Biomedical subjects

N Khodiguian

Publications and source records attributed to N Khodiguian.

10 recordsLinked to original sources

PubMed2002

Expression of the bilateral deficit during reflexively evoked contractions.

During maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically larger than the sum of forces exerted by the same muscles bilaterally. This phenomenon is known as the bilateral deficit (BLD), and it is suggested that this deficit is due to neural inhibition. It remains unclear, however, whether such inhibition is mediated by supraspinal mechanisms or by reflex pathways at the level of spinal cord. To further study the origin of likely neural influences, we tested for the presence of BLD under the condition of reflexive force generation. Force output and integrated electromyogram (iEMG) (quadriceps femoris) were measured in 17 male participants after initiation of the myotatic patellar reflex under unilateral and bilateral conditions. A significant BLD of 9.26 +/- 1.19 (P = 0.004) and 16.76 +/- 4.69% (P = 0.001) was found for force and iEMG, respectively. However, because similar findings were not evident during maximal isometric knee extensions, it is difficult to predict the contribution of a spinal mechanism to the BLD under the condition of maximal voluntary activation.

Adult↗

PubMed1996

A comparison of cross-sectional and longitudinal methods of assessing the influence of pregnancy on cardiac function during exercise.

To evaluate the influence of pregnancy on resting and exercise cardiac function, we studied 16 nonpregnant and 26 pregnant females in a two-phase study. During phase I, all pregnant subjects (P1) (mean gestational age = 29.5 +/- 7 weeks) were compared with 16 control (C) subjects. In phase II, 8 of the pregnant subjects (P2) (mean gestational age = 32.6 +/- 6 weeks) were evaluated again at 12.5 +/- 7 weeks postpartum (PP). Using Collier's CO2 rebreathing technique, exercise cardiac output (Q) was measured on a cycle ergometer during rest and at three submaximal work levels (25, 50, and 75 W), during the last minute of 5 to 7 minutes of steady-level power output. Metabolic parameters [ventilation (VE), heart rate (HR) and oxygen consumption (VO2)] were measured during the submaximal tests and throughout the progressive increase in work after the last measure of Q, until peak VO2 was achieved. The results from the phase I comparison indicated (as expected) higher resting heart rates [(90.0 +/- 3 P1; 81.8 +/- 3 bpm C), ventilation (9.5 +/- 0.3 P1; 7.5 +/- 0.5 L min-1 C), and resting oxygen consumption (0.263 +/- 0.07 P; 0.221 +/- 0.01 L min-1 C) associated with pregnancy, and these findings were similar when the pregnant subjects were compared with their postpartum values. Analysis of the various indices of cardiac function [Q, stroke volume (SV), and arteriovenous oxygen difference (A-VO2 diff)] resulted in statistically higher resting Q in pregnancy when compared with C and PP conditions. No resting differences were observed for SV or A-VO2 diff in either phase of the study. The results of the submaximal exercise tests indicated no significant differences in HR nor VO2 between P1 and C; however, P2 had significantly higher submaximal heart rates and oxygen consumption when compared with PP. Further, no significant differences were observed between P1 and C for Q, SV or A-VO2 diff, whereas P2 versus PP resulted in significantly lower SV and higher A-VO2 diff in the pregnant subjects. These findings suggest that pregnancy/control versus pregnancy/ postpartum studies yield statistically different results and that an effort needs to made by the research community to develop standardized methodologies to evaluate physiological processes in pregnancy.

Arteries↗

PubMed1996

A comparison of the ventilatory responses to exercise in pregnant, postpartum, and nonpregnant women.

