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Biomedical subjects

A Walmsley

Publications and source records attributed to A Walmsley.

14 recordsLinked to original sources
PubMed2006

Leg heating and cooling influences running stride parameters but not running economy.

To evaluate the effect of temperature on running economy (RE) and stride parameters in 10 trained male runners (VO2peak 60.8 +/- 6.8 ml . kg (-1) . min (-1)), we used water immersion as a passive temperature manipulation to contrast localised pre-heating, pre-cooling, and thermoneutral interventions prior to running. Runners completed three 10-min treadmill runs at 70 % VO2peak following 40 min of randomised leg immersion in water at 21.0 degrees C (cold), 34.6 degrees C (thermoneutral), or 41.8 degrees C (hot). Treadmill runs were separated by 7 days. External respiratory gas exchange was measured for 30 s before and throughout the exercise and stride parameters were determined from video analysis in the sagittal plane. RE was not affected by prior heating or cooling with no difference in oxygen cost or energy expenditure between the temperature interventions (average VO2 3rd-10th min of exercise: C, 41.6 +/- 3.4 ml . kg (-1) . min (-1); TN, 41.6 +/- 3.0; H, 41.8 +/- 3.5; p = 0.94). Exercise heart rate was affected by temperature (H > TN > C; p < 0.001). During minutes 3 - 5 of running the respiratory-exchange and minute ventilation/oxygen consumption ratios were greater in cold compared with thermoneutral (p < 0.05). Averaged over the full 10 min of exercise, stride length was shorter and stride frequency higher for the C trial compared to TN and H (p < 0.01). Leg temperature manipulation did not influence running economy despite changes in stride parameters that might indicate restricted muscle-tendon elasticity after pre-cooling. Larger changes in stride mechanics than those produced by the current temperature intervention are required to influence running economy.

Adult↗
PubMed2002

Role of duration and interval in perception of force pulses.

Three experiments investigated the perceptual threshold for a pulsed force stimulation of the middle phalanx of the forefinger. The first experiment (N = 5) manipulated duration of the pulse, and the second (N = 6) manipulated the interval between pulses. Both experiments held magnitude constant. The results confirmed high reliability and indicated that perceptual threshold decreased as both Duration and Interval increased. Although subjects responded consistently, they described the sensation as "muscular" and "diffuse." Exp. 3 (N = 12) covaried Duration and Interval and found effects similar to those of the first two studies. Also, Duration and Interval were independent. Additional research is needed to clarify the relations of duration, interval, and magnitude in contributing to conscious perception of the presence of applied force. Treating pulse magnitude as a dynamic variable by varying its rate of change within a train of force pulses could further our understanding of how perception of force changes depend upon rate.

Adult↗
PubMed2000

Response timing and muscular coordination in fencing: a comparison of elite and novice fencers.

Reaction time (RT), movement time (MT), total response time (RMT) and accuracy of elite and novice fencers was studied under three levels of target choice (single-, two- and four-targets) with three variations of movement distance (short, medium and long lunge). In addition, electromyographic activity (EMG) of selected upper and lower limb muscles was used to compare the two groups. The elite subjects were faster for RT and RMT and displayed a higher level of accuracy. The hypothesis that increasing choice would cause increases in RT was not upheld. Except for some differentiation between the short and the two longer distances, the effects of movement distance were not marked. Qualitative and quantitative analysis of EMG revealed the high consistency of response patterns within subjects and highlighted the synergistic roles of selected muscles in distinguishing between elite and novice fencers. These findings confirm that differences in the technical skill of fencers can be distinguished in the laboratory through a combination of response timing measures in association with measures of muscle action. They also draw attention to practical implications for individual skill assessment and training. Analysis of pre-movement muscle activity provided moderate support for the hypothesis that it was part of a single control process and indicates that a dual process can involve both the maintenance of postural stability and the generation of movement. It is suggested that different movement contexts can lead to different levels of coordination between the system controlling posture and that controlling movement.

Adult↗
PubMed2000

Response amendment in fencing: differences between elite and novice subjects.

