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Biomedical subjects

L Cordain

Publications and source records attributed to L Cordain.

18 recordsLinked to original sources
PubMed1997

Influence of moderate daily wine consumption on body weight regulation and metabolism in healthy free-living males.

OBJECTIVE: Although previous studies have clearly demonstrated that energy from alcohol may not be efficiently utilized to maintain body weight when it comprises 20% or more of the daily caloric intake, there is considerable debate regarding the influence of moderate alcohol consumption (< or = 5% of the total daily caloric intake) upon metabolism, substrate utilization and body weight regulation. Consequently, the objectives of this study were to determine whether moderate alcohol consumption could influence body weight via changes in substrate utilization, oxygen consumption or alterations in dietary macronutrient content. METHODS: Fourteen male subjects (mean age = 32.1 years) participated in a 12-week, free-living, crossover trial in which they either drank red wine (270 ml; 13% v/v ethanol) daily for 6 weeks and then abstained for the next 6 weeks or vice-versa. RESULTS: Whether wine was imbibed or not, no significant differences (p > 0.05) were demonstrated for any of the following variables: body weight, body fat percentage, skinfold thickness, resting metabolic rate, respiratory quotient, caloric intake, dietary macronutrient content, or fasting insulin or glucose concentrations. CONCLUSIONS: In free-living subjects over a 6-week period, the addition of two glasses of red wine to the evening meal does not appear to influence any measured variable which may adversely affect body weight or promote the development of obesity during this time period.

Adult↗
PubMed1994

Residual lung volume and ventilatory muscle strength changes following maximal and submaximal exercise.

In order to evaluate a mechanism which may be responsible for the often observed acute increase in residual lung volume (RV) following exercise, 12 non-smoking males (20-30 yrs) performed two bouts of exercise on separate days; one to maximal heart rate (HRmax) and one to 85% of HRmax for 20 min. Prior to exercise and at 5, 15, 30, 60 and 120 min post-exercise, the following parameters were measured: RV, forced vital capacity (FVC), forced expiratory volume (FEV1.0), forced expiratory flow (FEF75-85), maximal expiratory pressure (PEmax), and maximal inspiratory pressure (PImax). Significant (p < 0.05) increases occurred in RV at 5, 15 and 30 min following maximal exercise and at 5 and 30 min after submaximal exercise. Changes in RV between the two exercise bouts were generally greater (p < 0.05) for maximal exercise. Accompanying the increases in RV were significant (p < 0.05) decreases in PEmax and decreases in FVC, while FEV1.0 and FEF75-85 remained generally unchanged or were slightly elevated. The data suggest that decreases in expiratory muscle strength due to fatigue may in part be responsible for increases in RV.

Adult↗
PubMed1994

Exercise-induced changes in plasma vitamin B-6 concentrations do not vary with exercise intensity.

This study examined the effect of high vs moderate exercise intensity on changes in concentration of plasma pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid (4-PA) in human subjects. Eight physically active subjects were tested twice at 60% and 85% maximum oxygen consumption (VO2max) for 30 and 20 min, respectively, on a bicycle ergometer. Blood samples were obtained before and during exercise. Data were adjusted for changes in plasma volume calculated from changes in hematocrit. PLP concentrations significantly increased during exercise (P < 0.0001), with 79% of the rise in PLP concentration occurring within 5 min. 4-PA concentration increased steadily through exercise and was 23% higher at 20 min than at 0 min. Exercise intensity had no effect on the magnitude or rate of either increase for either PLP or 4-PA. PL concentration did not vary with exercise duration, but was significantly higher at 60% compared with 85% VO2max (P = 0.001). No significant differences were observed in glucose concentration. The data do not support hypotheses in the literature that PLP concentration rises during exercise to support exercise-induced shifts in substrate utilization.

Adolescent↗
PubMed1994

Influence of postexercise glucose ingestion upon serum potassium levels and ECG function.

