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Regulating exercise intensity using ratings of perceived exertion during arm and leg ergometry.

The purpose of this investigation was to examine the validity of regulating exercise intensity using ratings of perceived exertion (RPEs) during arm crank and leg cycle exercise at 50 and 70% peak oxygen consumption (VO2peak). Ten men and seven women [26 (1) years old; mean (SE)] participated in this study. Each subject completed a maximal estimation trial and two submaximal exercise bouts (production trials) on both an arm and leg ergometer. During each maximal estimation trial, subjects were asked to give a RPE for each stage of the exercise. RPEs, heart rates (HR), and power outputs (PO) equivalent to 50 and 70% VO2peak for each exercise mode were then estimated from plots of RPE versus oxygen consumption (VO2), HR versus VO2, and PO versus VO2, respectively. During the submaximal trials, subjects were instructed to select workloads on an arm and leg ergometer that produced the previously estimated RPEs. Comparisons were made for VO2, HR, and PO between the estimation and production trials for each mode at each exercise intensity. HR did not differ between the trials at either 50 or 70% VO2peak during arm and leg ergometry. In addition, VO2 and PO did not differ between the trials at either 50 or 70% VO2peak during arm ergometry and at 50% VO2peak during leg ergometry. However, these two parameters were lower (P < 0.05) during the production trial [1.88 (0.15) l x min(-1) and 89.1 (10.1) W, respectively] as compared to the estimation trial [2.08(0.14) l x min(-1) and 102.4 (6.5)W, respectively] during leg ergometry at 70% VO2peak. In conclusion, using RPEs to regulate exercise intensity is physiologically valid during arm ergometry at both 50 and 70% VO2peak and during leg ergometry at 50% VO2peak. However, this prescriptive approach remains questionable during leg cycle exercise at 70% VO2peak.

Adult↗

Biomechanical mechanism for transitions in phase and frequency of arm and leg swing during walking.

As humans increase walking speed, there are concurrent transitions in the frequency ratio between arm and leg movements from 2:1 to 1:1 and in the phase relationship between the movements of the two arms from in-phase to out-of-phase. Superharmonic resonance of a pendulum with monofrequency excitation had been proposed as a potential model for this phenomenon. In this study, an alternative model of paired pendulums with multiple-frequency excitations is explored. It was predicted that the occurrence of the concurrent transitions was a function of (1) changes in the magnitude ratio of shoulder accelerations at step and stride frequencies that accompany changes in walking speed and (2) proximity of these frequencies to the natural resonance frequencies of the arms modeled as a pair of passive pendulums. Model predictions were compared with data collected from 14 healthy young subjects who were instructed to walk on a treadmill. Walking speeds were manipulated between 0.18 and 1.52 m/s in steps of 0.22 m/s. Kinematic data for the arms and shoulders were collected using a 3D motion analysis system, and simulations were conducted in which the movements of a double-pendulum system excited by the accelerations at the suspension point were analyzed to determine the extent to which the arms acted as passive pendulums. It was confirmed that the acceleration waveforms at the shoulder are composed primarily of stride and step frequency components. Between the shoulders, the stride frequency components were out-of-phase, while the step frequency components were in-phase. The amplitude ratio of the acceleration waveform components at the step and stride frequencies changed as a function of walking speed and were associated with the occurrence of the transitions. Simulation results using these summed components as excitatory inputs to the double-pendulum system were in agreement with actual transitions in 80% of the cases. The potential role of state-dependent active muscle contraction at shoulder joints on the occurrence of the transitions was discussed. Due to the tendency of arm movements to stay in the vicinity of their primary resonance frequency, these active muscle forces were hypothesized to function as escapements that created limit cycle oscillations at the shoulder's resonant frequency.

Acceleration↗

Optimization of two-joint arm movements: a model technique or a result of natural selection?

The fossil record of early hominids suggests that their Arm length, and presumably stature and weight, had a tendency to increase. Using the minimum jerk principle and a related formulation of averaged specific power, ASP, with regard to selected two-joint Arm movements, the current paper explores relationships between ASP, hand trajectory length (or Arm length, or body mass) and mean movement speed, deriving relationships which indicate that ASP is proportional to cubic mean movement speed, but inversely proportional to hand trajectory length (or Arm length, or 1/3 power of body mass). Accordingly, an ;ecological niche' is modeled in a three-parameter space. Either ASP maximization for fixed movement time, or ASP minimization for fixed mean movement speed, taken as selective optimization criterion, allows the increasing of human Arm length during evolution, regardless of the arm-to-forearm length ratio.

