Biomedical subjects

Maria T Hopman

Publications and source records attributed to Maria T Hopman.

6 recordsLinked to original sources

PubMed2006

Rapid vascular adaptations to training and detraining in persons with spinal cord injury.

OBJECTIVE: To assess the time course of arterial adaptations during 6 weeks of functional electric stimulation (FES) training and 6 weeks of detraining in subjects with spinal cord injury (SCI). DESIGN: Intervention study (before-after trial). SETTING: University medical center. PARTICIPANTS: Volunteer sample of 9 subjects with SCI. INTERVENTIONS: Six weeks of twice weekly FES cycling and 6 weeks of detraining. MAIN OUTCOME MEASURES: Vascular characteristics were measured by plethysmography (baseline and peak blood flow of the thigh) and echo Doppler (diameter of the femoral artery and flow-mediated dilation [FMD]). RESULTS: After 2 weeks of FES training, arterial characteristics changed significantly; there was an increase in baseline and peak blood flow, an increase in femoral artery diameter, and a decrease in FMD of the femoral artery. Detraining reversed baseline and peak thigh blood flow, vascular resistance, and femoral diameter toward pretraining values within 1 week. However, detraining did not restore the FMD of the femoral artery, even after 6 weeks. CONCLUSIONS: Two weeks of hybrid FES training (4 exercise bouts) is sufficient to improve peak leg blood flow and arterial diameter, and to normalize FMD. In addition, detraining results in rapidly reversed vascular characteristics within 1 week.

Adaptation, Physiological↗

PubMed2006

Rapid and extensive arterial adaptations after spinal cord injury.

OBJECTIVE: To assess the time course of adaptations in leg vascular dimension and function within the first 6 weeks after a spinal cord injury (SCI). DESIGN: Longitudinal study design. SETTING: University medical center and rehabilitation clinic. PARTICIPANTS: Six men were studied serially at 1, 2, 3, 4, and 6 weeks after SCI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Diameter, blood flow, and shear rate levels of the common femoral artery (CFA), superficial femoral artery (SFA), brachial artery, and carotid artery were measured with echo Doppler ultrasound (diameter, blood flow, shear rate). Endothelial function in the SFA was measured with flow-mediated dilation (FMD). In addition, leg volume and blood pressure measurements were performed. RESULTS: Femoral artery diameter (CFA, 25%; SFA, 16%; P<.01) and leg volume (22%, P<.01) decreased simultaneously, and these reductions were largely accomplished within 3 weeks postinjury. Significant increases were observed for basal shear rate levels (64% increase at week 3; 117% increase at week 6; P<.01), absolute FMD responses (8% increase at week 3, 23% increase at week 6; P<.05) and relative FMD responses (26% increase at week 3, 44% increase at week 6; P<.001). CONCLUSIONS: Our findings show a rapid onset of adaptations in arterial dimension and function to extreme inactivity in humans. Vascular adaptations include extensive reductions in femoral diameter and leg volume, as well as increased basal shear rate levels and FMD responses, which all appear to be largely accomplished within 3 weeks after an SCI.

Adult↗

PubMed2006

Preserved cardiac function after chronic spinal cord injury.

OBJECTIVE: To assess the effect of chronic deconditioning on cardiac dimensions and function in subjects with high-level spinal cord injury (SCI), who represent a human in-vivo model of extreme inactivity. DESIGN: Cross-sectional study. SETTING: University medical center. PARTICIPANTS: Seven men with tetraplegia and 7 able-bodied controls. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Echocardiographic measurements of resting cardiac dimensions, systolic function, and global and long-axis diastolic function. RESULTS: Left ventricular mass index was significantly lower in the subjects with SCI than in the controls (90.8+/-26 g/m(2) vs 122+/-28.9 g/m(2); P=.05). In addition, dimensions of left ventricle, left atrium, and vena cava inferior were all significantly reduced in the subjects with SCI compared with controls (P<.05). There were no differences between the groups for any of the parameters reflecting systolic and global and long-axis diastolic function. CONCLUSIONS: Tetraplegia is associated with a reduction in cardiac mass and dimensions. Resting diastolic and systolic function is not altered with continued exposure to inactivity, however, which suggests a remodeling of the heart as a physiologic adaptive process.

