Search

Background Hallux valgus (HV) contributes to deficits in static balance and increased fall risk in older adults. Very limited research has examined dynamic balance deficits in walking in this population. These individuals generally walk slowly, as balance challenge is lesser at slow speeds. Research question How does the dynamic balance of older adults with HV differ from healthy controls at controlled slow and fast walking speeds? Methods Nineteen older adults with HV and 13 healthy controls completed 5 continuous walking trials at 1.0 and 1.3 m·s-1 as whole body marker position and ground reaction force data were captured. Dynamic balance was evaluated using whole body center of mass (COM) and center of pressure (COP) inclination angles (IA) and duration of double support. Results There were no differences in measures of dynamic balance between older adults with and without HV at slow and fast speeds. At the faster speed, the peak sagittal plane COM-COP IA increased and the double support duration decreased, while the peak frontal plane COM-COP IA were not affected. Significance Older adults with HV do not exhibit deficits in dynamic balance during continuous walking at comfortable speeds when compared to healthy older adults.

Characterization of proteins using NMR methods begins with assignment of resonances to specific residues. This is usually accomplished using sequential connectivities between nuclear pairs in proteins uniformly labeled with NMR active isotopes. This becomes impractical for larger proteins, and especially for proteins that are best expressed in mammalian cells, including glycoproteins. Here an alternate protocol for the assignment of NMR resonances of sparsely labeled proteins, namely ones labeled with a single amino acid type, or a limited subset of types, isotopically enriched with (15)N or (13)C, is described. The protocol is based on comparison of data collected using extensions of simple two-dimensional NMR experiments (correlated chemical shifts, nuclear Overhauser effects, residual dipolar couplings) to predictions from molecular dynamics trajectories that begin with known protein structures. Optimal pairing of predicted and experimental values is facilitated by a software package that employs a genetic algorithm, ASSIGN_SLP_MD. The approach is applied to the 36kDa luminal domain of the sialyltransferase, rST6Gal1, in which all phenylalanines are labeled with (15)N, and the results are validated by elimination of resonances via single-point mutations of selected phenylalanines to tyrosines. Assignment allows the use of previously published paramagnetic relaxation enhancements to evaluate placement of a substrate analog in the active site of this protein. The protocol will open the way to structural characterization of the many glycosylated and other proteins that are best expressed in mammalian cells.

Reduced stability while standing typically decreases the soleus muscle Hoffmann (H-) reflex amplitude, purportedly to prevent the Ia afferent signal from excessively activating spinal motor neurons during the unstable stance. H-reflex measures, however, by excluding the spindle do not reflect the actual effect of the Ia pathway (i.e. the combined effects of spindle sensitivity and Ia presynaptic inhibition) on motor neuron activation, as tendon tap reflex measures can. But the effect of stance stability on soleus muscle tendon tap reflex amplitude is largely unknown. This study examined 30 young adults (mean(s), 21(2) years) as they stood in a wide stable stance position and an unstable tandem stance with a reduced base of support. Standing body sway, the amplitude of the soleus muscle tendon tap reflex, background EMG and tap force were measured in both stances. A repeated measured design t-test was calculated for each variable. Most subjects (69%) decreased tendon tap reflex amplitude when in the tandem stance position (mean decrease 11.6%), compared to the wide stance (wide stance 0.248(0.124) mV, tandem stance 0.219(0.119) mV, p 0.05, Cohen's d = 0.24 small) with no significant differences in background soleus and tibialis anterior EMG, and tap force across the stances. There was no relationship between the modulation of the tendon tap reflex amplitude across the stances and standing body sway in the tandem stance. Results support the idea that for most subjects examined, during a less stable stance the Ia excitation of motor neurons is decreased, likely by presynaptic inhibition, thereby avoiding potential instability in the reflex loop or saturating the reflex pathway and possibly interfering with descending control of the involved spinal motor neurons.

Sparse isotopic labeling of proteins for NMR studies using single types of amino acid (15N or 13C enriched) has several advantages. Resolution is enhanced by reducing numbers of resonances for large proteins, and isotopic labeling becomes economically feasible for glycoproteins that must be expressed in mammalian cells. However, without access to the traditional triple resonance strategies that require uniform isotopic labeling, NMR assignment of crosspeaks in heteronuclear single quantum coherence (HSQC) spectra is challenging. We present an alternative strategy which combines readily accessible NMR data with known protein domain structures. Based on the structures, chemical shifts are predicted, NOE cross-peak lists are generated, and residual dipolar couplings (RDCs) are calculated for each labeled site. Simulated data are then compared to measured values for a trial set of assignments and scored. A genetic algorithm uses the scores to search for an optimal pairing of HSQC crosspeaks with labeled sites. While none of the individual data types can give a definitive assignment for a particular site, their combination can in most cases. Four test proteins previously assigned using triple resonance methods and a sparsely labeled glycosylated protein, Robo1, previously assigned by manual analysis, are used to validate the method and develop a criterion for identifying sites assigned with high confidence.