Algorithms↗

Two-arm trajectory planning in a manipulation task.

This paper addresses the trajectory planning problem for a task which requires positioning and orienting an object firmly grasped by two hands at a visually specified goal configuration in the horizontal plane. The motor task involves three degrees of freedom (two translational and one rotational), and the motions of the arms are constrained by the physical coupling through the held object. Experimentally measured trajectories of two arms in the coordinated positioning/orienting task are presented. The hypothesis that the rotational and translational components of motions are decoupled and independently planned is tested. Two explicit mathematical models to account for the kinematic features of the two-arm motions are formulated, and the predictions of the models are compared with the experimental data. Both models extend the minimum-jerk model to the two-arm coordinated motions case. The trajectories predicted by the models were found to be in qualitative agreement with the experimental data. However, neither model could account for the observed configuration dependence of the motions, nor for some of the properties of the measured velocity components of the motions. Our findings support the idea that the rotational and translational components of two-arm motions in the positioning/orienting task are independently planned in extra-personal space, and are further combined in a hierarchical fashion to produce the observed motions. The tested models may serve as a basis for further investigations of issues pertinent to the generation of two-arm trajectories.

Arm↗

Human arm stiffness and equilibrium-point trajectory during multi-joint movement.

By using a newly designed high-performance manipulandum and a new estimation algorithm, we measured human multi-joint arm stiffness parameters during multi-joint point-to-point movements on a horizontal plane. This manipulandum allows us to apply a sufficient perturbation to subject's arm within a brief period during movement. Arm stiffness parameters were reliably estimated using a new algorithm, in which all unknown structural parameters could be estimated independent of arm posture (i.e., constant values under any arm posture). Arm stiffness during transverse movement was considerably greater than that during corresponding posture, but not during a longitudinal movement. Although the ratios of elbow, shoulder, and double-joint stiffness were varied in time, the orientation of stiffness ellipses during the movement did not change much. Equilibrium-point trajectories that were predicted from measured stiffness parameters and actual trajectories were slightly sinusoidally curved in Cartesian space and their velocity profiles were quite different from the velocity profiles of actual hand trajectories. This result contradicts the hypothesis that the brain does not take the dynamics into account in movement control depending on the neuromuscular servo mechanism; rather, it implies that the brain needs to acquire some internal models of controlled objects.

Adult↗

Association of upper arm circumference at muscle flexion with lumbar spine bone mineral density.

We investigated the association of upper arm circumference at muscle flexion with lumbar spine (L2-L4) bone mineral density (BMD) in 252 postmenopausal Japanese women (mean age, 62.0 +/- 7.6 years; range, 43-78 years) with right-side dominance. Age, age at menopause, years since menopause (YSM), weight, and height were recorded. Dominant upper arm circumference (cm) was measured at muscle flexion. Lumbar spine BMD was measured by dual-energy X-ray absorptiometry (DXA). Correlations between BMD and variables were determined using Pearson's correlation coefficient. Significant predictors of the lumbar spine BMD were determined using stepwise multiple regression analysis. Upper arm circumference, weight, and height were positively correlated with BMD (r = 0.397, 0.343, and 0.323, respectively), whereas YSM and age were inversely correlated with BMD (r = -0.415 and -0.392, respectively). On stepwise multiple regression analysis, YSM, upper arm circumference, and weight were significant predictors of BMD (R2 = 0.322, P < 0.0001). Predicted value of the lumbar spine BMD was calculated by the following formula: Predicted BMD = 0.249 - 0.0078 (YSM) + 0.016 (upper arm circumference) + 0.0046 (weight). Dominant upper arm circumference at muscle flexion in combination with YSM and weight is a useful predictor of lumbar spine BMD.

Adult↗

Value of arm exercise testing in detecting coronary artery disease.