Thirteen trained runners were studied to determine whether postexercise glucose ingestion contributes to electrocardiogram (ECG) alterations by enhancing decreases in serum potassium (K+) concentrations. For the two randomly ordered trials, subjects ingested a 100 g (25% w/v glucose polymer) drink, either alone or with the addition of 3 g of potassium chloride (KCl), within 15 min following a 90-min run. ECG parameters, serum K+, and glucose concentrations were measured preexercise (Time 0), 2-3 min post-exercise (Time 1), and 25 (Time 2) and 60 (Time 3) min postexercise. The data suggest that postexercise glucose ingestion may cause ECG changes that are not directly related to the return of K+ to muscle, and that these changes, although characteristic of hypokalemia, may be related to serum glucose excursions rather than to absolute levels of serum K+. The addition of KCl may have prevented these changes by delaying gastric emptying of glucose.

Adult↗
PubMed1991

Wetsuits, body density and swimming performance.

To determine the influence of body composition upon swimming performance with and without wetsuits, 14 competitive female swimmers (mean (s.d.) age, 19.9 (0.9) years) were measured for body density while wearing both wetsuits and normal swimsuits. Subjects swam 400 and 1500 m trials with and without wetsuits, randomly, over a 12-day period. Six subjects participated in an additional trial while wearing neoprene leg-bands fitted over the wetsuit. Mean (s.d.) subject density without and with wetsuits was 1.048 (.009) and 1.021 (.007) g/ml respectively. Wetsuits reduced (P less than 0.05) swim times for the 400 (-4.96%) and 1500 m swim (-3.23%) compared with swimsuit trials. The neoprene bands increased (P less than 0.05) swim times relative to swimsuit and wetsuit trials. With wetsuits, swim times were inversely (P less than 0.05) related to density for the 400 (r = -0.46) and 1500 m swim (r = -0.54) suggesting that wetsuits increase performance by increasing buoyancy and that lean subjects benefit more from wearing wetsuits than do fatter subjects.

Adult↗
PubMed1990

Metabolic consequences of reduced frequency breathing during submaximal exercise at moderate altitude.

The intention of this study was to determine the metabolic consequences of reduced frequency breathing (RFB) at total lung capacity (TLC) in competitive cyclists during submaximal exercise at moderate altitude (1520 m; barometric pressure, PB = 84.6 kPa; 635 mm Hg). Nine trained males performed an RFB exercise test (10 breaths.min-1) and a normal breathing exercise test at 75-85% of the ventilatory threshold intensity for 6 min on separate days. RFB exercise induced significant (P less than 0.05) decreases in ventilation (VE), carbon dioxide production (VCO2), respiratory exchange ratio (RER), ventilatory equivalent for O2 consumption (VE/VO2), arterial O2 saturation and increases in heart rate and venous lactate concentration, while maintaining a similar O2 consumption (VO2). During recovery from RFB exercise (spontaneous breathing) a significant (P less than 0.05) decreases in blood pH was detected along with increases in VE, VO2, VCO2, RER, and venous partial pressure of carbon dioxide. The results indicate that voluntary hypoventilation at TLC, during submaximal cycling exercise at moderate altitude, elicits systemic hypercapnia, arterial hypoxemia, tissue hypoxia and acidosis. These data suggest that RFB exercise at moderate altitude causes an increase in energy production from glycolytic pathways above that which occurs with normal breathing.

Adult↗
PubMed1990

Lung volumes and maximal respiratory pressures in collegiate swimmers and runners.

To determine whether respiratory muscle strength is related to pulmonary volume differences in athletes and nonathletes, 11 intercollegiate female swimmers, 11 female cross-country runners, and two nonathletic control groups, matched to the athletes in height and age, were evaluated for pulmonary parameters including maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax). Swimmers exhibited larger (p less than .05) vital capacities (VC), residual lung volumes (RV), inspiratory capacities (IC), and functional residual capacities (FRC) than both the runners or the controls but no difference (p greater than .05) in either PImax or inspiratory flow (FIV 25%-75%). Timed expiratory volumes (FEV 0.5 and FEV 1.0) were significantly (p less than .05) lower in the swimmers than in the controls. These data suggest that an adaptational growth may be responsible, in part, for the augmented static lung volumes demonstrated in swimmers.

