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Biomedical subjects

John G Morris

Publications and source records attributed to John G Morris.

6 recordsLinked to original sources
PubMed2007

Exercise and postprandial plasma triacylglycerol concentrations in healthy adolescent boys.

PURPOSE: Atherosclerosis is initiated in childhood. Therefore, reducing postprandial triacylglycerol concentrations ([TAG]), even in young people, could potentially slow atherogenic progression. This study investigated whether continuous-exercise and intermittent-games activity would reduce postprandial [TAG] in adolescent boys. METHODS: Nineteen subjects were randomly assigned to either a continuous-exercise group (N = 10) or an intermittent-games group (N = 9) and underwent two 2-d trials. Trials were performed a minimum of 7 d apart in a randomized order, consisting of a rest trial and either a continuous-exercise or intermittent-games trial. In the rest trial, subjects took no exercise on day 1. On day 1 of the exercise trial, subjects completed four blocks (approximately 15 min each) of uphill treadmill walking or intermittent-games activity with 3 min of rest between each block. On day 2, subjects came to the laboratory after an overnight fast, and finger-prick blood samples were obtained in the fasted state. Subjects then consumed a test meal (1.25 g of fat, 1.07 g of carbohydrate, 0.20 g of protein, and 67 kJ.kg(-1) body mass). Further blood samples were collected at 30 and 45 min and at 1, 3, 4, and 6 h postprandially. RESULTS: The total area under the plasma [TAG] versus time curve was lower on day 2 after exercise than the rest condition in both groups (Student's t-tests for correlated means: continuous-exercise group 14%, P = 0.050; intermittent-games group 26%, P = 0.002). CONCLUSION: Both continuous-exercise and intermittent-games activity reduce [TAG] in healthy adolescent boys when performed the afternoon before ingesting a high-fat meal.

Adolescent↗
PubMed2006

Effects of intermittent games activity on postprandial lipemia in young adults.

PURPOSE: To investigate whether a single session of intermittent games activity would reduce postprandial lipemia. METHODS: Twelve male volunteers completed three 2-d trials: rest, continuous exercise, and intermittent games activity. Trials were performed a minimum of 6 d apart in a balanced crossover design. In the rest trial, subjects took no exercise on day 1. On day 1 of the continuous and intermittent games trials, subjects completed four blocks (approximately 15 min per block) of uphill treadmill walking or intermittent games activity with 3 min of rest between each block. On day 2, subjects came to the laboratory for an oral fat tolerance test (blood taken fasted and for 6 h following a high-fat test meal (1.25 g of fat and 1.07 g of carbohydrate per kilogram of body mass)). RESULTS: The intermittent games protocol elicited a higher exercise intensity than the continuous trial (lactate: 4.3+/-0.6 vs 2.4+/-0.3 mmol.L; % VO2max: 72+/-2 vs 62+/-1, respectively; mean+/-SE). The total area under the plasma triacylglycerol (TAG) concentration versus time curve was lower in both the intermittent games (25%, P=0.001) and the continuous (19%, P=0.028) trials than in the rest trial. CONCLUSION: These findings show for the first time that intermittent games activity can reduce postprandial lipemia, and confirm that continuous exercise reduces postprandial lipemia in young adults.

Adult↗
PubMed2004

Effect of frequency of carbohydrate feedings on recovery and subsequent endurance run.

PURPOSE: This study examined the effect of feeding pattern of a high glycemic index (GI) meal during a short-term recovery on subsequent endurance capacity. METHODS: Eight men ran at 70% .VO2max on a level treadmill for 90 min (T1) on two occasions, followed by 4-h recovery (R) and a further exhaustive run at the same speed (T2). During the R, subjects consumed a prescribed meal with a GI of 77 in either a "gorging" (GOR) or "nibbling" (NIB) intake pattern, providing 1.5 g carbohydrate (CHO) per kilogram body mass. In the GOR trial, the foods were consumed in a single bolus, 20 min after the end of T1. In the NIB trial, the same quantity of food was ingested in three equal portions; the first consumed 20 min after the end of T1 and the remainder at hourly intervals thereafter. RESULTS: The run time during T2 was similar between trials (GOR vs NIB: 68.1 +/- 8.2 vs 66.8 +/- 8.7 min, P > 0.05). However, CHO utilization was lower and fat utilization higher during T2 in the GOR trial compared with the NIB trial (GOR vs NIB: CHO: 94.4 +/- 11.4 vs 117.6 +/- 10.6 g, P < 0.05; FAT: 55.9 +/- 8.0 vs 44 +/- 8.6 g, P < 0.01). CONCLUSIONS: These results suggest that serial consumption of a high GI meal during a 4-h recovery increased the reliance on CHO oxidation for energy provision during a subsequent run when compared with a single feeding. However, there was no difference in the duration of the exhaustive run after the recovery between the GOR and NIB trials.

