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Abstract: A new software module for cardiovascular rehabilitation in robotics-assisted treadmill exercise is described; it is designed to evaluate and improve aerobic capacity for individuals with different neurological diseases. The Lokomat device was used in conjunction with a breath-by-breath cardiopulmonary monitoring system and a heart rate monitoring module to quantify the subjects’ exercise intensity and capacity, managed by the new software module. The intensity of the individuals’ exercise participation was estimated by a novel method which respects passive stiffness of the lower limbs and was guided by a custom human-in-the-loop feedback control system. Severely affected individuals’ participation was controlled by modifying body weight support or guidance force of the Lokomat system. Standard assessment and testing protocols were implemented and adapted to the target populations for cardiovascular rehabilitation tasks. Further intensity-control mechanisms provided by the software are feedback control of heart rate, oxygen uptake and metabolic work rate. The results demonstrated the technical feasibility of the software module for cardiovascular assessment and training in robotics-assisted treadmill exercise. Using one of the intensity control methods, cardiovascular responses were activated and controlled in healthy people, moderately to severely affected individuals early after stroke and also in individuals with spinal cord injury. [Copyright &y& Elsevier]

BACKGROUND: Robotics-assisted tilt table technology was introduced for early rehabilitation of neurological patients. It provides cyclical stepping movement and physiological loading of the legs. The aim of the present study was to assess the feasibility of this type of device for peak cardiopulmonary performance testing using able-bodied subjects.METHODS: A robotics-assisted tilt table was augmented with force sensors in the thigh cuffs and a work rate estimation algorithm. A custom visual feedback system was employed to guide the subjects' work rate and to provide real time feedback of actual work rate. Feasibility assessment focused on: (i) implementation (technical feasibility), and (ii) responsiveness (was there a measurable, high-level cardiopulmonary reaction?). For responsiveness testing, each subject carried out an incremental exercise test to the limit of functional capacity with a work rate increment of 5 W/min in female subjects and 8 W/min in males. RESULTS: 11 able-bodied subjects were included (9 male, 2 female; age 29.6 ± 7.1 years: mean ± SD). Resting oxygen uptake (&Vdot;O_{2}) was 4.6 ± 0.7 mL/min/kg and &Vdot;O_{2}peak was 32.4 ± 5.1 mL/min/kg; this mean &Vdot;O_{2}peak was 81.1% of the predicted peak value for cycle ergometry. Peak heart rate (HRpeak) was 177.5 ± 9.7 beats/min; all subjects reached at least 85% of their predicted HRpeak value. Respiratory exchange ratio (RER) at &Vdot;O_{2}peak was 1.02 ± 0.07. Peak work rate) was 61.3 ± 15.1 W. All subjects reported a Borg CR10 value for exertion and leg fatigue of 7 or more.CONCLUSIONS: The robotics-assisted tilt table is deemed feasible for peak cardiopulmonary performance testing: the approach was found to be technically implementable and substantial cardiopulmonary responses were observed. Further testing in neurologically-impaired subjects is warranted. [ABSTRACT FROM AUTHOR]

BACKGROUND: Robotics-assisted treadmill exercise (RATE) with focus on motor recovery has become popular in early post-stroke rehabilitation but low endurance for exercise is highly prevalent in these individuals. This study aimed to develop an exercise testing method using robotics-assisted treadmill exercise to evaluate aerobic capacity after severe stroke. METHODS: Constant load testing (CLT) based on body weight support (BWS) control, and incremental exercise testing (IET) based on guidance force (GF) control were implemented during RATE. Analyses focussed on step change, step response kinetics, and peak performance parameters of oxygen uptake. RESULTS: Three subjects with severe motor impairment 16-23 days post-stroke were included. CLT yielded reasonable step change values in oxygen uptake, whereas response kinetics of oxygen uptake showed low goodness of fit. Peak performance parameters were not obtained during IET. CONCLUSION: Exercise testing in post-stroke individuals with severe motor impairments using a BWS control strategy for CLT is deemed feasible and safe. Our approach yielded reasonable results regarding cardiovascular performance parameters. IET based on GF control does not provoke peak cardiovascular performance due to uncoordinated walking patterns. GF control needs further development to optimally demand active participation during RATE. The findings warrant further research regarding the evaluation of exercise capacity after severe stroke. [ABSTRACT FROM AUTHOR]