To evaluate the influence of pregnancy on resting and exercise pulmonary function, we studied 16 nonpregnant and 26 pregnant females in a two-phase study. During phase I, all pregnant subjects (P1) (mean gestational age = 29.5 +/- 7 weeks [X +/- SD]) were compared with 16 control (C) subjects. In phase II, 8 of the pregnant subjects (P2) (mean gestational age = 32.6 +/- 6 weeks) were evaluated again at 12.5 +/- 7 weeks' postpartum (PP). Exercise respiratory function was measured during work on a cycle ergometer during rest and at three submaximal work levels (25, 50, and 75 W), during the last minute of 5 to 7 minutes of steady-level power output. Ventilatory parameters [ventilation (VE), ventilatory frequency (VF), tidal volume (TV), ventilatory equivalent for oxygen (VE/VO2) and ventilatory equivalent for carbon dioxide (VE/VCO2)] and metabolic parameters [oxygen consumption (VO2), oxygen pulse, carbon dioxide production (VCO2), respiratory exchange ratio (RER), and plasma lactate (HLA)] were measured during the submaximal tests and throughout the progressive increase in work after the 75 W work load, until peak VO2 was achieved. The results from the phase I comparison indicated (as expected) higher resting ventilation, tidal volume, oxygen consumption, carbon dioxide production, and respiratory exchange ratio associated with pregnancy, and these findings were similar when the pregnant subjects were compared with their postpartum values. Plasma lactate levels, although similar in the phase I comparison, were significantly higher during pregnancy when compared with postpartum values. No resting differences were observed for VF, O2 pulse, VE/VO, or VE/VCO2 in either phase of the study. The results of the submaximal exercise tests indicated higher submaximal levels of VE, VF, VE/VO2, VE/VCO2 in P1 versus C; however, P2 had significantly higher VE, TV, VO2, VE/VCO2, when compared with PP. The influence of pregnancy on VCO2 and RER differed by workload in both sets of comparisons. Furthermore, no significant differences were observed between P1 and C and P2 and PP for plasma lactate levels. These findings suggest that pregnancy/control versus pregnancy/postpartum studies yield different results in both ventilatory and metabolic comparisons. Consideration must be given to the type of study when discussing and applying the findings.

Adult↗

PubMed1996

Body composition in pregnancy.

Concern over the influence of pregnancy-related alterations in hydration has prompted questions regarding the accuracy of using standard methods of determining body composition. We sought to investigate whether differences exist between body composition determined at 30 weeks and 39 weeks of gestation and postpartum, when measured by both bioelectrical impedance and hydrostatic weighing. This preliminary assessment of nine subjects suggests that the method used to calculate body composition during pregnancy can alter the influence of gestational age on body composition. The mechanisms underlying the differing results bear further investigation, as does the search for an accurate and reliable method for assessing body composition during pregnancy. Further research addressing these mechanisms is crucial to determining the relationship between changes in maternal fat and both maternal and fetal well-being.

Body Composition↗

PubMed1995

A comparison of cardiopulmonary adaptations to exercise in pregnancy at sea level and altitude.

OBJECTIVE: The purpose of this study was to compare maternal cardiopulmonary and fetal responses of lowlander pregnant women in the third trimester to exercise at sea level and at an altitude of 6000 feet. STUDY DESIGN: Seven women at 33.86 +/- 1 weeks' gestation performed a symptom-limited maximal exercise test and a submaximal cardiac output exercise test at sea level at an altitude of 6000 feet. Cardiopulmonary and metabolic variables were measured and compared at sea level and altitude. RESULTS: Maximal oxygen consumption and work levels were limited by short-term altitude exposure. Ventilatory variables were not significantly influenced by altitude exposure. During submaximal exercise no alteration in exercise efficiency or response was seen for most of the variables when altitude and sea level data were compared. Both cardiac output and stroke volume were elevated at altitude at rest but not during exercise, suggesting a lower reserve for both variables at altitude. Level of plasma glucose, lactate, norepinephrine, and epinephrine were not significantly influenced by altitude exposure. Fetal heart rate responses did not differ between the sea level and altitude conditions. CONDITIONS: Lowlander pregnant women in the third trimester have some limitations to maximal aerobic capacity but not submaximal exercise on short-term altitude exposure. No ominous fetal responses have been observed during this study. The results suggest that pregnant women may engage in at least brief moderate exercise bouts at moderate altitude without adverse consequences.

