Biomedical subjects

R J Dyson

Publications and source records attributed to R J Dyson.

8 recordsLinked to original sources

PubMed2006

Effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol.

RATIONALE: Sleep deprivation has a negative effect on cognitive and psychomotor performance and mood state, partially due to decreases in creatine levels in the brain. Therefore, creatine supplementation should lessen the negative effects of sleep deprivation. OBJECTIVES: The objective of this study was to examine the effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol. METHOD: Subjects were divided into a creatine group (n=10) and a placebo group (n=9). They took 5 g of creatine monohydrate or a placebo, dependent on their group, four times a time a day for 7 days, immediately prior to the experiment. The study was double blind. Subjects undertook tests of random movement generation (RMG), verbal and spatial recall, choice reaction time, static balance and mood state pre-test (0 h), after 6, 12 and 24 h of sleep deprivation, with intermittent exercise. They were tested for plasma concentrations of catecholamines and cortisol at 0 and 24 h. RESULTS: At 24 h, the creatine group demonstrated significantly less change in performance from 0 h (delta) in RMG, choice reaction time, balance and mood state. There were no significant differences between groups in plasma concentrations of catecholamines and cortisol. Norepinephrine and dopamine concentrations were significantly higher at 24 h than 0 h, but cortisol were lower. CONCLUSIONS: Following 24-h sleep deprivation, creatine supplementation had a positive effect on mood state and tasks that place a heavy stress on the prefrontal cortex.

Adult↗

PubMed2000

Development of a boxing dynamometer and its punch force discrimination efficacy.

The development of sport-specific dynamometers is an important step towards ecological validity in analysing athlete performance. Design limitations in previous punch-measuring devices have resulted in values which may not or cannot fully reflect the force and multidirectional components in a punch. In developing this boxing dynamometer, a triaxial force measurement system and a boxing manikin interface were combined. The repeatability and accuracy of the dynamomoter were assessed using simulated straight punches. Discrimination efficacy was assessed by comparison of the maximal punching force of seven elite, eight intermediate and eight novice boxers during simulated boxing, throwing straight punches. For the elite, intermediate and novice groups, respectively, the maximal straight punching forces (mean +/- s(mean)) were 4800 +/- 227 N, 3722 +/- 133 N and 2381 +/- 116 N for the rear hand, and 2847 +/- 225 N, 2283 +/- 126 N and 1604 +/- 97 N for the lead hand. For all groups, maximal forces were larger for the rear than the lead hand (P < 0.001). Maximal punching force was greater in the elite than the intermediate group, and greater in the intermediate than the novice group (P < 0.05). The boxing dynamometer discriminated effectively between punching performance at three standards of performance and between the punching force of the rear and lead hands.

Biomechanical Phenomena↗

PubMed1996

Electromyographic activity during windsurfing on water.

Electromyographic activity and the electrocardiogram were recorded during windsurfing on the water in six subjects (three females and three males). 'Beating' and 'reaching' (both with continuous pumping), 'running' and 'uphauling' were performed in light to moderate winds. The physiological signals were transmitted to a shore base by radio telemetry and recorded with synchronized video and audio information of movement. Heart rates were similar for the beating, reaching and running activities within the individuals, but varied between individuals (means of 145 to 173 beats min-1), due to performance conditions and related muscle activity levels. During beating and reaching, the trapezius, flexor carpi ulnaris, extensor carpi radialis, biceps brachii and tibialis anterior were very active, with the gluteus maximus being particularly important in beating. Running involved less general muscle activity, though the role of the tibialis anterior increased. Differences in technique were identified between the subjects, notably in the order of muscle recruitment to participate in the activities.

Electromyography↗

PubMed1996

Electromyographic activity of beating and reaching during simulated boardsailing.

