Craig Anthony Williams

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We report studies of six patients with the Angelman "Happy Puppet" syndrome and compare the data with those from previous reports. The results confirm the classic findings of severe mental retardation, "puppet-like" gait, characteristic craniofacial abnormalities, and frequent episodes of laughter and suggest that this syndrome is more common than(More)
Recent improvements in magnetic resonance imaging techniques now allow the developing brain to be visualized in sufficient detail to perform "in vivo neuropathology." In this study we compared the cortical morphology in six children with Angelman and four with Prader-Willi syndrome. These two syndromes are of special interest because, although they are both(More)
The jump performance of ten youth soccer players (mean age 15.8 years, s= 0.4) was assessed before and after 42 min of soccer-specific exercise performed on a non-motorized treadmill. A squat, countermovement, and drop jump were performed on a force platform and simultaneously surface EMG activity of four lower limb muscles was collected. Jump height(More)
This study tested the effects of low-cadence (60 rev min−1) uphill (Int60) or high-cadence (100 rev min−1) level-ground (Int100) interval training on power output (PO) during 20-min uphill (TTup) and flat (TTflat) time-trials. Eighteen male cyclists ( $$ \dot{V}{\text{O}}_{2\max } $$ : 58.6 ± 5.4 mL min−1 kg−1) were randomly assigned to Int60, Int100 or a(More)
This study examined whether critical power (CP) in adolescents: (1) provides a landmark for maximal steady-state exercise; and (2) can be determined using ‘all-out’ exercise. Nine active 14–15 year olds (6 females, 3 males) performed five cycling tests: (1) a ramp test to determine $$ \dot{V}{\text{O}}_{{2\,{\text{peak}}}} $$ ; (2) up to four constant power(More)
The aim of the current study was to investigate potential age-related differences in neural regulation strategies during maximal and sub-maximal hopping. Thirty-two boys from three different age groups (9-, 12- and 15-years), completed trials of both maximal and sub maximal hopping, and based on contact and flight times, measures of reactive strength index(More)
The aim of the study was to assess the reliability of a mobile contact mat in measuring a range of stretch-shortening cycle parameters in young adolescents. Additionally, vertical leg stiffness using contact mat data was validated against a criterion method using force-time data. The reliability study involved 18 youths completing a habituation and three(More)
This study tested the hypothesis that pulmonary VO₂ kinetics would be slowed during 'work-to-work' exercise in adults but not in children. Eight boys (mean age=12.5 ± 0.5 years) and nine men completed very heavy step transitions initiated from either 'unloaded' pedalling (U→VH) or unloaded-to-moderate cycling (i.e. U→M to M→VH). The phase II τ was(More)
OBJECTIVE To determine the importance of the provision of external exercise information to the setting of the pacing strategy, in subjects unfamiliar with a cycling task. DESIGN Twenty-two healthy, untrained cyclists (VO(2max), 50 ± 9 mL-(1)·kg-(1)·min-(1)) were randomly assigned to a control (CON) group or an experimental (EXP) group and two successive 4(More)
Although it is suggested that periods of naturally occurring accelerated adaptation may exist for various physical parameters, it would appear that no such evidence exists for stretch-shortening cycle (SSC) development. Two hundred and fifty male youths aged 7-17 years were tested for squat (SJ) and countermovement jump (CMJ) height, reactive strength index(More)