Objective Investigate the effects of shoulder elevation on repositioning errors in upright and supine body orientations, and examine these effects on anterior and posterior deltoid muscle activation. We hypothesized decreased errors, and altered anterior and posterior deltoid activation with increasing elevation, in both orientations. Design Crossover trial. Setting University laboratory. Participants Thirty-five college-aged participants. Intervention Subjects attempted to replicate target positions of various elevation angles in upright and supine body orientations. Also, anterior and posterior deltoid activation was recorded in each shoulder position and body orientation. Main outcome measures Vector and variable repositioning errors, anterior and posterior deltoid percentage of maximal contraction. Results Vector error was greater in supine compared to upright at 90° and 110°, but not at 70°. Variable error was larger in supine than upright, but was unaffected by elevation. Anterior deltoid activation increased with elevation in the upright posture only. Posterior deltoid activation increased with elevation across postures. Conclusions Muscle activation, external torque, and cutaneous sensations may combine to provide afferent feedback, and be used with centrally-generated signals to interpret the state of the limb during movement. Clinicians may prescribe open kinetic chain exercises in the upright posture with the shoulder elevated approximately 90–100°.

Background Creatine supplementation is recommended as an ergogenic aid to improve repeated sprint cycling performance. Furthermore, creatine uptake is increased in the presence of electrolytes. Prior research examining the effect of a creatine-electrolyte (CE) supplement on repeated sprint cycling performance, however, did not show post-supplementation improvement. The purpose of this double blind randomized control study was to investigate the effect of a six-week CE supplementation intervention on overall and repeated peak and mean power output during repeated cycling sprints with recovery periods of 2 min between sprints. Methods Peak and mean power generated by 23 male recreational cyclists (CE group: n = 12; 24.0 ± 4.2 years; placebo (P) group: n = 11; 23.3 ± 3.1 years) were measured on a Velotron ergometer as they completed five 15-s cycling sprints, with 2 min of recovery between sprints, pre- and post-supplementation. Mixed-model ANOVAs were used for statistical analyses. Results A supplement-time interaction showed a 4% increase in overall peak power (pre: 734 ± 75 W; post: 765 ± 71 W; p = 0.040; ηp 2 = 0.187) and a 5% increase in overall mean power (pre: 586 ± 72 W; post: 615 ± 74 W; p = 0.019; ηp 2 = 0.234) from pre- to post-supplementation for the CE group. For the P group, no differences were observed in overall peak (pre: 768 ± 95 W; post: 772 ± 108 W; p = 0.735) and overall mean power (pre: 638 ± 77 W; post: 643 ± 92 W; p = 0.435) from pre- to post-testing. For repeated sprint analysis, peak (pre: 737 ± 88 W; post: 767 ± 92 W; p = 0.002; ηp 2 = 0.380) and mean (pre: 650 ± 92 W; post: 694 ± 87 W; p

Mirrors are often used in an instructional environment where precise movements must be learned (e.g., martial arts, Pilates, dance). The potential for mirrors in the learning environment of a Pilates class, to affect the subsequent performance of a Pilates star movement when mirrors are not present, was examined. Twenty subjects learned the Pilates star movement over seven weeks, either with (n=11) or without (n=9), mirrors present in the Pilates studio. Performance of the star without mirrors present was assessed quantitatively before and after the training, by video analysis of the degree of lateral straightness of the subject's body at the start, middle, and end of the star movement. Performance of the star movement without a mirror present improved similarly for both the group that learned with, and the group that learned without, mirrors present (p

Literature examining the recruitment order of motor units during lengthening (eccentric) contractions was reviewed to determine if fast-twitch motor units can be active while lower threshold slow-twitch motor units are not active. Studies utilizing surface electromyogram (EMG) amplitude, single motor unit activity, spike amplitude-frequency analyses, EMG power spectrum, mechanomyographic, and phosphocreatine-to-creatine ratio (PCr/Cr) techniques were reviewed. Only single motor unit and PCr/Cr data were found to be suitable to address the goals of this review. Nine of ten single motor unit studies, examining joint movement velocities up to 225 degrees/s and forces up to 53% of a maximum voluntary contraction, found that the size principle of motor unit recruitment applied during lengthening contractions. Deviation from the size principle was demonstrated by one study examining movements within a small range of low velocities and modest forces, although other studies examining similar low forces and lengthening velocities reported size-ordered recruitment. The PCr/Cr data demonstrated the activation of all fibre types in lengthening maximal contractions. Most evidence indicates that for lengthening contractions of a wide range of efforts and speeds, fast-twitch muscle fibres cannot be selectively recruited without activity of the slow-twitch fibres of the same muscle.