Alternative methods of exercise testing are needed for patients with vascular, orthopedic or neurologic conditions who cannot perform leg exercise. To determine the sensitivity of arm exercise in detecting coronary artery disease (CAD), 30 patients with angina pectoris performed both arm ergometry and treadmill testing before coronary angiography. All patients had at least 70% diameter reduction in 1 or more major coronary arteries. Ischemic ST depression (greater than or equal to 1 mm) or angina occurred more frequently (86%, 26 patients) with leg exercise than with arm exercise (40%, 12 patients). There was no significant difference in peak rate-pressure product achieved with either test, although the peak oxygen consumption was greater during leg exercise than during arm exercise (18 vs 13 ml/kg/min, respectively, p less than 0.001). For concordantly positive tests, the oxygen consumption at onset of ischemia was significantly lower during arm testing than during leg testing (12 vs 17 ml/kg/min, respectively, p less than 0.001). There was no significant difference in heart rate during either test at onset ischemia. Thus, arm exercise testing is a reasonable, but not equivalent, alternative to leg exercise testing in patients who cannot perform leg exercise.

Aged↗

Stationary potentials after median nerve stimulation: changes with arm position.

We previously reported the presence of stationary negative potentials (N3, N6, N9) over the arm ipsilateral to the side of median nerve stimulation. In this study, we examined the effect of different arm positions upon these stationary peaks in 12 normal subjects. When arm position was changed from elbow extended to elbow flexed 90 degrees, we recorded a new negative peak, N4. The peak latency of N4 corresponded to the traveling impulse reaching the distal biceps brachii. With the elbow flexed, N3, N6 and N9 peak latencies significantly shortened compared to those recorded with the arm in the usual elbow extended position. In contrast, with the arm abducted at the shoulder, N6 and N9 latencies were significantly prolonged while N3 remained unchanged. Corresponding latency shifts were also observed in the bipolarly recorded traveling impulse. We consider 2 possible factors for N4 enhancement by elbow flexion. One is the change in conducting volume surrounding the nerve, i.e., increased muscle bulk of biceps brachii. The other is the change in axial orientation of the propagating nerve impulse by 90 degrees. We also propose that the latency shifts of the stationary potential as well as of a traveling wave can be attributed primarily to relaxation or stretching of the nerve trunk with change in arm position.

Adult↗

Exploiting interlimb coupling to improve paretic arm reaching performance in people with chronic stroke.

OBJECTIVE: To determine whether paretic arm reaching performance is improved in bilateral compared with unilateral conditions. DESIGN: Cohort study. SETTING: University human performance laboratory. PARTICIPANTS: Thirty-two subjects with chronic stroke (57+/-14y; on Fugl-Meyer Assessment arm score, 37+/-14). INTERVENTION: Unilateral and bilateral reaching. Bilateral tasks included varying levels of weight on the nonparetic hand. MAIN OUTCOME MEASURES: An electromagnetic tracking system recorded hand peak acceleration, velocity, and movement time. A 2-way repeated-measures analysis of variance and Tukey-adjusted pairwise comparisons were used to analyze the results (alpha=.05). RESULTS: Paretic differed significantly from nonparetic peak acceleration and velocity in unilateral reaching but not bilateral reaching. Within limbs, the paretic arm attained a higher peak acceleration (P<.001) and velocity (P=.03) in the bilateral compared with the unilateral task, but movement time was unchanged between tasks. Nonparetic peak acceleration was higher (P=.015), velocity was unchanged, and movement time increased (P=.005) in the bilateral compared with the unilateral task. The addition of a weight to the nonparetic arm during bilateral reaching did not result in further improvement in paretic arm performance. CONCLUSIONS: Interlimb coupling effects during bilateral reaching are retained even after chronic stroke and can be used to produce an immediate improvement in paretic arm reaching performance.

Adult↗

An identification technique for evaluating body segment parameters in the upper extremity from manipulator-hand contact forces and arm kinematics.