Reaction time (RT), movement time (MT), total response time (RMT), and accuracy of 3 elite and 3 novice fencers were studied under a dual response paradigm requiring a full lunge. Electromyographic activity (EMG) from selected arm and leg muscles was used to compare response profiles of the two groups. Although the elite subjects had slower MTs, their faster RTs resulted in significantly shorter total response times. The EMG analysis showed that in comparison to the novice subjects, onset of muscle activity was significantly faster for the elite group in five of the six muscles studied. In addition, the elite subjects showed more coherent muscle synergies and more consistent patterns of muscle coordination. Although the requirement to change targets (signalled by the arrival of a second stimulus) led to slightly more target misses for the elite group, the overall frequency was low, which indicates that it did not pose difficulty for either group. The present findings show that measures of response timing and neuromuscular coordination differentiate skill level in the fencing lunge and draw attention to practical implications for skill assessment and training.

Achievement↗
PubMed1999

Low dose bendrofluazide (1.25 mg) effectively lowers blood pressure over 24 h: results of a randomized, double-blind, placebo-controlled crossover study.

Previous studies indicate that low dose bendrofluazide (1.25 mg/day) has no deleterious effect on insulin sensitivity in contrast to conventional doses. To evaluate the antihypertensive effect of 1.25 mg bendrofluazide across 24 h, we studied 12 subjects in a randomized, double blind, cross-over trial, comprising 8 weeks of either 1.25 mg/day bendrofluazide or placebo. Twenty-four-hour blood pressure averages were significantly lower after bendrofluazide compared with placebo (systolic 125 +/- 4 v 136 +/- 3 mm Hg, P < .005; diastolic: 78 +/- 2 v 85 +/- 2 mm Hg, P < .01). Trough:peak ratios were 0.67 +/- 0.07 for systolic and 0.72 +/- 0.15 for diastolic blood pressure reduction. In conclusion, 1.25 mg bendrofluazide daily produced a useful antihypertensive effect across the full 24-h period.

Aged↗
PubMed1997

Characterization of the substrate specificity of the major cysteine protease (cruzipain) from Trypanosoma cruzi using a portion-mixing combinatorial library and fluorogenic peptides.

The substrate specificity of the major cysteinyl proteinase of the parasitic protozoan Trypanosoma cruzi (cruzipain) was investigated, by combinatorial replacement of amino acid residues at positions P5-P'5, using a fluorescent quenched solid-phase library assay. Positively charged residues appear to be a general preference in the P5-P3 and the P'5-P'3 positions, while a hydrophobic residue was always required at the P2 position. A broad range of amino acids could be accepted at the P'1 position. A clear difference in terms of specificity between cruzipain and human cathepsin L was observed for the accommodation of Pro at the P2 position. The P1 specificity was investigated by a more detailed enzyme kinetic analysis using peptidyl-MCA (where MCA is methylcoumarin amide) and Abz-peptidyl-EDDnp [where Abz is o-aminobenzoic acid and EDDnp is N-(2,4-dinitrophenyl)ethylenediamine] as substrates, and the results were compared with those obtained using human cathepsin L. Cruzipain showed a clear preference for benzyl-Cys or Arg at the P1 position. Human cathepsin L presented similar behaviour to that of cruzipain for the hydrolysis of the epsilon-NH2-Cap-Leu-Xaa-MCA (where Cap is epsilon-aminocaproyl) and Abz-Lys-Leu-Xaa-Phe-Ser-Lys-Gln-EDDnp series, whereas the mammalian enzyme was able to tolerate large P1 residues, such as phenylalanine, better than cruzipain in the latter series.

Alanine↗
PubMed1997

Plant-derived immunocontraceptive vaccines.

The use of transgenic or virus-infected plants to produce vitally needed vaccines for developing nations has been made possible by rapid advances in plant molecular biology and biotechnology during the last decade. Plant-based vaccines would be a welcome development for many impoverished countries that lack the capital-intensive infrastructure required to produce much-needed vaccines. The approach would also be ideally suited to the delivery of oral immunocontraceptive vaccines to a wide range of herbivore species. This review looks at the progress made to date in the use of plants for vaccine production, how this technology may be used in the future to deliver immunocontraceptive vaccines to free-ranging wildlife species, and the many problems that will have to be overcome if this promising approach is to ever 'bear fruit'.