Context Joint position sense (JPS) is a key neuromuscular factor for developing and maintaining control of muscles around a joint. It is important when performing specialized tasks, especially at the shoulder. No researchers have studied how Kinesio Tape (KT) application affects JPS. Objective To investigate the effects of KT application and no tape on shoulder JPS at increasing shoulder elevations in athletes. Design Cross-sectional study. Setting University laboratory. Patients or Other Participants A total of 27 healthy athletes who did not participate in overhead sports (age = 20.44 ± 1.05 years, height = 175.02 ± 11.67 cm, mass = 70.74 ± 9.65 kg) with no previous pathologic shoulder conditions volunteered for the study. All participants were from 1 university. Intervention(s) Shoulder JPS was assessed at increasing elevations with and without KT application. Participants attempted to actively replicate 3 target positions with and without the KT and without visual guidance. Main Outcome Measure(s) We examined absolute and variable repositioning errors at increasing shoulder-elevation levels with and without KT application. Results Data revealed an interaction between tape and position for absolute error (F2,52 = 4.07, P = .02); simple effects revealed an increase in error, with KT demonstrating a 2.65° increase in error at 90° of elevation compared with no tape (t26 = 2.65, P = .01). The effect size was medium (ω2 = .135). Variable error showed no interaction of tape and position (F2,52 = .709, P = .50). Further analysis of simple effects was not needed. However, we still calculated the effect size and observed small effect sizes for tape (ω2 = .002), position (ω2 = .072), and tape by position (ω2 = .027). Conclusions At 90° of elevation, shoulder JPS was impaired by the application of KT.

Health professionals and members of the public are often interested in locating exercise information on the World Wide Web (the Web). There is a large amount of information available on the Web; however, the challenge for all people is to identify the high quality information that can be depended upon. Much of the quality exercise information on the Web is hidden within sites of reputable organizations concerned with exercise and health. This article examines several categories of commonly needed exercise related information. For each category, a few high quality sources of exercise information are listed. Combined, these Web sites provide an excellent and extensive body of knowledge for a person who is not experienced with exercise and wants to get started learning, or for a person with a moderate level of experience and knowledge who wants to learn more.

Soleus Hoffmann-reflex (H-reflex) modulation during walking was examined in 7 young and 13 elderly adults. H-reflex size was measured in 16 equal time divisions (phases) of the step cycle. In both the elderly and the young groups, the H reflex was minimal at the time of heel contact, rose to a maximum shortly after midstance, decreased rapidly as toe-off neared, then was minimal during swing. There was a significant interaction between age group and step cycle phase (p < .05). During midstance of walking, the elderly participants had a smaller H-reflex size during two of the 16 time phases of the step cycle (p < .05), despite no significant difference in H-reflex size between the age groups while standing. The smaller H-reflex size during the stance phase of walking may reflect changes in central reflex mechanisms that may impact stretch reflex contribution to ankle extensor neural drive and ankle stiffness in elderly persons during walking.

Exercise science and human anatomy and physiology textbooks commonly report that type IIB muscle fibers have the largest cross-sectional area of the three fiber types. These descriptions of muscle fiber sizes do not match with the research literature examining muscle fibers in young adult nontrained humans. For men, most commonly type IIA fibers were significantly larger than other fiber types (six out of 10 cases across six different muscles). For women, either type I, or both I and IIA muscle fibers were usually significantly the largest (five out of six cases across four different muscles). In none of these reports were type IIB fibers significantly larger than both other fiber types. In 27 studies that did not include statistical comparisons of mean fiber sizes across fiber types, in no cases were type IIB or fast glycolytic fibers larger than both type I and IIA, or slow oxidative and fast oxidative glycolytic fibers. The likely reason for mistakes in textbook descriptions of human muscle fiber sizes is that animal data were presented without being labeled as such, and without any warning that there are interspecies differences in muscle fiber properties. Correct knowledge of muscle fiber sizes may facilitate interpreting training and aging adaptations.

The purpose of this study was to compare the acute effect of the contract-relax (CR) stretching technique on knee active range of motion (ROM) using target muscle contraction or an uninvolved muscle contraction.pre-test post-test control experimental design.Clinical research laboratory.Sixty healthy men were randomly assigned to one of three groups.The Contract-Relax group (CR) performed a traditional hamstring CR stretch, the Modified Contract-Relax group (MCR) performed hamstring CR stretching using contraction of an uninvolved muscle distant from the target muscle, and the Control group (CG) did not stretch.Active knee extension test was performed before and after the stretching procedure.Two-way between-within analysis of variance (ANOVA) results showed a significant interaction between group and pre-test to post-test (p 0.001). Post-hoc examination of individual groups showed no significant change in ROM for the CG (0.8°, p = 0.084), and a significant moderate increase in ROM for both the CR (7.0°, p 0.001) and MCR (7.0°, p 0.001) groups.ROM gain following a CR PNF procedure is the same whether the target stretching muscle is contracted, or an uninvolved muscle is contracted.

Soleus Hoffman-reflex (H-reflex) gain was compared at the same background level of electromyographic activity across lying, natural standing, and tandem stance postures, in 12 young and 16 elderly adults. When compared to a lying posture, young adults significantly depressed soleus H-reflex gain when in a natural standing (19% decrease) and a tandem stance position (30% decrease; p