OBJECTIVE: To show that it is possible to determine segment masses and segment centers of mass by measuring manipulator-hand contact forces and joint angles during upper extremity movement. BACKGROUND: The method serves as a quick subject specific body segment parameter evaluation technique. Clinically we see this method as an alternative upper extremity body segment parameter evaluation study especially useful in rehabilitation treatment activities. METHODS: The experiment is based on coupling the human arm with a robotic manipulator which is then used for imposing a specified sagittal plane trajectory. Joint angles and forces in the contact point serve as input to the identification procedure. For verification purposes the proposed identification procedure was first performed on a mechanical arm. Afterwards a low velocity trajectory was imposed into all joints of the human upper extremity, with very small angular deviations. Within this small angular region the arm was assumed to be represented as a linear system. FINDINGS: The outcome of the identification procedure is an estimate of masses and center of mass coordinates for the lower arm and palm segments, their products for the upper arm and the passive moments around the measured angle of all joints in the sagittal plane. The results obtained for three particular human arms are eventually compared to the average population based literature. CONCLUSION: From the clinical point of view the study can become useful for biomechanical evaluation and for evaluating biomechanical properties of lower extremities or other body segments. This method may also provide a foundation to measuring body segment moments of inertia and joint viscoelastic parameters.

Adult↗

3-D scapular kinematics during arm elevation: effect of motion velocity.

BACKGROUND: No three-dimensional (3-D) data exist on the influence of motion velocity on scapular kinematics. The effect of arm elevation velocity has been studied only in a two-dimensional setting. METHODS: Thirty healthy subjects performed dominant (right) arm elevation in two planes, sagittal and frontal, and at slow and fast self-selected arm speed. Scapular orientation and humeral elevation were measured at 30 Hz recording frequency with use of a 6-degree-of-freedom electromagnetic system (Polhemus Fastraka). Motion was computed according to the International Society of Biomechanics standards. Scapular orientation was also determined with the arm held in different static positions. FINDINGS: We obtained a full 3-D kinematic description of scapula achieving a reliable, complex 3-D motion during humeral elevation and lowering. The maximal sagittal arm elevation showed a characteristic "M"-shape pattern of protraction/retraction curve. Scapular rotations did not differ significantly between slow and fast movements. Moreover, protraction/retraction and tilt angular values did not differ significantly between static and dynamic tasks. However, scapular lateral rotation values differed between static and dynamic measurements during sagittal and frontal arm elevation. Lateral scapular rotation appears to be less in static than in dynamic measurement, particularly in the sagittal plane. INTERPRETATION: Interpolation of statically recorded positions of the bones cannot reflect the kinematics of the scapula.

Adult↗

Modulations of interlimb and intralimb cutaneous reflexes during simultaneous arm and leg cycling in humans.

OBJECTIVE: We investigated to what extent intralimb and interlimb cutaneous reflexes are altered while simultaneously performing arm and leg cycling (AL cycling) under different kinematic and postural conditions. METHODS: Eleven subjects performed AL cycling under conditions in which the arm and leg crank ipsilateral to the stimulation side were moved synchronously (in-phase cycling) or asynchronously (anti-phase cycling) while sitting or standing. Cutaneous reflexes following superficial radial or superficial peroneal nerve stimulation (2.0-2.5 times radiating threshold, 5 pulses at 333 Hz) were recorded at 4 different pedal positions from 12 muscles in the upper and lower limbs. Cutaneous reflexes with a peak latency of 80-120 ms were then analyzed. RESULTS: The magnitude of interlimb and intralimb cutaneous reflexes in the arm and leg muscles was significantly modulated depending on the crank position for the relevant limb (phase-dependent modulation). A significant correlation between the magnitude of the cutaneous reflex and background EMG was observed in the majority of muscles during static contraction, but not during AL cycling (task-dependent modulation). No significant difference was found in comparisons of the magnitude of intralimb and interlimb cutaneous reflexes obtained during in- and anti-phase AL cycling. Qualitatively, the same results were obtained during AL cycling while sitting or standing. In addition, the modulation of cutaneous reflexes in arm muscles was identical among in-phase, anti-phase and isolated arm cycling. Results were the same for leg muscles. CONCLUSIONS: Cutaneous reflexes in arm muscles are little influenced by rhythmic movement of the legs and vice versa during AL cycling. It is likely that neural components that control interlimb reflexes are loosely coupled during AL cycling while sitting or standing. SIGNIFICANCE: Our results provide a better understanding of the coordination between the upper and lower limbs during rhythmic movement.

Adult↗

The direction of oscillation in spiral drawings can be used to differentiate distal and proximal arm tremor.

