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A gender difference in ability using the stretch-shortening cycle (SSC ability) in the upper extremities has not been studied in detail. This study aimed to devise an index to evaluate SSC ability during powerful elbow flexion and to examine its gender differences. Thirty-three men athletes (19.9 [+ or -] 1.0 years) and 21 women athletes (20.6 [+ or -] 1.2 years) with mastered SSC movements participated in this study. They pulled a 20% load of maximal voluntary contraction (MVC) by elbow flexion as quickly as possible with the dominant upper extremity from the following two preliminary conditions: a static relaxed muscle state (SR condition) and using a countermovement (SSC condition). The muscle power was measured accurately by a power measurement device, which adopted the weight loading method. The peak power under both conditions showed significantly higher values in men than in women. In both genders, the peak power showed significantly lower values in the SSC condition than in the SR condition (p < 0.05). The potentiation of using the SSC was not found in the peak power test. However, the initial power showed significantly higher values under the SSC condition (men: 37.2 [+ or -] 6.4 W; women: 17.4 [+ or -] 5.1 W) than in the SR condition (men: 18.3 [+ or -] 4.3 W; women: 11.2 [+ or -] 3.1 W). Hence, assuming a difference between initial muscle power outputs of the SR and SSC conditions as a difference in SSC ability, an SSC index was devised to evaluate the above ability. The SSC index showed significantly higher values in men (50.1 [+ or -] 12.4) than in women (32.1 [+ or -] 23.2). However, the individual difference of SSC ability was very large in women. The ability of women to use SSC in the upper extremities may be inferior to that of men. Key Words elbow flexion, muscle power, rotary encoder, countermovement

The study examines if the low ankle brachial index (ABI) adequately predicts the risk of cardiovascular events and mortality independently of the Framingham risk score (FRS). Findings indicate that measurement of the ABI could improve the accuracy of cardiovascular prediction separately from the FRS.

We sought to investigate arterial baroreflex (ABR) control of muscle sympathetic nerve activity (MSNA) in the transition from rest to steady-state dynamic exercise. This was accomplished by assessing the relationship between spontaneous variations in diastolic blood pressure (DBP) and MSNA at rest and during the time course of reaching steady-state arm cycling at 50% peak oxygen uptake ([Vo.sub.2peak]). Specifically, DBP-MSNA relations were examined in eight subjects (25 [+ or -] 1 yr) at the start of unloaded arm cycling and then during the initial and a later period of arm cycling once the 50% [Vo.sub.2peak] work rate was achieved. Heart rate and arterial blood pressure were progressively increased throughout exercise. Although resting MSNA [16 [+ or -] 2 burst/min; 181 [+ or -] 36 arbitrary units (au) total activity] was unchanged during unloaded cycling, MSNA burst frequency and total activity were significantly elevated during the initial (27 [+ or -] 4 burst/min; 367 [+ or -] 76 au; P < 0.05) and later (36 [+ or -] 7 burst/min; 444 [+ or -] 91 au; P < 0.05) periods of exercise. The relationships between DBP and burst incidence, burst strength, and total MSNA were progressively shifted rightward from unloaded to the initial to the later period of 50% [Vo.sub.2peak] arm cycling without any changes in the slopes of the linear regressions (i.e., ABR sensitivity). Thus a continuous and dynamic resetting of the ABR control of MSNA occurred during the transition from rest to steady-state dynamic exercise. These findings indicate that the ABR control of MSNA was well maintained throughout dynamic exercise in humans, progressively being reset to operate around the exercise-induced elevations in blood pressure and MSNA without any changes in reflex sensitivity. arterial blood pressure; sympathetic nervous system; arm cycling; exercise onset

