forearm muscle activities and wrist motion during screw-driving work. [Subjects] Fourteen males aged 20–30 years, were recruited. [Methods] We measured the forearm muscle activities using a MP 150 System and wrist motion using a 3D motion system. The subjects performed screw-driving tasks with different screwdriver handle sizes. [Results] The wrist flexion and ulnar deviation angles and flexor carpi ulnaris muscle activity significantly increased and wrist extension angle significantly decreased during screwdriver work with a thin handle. [Conclusion] We consider that industrial workers should perform screw-driving work using a screwdriver with a thick handle.Key words: Handle size, Screw-driving work, Wrist pain     

Splinting the hand in the functional position after brain impairment: a randomized,controlled trial

OBJECTIVE: To evaluate the effects of 4 weeks of hand splinting on the length of finger and wrist flexor muscles, hand function, and pain in people with acquired brain impairment. DESIGN: Randomized, assessor-blinded trial. SETTING: Rehabilitation center in Australia. PARTICIPANTS: Twenty-eight adults with acquired brain impairment, all within 6 months of the first injury. There was 1 withdrawal. INTERVENTIONS: Subjects in both experimental (n=17) and control (n=11) groups participated in routine therapy-motor training for upper-limb use and upper-limb stretches-5 days a week. The experimental group also wore an immobilizing hand splint in the functional position (10 degrees -30 degrees wrist extension) for a maximum of 12 hours each night for the duration of the 4-week intervention period. MAIN OUTCOME MEASURES: The length of the wrist and extrinsic finger flexor muscles was evaluated by measuring the torque-controlled range of wrist extension with the fingers extended. Functional hand use was evaluated with the Motor Assessment Scale. Pain was evaluated with a visual analog scale. RESULTS: The effects of splinting were statistically nonsignificant and clinically unimportant. At follow-up, estimates of treatment effects slightly favored the control group: range of motion at the wrist favored controls by 2 degrees (95% confidence interval [CI], -7.2 degrees to 3.2 degrees ), function favored controls by 0.2 points (95% CI, -2.7 to 2.3), and pain favored the experimental group by 1cm (95% CI, -4.6 to 2.2). CONCLUSIONS: An overnight splint-wearing regimen with the affected hand in the functional position does not produce clinically beneficial effects in adults with acquired brain impairment.     

Botulinum toxin injection of spastic finger flexors in hemiplegic patients

OBJECTIVE: To assess the outcomes of botulinum toxin injection of spastic finger flexors followed by intensive training of finger extensors. DESIGN: Fourteen subjects with chronic hemiplegia spasticity of the upper limb had electromyographic-guided botulinum toxin injection into the long finger flexors. All patients presented with minimal active finger extension with the wrist flexed, sustained clonus of the finger flexors, functional proximal arm function, and absence of fixed contracture. Cadaver dissections directed selection of two injection sites: the flexor digitorum sublimis and the flexor digitorum profundus. Fifty mouse units of botulinum toxin were injected into each muscle. After injection, the subjects were instructed in a home program of stretching the long finger flexors, upper limb weight bearing with a weight-bearing splint, and exercise to improve finger extension control. RESULTS: Compared with preinjection measures, assessment the first week after the initial injection showed significantly reduced tone, reduced clonus, and greater active finger extension with the wrist in the neutral position. Four months later, the Ashworth scale increased to preinjection levels in the six subjects with repeated injections but was again decreased postinjection. Active finger extension with the wrist in the neutral position and clonus showed a statistically nonsignificant trend toward cumulative improvement after the second injection. CONCLUSION: The greatest change in finger extension and spasticity reduction occurred after the first injection. Continued significant improvement in finger extension was not observed.     

Biofeedback treatment of upper extremity dysfunction in Guillain-Barré syndrome

Two cases are presented of the application of electromyographic biofeedback for increasing activity of wrist and finger musculature in patients with Guillain-Barré syndrome. Patient 1, a 59-year-old woman, quadriplegic, and on a portable respirator for more than five years prior to biofeedback was given visual and auditory feedback for increased output of wrist flexor, finger flexor, and thumb opposition muscles, bilaterally. All muscles improved in activity, 9/12 significantly, although no marked improvements in activities of daily living functions were noted. Patient 2, a 51-year-old man who had experienced good motoric return following onset of the disease, was given feedback for increased activity of finger extensor, finger adductor, thumb and fifth finger opposition, wrist extensor, and finger flexor muscles, bilaterally. Of 18 muscles or muscle groups treated, 17 showed significant increases in output. This patient became ADL functional. It is believed that biofeedback can be an important modality of treatment in this disease even following termination of more traditional therapies, as was true in the present cases, and that greater attention should be paid to patients with Guillain-Barré syndrome than has been to date. It is suggested that biofeedback be initiated, along with other therapies, once the acute stage of the disease is past.     

