Biomedical subjects

Robert J Moffatt

Publications and source records attributed to Robert J Moffatt.

6 recordsLinked to original sources

PubMed2005

Reliability of heart rate responses at given ratings of perceived exertion in cycling and walking.

Eleven healthy men (M age = 27 years, SD = 4) completed three cycling and three walking trials in an alternating order. During each trial, participants were allowed, within 3 min, to adjust the work rate to correspond to given rating of perceived exertion (RPE) values according to the following order: RPE 11, 13, and 15. For cycling as well as walking, at each RPE there were no significant differences between mean heart rate responses across the three trials (p > .05). Mode-specific estimates for heart rate intraclass correlation coefficient and coefficient of variation ranged between .80 and .91, and 5.6% and 8.3%, respectively. This study provides absolute reliability estimates for heart rate responses when using RPE in a production format and suggests there may be RPE- (and mode) specific practice requirements for achieving a reliable heart rate response at a given RPE.

Adult↗

PubMed2005

Running performance differences between men and women:an update.

More than a decade ago it was reported in the journal Nature that the slope of improvement in the men's and women's running records, extrapolated from mean running velocity plotted against historical time, would eventually result in a performance intersection of the sexes across a variety of running distances. The first of these intersections was to occur for 42 000 m before the 21st century. Most of the error in this prediction is probably explained by the linear mathematical treatment and extrapolation of limited performance data, since including world record-setting running performances for women before and after 1985 results in a non-linear data fit. The reality of early, disproportionate improvements in women's running that gave the appearance of an impending convergence with men is best explained by an historical social sports bias. Women's times have now reached a plateau similar to that observed for men at comparative performance milestones in the marathon. Sex differences at distances from 100 to 10 000 m show similar trends. The remaining sex gaps in performance appear biological in origin. Success in distance running and sprinting is determined largely by aerobic capacity and muscular strength, respectively. Because men possess a larger aerobic capacity and greater muscular strength, the gap in running performances between men and women is unlikely to narrow naturally.

Adult↗

PubMed2004

Acute exposure to environmental tobacco smoke reduces HDL-C and HDL2-C.

BACKGROUND: Chronic environmental tobacco smoke (ETS) exposure increases individuals risk of coronary artery disease by reducing high-density lipoprotein cholesterol (HDL-C). Currently, there is limited research on the acute effects of ETS on HDL-C. This study examined the acute influence of ETS on HDL-C and its subfractions. METHODS: Twelve male subjects (25.7 +/- 3.0 years) were examined to determine the influence of an acute 6-h exposure to ETS on lipid and lipoprotein levels. Baseline blood samples were drawn before ETS exposure from an antecubital vein at 6 am, 2 pm, and 10 pm. The following day, subjects were exposed to 6 h of ETS, approximately 4-10 pm. Blood was again collected at 8, 16 and 24 h following ETS exposure. Blood was assayed for total cholesterol (TC), HDL-C and its subfractions HDL(2)-C and HDL(3)-C. RESULTS: As a result of ETS exposure, HDL-C and HDL(2)-C levels were significantly reduced by 18% and 37%, respectively. This effect was sustained, with a decrease in HDL-C of 13% and HDL2-C of 28% still evident at 24-h post-exposure. TC was unchanged (pre- 187.3 +/- 41.6 and post- 187.0 +/- 46.3); however, there were significant decreases in the TC/HDL-C and HDL2-C/HDL3-C ratios by 16% and 29%, respectively, which were sustained for 24 h. CONCLUSIONS: The findings of this study demonstrate that a 6-h exposure has a negative impact on lipid and lipoprotein profiles and that these levels remained depressed for at least 24 h.

Adult↗

PubMed2004

Acute effects of premeal versus postmeal exercise on postprandial hypertriglyceridemia.

OBJECTIVE: The objective of this study was to examine the effects of the timing of exercise relative to the consumption of a fat-rich meal (81% fat) on postprandial hypertriglyceridemia. DESIGN: A single bout of exercise was either completed 30 minutes before the fat meal (EM trial) or initiated 90 minutes after the fat meal (ME trial). A third trial, fat meal only, served as a control (CON trial). The trials performed in a random order, and venous blood samples were drawn before and 1.5, 3.5, 5.5, and 7.5 hours after the meal for the determination of triglycerides, glycerol, insulin, glucose, and free fatty acids. PARTICIPANTS: Ten untrained healthy males 25.2 +/- 0.9 years old (mean +/- SE) with maximal oxygen uptake (VO2max) of 46.6 +/- 3.0 mL.kg(-1).min(-1). INTERVENTION: Walking exercise performed at 50% VO2max for 90 minutes. MAIN OUTCOME MEASURE: Postprandial hypertriglyceridemia, which was quantified by calculating the area under the triglycerides curve over the 7.5-hour postprandial period. RESULTS: The mean incremental area under the curve (total area adjusted to baseline) describing postprandial hypertriglyceridemia was lower both in the EM trial (3.16 +/- 0.99 mmol.L(-1).8 h) and in the ME trial (2.96 +/- 0.69 mmol.L(-1).8 h) compared with CON trial (6.18 +/- 1.10 mmol.L(-1).8 h; P<0.05). The corresponding areas under the curve describing the postprandial insulinemia were not different between trials (ME: 38.56 +/- 8.36 uIU.mL(-1).8 h; EM: 21.65 +/- 3.80 uIU.mL(-1).8 h; CON: 25.06 +/- 5.15 uIU.mL(-1).8 h; P>0.05). CONCLUSION: A single bout of moderate intensity exercise decreases postprandial hypertriglyceridemia irrespective of the timing of the exercise relative to a high-fat meal.