The repeated bout effect (RBE) is a phenomenon characterized by less delayed onset muscle soreness (DOMS) and torque deficit after the second of 2 separate eccentric exercise bouts. Previous investigators have reported that shifting of optimum angle after an initial bout of eccentric exercise mediates the RBE. We hypothesized that an RBE for elbow extensor exercise occurs after an initial bout performed at long (starting position of 50[degrees] to an end position of 130[degrees]) but not short (starting position of 0[degrees] to an end position of 80[degrees]) muscle length because strain at long length evokes a shifting of the optimum angle to a longer length. Untrained women performed an initial bout at either long or short length (n = 9 per group) followed 1 week later by a repeated bout (RB) through the full ROM (0-130[degrees]). Extensor torque and optimum angle was evaluated before, immediately after, and 2 days after each bout. A mechanical transducer depressed on the triceps brachii quantified DOMS. Torque deficits were 3% and 7% after exercise at short vs. long length, respectively. Two days after the RB, torque deficit was 8% and 1% for those previously exercising at short vs. long length (group x bout, p < 0.05). Greater DOMS (N) was observed after exercise at long (16 [+ or -] 3) vs. short (23 [+ or -] 2) length; whereas greater DOMS occurred for the short-length (17 [+ or -] 2) vs. long (26 [+ or -] 3) group after the RB (group x bout, p < 0.05). Optimum angle shifted to a longer length after exercise at long (+10 [+ or -] 4[degrees]) vs. short (+1 [+ or -] 3[degrees]) length (group x bout, p < 0.05). After the RB, those exercising previously at short length experienced a shift of + 15 [+ or -] 4[degrees] (main effect, p < 0.05). The findings of this study indicate that the repetitive strain at long but not short muscle length evokes both immediate and sustained shifts in optimum angle to longer lengths, and that this shifting mediates ([r.sup.2] = 0.71) the RBE. Key Words. delayed onset muscle soreness, eccentric exercise, popped sarcomere hypothesis, optimum angle

The myoelectric signal of the sternoclavicular and clavicular portions of the pectoralis major, the biceps brachii, and the lateral head of triceps brachii of 12 healthy men was collected during an isometric hold of 5 different bench press exercises. Grip width (narrow, mid, and wide) and the level of supination/pronation was varied to determine how these factors influence myoelectric amplitude during the flat bench press. A supinated grip resulted in increased activity for the biceps brachii and the clavicular portion of the pectoralis major. Additionally, moving from wide to narrower grip widths increased triceps activity and decreased the sternoclavicular portion of the pectoralis major. However, if the grip was supinated, moving to a narrower grip position did not result in a decrease in muscle activity of the sternoclavicular portion of the pectoralis major. The increase in triceps brachii activity when moving to a narrower grip width was not influenced by the level of supination. Considering the small changes that occur during changes in grip width, the choice of grip position should be determined by the positions athletes adopt during their sport. Sport specificity should supercede attempts to train specific muscle groups. Key Words. electromyographic, bench press, shoulder stability, pectoralis major, biceps brachii

Byline: L. A. Grebenyuk (1) Abstract: The acoustic anisotropy of the skin was studied in healthy children and adults, in patients with a congenitally short extremity or hand syndactyly, and in healthy patients who had their lower extremities lengthened for cosmetic purposes. The age of the subjects varied between 6 and 39 years. In healthy individuals of different ages, the acoustic anisotropy of the skin of the extremities was low. Its character changed after dosed traction of all structures of an extremity segment. A relation between the transition of investing tissue to the oriented and stressed--deformed state and the direction of the traction vector was established. Author Affiliation: (1) Ilizarov Research Center for Restorative Traumatology and Orthopedics, Kurgan, 640014, Russia Article History: Registration Date: 06/10/2004

Byline: L. I. Gerasimova (1), T. V. Varlamova (1), E. G. Antonen (1), E. S. Antropova (1), A. Yu. Meigal (1) Abstract: The number of turns, the mean amplitude, and the peak ratio of the electromyogram (EMG) recorded in m. biceps brachii at different levels of isometric contraction were analyzed in nine age groups (from 1 month to 72 years, N = 192). Regression equations describing the age-related changes in number of EMG turns and mean EMG amplitude were respectively y = --A(2.48 +- 0.14) -- M(1.32 +- 0.17) + B(11.02 +- 0.68) + (194.71 +- 7.81) (P &lt 0.001) and y = --A(2.47 +- 0.19) -- M(1.87 +- 0.23) + B(10.03 +- 0.88) + (321.57 +- 11.05) (P &lt 0.001), where A is the age, years M is the body mass, kg and B is the load, kg. With increasing age, the interference EMG tended to assume a so-called neurogenic form as a result of age-specific organization of motor functions at the segmental level. Author Affiliation: (1) Petrozavodsk State University, Petrozavodsk, Karelia, 185640, Russia Article History: Registration Date: 06/10/2004

Research measuring the bone density of dominant and nodominant arms in older and younger women is presented. Bone density was heaviest in the dominant arm of the older women, implying that the difference in bone mineral density accumulates over years of loading physical activity and energy expenditure onto the dominant arm.

