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Biomedical subjects

H E Parker

Publications and source records attributed to H E Parker.

At least 19 recordsLinked to original sources
PubMed2003

Long term retention of safe diving skills.

This short report describes a 20-month follow-up of safe diving skills, extending the 8-month retention period previously published in this journal. Thirty-four recreational swimmers with poor diving skills were evaluated before and immediately after a diving skills intervention program. Twenty-two returned for the eight-month follow-up evaluation and 16 returned 20 months post. As with the earlier study, Treadwater, Deck, Block and Running dives were video-recorded, and maximum depth, distance, velocity, entry angle and flight distance were compared. Underwater hand and arm positions were examined. Pre-intervention, a breaststroke arm action before maximum depth occurred in 18% of all dives and 38% of Treadwater dives. This was eliminated post-intervention, improving head protection. The Treadwater dive elicited the greatest mean maximum depth, and ANOVA showed depth for this entry decreased (improved) following intervention and remained shallower at the eight-month and 20-month post follow-ups. The Block dive also became shallower following intervention while the Deck dive remained unchanged. As seven 10-minute skills sessions resulted in shallower dives with safer hand and arm positions, and these skills were retained over a 600 day non-practice period, it is reliable to consider that the inclusion of safe diving skills in learn-to-swim programs can provide a diving spinal cord injury prevention strategy.

Adult↗
PubMed1997

Gravity constraints in infant motor development.

The effect of gravity in determining if and when during infancy movements eventuate and the rate at which they develop is unknown. In accordance with intersegmental relationships (Hof, 1992), a muscle moment during infancy would have to develop more rapidly than the gravitational moment before movement could occur. In this investigation, the effect of growth through the influence of gravity on the joint moments in the axial region when infants were in a prone or supine posture was examined. A mathematical model that considers the body to be composed of transverse elliptical cylinders, 1 cm deep and of known density, was used in estimating the mass of the 16 segments of the body. The gravitational moments about 3 joints within the axial region (C7-T1, T12-L1, and the hip) were determined by summation, using the radii from the joint transverse axis to the center of mass of the segments. Infants (N = 27) aged between 9 and 36 weeks at the beginning of the study were tested monthly 6 times, and the effect of growth on the gravitational moments was represented by first-order polynomials. Age x Joint analysis of variance (ANOVA) of the mean slopes of the regressions for the gravitational moments revealed significant main effects for age and joint. The means increased monotonically with the number of segments and decreased as infants aged. The mean slopes of the neck and trunk joints were significantly smaller than that of the hip joint. With increasing age, the gravitational slope was significantly smaller. The changes in the gravitational moments during infancy are seen as likely control parameters effecting phase shifts in motor patterns during development.

Aging↗
PubMed1997

Starting age and aquatic skill learning in young children: mastery of prerequisite water confidence and basic aquatic locomotion skills.

This study examined whether an optimal starting age emerged for acquiring water confidence (Level 1) or basic aquatic locomotion skills (Level 2). Analysis of 264 children between 2 and 7 years of age was made by examining numbers of lessons, age at reaching a given standard and the time duration required for each swim level. At 4 years of age, children demonstrated the ability to achieve the levels of water confidence and basic locomotion skills whereas earlier introduction to aquatic instruction did not translate into earlier mastery of these basic skills.

Age Factors↗
PubMed1995

Children's readiness for learning front crawl swimming.

This study attempted to establish whether an optimal age could be identified at which children were ready to learn the front crawl swimming stroke. The variables examined were: the number of lessons, the age of commencing lessons and the time duration for learning to swim 10m front crawl (Level 3). Longitudinal records of 326 children, aged between 2 and 8 years, were analysed using General Linear Model two-way (Age x Sex) analysis of variance procedures. The main effect for age was significant (p < 0.001) for all three variables. Post hoc analysis revealed that the children who started at 5 years of age received significantly fewer number of lessons and took shorter duration compared to those who commenced learning to swim at an earlier age. Whether pupils started lessons at 2, 3 or 4 years of age, they achieved Level 3 at approximately the same mean age of 5 1/2 years. The optimal readiness period was identified in this study to be between 5 and 6 years of age. There was little evidence of gender differences for all three variables.

Age Factors↗
PubMed1993

Stability and change in children's skill.

This paper explores age-related performance variability, both within trials and between sessions, in repetitive hopping. The mean, the standard deviation (SD), and the coefficient of variation (CV) of several timing and ground-reaction-force variables of hopping were analysed by repeated-measures ANOVA for age-related effects across test sessions and foot used. Forty-five subjects in five age groups (3-4 years, 4-5 years, 6-7 years, 8-9 years, or Adult) performed self-paced, one-footed hopping on three occasions within one week. As was expected, the results showed main effects for Age in all force and time variables, with the exception of CV of medio-lateral force. No significant main effects for Feet were revealed. However, significant Feet x Session interactions were found in flight-time measures, with higher flight-time SD and lower CV for the non-preferred foot in Session 1, a reversal in Session 2, and a negligible difference in Session 3. Across sessions, decreased SD and CV for both vertical and medio-lateral force and shorter flight time indicated more efficient hopping. Overall, it was concluded that SD and CV measures were more sensitive measures of children's performance across repeated sessions than were mean scores and that the order of testing the limbs is an important consideration in experimental protocols when lateralized tasks are measured.

Adolescent↗
PubMed1978

Effects of environmental temperature on the iodine requirements of young chickens.

Growth rate of chicks maintained at 32 C was reduced as compared with chicks maintained at 21 C. Environmental temperature did not influence the iodine requirement for growth which appeared to be met with a level of approximately 75 ppb in both environments. Thyroid enlargement was observed in both environments for chicks fed low levels of iodine, but the magnitude of the enlargement was much greater at 21 C than at 32 C. A level of 75 ppb iodine was adequate for normal thyroid size at 32 C, but was inadequate to prevent thyroid enlargement at 21 C.

Animals↗