Adult↗

PubMed2003

Effects of low and moderate exercise intensity on postprandial lipemia and postheparin plasma lipoprotein lipase activity in physically active men.

This study was designed to assess differences in the intensity of exercise to attenuate postprandial lipemia (PPL). Thirteen healthy men (age 23.8 +/- 0.9 yr) participated in three random-ordered trials: in low-(25% peak oxygen consumption; Low) and moderate-intensity (65% peak oxygen consumption; Mod) exercise trials, which were completed 1 h before a high-fat meal (1.3 g fat/kg body mass), and a control (Con), fat meal only, trial. Venous blood samples were obtained before the fat meal, and at 2, 4, 6, 8, and 20 h after the fat meal. PPL in the Mod trial (267 +/- 50 mg.dl-1.8 h) was lower compared with that in either Con (439 +/- 81 mg.dl-1.8 h) or Low (403 +/- 91 mg.dl-1.8 h) trials (P < 0.05), whereas there was no difference in PPL between Con and Low trials (P > 0.05). High-density lipoprotein cholesterol (HDL-C) and HDL subtype 2 cholesterol were not different between or within trials (P > 0.05). Postprandial insulinemia was lower in the Mod trial (20.5 +/- 5.7 microIU.ml-1.8 h; P < 0.05), but not in the Low trial (31.4 +/- 4.7 microIU.ml-1.8 h), compared with that in the Con trial (34.9 +/- 5.0 microIU.ml-1.8 h). Postheparin lipoprotein lipase activity at 8 h was higher in the Low trial compared with that in either Con or Mod trials, whereas there were no differences between trials at 20 h. These results suggest that, when exercise is performed 1 h before a fat meal, only exercise of moderate but not of low intensity attenuates PPL and that this effect is not associated with changes in postheparin lipoprotein lipase activity.

Adult↗

PubMed2003

Blood glucose threshold and the metabolic responses to incremental exercise tests with and without prior lactic acidosis induction.

This study compared the metabolic-ventilatory responses and the glycemic threshold identified during lactate minimum (LM) and individual anaerobic threshold (IAT) tests. In addition, the ability to determine the anaerobic power, aerobic-anaerobic transition (Trans) (e.g. ventilatory threshold; VT) and the maximal oxygen consumption (VO(2max)) all within a single incremental treadmill test (IT) was investigated. Fifteen physically fit men [25.9 (5.5) years; 77.4 (6.5) kg] performed the following: test 1, IT for IAT; and test 2, LM: 30-s Wingate test followed by 8 min rest and then an IT that was the same as test 1. Blood lactate concentration [lac], glucose concentration [gluc], pH, PO(2), PCO(2), base excess (BE) and ventilatory variables were measured. At the beginning of the IT for LM, the ventilation, PO(2) and VO(2) were higher and the pH, BE and PCO(2) were lower in relation to IAT ( P<0.05), while no differences were observed after reaching LM intensity during IT. Moreover, the Trans could be identified by [lac] (IAT, LM), minute ventilation [V(E;) VT identified during IAT protocol (VT-IAT) and VT identified during LM protocol (VT-LM)], and [gluc] (IGT, GM) during the IT for IAT and LM. The velocities (kilometers per hour) corresponding to IAT (12.6+/-1.6), VT-IAT (12.5+/-1.7), IGT (12.6+/-1.6), LM (12.5+/-1.5), VT-LM (12.3+/-1.5), and GM (12.6+/-1.9) were not different from each other and the LM and IAT protocols resulted in the similar VO(2max). We concluded that: (1) after reaching the LM the metabolic responses during IT are similar to IAT; (2) performing a Wingate test prior to an IT does not interfere with the Trans and VO(2max) attainment; (3) and the IGT and GM can predict the Trans.

Acidosis, Lactic↗