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C Burleson

Publications and source records attributed to C Burleson.

5 recordsLinked to original sources
PubMed1997

Comparison of methods for evaluating exercise-induced changes in thromboxane B2 and beta-thromboglobulin.

This study compared the effects of exercise or TXB2 and beta-TG when evaluated by four methods: 1) not adjusted; 2) adjusted for plasma volume changes (PV); 3) standardized per 10(5) platelets (PC); 4) or both PC and PV (PC-PV). Blood was collected from 16 men (41.3 +/- 8.1 yr) at rest after 30 min of exercise (IPE) and after 30 min recovery. Resting TXB2 and beta-TG concentrations were 62.0 +/- 6.2 pg.mL-1 and 129.8 +/- 12.5 ng.mL-1, respectively. When expressed on a per 10(5) platelet basis, resting PCTXB2 was 23.8 +/- 2.8 pg.mL-1.10(5-1) platelets and PC beta-TG was 50.77 +/- 6.0 ng.mL-1. 10(5-1) platelets. At IPE, TXB2 decreased 20.5% and beta-TG increased 13.6%. Thirty minutes after exercise TXB2 was 4.2% lower than resting values, whereas beta-TG was 26% higher. TXB2, beta-TG, PVTXB2, and PV beta-TG were not significantly altered by exercise. The only significant changes in TXB2 occurred at IPE when values were adjusted for changes in platelet count. At IPE, PCTXB2, and PC-PVTXB2 decreased 32.8% and 33.6%, respectively (P < 0.05). Similarly, beta-TG were not altered significantly by exercise except when the samples taken after 30 min of recovery were adjusted for changes in platelet count. At 30 min post-exercise PC beta-TG and PC-PV beta-TG were 21.2% and 28.4% greater (P < 0.05) than the resting beta-TG values. These data suggest that methods used to adjust concentrations of platelet derived substances for changes owing to exercise may influence conclusions about the effect of exercise on platelet function. Thus, it is imperative that researchers consider the purpose for which they are collecting TXB2 and beta-TG, as well as other constituents derived from blood cells, before they determine which methods of analysis to use.

Adult↗
PubMed1994

Daily variability in exercise ventilation.

The purpose of this study was to quantify daily variability in ventilation (VE) during submaximal exercise and establish the number of testing sessions required to produce stable exercise ventilation measures. Following 60 min of treadmill accommodation, four male (M) and four female (F) distance runners completed 5 weeks of daily treadmill testing at the same time of day while engaged in a normal routine of training and racing. During each test session, subjects completed three 6-min level treadmill runs at either 3.13, 3.57, and 4.02 m.sec-1 for F or 3.57, 4.02, and 4.47 m.sec-1 for M. Measures of VE were obtained during the last 2 min of each 6-min run. Results indicated that the mean coefficient of variation (CV) for VE across speeds was 4.33%. Reliability analyses examining all possible combinations of testing days over the 5-week period revealed that 97% of the variation in mean VE was accounted for in either 2 consecutive or non-consecutive days, while 98% of the variation in mean VE was accounted for in 5 consecutive days. These data suggest that when treadmill exposure and circadian variation are controlled, intraindividual differences in exercise VE are relatively small in male and female subjects following an unrestricted program of training and competitive racing. Additionally, acceptably stable VE values in this cohort can be derived by averaging duplicate measures obtained from consecutive or non-consecutive testing sessions.

Adult↗
PubMed1994

Daily variation in step length of trained male runners.

The purpose of this study was to quantify daily intra-individual variability in mean step length, a basic descriptor for the running pattern. Following 60 minutes of treadmill accommodation, nine trained male subjects (X age = 34.2 yrs +/- 7.2, X VO2max = 57.0 +/- 4.8 ml.kg-1.min-1) performed daily (Mon-Fri) 6-minute treadmill runs at three submaximal speeds (2.68, 3.13 and 3.58 m.s-1) over a 4-week period. To minimize extraneous influences, subjects refrained from road racing and completed the 20 running sessions (5 d.wk-1.4 weeks for each speed) at the same time of day and in the same footwear. Treadmill velocity was calibrated for each 6-minute running bout and step length was determined during the last 2 minutes of each run. Results indicated that mean step length and coefficient of variation values were 0.984 m and 2.50% at 2.68 m.s-1, 1.124 m and 2.22% at 3.13 m.s-1, and 1.254 m and 2.26% at 3.58 m.s-1. Reliability analyses indicated that the percentage of variation accounted for in step length across all speeds was high and improved very little as test number increased (range = 96% for two days vs 99% for five days). Taken together, these findings suggest that when testing conditions are controlled, within-subject variability in step length measures obtained at multiple submaximal running speeds is small in trained subjects and that criterion step length values can be obtained by averaging duplicate measurements.

Adult↗
PubMed1994

Combined effects of age and exercise on thromboxane B2 and platelet activation.

Nine healthy young (27.8 +/- 0.8 yr old, YM) and nine healthy older men (55.4 +/- 1.3 yr old, OM) ran on a treadmill at 70-75% of maximal O2 consumption for 30 min to determine the combined effects of age and acute exercise on plasma thromboxane B2 (TxB2) and beta-thromboglobulin (beta-TG). Blood samples (10 ml) were collected in tubes containing 0.5 ml of 4.5 mM EDTA, 30 mM acetylsalicylic acid, and 1 microM prostaglandin E1 after 15 min of rest, immediately after exercise, and at 30 min of recovery. Concentrations of TxB2 and beta-TG were determined by radioimmunoassay. Samples were adjusted for hemoconcentration and changes in platelet count not accounted for by plasma volume shifts. Data were analyzed with repeated-measures analysis of variance and Tukey's post hoc technique. Resting TxB2 was 53.3 +/- 9.6 and 79.0 +/- 18.2 pg/ml for the YM and OM, respectively. beta-TG at rest was 152.5 +/- 13.9 and 114.0 +/- 10.9 ng/ml for the YM and OM, respectively. No significant age group or exercise-induced differences for TxB2 or beta-TG were found immediately after exercise. TxB2 in the OM (101.7 +/- 16.4 pg/ml) 30 min after exercise was significantly (P = 0.05) higher than that in the YM (54.4 +/- 6.2 pg/ml). beta-TG values 30 min after exercise were not significantly different: 183.3 +/- 26.9 and 169.9 +/- 17.0 ng/ml in the OM and YM, respectively. These data suggest that OM may experience greater increases in TxB2 than YM 30 min after exercise and may be more predisposed to platelet activation.

Adult↗