The effects of a weight belt on trunk and leg muscle activity and joint kinematics during the squat exercise.

Fourteen healthy men participated in a study designed to examine the effects of weight-belt use on trunk- and leg-muscle myoelectric activity (EMG) and joint kinematics during the squat exercise. Each subject performed the parallel back squat exercise at a self-selected speed according to his own technique with 90% of his IRM both without a weight belt (NWB) and with a weight belt (WB). Myoelectric activity of the right vastus lateralis, biceps femoris, adductor magnus, gluteus maximus, and erector spinae was recorded using surface electrodes. Subjects were videotaped from a sagittal plane view while standing on a force plate. WB trials were completed significantly faster (p < 0.05) than NWB trials over the entire movement and in both the downward phase (DP) and upward phase (UP). No significant differences in EMG were detected between conditions for any of the muscle groups or for any joint angular kinematic variables during either phase of the lift. The total distance traveled by the barbell both anteriorly and vertically was significantly greater (p < 0.01) in the WB condition than the NWB condition. The velocity of the barbell was significantly greater (p < 0.01) both vertically and horizontally during both the DP and UP in the WB condition as compared with the NWB condition. These data suggest that the use of a weight belt during the squat exercise may affect the path of the barbell and speed of the lift without altering myoelectric activity. This suggests that the use of a weight belt may improve a lifter's explosive power by increasing the speed of the movement without compromising the joint range of motion or overall lifting technique.

Relationship between the pharmacokinetics and the analgesic and respiratory pharmacodynamics of epidural sufentanil.

To establish the relationships between epidural sufentanil analgesia and respiratory effects and to determine the pharmacokinetics of the drug, 22 adult patients undergoing thoracotomy were put into a randomized, double-blind study and received either 30, 50, or 75 micrograms per dose in 20 ml normal saline solution. Repeated doses were given on request for the 24-hour study period. There was a weak but significant nonlinear correlation between length of effective analgesia and the cumulative dose of the drug (r = 0.26, p less than 0.001). In 12 of 22 patients, the maximal length of effective analgesia was reached before the last dose and the effect tended to taper off thereafter. The mean maximal length of effective analgesia was 4.69 +/- 0.32 hours (mean +/- SEM), whereas the length of effective analgesia with the last dose was only 3.34 +/- 0.46 hours (p less than 0.0005). There was a significant correlation between the peak serum concentrations of sufentanil during the dose interval and the length of effective analgesia (r = 0.44, p less than 0.0001). Area under the concentration-time curve was proportional to the size of the epidural dose, and with all three doses tested there was a gradual accumulation of sufentanil in the serum. Mean time-to-peak concentration (tmax) increased with repeated doses (p less than 0.05). Mean serum concentration of sufentanil during periods of slow respiratory rate (0.47 +/- 0.05 ng/ml) was significantly higher than during episodes without adverse respiratory effects (0.37 +/- 0.05 ng/ml, p less than 0.05). The above data suggest that an important part of the analgesic and adverse effects of sufentanil are mediated centrally, after this opioid is absorbed systemically.

Analgesic and respiratory effects of epidural sufentanil in patients following thoracotomy.

Immediately following thoracotomy, 22 patients were entered into a randomized, double blind study comparing the effects of three lumbar epidural doses of sufentanil on postoperative pain and respiratory pattern. Patients were given either 30 micrograms (group I), 50 micrograms (group II), or 75 micrograms (group III) of epidural sufentanil in 20 ml N saline. Repeat doses were given on request for the 24-h study period. Linear analogue pain score (PS), heart rate (HR), and mean arterial pressure (MAP) were measured at 15-min intervals after each dose. Respiratory depression was assessed by the presence of: 1) slow respiratory rate (SRR--less than 10 breaths per minute for greater than 5 min), 2) apnea (AP--cessation of tidal ventilation for greater than 15 s), and 3) increased PaCO2 in arterial blood gases (ABG) drawn at regular intervals. SRR and AP were measured using respiratory inductive plethysmography (RIP). A further group of ten patients (group IV) underwent preoperative RIP monitoring during sleep and in the absence of any drug. Maximum analgesia was achieved within 15 min after a dose of sufentanil for all groups. Analgesia was not significantly prolonged by increasing the dose of sufentanil. SRR occurred in all four groups (group I: 2/9; group II: 2/6; group III: 7/7; group IV: 2/10 P less than 0.05 I, IV:II, I, IV:III, II:III). The number of episodes of SRR/hr was highest in group II (group I: 0.6 +/- 0.8, group II: 4.12 +/- 0.6, group III: 1.8 +/- 2.0, group IV: 0.5 +/- 0.2) (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Kinematic analysis of human upper extremity movements in boxing.

Using two synchronized cameras, four experienced boxers were filmed while they threw a series of punches at a practice bag. Three-dimensional (3D) coordinates of each boxer's shoulder, elbow, wrist, and glove were used to estimate linear and angular kinematics of the upper extremity. Average velocities at contact ranged from 5.9 to 8.2 m/s with peak velocities of 6.6 to 12.5 m/s reached 8 to 21 ms prior to hand/grove contact with the bag. Significant differences in shoulder and wrist velocitie, elbow angle excursions, and elbow angular velocities were seen when comparing hooks and jabs. Few differences were evident when comparing the kinematics of gloved versus bare-handed punches. Results are significant in providing kinematic data characteristic of experienced performers, which may be used in a kinetic model of punch impact and its relationship to potential injury mechanisms.

Mechanical output of the cat soleus during treadmill locomotion: in vivo vs in situ characteristics.

