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To test the hypothesis that cycling exercise modulates heart rate variability (HRV), we applied a short-time Fourier transform on the electrocardiogram of subjects performing a maximal graded cycling test. A pedaling frequency component (PFC) in HRV was continuously observed over the time course of the exercise test and extracted from R-R interval series obtained from 15 healthy subjects with a heterogeneous physical fitness, exercising at three different pedaling frequency ( n = 5): 70, 80, and 90 rpm. From 30 to 50% of the maximal power output (Pmax), in the 90 rpm group, spectral aliasing caused PFC to overlap with the respiratory sinus arrhythmia (RSA) band, significantly overestimating the PFC amplitude ( APFC). In the meantime, APFC did not increase significantly from its minimal values in the 70 rpm (∼1.26 ms) and 80 rpm (∼1.20 ms) groups. Then, from 60 to 100% maximal power output (Pmax), workload increase caused a significant ∼2.8-, ∼3.3-, and ∼3.4-fold increase in APFC in the 70, 80, and 90 rpm groups, respectively, with no significant difference between groups. At peak exercise, APFC accounted for ∼43, ∼39, and ∼49% of the total HRV in the 70, 80, and 90 rpm groups, respectively. Our findings indicate that cycling continuously modulates the cardiac chronotropic response to exercise, inducing a new component in HRV, and that workload increase during intense exercise further accentuates this cardiolocomotor coupling. Moreover, because PFC and RSA overlapped at low workloads, methodological care should be taken in future studies aiming to quantify RSA as an index of parasympathetic activity.

This study was conducted to investigate the effects of giving short-term doses of creatine by mouth to healthy older male subjects, taking into account their training status. A group of 42 volunteers was divided into three: a sedentary group composed of elderly sedentary men [n = 14, mean age 70.1 (SEM 1.2) years], a trained group composed of elderly trained cyclists [n = 14, mean age 66.4 (SEM 1.4) years] and a young group composed of young sedentary men [n = 14, mean age 26.0 (SEM 1.2) years]. In each group, double-blind randomization was carried out: one half was given creatine (3x5 g x day(-1)), and the other was given an iso-nitrogenated placebo (3x10 g x day(-1)). Before and after the 5 days during which the supplements were given, all subjects performed five all-out 10-s sprints separated by 60-s intervals of passive recovery, seated on a cycle ergometer. Power output, work done and heart rate data were recorded during each sprint. The elderly and the young sedentary subgroups given creatine showed significant (P < 0.05) improvements in maximal power (+3.7% and +2.0%, respectively) and work done (+4.1% and +5.1%, respectively) in the subsequent tests. In contrast, no significant change in pedalling performances was observed in the trained elderly subjects. The creatine did not change the exercise and recovery heart rate profiles, in any group. Our study suggested that creatine given by mouth increases the anaerobic power and work capacity of sedentary people of different ages during maximal pedalling tasks. However, the level of physical activity seems to be a determinant of the ergogenic effect of creatine in older subjects.

Twenty malnourished subjects (average age 67 years old) treated by cyclic enteral nutrition were assigned to an active or control group according to whether they took part or not in a 3-week aerobic training program. Subjects underwent the following tests on d(0)-d(1) and d(20)-d(21): calculation of a global nutritional deficiency index (GND), bioelectrical impedance analysis, evaluation of daily energy expenditures using a 24 h heart rate (HR) recorder and a pedometer, maximal voluntary isometric strength assessment (MVIS), and symptoms limited maximal oxygen uptake ((.)VO(2 max. SL) estimation. Although energy intakes were similar in both groups, active subjects showed greater improvements (P0.05) than control subjects regarding GND (-9.8 vs -4.8%), serum albumin and prealbumin. Active subjects also showed a greater increase (P0.05) in pedometer readings compared to control subjects. Reduction of resting HR was observed in active (-5 beat/mn, P0.05) whereas no significant changes in average HR were noted in either group, reflecting increased metabolic activity. Compared to control, active subjects showed significant (P0.05) improvements in MVIS (0.8 vs 0.1 N/kg) and (.)VO(2 max. SL) (5.5 vs 1.4 mL/min/kg). Short-term aerobic training has positive effects on nutritional recovery and functional capacities in elderly malnourished subjects and should be recommended whenever possible.

International audience; It has been shown that a pedaling frequency component can be extracted from the heart rate variability (HRV) signal using a time-varying filter. It is shown that this filter can be implemented directly in the time-frequency plane with different approaches. The need of resampling the data is also discussed with regard to the artifacts produced when the shanon condition is not fulfilled. In order to interpret the similar amplitude profiles of the pedaling component for untrained and trained subjects, an attempt for the model parameters setting is proposed. Consistent results on a large data set illustrate the feasibility of such processing.

Switching delays of partially-depleted SOI (PDSOI) CMOS gates are subject to variability depending on the switching history (S. Fung et al., 2000). This variability results from modulation of the threshold voltage by the floating body potential. To characterize this behavior it is important to study device response over a wide range of floating body potentials. We accomplish this by configuring NFETs and PFETs as single ended passgates driven by inverters with the input arrival times at both the source and the gate controlled independently. Representative data from a chip fabricated in an experimental 0.18 /spl mu/m PDSOI technology is presented and discussed.