Adolescent↗
PubMed1990

Normoxic and acute hypoxic exercise tolerance in man following acetazolamide.

The influence of acetazolamide (ACZ) upon the ability to perform and sustain maximal and submaximal exercise bouts under normoxic and hypoxic conditions was examined in four groups of healthy male subjects (N = 27). ACZ (500 mg) or inert placebo (Pla) was administered prior to exercise in a quasi-randomized, double-blind, crossover fashion. ACZ was shown to lower venous pH (ACZ, 7.31 +/- 0.01, vs Pla, 7.35 +/- 0.08) and bicarbonate (ACZ, 22.4 +/- 0.27 mM, vs Pla, 25.4 +/- 0.6 mM) and to elevate urine pH (ACZ, 7.36 +/- 0.06, vs Pla, 5.84 +/- 0.19) and tended to elevate VE (P = 0.07) at rest. Peak VO2 measured using a continuous incremental protocol was unaltered in normoxia, while peak VCO2 and RER were lowered by ACZ. No significant effect of ACZ upon VO2, VCO2, RER, or heart rate (HR) was observed during submaximal exercise (75% of peak VO2) although VE was increased by 14% and time to exhaustion (EXHt) was reduced by 29%. During acute hypoxia at a simulated altitude of 4,270 m (Pbar = 446 mm Hg), no significant differences were noted in VE, VO2, VCO2, RER, HR, or arterial saturation (SaO2) at rest. Prior to exercise, venous pH (ACZ, 7.39 +/- 0.04, vs Pla, 7.44 +/- 0.007) and bicarbonate were lower with ACZ (ACZ, 21.6 +/- 0.46 mM, vs Pla, 24.2 +/- 0.25 mM), while urine pH was higher (ACZ, 7.6 +/- 0.07, vs Pla, 5.9 +/- 0.25). Other than a higher PCO2 and lower venous lactate with ACZ, no significant differences were identified at peak VO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1989

Potassium content of the fat free body in children.

Previous estimates of body composition in children by measurement of total body potassium (TBK) have employed adult derived values for the ratio of K/fat free body mass (FFBM) to calculate the FFBM. To evaluate the appropriateness of this practice, body composition was determined in 30 children (14 boys, 16 girls) between the ages of 9 and 14 years by hydrostatic weighing, bioelectric impedance, and whole body counting of 40K. Estimates of body fat percentage by TBK measurements were significantly greater (p less than 0.05) than by either the hydrostatic or bioelectric impedance techniques. When current estimates for the FFBM density in children were employed to derive the K/FFBM, the value for boys was 58.9 mEq and for girls, 54.2 mEq. These data indicate that the FFBM will be underestimated in pediatric populations when adult derived values for K/FFBM are used.

Adipose Tissue↗
PubMed1988

Body composition determination in children using bioelectrical impedance.

Estimation of body composition by measurement of tetrapolar bioelectrical resistive impedance (R) is a technique only recently validated in adults. To evaluate this technique in children, 16 girls aged 11.6 +/- 0.9 yr (mean +/- SD) and 14 boys aged 12.5 +/- 1.0 yr were assessed for fat free mass (FFM) by hydrostatic weighing, total body potassium (TBK) by whole body counting of 40K, and R by an electrical impedance plethysmograph. Significant relationships (P less than 0.001) were demonstrated between TBK and ht2/R (r = 0.92), and FFM and ht2/R (r = 0.83). The reliability coefficient for the impedance measurements was r = 0.97. The following equation describes FFM in the present group of children: FFM (kg) = 6.86 + 0.81 x (ht2/R), r = 0.83, P less than 0.001, SEE = 4.08. These data suggest that impedance measurements are valid and reliable predictors of FFM in pediatric populations.