Segmentation of apparently continuous movement has been reported for over a century by human movement researchers, but the existence of primitive submovements has never been proved. In 20 patients recovering from a single cerebral vascular accident (stroke), we identified the apparent submovements that composed a continuous arm motion in an unloaded task. Kinematic analysis demonstrated a submovement speed profile that was invariant across patients with different brain lesions and provided experimental verification of the detailed shape of primitive submovements. The submovement shape was unaffected by its peak speed, and to test further the invariance of shape with speed, we analyzed movement behavior in a patient with myoclonus. This patient occasionally made involuntary shock-like arm movements, which occurred near the maximum capacity of the neuromuscular system, exhibited speed profiles that were comparable to those identified in stroke patients, and were also independent of speed.

Although the straightness of hand paths is a widely accepted feature of human multijoint reaching movement, detailed examinations have revealed slight curvatures in some regions of the workspace. This observation raises the question of whether planned trajectories are straight or curved. If they are straight, 3 possible factors can explain the observed curvatures: (a) imperfect control, (b) visual distortion, or (c) interaction between straight virtual trajectories and the dynamics of the arm. Participants instructed to generate straight movement paths produced movements much straighter than those generated spontaneously. Participants generated spontaneously curved trajectories in the frontoparallel plane, where visual distortion is not expected. Electromyograms suggested that participants generated straighter paths without an increase in arm stiffness. These findings argue against the 3 factors. It follows that planned trajectories are likely to be curved.

We propose a new approach based on dynamic recurrent neural networks (DRNN) to identify, in human, the relationship between the muscle electromyographic (EMG) activity and the arm kinematics during the drawing of the figure eight using an extended arm. After learning, the DRNN simulations showed the efficiency of the model. We demonstrated its generalization ability to draw unlearned movements. We developed a test of its physiological plausibility by computing the error velocity vectors when small artificial lesions in the EMG signals were created. These lesion experiments demonstrated that the DRNN has identified the preferential direction of the physiological action of the studied muscles. The network also identified neural constraints such as the covariation between geometrical and kinematics parameters of the movement. This suggests that the information of raw EMG signals is largely representative of the kinematics stored in the central motor pattern. Moreover, the DRNN approach will allow one to dissociate the feedforward command (central motor pattern) and the feedback effects from muscles, skin and joints.

A mathematical model of the arm tissue mechanical behavior under the effect of external pressure loads is presented. The model has been used to study stress and strain distribution across the tissue, and pressure transmission to the brachial artery, when the arm is compressed by two adjacent cuffs independently inflated. Using this configuration, the tissue elastic parameters (Young modulus and Poisson ratio) can be individually identified using a simple and noninvasive experimental procedure. Model validation has been achieved by comparing its results with data obtained experimentally on 10 subjects. These comparisons demonstrate that the proposed model may constitute a simple but valid new tool able to describe tissue behavior, subjected to external pressures, with sufficient accuracy. Joined with a model of brachial hemodynamics, it might contribute to improve our understanding of noninvasive blood pressure estimation techniques.

When walking at normal and fast speeds, humans swing their upper limbs in alternation, each upper limb swinging in phase with the contralateral lower limb. However, at slow and very slow speeds, the upper limbs swing forward and back in unison, at twice the stride frequency of the lower limbs. The change from 'single swinging' (in alternation) to 'double swinging' (in unison) occurs consistently at a certain stride frequency for agiven individual, though different individuals may change at different stride frequencies. To explain this change in the way we use our upper limbs and individual variations in the occurrence of the change, the upper limb is modelled as a compound pendulum. Based on the kinematic properties of pendulums, we hypothesize that the stride frequency at which the change from 'single swinging' to 'double swinging' occurs will be at or slightly below the natural pendular frequency (NPF) of the upper limbs. Twenty-seven subjects were measured and then filmed while walking at various speeds. The mathematically derived NPF of each subject's upper limbs was compared to the stride frequency at which the subject changed from 'single swinging' to 'double swinging.' The results of the study conform very closely to the hypothesis, even when the NPF is artificially altered by adding weights to the subjects' hands. These results indicate that the pendulum model of the upper limb will be useful in further investigations of the function of the upper limbs in human walking.