Adaptation, Physiological↗

PubMed1993

[Regular exercise therapy in disorders of carbohydrate metabolism in pregnancy--results of a prospective, randomized longitudinal study].

Regular exercise has long been known as an adjunct in the therapy of diabetes mellitus. There are, however, only few reports on the impact of this therapy during pregnancy. This study aims at presenting an exercise programme for patients with insulin-requiring gestational diabetes (GDM) and its short-term and long-term effects on carbohydrate metabolism, on the foetus and on the course of pregnancy. Between the 26th and 32nd week of gestation, 41 pregnant subjects were randomised into either an exercise and diet group (EXE) or an Insulin and diet group (INS). The EXE patients (N = 21) trained three times per week at 50% VO2max. For 3 x 15 minutes on a recumbent bicycle ergometer throughout pregnancy with blood glucose monitoring before and after exercise). Blood glucose metabolism was followed by daily home monitoring and weekly fasting blood glucose sampling (FBG). The FBG results were comparable in the study and the control group (< 105 mg/dl); the maternal and foetal complications did not differ significantly between the two groups. The glycaemic parameters indicate a persistent decrease in blood glucose and an increase in insulin sensitivity induced by regular physical activity. We conclude, that such a medically supervised exercise programme can be safely conducted in women with GDM resulting in normoglycaemia for the mother and thus preventing insulin therapy.

Adult↗

PubMed1993

Therapeutic exercise for insulin-requiring gestational diabetics: effects on the fetus--results of a randomized prospective longitudinal study.

Regular physical activity is an established therapeutic adjunct in diabetes, but has not been offered to pregnant diabetics in the past; for sports might induce significant cardiovascular and hormonal changes that are able to reduce blood flow to the uterus and thus limit oxygen transfer to the fetus. Studying the impact of a medically supervised exercise program on gestational diabetes mellitus [GDM) in a randomised prospective longitudinal study, this paper aims to assess the effects of maternal moderate and strenuous exercise on the fetus. By evaluating shortterm fetal responses as reflected in heart rate patterns (FHR) and longterm-pregnancy complications and neonatal outcome, our results suggest that--in absence of ominous FHR changes or significant changes in uterine activity following the exercise sessions or increased diabetes-related peri- and neonatal morbidity--regular physical activity seems to be a safe therapeutic option for the fetus of GDM mothers.

Adult↗

PubMed1993

Intrapartum fetal heart rate responses to maternal exercise. Case reports.

Intrapartum fetal heart responses to a maternal exercise routine are described in two volunteers. The fetal heart rates were not affected by a brief exercise, which intensity was approximately 60% of the maximum aerobic capacity. These patients reported decreased pain perception during the exercise in labor.

Adult↗

PubMed1991

Exercise in gestational diabetes. An optional therapeutic approach?

Forty-one patients with gestational diabetes requiring insulin were enrolled in a randomized study to investigate the efficacy of an exercise program in normalizing glucose tolerance. Seventeen of 21 patients completed the exercise program while maintaining normoglycemia and obviating insulin therapy. Maternal and neonatal complications did not differ between the study and control groups. The type of program described appears to be safe and can serve as a model for exercise prescription for pregnant diabetic women to attain improved glucose tolerance.

Adult↗

PubMed1989

Exercise prescription in pregnancy: weight-bearing versus non-weight-bearing exercise.

Bicycle ergometry (non-weight-bearing exercise) and treadmill (weight-bearing exercise) were compared to assess physiologic responses to similar work loads. A total of 22 subjects at 29.3 +/- 1.6 (+/- SEM) weeks' gestation who performed non-weight-bearing exercise were compared with 15 similarly fit subjects at 26.1 +/- 2.3 weeks' gestation who performed weight-bearing exercise at three submaximal levels. Measurements by indirect calorimetry indicate preferential carbohydrate use during non-weight-bearing exercise at submaximal levels.

Adult↗