Adipose Tissue↗
PubMed1988

Metabolic and heart rate responses to submaximal arm lever and arm crank ergometry.

Previous studies have shown that arm cranks and arm levers, working as propulsion mechanisms for nonambulatory individuals, may have mechanical and physiologic advantages over standard handrim wheelchairs. This study evaluated physiologic responses to arm lever and arm crank ergometry using identical workloads. An arm lever ergometer (ALE) was constructed and adapted to an arm crank ergometer (ACE) so that equal workloads could be applied with both ergometers. Fifteen able-bodied men and 15 able-bodied women exercised at a low (15 watts) and a high (45 watts) workload, with a three-minute rest interval. While exercising at each level, oxygen consumption (VO2), minute ventilation (VE), and heart rate (HR) were monitored. When low workloads with ALE and ACE were compared, no significant differences (p greater than 0.05) were demonstrated in any of the variables for men or women. For the men, at the high workload, the ALE elicited significantly lower (p less than 0.05) VO2 (by 9.8%), HR (by 6.3%), and VE (by 7.5%), than did the ACE. For the women, at the high workload, VO2 was significantly lower (p less than 0.05) (by 7.6%) with the ALE, as was VE (by 7.5%), but HR, although 3.3% lower with the ALE, was not significantly different (p greater than 0.05) from the ACE. These data suggest that the ALE is physiologically less stressful than the ACE at high workloads. Arm levers may, therefore, provide an advantage for handicapped persons when they propel themselves in wheelchairs.

Arm↗
PubMed1987

Maximal respiratory pressures and pulmonary function in male runners.

To determine the effects of long term exercise on respiratory muscle strength, maximal inspiratory (Pl max) and expiratory (PE max) pressures, pulmonary volumes and capacities and anthropometric parameters were measured in a group of 101 male runners aged 16 to 58 years. The runners exhibited significantly (p less than 0.05) lower PE max (202 +/- 41 cm H2O and significantly greater residual lung volumes (RV) (2.08 +/- 0.49 L) than predicted values for normal subjects of similar height and age. Forced vital capacities were not different (p greater than 0.05) from values reported for normal non-smoking populations. These data suggest that running may cause a non-pathological increase in RV, perhaps mediated by reductions in expiratory muscle strength. Additionally, current RV regression equations developed for normal subjects may be inappropriate for use in running populations.

Adolescent↗
PubMedDate not supplied

Arterial O2 saturation and maximum O2 consumption in moderate-altitude runners exposed to sea level and 3,050 m.

Twelve trained runners, who were moderate-altitude (1,520 m) residents, were acutely exposed to sea level and 3,050-m altitude in a hypo-hyperbaric chamber. At 1,520 m, maximum O2 consumption (VO2 max) was 67.7 +/- 0.9 mL/kg/min, minute ventilation (V) at maximum exercise was 169.8 +/- 4.6 L/min, and arterial O2 saturation (SaO2) decreased from 93.3% +/- 0.9% at rest, to 84.5% +/- 1.6% at maximum exercise. Exposure to 3,050 m produced a lower VO2max (56.5 +/- 1.5, -16.5%), a similar V at maximum exercise (169.9 +/- 6.0), and a similar fall in SaO2 (from 89.1% +/- 0.8% to 79.5% +/- 0.8%). Exposure to sea level increased VO2max to 72.4 +/- 1.4 (+6.9%), reduced V at maximum exercise to 158.8 +/- 6.5, and induced a smaller fall in SaO2 (from 96.9% +/- 0.4% to 92.1% +/- 1.0%). These changes are comparable with those reported previously in athletes at sea level exposed to similar altitudes, suggesting that residence at 1,520 m does not improve VO2max in highly trained athletes acutely exposed to lower or higher altitudes.

Adolescent↗