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Notes: The present study sought to investigate the role of EMG activity during passive static stretch. EMG and passive resistance were measured during static stretching of human skeletal muscle in eight neurologically intact control subjects and six spinal cord-injured (SCI) subjects with complete motor loss. Resistance to stretch offered by the hamstring muscles during passive knee extension was defined as passive torque (Nm). The knee was passively extended at 5o/s to a predetermined final position, where it remained stationary for 90 s (static phase) while force and integrated EMG of the hamstring muscle were recorded. EMG was sampled for frequency domain analysis in a second stretch maneuver in five control and three SCI subjects. There was a decline in passive torque in the 90-s static phase for both control and SCI subjects, P〈0.05. Although peak passive torque was greater in control subjects, P〈0.05, there was no difference in time-dependent passive torque response between control (33%) and SCI (38%) subjects. Initial and final 5-s IEMG ranged from 1.8 to 3.4 μ V.s and did not change during a stretch or differ between control and SCI subjects. Frequency domain analysis yielded similar results in both groups, with an equal energy distribution in all harmonics, indicative of ‘white noise’. The present data demonstrate that no measurable EMG activity was detected in either group during the static stretch maneuver. Therefore, the decline in resistance to static stretch was a viscoelastic stress relaxation response.

Notes: The load-displacement and stress–strain characteristics of the human triceps surae tendon and aponeurosis, in vivo, was examined during graded maximal voluntary plantarflexion efforts in runners who trained 80 km/ week or more and age-matched non-runners. Synchronous real-time ultrasonography of triceps surae tendon and aponeurosis displacement, electromyography of the gastrocnemius, soleus and dorsiflexor muscles, and joint angular rotation were obtained. Tendon cross-sectional area and ankle joint moment arm were obtained from magnetic resonance imaging. Tensile tendon force was calculated from the joint moments and tendon moment arm and stress was obtained by dividing force by cross-sectional area. Strain was obtained from the displacements normalized to tendon length. Antagonist coactivation and small amounts of ankle joint rotation significantly affected tensile tendon force and aponeurosis and tendon displacement, respectively (P 〈 0.01). Plantarflexion moment was similar in runners (138 ± 27 Nm, mean ± SEM) and non-runners (142 ± 17 Nm). Tendon moment arm was alike in non-runner (58.3 ± 0.2 mm) and runners (55.1 ± 0.1 mm). Similarly, there was no difference in tendon tensile force between runners (2633 ± 465 N) and non-runners (2556 ± 401 N). The cross-sectional area of the Achilles tendon was larger in runners (95 ± 3 mm2) than non-runners (73 ± 3 mm2) (P 〈 0.01). The load-deformation data yielded similar stiffness (runners 306 ± 61 N/mm, non-runners 319 ± 42 N/mm). The maximal strain and stress was 4.9 ± 0.8% and 38.2 ± 9.8 MPa in non-runners and 4.1 ± 0.8% and 26.3 ± 5.1 MPa in runners. The larger tendon cross-sectional area in trained runners suggests that chronic exposure to repetitive loading has resulted in a tissue adaptation.

Notes: The present study investigated factors that contribute to the formation of a previously reported knee joint flexor moment during the stance phase of walking. Contradictory results have been reported on this flexor moment, which some but not all individuals exhibit. Seven healthy male subjects were high speed filmed while walking across a force platform, and EMG recordings were obtained from five leg muscles. To investigate segment interactions, net joint moments about the ankle, knee and hip joint were calculated by inverse dynamics and each term in the equation used for the moment calculation was evaluated during the timeecourse of the step cycle. To test the hypothesis that net joint moments are balanced by an external moment formed by the resulting ground reaction vector multiplied by the perpendicular distance to the actual joint, external moment arms were calculated by the floor reaction force vector approach (FRFV). Contrasting two subjects with different net joint moments about the knee and ankle joint revealed that the knee joint flexor moment could not be explained by an opposite external moment. The external moments were calculated by a simplified method (FRFV) in which the point of force application is incorrect for joints above the ankle joint. However, at the ankle joint the net joint moment was always opposed by an external moment of opposite polarity. A detailed examination of the equation used for the net joint moment calculation showed that a knee joint flexor moment can be caused directly by a large plantar flexor moment about the ankle joint. For example, the soleus muscle can pull the tibia and generate an extensor moment about the knee joint, which in turn has to be opposed by a knee flexor moment from the hamstring muscles. Otherwise the desired joint angles cannot be obtained during human walking. It is therefore suggested that the kinematics regarding how the foot is placed on the ground may influence the net ankle joint moment, while the moment patterns about the knee and hip joint are determined by segment interaction and the requirements for controlling the direction of the resulting ground reaction vector. In vertical jumping it is advantageous to generate extensor moments about the knee and hip joint simultaneously, while in horizontal locomotion this would result in inefficient vertical movements.