Persistence of respiratory sinus arrhythmia (RSA) has been described in humans during intense exercise and attributed to an increase in ventilation. However, the direct influence of ventilation on RSA has never been assessed. The dynamic evolution of RSA and its links to ventilation were investigated during exercise in 14 healthy men using an original modeling approach. An evolutive model was estimated from the detrended and high-pass-filtered heart period series. The instantaneous RSA frequency ( FRSA, in Hz) and amplitude ( ARSA, in ms) were then extracted from all recordings. ARSA was calculated with short-time Fourier transform. First, measurements of FRSA and ARSA were performed from data obtained during a graded and maximal exercise test. Influences of different ventilation regimens [changes in tidal volume (VT) and respiratory frequency ( FR)] on ARSA were then tested during submaximal [70% peak O2 consumption (V̇o2peak)] rectangular exercise bouts. Under graded and maximal exercise conditions, ARSA decreased from the beginning of exercise to 61.9 ± 3.8% V̇o2peak and then increased up to peak exercise. During the paced breathing protocol, normoventilation (69.4 ± 8.8 l/min), hyperventilation (81.8 ± 8.3 l/min), and hypoventilation (56.4 ± 6.2 l/min) led to significantly ( P < 0.01) different ARSA values (3.8 ± 0.5, 4.6 ± 0.8, and 2.9 ± 0.5 ms, respectively). In addition, no statistical difference was found in ARSA when ventilation was kept constant, whatever the FR-VT combinations. Those results indicate that RSA persists for all exercise intensities and increases during the highest intensities. Its persistence and increase are strongly linked to both the frequency and degree of lung inflation, suggesting a mechanical influence of breathing on RSA.

To investigate the effects of an oral creatine supplementation in older adults, 32 elderly subjects (67-80 years; 16 females, 16 males) were randomly assigned to four equivalent subgroups (control-creatine; control-placebo; trained-creatine; trained-placebo) based on whether or not they took part in an 8-week strength training programme and an 8-week oral creatine monohydrate creatine supplementation programme. The strength training programme consisted of three sets of eight repetitions at 80% of one-repetition maximum, for leg press, leg extension and chest press, 3 days a week. The 52-day supplementation programme consisted of 20 g of creatine monohydrate (or glucose) and 8 g of glucose per day for the initial 5 days followed by 3 g of creatine monohydrate (or glucose), and 2 g of glucose per day. Prior to and after the training and supplementation periods, body mass, body fat, lower limb muscular volume, 1-, 12-repetitions maxima and isometric intermittent endurance tests for leg press, leg extension and chest press were determined. In all groups, no significant changes in anthropometric parameters were observed. For all movements, the increases in 1- and 12-repetitions maxima were greater (P < 0.02) in trained than control subjects. No significant interactions (supplementation/training/time) were observed for the 1-, 12-repetitions maxima, and the isometric intermittent endurance, whatever the movement considered. We conclude that oral creatine supplementation does not provide additional benefits for body composition, maximal dynamical strength, and dynamical and isometric endurances of healthy elderly subjects, whether or not it is associated with an effective strength training.

This letter describes the first system level test vehicle in Josephson technology. The experiment consists of four circuit chips assembled on two cards in a high density, 3-dimensional, card-on-board package. A data path, which is representative of a critical path of a future prototype processor, was successfully operated with a minimum cycle time of 3.7ns. The path simulates a jump control sequence and a cache access in each machine cycle. This experiment incorporates the essential components of the logic, power and package portions of a Josephson technology prototype.

A novel magnetic monopole detection scheme using superconducting high-order planar gradiometers has been successfully designed and tested. A prototype of two parallel gradiometers monitored by two independent SQUIDs was built and operated for a period of more than 5 months. With no monopole events observed, it established an upperbound of monopole flux of 1.7 × 10−10 cm−2 sr−1 s−1 at a 90% confidence level. A larger detector of six planar gradiometers on the facets of a parallelopiped with a coincident detection area 40 times that of the prototype is currently running. A flux bound of 2.0 × 10−11 cm−2 sr−1 s−1 at a 90% confidence level has been established by this detector as of February 1984. An even larger detector with a coincident detection area about 3 m2 is now in the planning stage.

A GaAs MESFET 16x16 crosspoint switch has been fabricated on a 3-mm x 4-mm chip using a 1-μm super buffer logic (SBL) design containing approximately 10000 FETs and operating at 800 mW of power. A 99% confidence bit error rate (BER) better than 1*10/sup -3/ was obtained at 1.7 Gb/s rate using a 2/sup 7/ -1 pseudorandom NRZ (nonreturn-to-zero) sequence. The BER test was done on one path using a probe card. The chip has 255 out of 256 good crosspoints. The bad crosspoint was a repeating error from a mask defect. An advanced refractory-gate MESFET process was used to fabricate the chip. A lightly doped drain structure was used to reduce parasitic gate capacitance while maintaining acceptable source resistance, to reduce short-channel effects, to increase breakdown voltage compared to devices where the heavy source/drain implant is directly self-aligned to the gate edge. >

The arch or inverted arch signals are characterizing patterns of the Respiratory Sinus Arrhythmia. The ability of any model in generating these patterns can be a good criteria for their selection. We show that using the tidal volume signal as the input of the model, an alternative to the IPFM can be proposed. The relevance of our model is shown with synthesized and real signals.