Adult↗
PubMed2003

A Cartesian coordinate system for human cerebral cortex.

The most commonly used method for specifying the locations of functional areas in the human cerebral cortex is the coordinate system of Talairach and Tournoux (Co-planar Stereotaxic Altas of The Human Brain (1988) Georg Thieme Verlag, Stuttgart). It was designed to locate subcortical nuclei by reference to an axis joining the anterior and posterior commissures. The coordinate system has difficulties, however, when applied to cortical locations: (1) it can be difficult to locate the posterior commissure (PC); (2) the fundamental axis is short, and errors in specifying the axis lead to large errors at the cortical surface; (3) there is no normalisation for brain size. We sought to rectify these problems with a new coordinate system, the Sydney system, in which the fundamental axis runs in the medial sagittal plane from the anterior edge of the corpus callosum to the posterior end of the parieto-occipital sulcus. Normalisation is achieved by dividing all distances by the length of the fundamental axis. Using functionally important points and anatomical landmarks on cadaveric specimens and magnetic resonance images (MRI), three-dimensional coordinates were measured in both the Talairach and Sydney systems. The Sydney system has the following advantages over the Talairach system: (1) the fundamental axis is more than four times longer and is easier to identify; (2) the Sydney system is more precise, in that it reduces the spread of points across the sample; (3) the normalised coordinates allow locations to be compared across individuals, regardless of brain size. We conclude that for the mapping of cortical areas, the Sydney system is potentially an improvement on Talairach's.

Adult↗
PubMed2003

The influence of a 6.5% carbohydrate-electrolyte solution on performance of prolonged intermittent high-intensity running at 30 degrees C.

Nine male student games players consumed either flavoured water (0.1 g carbohydrate, Na+ 6 mmol x l(-1)), a solution containing 6.5% carbohydrate-electrolytes (6.5 g carbohydrate, Na+ 21 mmol x l(-1)) or a taste placebo (Na+ 2 mmol x l(-1)) during an intermittent shuttle test performed on three separate occasions at an ambient temperature of 30 degrees C (dry bulb). The test involved five 15-min sets of repeated cycles of walking and variable speed running, each separated by a 4-min rest (part A of the test), followed by 60 s run/60 s rest until exhaustion (part B of the test). The participants drank 6.5 ml x kg(-1) of fluid as a bolus just before exercise and thereafter 4.5 ml x kg(-1) during every exercise set and rest period (19 min). There was a trial order effect. The total distance completed by the participants was greater in trial 3 (8441 +/- 873 m) than in trial 1 (6839 +/- 512, P < 0.05). This represented a 19% improvement in exercise capacity. However, the trials were performed in a random counterbalanced order and the participants completed 8634 +/- 653 m, 7786 +/- 741 m and 7099 +/- 647 m in the flavoured water (FW), placebo (P) and carbohydrate-electrolyte (CE) trials, respectively (P = 0.08). Sprint performance was not different between the trials but was impaired over time (FW vs P vs CE: set 1, 2.41 +/- 0.02 vs 2.39 +/- 0.03 vs 2.39 +/- 0.03 s; end set, 2.46 +/- 0.03 vs 2.47 +/- 0.03 vs 2.47 +/- 0.02 s; main effect time, P < 0.01). The rate of rise in rectal temperature was greater in the carbohydrate-electrolyte trial (rise in rectal temperature/duration of trial, degrees C x h(-1); FW vs CE, P < 0.05; P vs CE, N.S.). Blood glucose concentrations were higher in the carbohydrate-electrolyte than in the other two trials (FW vs P vs CE:rest, 4.4 +/- 0.1 vs 4.3 +/- 0.1 vs 4.2 +/- 0.1 mmol x l(-1); end of exercise, 5.4 +/- 0.3 vs 6.4 +/- 0.6 vs 7.2 +/- 0.5 mmol x l(-1); main effect trial, P < 0.05; main effect time, P < 0.01). Plasma free fatty acid concentrations at the end of exercise were lower in the carbohydrate-electrolyte trial than in the other two trials (FW vs P vs CE: 0.57 +/- 0.08 vs 0.53 +/- 0.11 vs 0.29 +/- 0.04 mmol x l(-1); interaction, P < 0.01). The correlation between the rate of rise in rectal temperature (degrees C x h(-1)) and the distance completed was -0.91, -0.92 and -0.96 in the flavoured water, placebo and carbohydrate-electrolyte conditions, respectively (P < 0.01). Heart rate, blood pressure, plasma ammonia, blood lactate, plasma volume and rate of perceived exertion were not different between the three fluid trials. Although drinking the carbohydrate-electrolyte solution induced greater metabolic changes than the flavoured water and placebo solutions, it is unlikely that in these unacclimated males carbohydrate availability was a limiting factor in the performance of intermittent running in hot environmental conditions.

Adult↗