The effect of electro-acupuncture on spasticity of the wrist joint in chronic stroke survivors

OBJECTIVE: To quantitatively assess the change in spasticity of the impaired wrist joint in chronic stroke patients after electro-acupuncture treatment. DESIGN: Crossover design. SETTING: University medical center research laboratory. PARTICIPANTS: Seven chronic stroke subjects (age, 63.14+/-7.01y). INTERVENTION: Participants received two 6-week treatment regimens: combined electro-acupuncture and strengthening twice a week, and strengthening twice a week only. Muscle strength and spasticity of the wrist joint were quantified by using the Biodex multijoint System 3 Pro. Electro-acupuncture was given through a commercial electro-acupuncture device. MAIN OUTCOME MEASURES: Velocity sensitivity of averaged speed-dependent reflex torque (VASRT); segmented averaged speed-dependent reflex torque (SASRT); Modified Ashworth Scale (MAS) scores; and integrated electromyographic activity of the affected wrist flexors during passive stretch of the affected wrist joint. RESULTS: VASRT was reduced significantly in the combined treatment group (P=.02) after the 6-week period, but not in the strengthening-only group (P=.23); however, no significant immediate effect of electro-acupuncture was observed (P>.05). MAS scores also showed a significant reduction (P<.01). SASRT did not differ significantly across different positions of the joint or across velocity; however, significant differences were present between the 2 treatment groups (P<.05) for each position and at all the velocities except at 20 degrees /s. Integrated electromyographic activity showed a trend for reduction after the combined treatment. CONCLUSIONS: A combination of electro-acupuncture and muscle strengthening exercise for 6 weeks significantly reduced spasticity. The effect of spasticity reduction was consistent across different joint positions and different velocities of passive stretch.     

Effect of computer keyboard slope on wrist position and forearm electromyography of typists without musculoskeletal disorders

BACKGROUND AND PURPOSE: Positioning a computer keyboard with a downward slope reduces wrist extension needed to use the keyboard and has been shown to decrease pressure in the carpal tunnel. However, whether a downward slope of the keyboard reduces electromyographic (EMG) activity of the forearm muscles, in particular the wrist extensors, is not known. SUBJECTS AND METHODS: Sixteen experienced typists participated in this study and typed on a conventional keyboard that was placed on slopes at angles of 7.5, 0, -7.5, and -15 degrees. Electromyographic activity of the extensor carpi ulnaris (ECU), flexor carpi ulnaris (FCU), and flexor carpi radialis (FCR) muscles was measured with surface electrodes, while the extension and ulnar deviation angles of the right and left wrists were measured with electrogoniometers. RESULTS: Wrist extension angle decreased from approximately 12 degrees of extension while typing on a keyboard with a 7.5-degree slope to 3 degrees of flexion with the keyboard at a slope of -15 degrees. Although the differences were in the range of 1% to 3% of maximum voluntary contraction (MVC), amplitude probability distribution function (APDF) of root-mean-square EMG data points from the ECU, FCU, and FCR muscles varied across keyboard slopes. DISCUSSION AND CONCLUSION: Wrist extension decreased as the keyboard slope decreased. Furthermore, a slight decrease in percentage of MVC of the ECU muscle was noted as the keyboard slope decreased. Based on biomechanical modeling and published work on carpal tunnel pressure, both of these findings appear to be positive with respect to comfort and fatigue, but the exact consequences of these findings on the reduction or prevention of injuries have yet to be determined. The results may aid physical therapists and ergonomists in their evaluations of computer keyboard workstations and in making recommendations for interventions with regard to keyboard slope angle.     

Dose-dependent response to intramuscular botulinum toxin type A for upper-limb spasticity in patients after a stroke

OBJECTIVE: To test the hypothesis that intramuscular (IM) botulinum toxin type A (BTX) reduces excessive muscle tone in a dose-dependent manner in the elbow, wrist, and fingers of patients who experience spasticity after a stroke. DESIGN: Randomized, double-blind, placebo-controlled, multicenter, 24-week trial. SETTING: Six academic and 13 private US outpatient medical centers. PARTICIPANTS: Ninety-one patients with a mean age of 60 years (range, 30-79 y). Mean time elapsed from ischemic or hemorrhagic stroke to study enrollment was 25.8 months (range, 0.9-226.9 mo). INTERVENTIONS: Up to 2 treatments of placebo, or 90, 180, or 360U of BTX. Concurrent splinting and physical therapy protocols were permitted, but no changes were allowed during the study. MAIN OUTCOME MEASURES: Wrist, elbow, and finger flexor tone assessed by the Modified Ashworth Scale, physician and patient global assessments, pain, FIM instrument, and Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). RESULTS: Muscle tone decreased more with injections of BTX than with placebo in the wrist flexors at weeks 1, 2, 3, 6, and 9 (P< or =.026); in the elbow flexors at weeks 1, 2, 3, 4, 5, and 9 (P< or =.033); and in the finger flexors at weeks 1 and 3 (P< or =.031). A dose-dependent response was generally observed in tone reduction but not in pain, FIM, or SF-36 measures. CONCLUSIONS: IM BTX reduced muscle tone in a dose-dependent manner in the elbow, wrist, and fingers of patients who experience spasticity after a stroke but did not appear to affect global quality of life or disability.     