The assessment of the extent of involvement of the distal and proximal joints in a complex arm tremor is important clinically, as tremor generated around the distal and proximal arm joints can be differentially alleviated by surgical intervention to the thalamic and subthalamic targets, respectively. We observed that the tremor present in spiral drawings shows a diagonal directional preference. We hypothesized that the directional preference of tremor within spiral drawings could be related to the involvement of different arm joints. In this study, we tested this hypothesis by: (1) studying simulated tremulous drawings performed by healthy subjects with the joints selectively restrained; (2) recording surface EMGs from the forearm extensor and deltoid muscles during drawing; and (3) mathematical modelling the kinematics of the arm in 2D drawings. Our data showed that a "main diagonal" axis of orientation of the tremor along the orientation of the forearm indicates a predominantly proximal tremor driven by the shoulder, and a "cross diagonal" axis of orientation of tremor (i.e. perpendicular to the forearm) indicates that the tremor is predominantly distal and driven by the elbow or wrist. We conclude that the spiral drawing task can be used as an objective and quantitative method for differentiating the involvement of the proximal and distal arm joints in complex arm tremors.

Activity Cycles↗

Is impairment similar between arm and leg cranking exercise in COPD patients?

UNLABELLED: Impaired skeletal muscle function has been reported in patients with chronic obstructive disease (COPD), but such impairment is not homogenous and its distribution between the upper and the lower limbs is still unclear. The present study was designed to assess and compare upper and lower limb capacities in patients with moderate to severe COPD during incremental and constant-load exercises. Thirteen COPD patients of similar age with moderate to severe air flow limitation (FEV(1): 35%+/-5% predicted) and 19 healthy subjects were studied. Four sessions were organized: two incremental and two constant-load cycling exercises with arm or leg in randomized order. As observed in a previous study involving incremental and constant tests, power, VO(2), RER, VE, and HR were all significantly lower in the upper and lower limbs of patients with COPD than in healthy controls. In the healthy population, aerobic capacity and mechanical efficiency (ME) were lower in the course of arm exercises than in leg exercises. For the same relative workload, dyspnea and blood lactate production were higher during arm exercise. In contrast, no significant difference was observed between arm and leg capacities for any of these parameters in COPD patients. CONCLUSION: Although aerobic capacity is impaired in COPD patients, arm aerobic capacity is relatively preserved. Given the lack of significant difference between arm and leg capacities in COPD, we hypothesize that upper limb muscles are less compromised than lower limb muscles in this patient population.

Aged↗

Changes in blood coagulation of arm and leg veins during a simulated long-haul flight.

INTRODUCTION: Long-haul flights are associated with an increased incidence for venous thromboembolic events. At present, markers of coagulation and fibrinolysis were only analyzed from arm veins after long distance travel. Respective data from leg veins are missing. MATERIALS AND METHODS: Here, we measured these parameters in healthy volunteers (n=12) before and after 10 h sitting in modern aircraft chairs under normobaric hypoxia (corresponding to 2400 m altitude). Blood was collected from arm and leg veins before, immediately after and 1 day after sitting in the hypoxic chamber. RESULTS: We did not find any evidence for a significant intravasal thrombin and fibrin formation and a changed fibrinolytic activity, neither in arm nor in leg vein blood. TAT, PAP, and PAI-1 remained unchanged, and the increases of F1+2 in arm veins and of d-dimer in leg veins were within the upper reference limits. Moreover, there was no evidence of activation of coagulation as measured by thrombelastography (ROTEM(R)) and the new Thrombin Dynamic Test at both locations. There was no evidence of arm or leg hemoconcentration. CONCLUSIONS: In healthy volunteers, prolonged sitting in ergonomically superior aircraft seats does not induce significant changes in blood coagulation and fibrinolysis in venous blood of arm or leg. Since this study was performed under moderate hypoxia, reduction in oxygen pressure seems not to be a crucial factor for venous thrombosis at long-haul flights.

Adult↗

Predicting birth weight by fetal upper-arm volume with use of three-dimensional ultrasonography.

