Introduction: Bed rest is a terrestrial experimental analogue of unloading experienced during exposure to microgravity. Such unloading causes atrophy predominantly of the postural muscles, especially those of the lower limbs. Methods: We tested the hypothesis that 35 d horizontal bed rest alters thermoregulatory responses of subjects (N = 10) immersed in 15°C water, particularly the heat produced by the shivering tremor of the skeletal muscles. Before and after bed rest we measured the thickness of the gastrocnemius medialis (GM), vastus lateralis (VL), tibialis anterior (TA), and biceps brachii (BB) muscles by ultrasonography. During the immersions, we monitored rectal and skin temperatures, heat flux, heart rate, and oxygen uptake. Results: After bed rest, muscle thickness decreased significantly by 12.2 ± 8.8% and 8.0 ± 9.1% in the GM and VL, respectively. No changes were observed in the TA and BB muscles. The 35-d bed rest caused a significant reduction in aerobic power, as reflected in maximal oxygen uptake. There were no significant differences in any of the observed thermoregulatory responses between the pre- and post-bed rest immersions. Conclusions: Cardiovascular and muscular deconditioning had no effect on the heat production and heat loss responses. Due to the significant reduction in the mass of the muscles in the lower limbs, concomitant with no change in heat production, we conclude that leg muscles do not play a significant role in shivering thermogenesis.
COBISS.SI-ID: 25699111
This study investigated the effects of four exposures to normobaric hypoxia (SIH group; FIO2=0.120,N = 10) or placebo-control normoxia (Control group; FIO2=0.209,N = 9) on cardio-respiratory responses to hypoxic exercise. Before and after the exposures all subjects performed a constant power test (CP) to exhaustion in hypoxia (FIO2=0.120) at a work load corresponding to 75% of previously determined normoxic . Arterial oxygen saturation (SpO2) and minute ventilation were measured continuously. NIRS was used to monitor regional changes in oxygenated, de-oxygenated and total hemoglobin concentrations of the frontal cortex, vastus lateralis and serratus anterior. Although neither group improved CP time, the SIH group exhibited increases in both (+15%; P ( 0.05) and SpO2 (+4%; P ( 0.05) after intermittent hypoxia. No physiologically significant differences were observed during exercise in vastus lateralis, serratus anterior and cerebral oxygenation between groups and testing periods. These data suggest that normobaric SIH enhances hypoxic exercise and SpO2, without affecting regional oxygenation or time to exhaustion.
COBISS.SI-ID: 25708839
General-purpose autonomous robots must have the ability to combine the available sensorimotor knowledge in order to solve more complex tasks. Such knowledge is often given in the form of movement primitives. In this paper, we investigate the problem of sequencing of movement primitives. We selected nonlinear dynamic systems as the underlying sensorimotor representation because they provide a powerful machinery for the specification of primitive movements. We propose two new methodologies which both ensure that consecutive movement primitives are joined together in a continuous way (up to second-order derivatives). The first is based on proper initialization of the third-order dynamic motion primitives and the second uses online Gaussian kernel functions modification of the second-order dynamic motion primitives. Both methodologies were validated by simulation and by experimentally using a Mitsubishi PA-10 articulated robot arm. Experiments comprehend pouring, table wiping, and carrying a glass of liquid.
COBISS.SI-ID: 25192487
Aim: To investigate the effect of carbon monoxide (CO) in the inspired air as anticipated during peak hours of traffic in polluted megalopolises on cerebral, respiratory and leg muscle oxygenation during a constant-power test (CPT). In addition, since O2 breathing is used to hasten elimination of CO from the blood, we examined the effect of breathing O2 following exposure to CO on cerebral and muscle oxygenation during a subsequent exercise test under CO conditions. Methods: Nine men participated in three trials: (i) 3-h air exposure followed by a control CPT, (ii) 1-h air and 2-h CO (18.9 ppm) exposure succeeded by a CPT under CO conditions (CPTCOA), and (iii) 2-h CO and 1-h 100% normobaric O2 exposure followed by a CPT under CO conditions (CPTCOB). All exercise tests were performed at 85% of peak power output to exhaustion. Oxygenated (Δ[O2Hb]), deoxygenated (Δ[HHb]) and total (Δ[tHb]) haemoglobin in cerebral, intercostal and vastus lateralis muscles were monitored with near-infrared spectroscopy throughout the CPTs. Results: Performance time did not vary between trials. However, the vastus lateralis and intercostal Δ[O2Hb] and Δ[tHb] were lower in CPTCOA than in CPT. During the CPTCOB, the intercostal Δ[O2Hb] and Δ[tHb] were higher than in the CPTCOA. There were no differences in cerebral oxygenation between the trials. Conclusion: Inspiration of 18.9 ppm CO decreases oxygenation in the vastus lateralis and serratus anterior muscles, but does not affect performance. Breathing normobaric O2 moderates the CO-induced reductions in muscle oxygenation, mainly in the intercostals, but does not affect endurance.
COBISS.SI-ID: 25109799
Autonomous robots cannot be programmed in advance for all possible situations. Instead, they should be able to generalize the previously acquired knowledge to operate in new situations as they arise. A possible solution to the problem of generalization is to apply statistical methods that can generate useful robot responses in situations for which the robot has not been specifically instructed how to respond. In this paper we propose a methodology for the statistical generalization of the available sensorimotor knowledge in real-time. Example trajectories are generalized by applying Gaussian process regression, using the parameters describing a task as query points into the trajectory database. We show on real-world tasks that the proposed methodology can be integrated into a sensory feedback loop, where the generalization algorithm is applied in real-time to adapt robot motion to the perceived changes of the external world.
COBISS.SI-ID: 25861415