Passive properties of the forearm musculature with reference to hand and finger postures

OBJECTIVE: To quantify individual forearm muscle passive forces and evaluate their impact on hand function. DESIGN: The passive force-length properties of the 24 extrinsic hand and wrist muscles were determined in five fresh frozen cadaver arms. BACKGROUND: Muscle force production is a summation of the active and passive force components. The passive properties of the extrinsic finger musculature and wrist musculature appear to strongly affect both hand posture and hand movement. METHODS: The passive force-length properties of extrinsic hand and wrist muscles were determined by applying a slow, continuous extension to each muscle and recording the resulting tension. Each force-length curve was fit using exponential regression and were related to specific joint rotations and seven hand postures by calculating the muscle excursions for those postures. RESULTS: The exponential passive force-length relationship explained over 97% of the experimental variance. The largest passive forces were elicited in the digital extensors in grips involving large flexion angles such as tip pinch, key pinch, and a briefcase grip. CONCLUSIONS: The passive properties of the extrinsic finger musculature and wrist musculature affect both hand posture and movement especially in postures with flexed wrist and fingers.     

Skeletal muscle response to exercise training in congestive heart failure.

To examine the ability of the skeletal muscle of congestive heart failure (CHF) patients to adapt to chronic exercise, five patients performed localized nondominant wrist flexor training for 28 d. Inorganic phosphate (Pi) and phosphocreatine (PCr) were monitored by magnetic resonance spectroscopy in both forearms at rest and during submaximal wrist flexion exercise at 6, 12, 24, and 36 J.min-1 before and after exercise training. Simultaneous measurements of limb blood flow were made by plethysmography at 12, 24, and 36 J.min-1. Forearm muscle mass and endurance were measured by magnetic resonance imaging and wrist flexion exercise before and after training. The Pi/PCr ratio and pH were calculated from the measured Pi and PCr. Exercise cardiac output, heart rate, plasma norepinephrine, and lactate measured during training were not elevated above resting values, confirming that training was localized to the forearm flexor muscles. After training, muscle bioenergetics, as assessed by the slope of the regression line relating Pi/PCr to submaximal workloads, were improved in the trained forearm of each patient, although muscle mass, limb blood flow, and pH were unchanged. Forearm endurance increased by greater than 260% after training. In the dominant untrained forearm, none of the measured indices were affected. We conclude that localized forearm exercise training in CHF patients improves muscle energetics at submaximal workloads in the trained muscle, an effect which is independent of muscle mass, limb blood flow, or a central cardiovascular response during training. These findings indicate that peripheral muscle metabolic and functional abnormalities in CHF can be improved without altering cardiac performance.     

Stroke pattern and handrim biomechanics for level and uphill wheelchair propulsion at self-selected speeds

OBJECTIVES: To investigate the natural stroke patterns of wheelchair users pushing on a level surface, to determine if users adapt their stroke patterns for pushing uphill, and to assess whether there are biomechanic advantages to one or more of the stroke patterns. DESIGN: Case series. SETTING: Biomechanics laboratory. PARTICIPANTS: Twenty-six manual wheelchair users with a spinal cord injury. INTERVENTION: Subjects pushed their own wheelchairs at self-selected speeds on a research treadmill set to level, 3 degrees , and 6 degrees grades. Stroke patterns were measured using a motion capture system. Handrim biomechanics were measured using an instrumented wheel. MAIN OUTCOME MEASURES: Stroke patterns were classified for both level and uphill propulsion according to 1 of 4 common classifications: arcing, semi-circular, single-looping (SLOP), and double-looping (DLOP). Biomechanic outcomes of speed, peak handrim force, cadence, and push angle were all compared across stroke classifications using an analysis of variance. RESULTS: Only 3 of the 4 stroke patterns were observed. None of the subjects used the semi-circular pattern. For level propulsion, the stroke patterns were fairly balanced between arcing (42%), SLOP (31%), and DLOP (27%). Subjects tended to change their stroke pattern for pushing uphill, with 73% of the subjects choosing the arcing pattern by the 6 degrees grade. No statistically significant differences were found in handrim biomechanics or subject characteristics across stroke pattern groups. CONCLUSIONS: Wheelchair users likely adapt their stroke pattern to accommodate their propulsion environment. Based on the large percentage of subjects who adopted the arcing pattern for pushing uphill, there may be benefits to the arcing pattern for pushing uphill. In light of this and other recent work, it is recommended that clinicians not instruct users to utilize a single stroke pattern in their everyday propulsion environments.