Notes: Phytohaemagglutinin-induced human T-lymphocyte colony formation in semisolid agar culture is the properly of erythrocyte rosette-forming cells (E-RFC) negative for the 7S IgG receptor (FcR−). E-RFC positive for the 7S IgG receptor (FcR+), on the other hand, exhibit a limited capacity for colony formation and suppress colonies formed by FcR− E-RFC. T colonies are composed of small lymphocytes and lymphoblasts, the vast majority being negative for the Fc receptor. Most colony cells (86%) carry the Leu 3a antigen, suggesting that they belong to the inducer/helper T-cell subset, FcR+ colony suppressor cells are small, slowly sedimenting cells (sedimentation velocity 〈 3.8 mm/h) and are strongly adherent to plastic, and their activity depends on the ability to synthesize DNA.

Notes: Physiological alterations following unaccustomed eccentric exercise in an isokinetic dynamometer of the right m. quadriceps until exhaustion were studied, in order to create a model in which the physiological responses to physiotherapy could be measured. In experiment I (exp. I), seven selected parameters were measured bilaterally in 7 healthy subjects at day 0 as a control value. Then after a standardized bout of eccentric exercise the same parameters were measured daily for the following 7 d (test values). The measured parameters were: the ratio of phosphocreatine to inorganic phosphate (PCr/Pi), the ratio of inorganic phosphate to adenosintriphosphate (Pi/ATP), the ratio of phosphocreatine to adenosintriphosphate (PCr/ATP) (all three ratios measured with 31P-nuclear magnetic resonance spectroscopy), dynamic muscle strength, plasma creatine kinase (CK), degree of pain and “muscle” blood flow rate (133Xenon washout technique). This was repeated in experiment II (exp. II) 6–12 months later in order to study reproducbility. In experiment III (exp. III), the normal fluctuations over 8 d of the seven parameters were measured, without intervention with eccentric exercise in 6 other subjects.All subjects experienced pain, reaching a maximum 48 h after eccentric exercise in both exp. I and II. A systematic effect over time for CK (increasing 278% resp. 308%), muscle strength (decreasing more than 10%), PCr/Pi (decreasing 31% resp. 43%) and Pi/ATP (increasing 55% resp. 99%) was found in both exp. I and II (P〈0.05), but not in exp. III. No significant difference was observed between exp. I and II for CK, blood-flow rate, concentric muscle strength, PCr/Pi, Pi/ATP and PCr/ATP. It is concluded that pathophysiological alterations in m. quadriceps following eccentric exercise can be induced and can be reproduced after an interval of 6 months. Thus, this model can be used to study the effects of physiotherapy.

Notes: The typical response of the x-ray converter material to the passage of a high-powered relativistic electron beam is vaporization and rapid dispersal. The effect of this dispersal on subsequent pulses for multi-pulse radiography is the collective effects on the propagation of the electron beam through the expanding plasma and the reduced number of electron to photon interactions. Thus, for the dual-axis radiographic hydrodynamic test facility, the converter material must either be replaced or confined long enough to accommodate the entire pulse train. Typically the 1-mm-thick high Z and full density converter material is chosen to give peak dose and minimum radiographic spot. For repeated pulses we propose a modified converter, constructed of either low density, high Z material in the form of foam or of foils spaced over ten times the axial thickness of the standard 1 mm converter. The converter material is confined within a tube to impede outward motion in radius outside the beam interaction region. We report single-pulse experiments which measure the dose and spot size produced by the modified converter and compare them to similar measurements made by the standard converter. For multiple pulses over a microsecond time scale, we calculate the radial and axial hydrodynamic flow to study the material reflux into the converter volume and the resultant density decrease as the electron beam energy is deposited. Both the electron transport through the expanding low density plasma and beam in the higher density material are modeled. The x-ray source dose and spot size are calculated to evaluate the impact of the changing converter material density distribution on the radiographic spot size and dose. The results indicate that a multiple-pulse converter design for three or four high-power beam pulses is feasible. © 2001 American Institute of Physics.