OBJECTIVE: Our purpose was to determine the usefulness and accuracy of the three-dimensional ultrasonography assessed fetal upper-arm volume in predicting birth weight. STUDY DESIGN: From June 1996 to October 1996, we performed a prospective study of ultrasonography on 105 pregnant women without fetal structural anomaly or aneuploidy. Both the traditional two-dimensional ultrasonographic parameters and three-dimensional ultrasonography for fetal upper arm volume were measured within 48 hours of delivery. RESULTS: The upper arm volume correlated well with birth weight (r = 0.92, n = 105, p < 0.0001). With use of linear and polynomial regression, we obtained a best-fit new formula, Birth weight = 1088.60 + 36.024 x Upper-arm volume. The accuracy of this new formula is compared with that of two Chinese equations predicting fetal weight reported before and other formulas commonly used in the world as well. Our formula is more accurate in predicting birth weight than all the other formulas by traditional two-dimensional ultrasonography, either in error, percentage error, or absolute error. Another group by prospective validation further proved this finding. CONCLUSION: The upper-arm volume assessed by three-dimensional ultrasonography can accurately predict birth weight, and its accuracy is superior to the previous, formulas. Our study has at least validated the application of upper-arm volume by three-dimensional ultrasonography in estimating fetal weight. Further larger series are needed to confirm our findings.

Adult↗

Postural responses to unilateral arm perturbation in young, elderly, and hemiplegic subjects.

OBJECTIVE: To compare postural responses during standing associated with self-paced unilateral arm flexion exhibited by young and elderly healthy subjects and subjects with hemiplegia from stroke. DESIGN AND SETTING: Descriptive cross-sectional study in a laboratory setting. PATIENTS: Ten young, 10 elderly healthy subjects, and 12 volunteers with longstanding hemiparesis following stroke were tested. The hemiplegic group had good functional balance scores on the Berg Balance Scale (BBS). MAIN OUTCOME MEASURES: The peak arm acceleration, center of pressure (CP) excursion speed, and the electromyographic activity in the posterior leg muscles (bilateral hamstrings and triceps surae) were monitored during self-initiated rapid unilateral arm flexion and during quiet stance. RESULTS: During unilateral arm flexion, the young group showed the highest arm accelerations and lowest CP excursion speeds. The variability of postural responses was largest in the elderly and hemiplegic groups with hemiplegic subjects showing the greatest CP excursion speeds for the lowest arm accelerations. The first burst of activity in ipsilateral hamstrings muscle was the same in all subjects. However, the hemiplegic group had less activation (latency and amplitude) of other posterior leg muscles. CONCLUSION: The elderly subjects had more variable responses to perturbation than the young subjects despite similar BBS scores. This may indicate that the BBS fails to detect differences in balance at the high end of the scale. Although the hemiplegic subjects demonstrated some anticipatory control of standing balance, they consistently performed poorer than elderly and young controls. The failure to coordinate postural leg muscle activity with focal movement may contribute to the instability of subjects with hemiplegia.

Adult↗

Bilaterally decreased motor performance of arms in patients with chronic tennis elbow.

OBJECTIVE: To measure the motor performance of arms in patients with chronic unilateral tennis elbow. DESIGN: Cross-sectional case-control study. SETTING: University hospital clinic admitting chronic hand patients. SUBJECTS: Thirty-two patients with chronic unilateral tennis elbow syndrome and 32 age- and gender-matched controls. MAIN OUTCOME MEASURES: The motor performance of arms was measured with the Human Performance Measurement/Basic Elements of Performance system using the module for hands and the protocol of the device. Reaction times, speed of movement, and coordination as a combination of speed of movement and accuracy (number of correct hits) were measured. The results were compared between patients and controls. RESULTS: Simple one-choice and two-choice reaction times were 19% to 36% slower in the patients than in the controls, and speed of movement was 31% to 32% slower in the patients than in the controls. The differences were statistically significant. The coordination results were 9.6bits/sec in the patients and 9.7bits/sec in the controls. The difference was not statistically significant. The reaction times and speed of movement did not differ significantly between the patients' involved and healthy arms. The patients' healthy arms showed significantly slower reaction times and speed of movement than the corresponding arms of the controls. CONCLUSIONS: Unilateral chronic tennis elbow patients have bilaterally decreased reaction times and speed of movement of arms compared with age- and gender-matched controls. The cause for this phenomenon is unclear; the decreased motor performance may be primary and show an increased susceptibility to develop the tennis elbow syndrome or it may be a result of chronicity.

Adult↗