To study the mechanical output of skeletal muscle, four adult cats were trained to run on a treadmill and then implanted under sterile conditions and anesthesia with a force transducer on the soleus tendon and EMG electrodes in the muscle belly. After a two-week recovery period, five consecutive step cycles were filmed at treadmill speeds of 0.8, 1.3 and 2.2 m s-1. Locomotion data in vivo included individual muscle force, length and velocity changes and EMG during each step cycle. Data for an average step cycle at each speed were compared to the force-velocity properties obtained on the same muscle under maximal nerve stimulation and isotonic loading conditions in situ. Results indicate that the force and power generated at a given velocity of shortening during late stance in vivo were greater at the higher speeds of locomotion than the force and power generated at the same shortening velocity in situ. Strain energy stored in the muscle-tendon unit during the yield phase in early stance is felt to be a major contributor to the muscle's enhanced mechanical output during muscle shortening in late stance.

Ground reaction forces and center of pressure patterns in the gait of children with amputation: preliminary report.

Ground reaction forces and center of pressure (CP) were studied during gait in children with unilateral lower extremity amputations. Five children, three with knee disarticulations and two with above-knee amputations, walked at slow, normal, and fast speeds, while wearing a conventional SACH prosthetic foot and again, while wearing an experimental CAPP prosthetic foot. Fore-aft (F-A) and vertical force (VF) components and CP patterns were examined for a total of 90 trials. Walking speed had a significant effect on both F-A and VF amplitudes. No differences, however, were found between the force amplitudes of the SACH foot and CAPP foot. Significant asymmetries were found in the force and amplitudes of a child's natural limb versus the prosthetic limb; the retarding and propelling F-A forces in the prosthetic limb were significantly less than the corresponding forces in a child's natural limb. The CP patterns during stance phase were markedly different for a child's natural limb, prosthetic limb with the SACH foot, and prosthetic limb with the CAPP foot. With the CAPP foot, the CP remained in the forefoot region during stance. In contrast with the CAPP foot, the SACH foot had a potential for producing a flexor moment at the knee joint at the initiation of the foot-ground contact. Stability in the prosthetic knee was enhanced when the children wore a CAPP prosthetic foot.

Three-dimensional cinematographic analysis of water polo throwing in elite performers.

Thirteen members of the United States Men's Water Polo Team were filmed using two synchronized cameras while shooting at a goal. Three-dimensional (3D) coordinates of the throwers' shoulder, elbow, wrist, and the ball were used to estimate elbow angle, elbow angular velocity, and ball velocity at release. Ball release velocities ranged from 14.5 to 25.8 m/sec, with peak elbow angular velocities averaging 1137 degrees/sec. Peak elbow angular velocity typically was reached just prior (x = 28 msec) to release as the elbow approached full extension. Results are significant in establishing the efficacy of 3D techniques in evaluating throwing mechanics and may prove useful in: identifying characteristics of superior performers, assessing differences in throwing technique between injured and non-injured populations, and providing a kinematic data base for further studies of throwing kinetics and potential injury mechanisms.

A technique for estimating mechanical work of individual muscles in the cat during treadmill locomotion.

Mechanical work, the product of force and length change, was assessed in selected hindlimb extensors of two adult cats during three different speeds of unrestrained treadmill locomotion. Forces were measured using implanted transducers placed on the soleus (SOL) and medial gastrocnemius (MG) tendons. A three dimensional technique of muscle length estimation using high speed cinematography was found preferable to either two dimensional or trigonometric measurements derived from anatomical and kinematic parameters. Length excursions increased in both muscles as treadmill speed increased. However, at all speeds of locomotion, the uniarticular SOL exhibited a greater range of motion than the biarticular MG. Increases in treadmill speed resulted in higher peak forces in the MG and constant or slightly lower peak forces in the SOL. These speed-dependent changes in length and force resulted in higher total positive work, lower total negative work, and higher net work for both muscles with increasing speeds. These data illustrate the importance of three-dimensional kinematics in determining changes in muscle length and describe the relative force and work changes in a slow and fast ankle extensor with changes in speed of locomotion.

Correlation of movement patterns via pattern recognition.

A structural pattern recognition method for the quantitative determination of equivalence or similarity between movement patterns was examined. A chain encoding technique was implemented for the analysis of lower limb trajectories during walking and running. Conjoint angular displacement or angular velocity patterns provided kinematic data which were cross-correlated to determine geometric congruity of within and between subject motor patterns. The correlations of the movement patterns during different speeds of locomotion revealed numerical coefficients which consistently and quantitatively discriminated the similarity or dissimilarity of limb movement patterns.

Stride kinematics and knee joint kinetics of child amputee gait.

As a few quantitative data exist characterizing the gait of child lower extremity amputee (CLEA), this study provides such data by examining selected kinematic and kinetic variables during locomotion. Five unilateral CLEA were analyzed in an experimental design which comprised 3 different speeds of walking, 2 types of prosthetic feet (SACH-foot and an experimental CAPP-foot), and normal versus prosthetic limbs for a total of 104 trials. Cinematographic data and footprint information where used to quantify walking speed and uniplanar lower extremity angles. A rigid-body, linked model was used to evaluate the extent and range to thigh and leg motion and moments of force at the knee joint. The kinematic and kinetic characteristics of CLEA gait were affected significantly by variations in walking speed. Stride length, step length, and walking velocity decreased and stride width increased when the children used the experimental foot component; as speed of walking increased, stride length and step length increased with both prosthetic feet. Foot angles increased with walking velocity except for fast walking with the experimental foot component. Joint angles were significantly different between the normal and prosthetic limb. The only significant limb angle differences between the 2 prosthetic feet were in maximum hip flexion and the total range of thigh movement; the experimental foot elicited less hip flexion and and smaller range of thigh movement.