Notes: The aim of this study was to measure if passive stretching would influence delayed onset muscle soreness (DOMS), dynamic muscle strength, plasma creatine kinase concentration (CK) and the ratio of phosphocreatine to inorganic phosphate (PCr/Pi) following eccentric exercise. Seven healthy untrained women, 28–46 years old, performed eccentric exercise with the right m. quadriceps in an isokinetic dynamometer (Biodex, angle velocity: 60°. s−1) until exhaustion, in two different experiments, with an interval of 13-23 months. In both experiments the PCr/Pi ratio, dynamic muscle strength, CK and muscle pain were measured before the eccentric exercise (day 0) and the following 7 d. In the second experiment daily passive stretching (3 times of 30 s duration, with a pause of 30 s in between) of m. quadriceps was included in the protocol. The stretching was performed before and immediately after the eccentric exercise at day 0, and before measurements of the dependent variables daily for the following 7 d. The eccentric exercise alone led to significant decreases in PCr/Pi ratio (P〈0.001) and muscle strength (P〈0.001), and an increase in CK concentration (P〈0.01). All subjects reported pain in the right m. quadriceps with a peak 48 h after exercise. There was no difference in the reported variables between experiments one and two. It is concluded that passive stretching did not have any significant influence on increased plasma- CK, muscle pain, muscle strength and the PCr/Pi ratio, indicating that passive stretching after eccentric exercise cannot prevent secondary pathological alterations.

Notes: The purpose of the study was to develop a method to record intramuscular electromyogram (EMG) from the iliopsoas muscle and to relate this activity to the kinetics during the soccer place kick. Seven skilled soccer players performed 3 maximal velocity place kicks. The kicks were filmed with a high-speed camera (400 Hz) and EMG recordings were obtained from 5 muscles of the kicking leg, including wire electrodes inserted into the m. iliopsoas. The EMG signals were compared to the kinetics of the kicking leg, which were calculated from the digitised film. The results showed hardly any torque reversal about the hip joint before impact. Angular deceleration of the thigh segment did not increase the angular velocity of the shank (work -3.57 to 0.0%). M. iliopsoas was active during the entire kicking motion (average EMG 65.1–100.9%), even in the period when the thigh was decelerating. Wire electrodes can succesfully be applied to EMG recordings of fast unloaded movements.

Notes: The nucleotide sequence of two kilobase pairs (kb) 5′ to the orfE-pyrE operon has been determined. The sequence revealed two open reading frames, orfX and orfY, consisting of 286 and 274 codons, respectively, and having a transcriptional orientation opposite that of the orfE-pyrE operon. Analysis of transcription initiations showed that the promoters of orfE and orfX constitute a pair of divergent promoters with overlapping -35 regions and that orfY is transcribed from an independent promoter. Translational analysis indicated that the orfs are expressed in Escherichia coli.The orfE, orfX, and orfY genes were inactivated on the bacterial chromosome by deletion-insertion mutagenesis using a kanamycin resistance cassette. The mutants were all viable. However, the orfE deletion caused a dramatic reduction in the level of pyrE expression and a partial pyrimidine requirement, because this mutation prevented transcription of pyrE. The orfE protein seemed without significance for pyr-gene expression in E. coli, and the mutations in orfX and orfY were without detectable phenotypes.

Notes: Expression of the Escherichia coli pyrE gene is regulated by transcription attenuation in the intercistronic orfE–pyrE region and modulated by the distance between the transcribing RNA polymerase and the leading ribosome as a function of the supply of UTP and GTP. In this communication we show that pyrE expression is hyper-repressed in vivo following addition of uracil in strains carrying the nusAcs10 mutation. This phenotype, previously seen in rpsL 1204 strains whose ribosomes are pseudodependent on streptomycin and work at suboptimal elongation rate, indicates that RNA polymerase escapes from the ribosomes in the pyrE attenuator region in the nusA mutant. In vitro transcription studies revealed that the build-up of the full-length attenuated orfE transcript occurred more slowly in the presence of the NusA protein than in its absence. Moreover, the NusA protein enhanced several transcription pauses through the orfE gene. These effects were more pronounced when low concentrations of either UTP or GTP were used than at low concentrations of either CTP or ATP. The results indicate that the NusA protein is required for proper regulation of pyrE gene expression and is involved, together with the NTP pools, in maintaining the coupling between transcription and translation in the pyrE attenuator region by inhibiting RNA chain elongation.