Adult↗

PubMed2005

Mental and physical effort affect vigilance differently.

Both physical and mental effort are thought to affect vigilance. Mental effort is known for its vigilance declining effects, but the effects of physical effort are less clear. This study investigated whether these two forms of effort affect the EEG and subjective alertness differently. Participants performed a physical task and were subsequently presented with a mental task, or vice versa. Mental effort decreased subjective alertness and increased theta power in the EEG. Both results suggest a vigilance decline. Physical effort, however, increased subjective alertness and alpha and beta1 power in the EEG. These findings point towards an increase in vigilance. Beta2 power was reduced after physical effort, which may reflect a decrease in active cognitive processing. No transfer effects were found between the effort conditions, suggesting that the effects of mental and physical effort are distinct. It is concluded that mental effort decreases vigilance, whereas physical effort increases vigilance without improving subsequent task performance.

Adult↗

PubMed2004

The effect of varied fractional inspired oxygen on arm exercise performance in spinal cord injury and able-bodied persons.

OBJECTIVE: To examine the effect of different levels of fractional inspired oxygen (FiO(2)) (15%, 21%, 50%) on peak oxygen consumption (VO(2)peak) during arm exercise in persons with spinal cord injury and in able-bodied controls. DESIGN: Case-control study. SETTING: University medical center in the Netherlands. PARTICIPANTS: Ten able-bodied controls, 6 persons with paraplegia, and 6 persons with tetraplegia. INTERVENTIONS: Inspiration of 15%, 21%, and 50% oxygen during a 15-minute period before and during arm exercise. MAIN OUTCOME MEASURES: Oxygen uptake (VO(2)peak, VO(2)peak/kg), power output, ventilation, and base excess. RESULTS: In the able-bodied controls, significant FiO(2) dependency was seen in power output, VO(2)peak, and VO(2)peak/kg. Persons with paraplegia showed significant FiO(2) dependency in VO(2) and VO(2)/kg. In persons with tetraplegia, no FiO(2) dependency was observed; however, VO(2) and VO(2)/kg were significantly higher at 50% than at 15% FiO(2). Ventilation and base excess did not change in able-bodied controls or in persons with paraplegia with different levels of FiO(2). In persons with tetraplegia, ventilation was significantly higher at 15% than at 50% FiO(2), and base excess did not change. No significant interactions between groups and FiO(2) were observed. CONCLUSIONS: Oxygen consumption during peak arm-cranking exercise is enhanced with an increased inspiratory oxygen fraction in able-bodied controls as well as in persons with paraplegia and to a lesser extent in persons with tetraplegia, indicating that peak oxygen consumption during arm exercise is limited by oxygen supply rather than by the small muscle mass and related biochemical limitations.

Adult↗

PubMed2003

Blood flow response to electrically induced twitch and tetanic lower-limb muscle contractions.

OBJECTIVES: To compare the effect of electric stimulation (ES)-induced twitch with tetanic leg muscle contractions on blood flow responses and to assess blood flow responses in the contralateral inactive leg. DESIGN: Intervention with within-subject comparisons. SETTING: University research laboratory. PARTICIPANTS: A volunteer sample of 12 healthy men (mean age, 25.1+/-3.0y). INTERVENTION: ES was applied at 1 and 3Hz to induce twitch contractions and at 35Hz to induce tetanic contractions of the lower- and upper-leg muscles. Exercise periods consisted of ES/rest cycles (6s/20s) for 5 minutes. MAIN OUTCOME MEASURES: Blood flow velocity changes measured by echo Doppler ultrasonography at rest and during the first 2 subsequent ES cycles. RESULTS: Blood flow significantly increased from resting values for the tetanic 2-leg, tetanic 1-leg, and 3-Hz conditions, but not for the 1-Hz twitch condition or in the inactive leg. CONCLUSIONS: Both tetanic and 3-Hz twitch contractions, but not 1-Hz twitch contractions, increased leg blood flow in humans. Because blood flow elevations induced by the 3-Hz contractions did not differ statistically from those induced by the tetanic contractions but were realized with less discomfort, this mode is preferable for therapeutic interventions. Because stimulation of the ipsilateral leg muscles did not change blood flow in the contralateral inactive leg, the muscles in the area of desired effect must be stimulated.

Analysis of Variance↗