This study examined the responses of six competitive boardsailors (three males, three females) during laboratory-based simulation tasks while the electromyographic activity of up to 13 muscles was recorded. A sailboard, mounted in a steel frame and resting on a waterbed, allowed simulation of roll and pitch movements. Wind force was simulated by attaching the boom to a weight stack with a hydraulically controlled buffered release phase. The progression of the simulation test was controlled by the sailor copying movements on an edited video of each subject boardsailing on the open water. Analysis of individual pumping movements for mean peak percentage of maximal enveloped voluntary contraction (%MEVC) in 'beating' and 'reaching' showed that muscular activity in the arm (flexor carpi ulnaris, extensor carpi radialis and biceps brachii) was greatest (66-94% MEVC), with considerable activity (58-75% MEVC) in the deltoid and trapezius shoulder muscles, but much less activity in the leg muscles (16-40% MEVC). For the combined upper and lower body muscles there was a significant difference (P < 0.001) between 'beating' and more physically demanding 'reaching' pumping activity. Electromyographic activity was higher than reported previously during simulation, reflecting the current dynamic nature of the sport.

Adult↗

PubMed1985

Thermal environmental monitoring of divers using a twelve channel multiplexing instrument.

A 12-channel temperature monitoring instrument designed for use by divers while immersed or within pressure chambers is described. Data are multiplexed at the diver and transmitted to the surface, bell, submarine, or chamber exterior through a two-core electrical cable. In the case of the immersed diver the cable may be incorporated into the diver's umbilical cable. Details of the method and special construction techniques used in the design of the diver-borne multiplexer are given. At the dive control station the 12 individual temperatures may be displayed in either digital or analogue format. The temperature data may also be stored on one track of a battery-powered magnetic tape recorder for subsequent off-line analysis.

Body Temperature↗

PubMed1984

Monitoring of the neonatal electroencephalogram using an infrared multichannel telemetry system.

A 3-channel neonatal medical monitoring system is described which uses infrared light instead of electrical leads to transmit physiological signals from the neonate to monitoring equipment. This system is especially applicable to situations where low level physiological signals such as the EEG need to be monitored in the vicinity of other life support and monitoring equipment that is likely to introduce electrical interference. Examples of EEG activity showing the progress of a neonate, who had experienced asphyxia, are presented.

Asphyxia Neonatorum↗

PubMed1984

EEG electrode positions outside the hairline to monitor sleep in man.

This study investigated the use of electroencephalographic (EEG) electrode placements outside the hairline to monitor sleep. Six subjects slept for 1 night during which the EEG was recorded from "standard" electrode placements and simultaneously from the "test" placements outside the hairline where adhesive pregelled electrodes could be used. Each subject's EEG record was scored independently by two observers. The standard and test electrode placements were assessed separately. Cohen's kappa (kappa) was used to quantify the agreement in the sleep scores (a) between observers when both scored the standard placements and (b) between the test and standard placements when scored by the same observer. The agreement for all stages between observers (a) was excellent (kappa = 0.82); and the agreement within observers, between placements (b) was even better [kappa = 0.86 for the six sleep stages considered separately; when stages awake/1 and 3/4 were combined (a) kappa = 0.88 and (b) kappa = 0.09]. It is concluded that EEG electrode placements outside the hairline can be used effectively to record sleep EEGs. The adoption of these electrode placements would simplify the monitoring procedure for many applied physiological studies especially when usual laboratory techniques for EEG are precluded.

Adult↗

PubMed1981

Fetal electroencephalography using a new, flexible electrode.

A single flexible active electrode for monitoring the fetal electroencephalogram (FEEG), has been designed specifically for use in routine obstetrics. It does not require penetration of or adherence to the fetal scalp, and it is reusable. The equipment's performance has been tested in 20 normal labours. The recordings obtained were not contaminated by the fetal electrocardiogram and were relatively free from artefact so that minimal filtering of the signal was required. No FEEG signal was obtained if the electrode was applied to breech presentations. The trace obtained from a healthy fetus was comparable with that recorded after delivery.

Electrodes↗