Animals↗
PubMed1997

Instrumentation of an ergometer to monitor the reliability of rowing performance.

The aim of this study was to develop a portable data-acquisition system to measure the stroke-by-stroke power output and the force developed at the feet during simulated rowing, and to use the system to investigate the reliability of selected variables used to describe rowing performance. Using a Concept II rowing ergometer, the instantaneous power output was calculated as the product of the force at the handle, measured using a small transducer mounted near the handle, and the velocity of the handle, measured using an infra-red emitter-receiver to detect the passage of each vane of the flywheel. The cumulative force at the feet was measured using two force-plates, one mounted under each foot. The outputs from all transducers were sampled at 30 Hz using an 80386SX computer running Asyst data-acquisition software. Excellent linearity in all transducers was established and a calibration of the system revealed measurement errors of less than 3%. The reliability of the variables used to describe rowing performance was studied using a repeated 90 s maximal test on seven experienced oarsmen. Statistical analysis indicated that, of the 14 variables used, only two failed to meet the set criterion. In conclusion, it was found that a rower's performance during simulated rowing was very reliable and that the selected variables used in this study could be used to objectively describe performance on a rowing ergometer.

Adult↗
PubMed1994

Rapid-fire pistol shooting as a dynamic problem.

The kinetic aspects of the aiming phase of a pistol-shooting task were examined in the light of the previous finding of relative timing invariance in the shooting phase of the same task. A single highly skilled marksman executed a total of 45 trials over three timing conditions in a normal competition setting. Data from a tri-axial accelerometer fixed to the pistol were used to produce phase plane trajectories of the movement in each of the three timing conditions. These trajectories showed marked consistency across timing conditions which indicated that the marksman applied a single kinetic solution to his motor problem.

Attention↗
PubMed1991

The perception of torque pulses.

The reliability of perception of a series of torque pulses and the influence of practice on the perceptual threshold were assessed. Eleven subjects were tested. Analysis showed distinctive cumulative frequency curves with the threshold of perception ranging from 0.016 Nm to 0.049 Nm. The reliability of individual differences over 100 trials was .998 and, when the number of trials was reduced to 25, reliability was .992. There was little evidence of a practice effect. It was clear that individual differences in torque perception could be accurately measured.

Adult↗
PubMed1988

Comparison of a total intravenous anaesthetic technique using a propofol infusion, with an inhalational technique using enflurane for day case surgery.

A total intravenous anaesthetic technique with a propofol infusion for maintenance of anaesthesia was compared with an inhalational technique that used oxygen, nitrous oxide and enflurane in 98 unpremedicated patients who presented for day case surgery. Overall quality of anaesthesia during induction and maintenance was comparable in both groups. Quality of maintenance of anaesthesia in the propofol group was improved by an increase of the initial infusion rate from 12 to 15 mg/kg/hour. There was a larger decrease in arterial blood pressure after induction in the propofol group but no difference in blood pressure between the groups during maintenance. Recovery times and scores using the Steward scoring system were not significantly different. Nausea and vomiting were slightly less frequent in the propofol group.

Adult↗
PubMed1986

Anaesthetic temperature and shivering in epidural anaesthesia.

The mechanism of shivering during epidural analgesia remains unclear. This study investigates the role of the temperature of the local anaesthetic injected extradurally. Forty patients admitted for elective caesarean section under epidural anaesthesia were studied; 20 were given bupivacaine warmed to 37 degrees C (warm group) and 20 were given bupivacaine stored at 4 degrees C (cold group); the occurrence of shivering in both groups was recorded. The overall incidence of shivering was 27.5%; two patients of the warm group and nine patients of the cold group shivered. This difference was statistically significant (P less than 0.03). The results suggest that there are thermosensory mechanisms in the human spinal canal. In our view, epidural anaesthetic solutions should be warmed to body temperature prior to injection to reduce the incidence of shivering.

Adult↗