Browsing by Author "St Clair Gibson, Alan"

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    Effects of elevated plasma adrenaline levels on substrate metabolism, effort perception and muscle activation during low-to-moderate intensity exercise
    (2005) West, Sacha J; Goedecke, Julia H; Van Niekerk, Lizl; Collins, Malcolm; St Clair Gibson, Alan; MacDonald, Ian A; Noakes, Timothy D; Lambert, Estelle V
    The aim of this study was to differentiate the role of raised plasma adrenaline (Adr) concentrations from sympathoadrenal activation associated with moderate-intensity exercise, on muscle activation, cardiopulmonary responses, fuel metabolism, and ratings of perceived exertion (RPE) during low-intensity exercise. Two groups of subjects (MOD, n=6; LOW, n=7) cycled on two occasions for 90 min. MOD cycled at 68% VO2max with saline infusion, and at 34% VO2max with Adr infusion. LOW cycled twice at 34% VO2max, with either Adr or saline infusion. Infusions (0.015 g Adr/kg/min) started at 15 min and increased plasma [Adr] somewhat higher than during exercise at 68% VO2max (~1.9 vs. 1.4 nM, at 75 min). Mean plasma glucose and lactate concentrations during LOW were significantly higher with Adr than saline infusion (5.1±0.6 vs. 4.4±0.3 mmol/l, P<0.01 and 2.1±0.8 vs. 1.3±0.5 mmol/l, P<0.01, respectively). Elevated [Adr], without increased exercise intensity, did not alter glycogenolysis. There were also no effects of Adr infusion at 34% VO2max on heart rate, oxygen consumption, [FFA], respiratory exchange ratio, intramuscular triglyceride utilization, muscle activation or RPE. In conclusion, elevated [Adr] similar to those found during moderate-intensity exercise increased plasma glucose and lactate availability, but did not alter intramuscular fuel utilization, effort perception or muscle activation.
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    Exercise associated muscle cramping : investigating a novel hypothesis
    (2003) Sulzer, Nicole Uschi; Schwellnus, Martin P; St Clair Gibson, Alan
    This thesis on Exercise Associated Muscle Cramping (EAMC) comprised three individual studies. The aims of this series of investigations were firstly to investigate the nature and prevalence of EAMC in a group of lronman triathletes with a past history of EAMC, secondly to compare the serum electrolyte concentrations in cramping and control Ironman triathletes as well as to record the baseline electromyography (EMG) of cramping lronman triathletes during recovery and thirdly to compare the EMG activity of cramping and control runners before, during and after a fatiguing bout of exercise.
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    Fatigue, aging and the neuromuscular system
    (2001) St Clair Gibson, Alan; Noakes, Tim; Lambert, Mike
    The aim of this thesis was to investigate the relationship between chronic exercise activity, aging, the neuromuscular system and the symptom of fatigue in a series of studies. The hypothesis of the thesis was that in contrast to the accepted dogma that exercise is beneficial to an individual, increasing longevity and improving quality of life, excessive or chronic exercise activity may accelerate the aging process, lead to neuromuscular damage, and cause the development of pathological symptoms or levels of fatigue.
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    Short-latency afferent inhibition during selective finger movement
    (2005) Voller, Bernhard; St Clair Gibson, Alan; Dambrosia, James; Richardson, Sarah Pirio; Lomarev,Mikhail; Dang, Nguyet; Hallett, Mark
    During individual finger movement, two opposite phenomena occur at the level of the central nervous system that could affect other intrinsic hand muscle representations, unintentional co-activation, and surround inhibition (SI). At rest, excitability in the motor cortex (M1) is inhibited at about 20 ms after electric stimulation of a peripheral nerve [short-latency afferent inhibition (SAI)]. We sought to determine whether SAI changes during selective index finger movement. Effects were measured by the response to transcranial magnetic stimulation in two functionally distinct target muscles of the hand [abductor digiti minimi muscle (ADM), first dorsal interosseus muscle (FDI)]. An increase in SAI in the ADM during index finger movement compared to at rest could help explain the genesis of SI. Electrical stimulation was applied to either the little finger (homotopic for ADM, heterotopic for FDI) or the index finger (heterotopic for ADM, homotopic for FDI). During index finger movement, homotopic SAI was present only in the ADM, and the effect of peripheral stimulation was greater when there was less co-activation. Heterotopic SAI found at rest disappeared with movement. We conclude that during movement, homotopic SAI on the muscle in the surround of the intended movement may contribute to SI.