Research and development in the art of cycling using functional electrical stimulation (FES) of the paralysed leg muscles has been going on for around thirty years. A range of physiological benefits has been observed in clinical studies but an outstanding problem with FES-cycling is that efficiency and power output are very low. The present work had the following aims: (i) to provide a tutorial introduction to a novel framework and methods of estimation of metabolic efficiency using example data sets, and to propose benchmark measures for evaluating FES-cycling performance; (ii) to systematically review the literature pertaining specifically to the metabolic efficiency of FES-cycling, to analyse the observations and possible explanations for the low efficiency, and to pose hypotheses for future studies which aim to improve performance. We recommend the following as benchmark measures for assessment of the performance of FES-cycling: (i) total work efficiency, delta efficiency and stimulation cost; (ii) we recommend, further, that these benchmark measures be complemented by mechanical measures of maximum power output, sustainable steady-state power output and endurance. Performance assessments should be carried out at a well-defined operating point, i.e. under conditions of well controlled work rate and cadence, because these variables have a strong effect on energy expenditure. Future work should focus on the two main factors which affect FES-cycling performance, namely: (i) unfavourable biomechanics, i.e. crude recruitment of muscle groups, non-optimal timing of muscle activation, and lack of synergistic and antagonistic joint control; (ii) non-physiological recruitment of muscle fibres, i.e. mixed recruitment of fibres of different type and deterministic constant-frequency stimulation. We hypothesise that the following areas may bring better FES-cycling performance: (i) study of alternative stimulation strategies for muscle activation including irregular stimulation patterns (e.g. doublets, triplets, stochastic patterns) and variable frequency stimulation trains, where it appears that increasing frequency over time may be profitable; (ii) study of better timing parameters for the stimulated muscle groups, and addition of more muscle groups: this path may be approached using EMG studies and constrained numerical optimisation employing dynamic models; (iii) development of optimal stimulation protocols for muscle reconditioning and FES-cycle training. [ABSTRACT FROM AUTHOR]

Abstract: A novel approach is presented which suggests the use of human metabolic work rate to define and regulate exercise intensity during robotics-assisted treadmill training. The work describes the design and technical validation of the new method. A feedback structure is proposed which provides automatic regulation of metabolic work rate, in conjunction with an embedded feedback loop for volitional control of mechanical work rate. Human metabolic work rate was derived in real time from breath-by-breath measurements of oxygen uptake and carbon dioxide output. The results show that the feedback method provides close to nominal performance for square-wave and ramp reference tracking tasks and that good disturbance rejection properties are obtained. A collateral finding of this work is an estimate of 14.5% of the metabolic efficiency of robotics-assisted treadmill exercise. The use of feedback control of human metabolic work rate provides a direct measure of exercise intensity as perceived by the exercising human as it directly reflects the energy requirements of the working muscles. This complements previous approaches to guiding robotics-assisted treadmill training based on mechanical work rate, heart rate or oxygen uptake. The new approach based on metabolic work rate may have advantages in populations with compromised and widely varying exercise responses. This provides a new approach for driving and controlling active patient participation during robotics-assisted treadmill exercise. [Copyright &y& Elsevier]

Purpose: The efficiency of functional electrical-stimulation (FES) cycling in spinal cord injured and anaesthetised able-bodied cyclists has been found to be about one third of that reported during volitional cycling. The stimulation paradigm itself appears to be the main source of this inefficiency. It is unknown whether a period of high-volume training can induce adaptations that may influence the metabolic and electrical cost of FES cycling. Method: 11 individuals with paraplegia completed a 12-month, home-based, progressive FES cycle training programme (up to 5 &times 60 min per wk). Stimulation cost, oxygen cost, efficiency and markers of anaerobic metabolism were determined before and after 6 and 12 months of training, during constant work-rate tests. Results: Oxygen cost and efficiency did not significantly change after training. Total stimulation cost and blood lactate values reduced overall, while respiratory exchange ratios remained relatively high. Conclusions: The high metabolic cost of FES cycling is a result of non-physiological recruitment of predominantly fast muscle fibres. The electrical cost of cycling reduced by 37%, probably due to motor unit hypertrophy, and lactate oxidation capacity improved. [ABSTRACT FROM AUTHOR]

Abstract: Functional electrical stimulation can be used to enable spinal cord injured children to participate in cycling training as part of a fitness programme or exercise testing procedure. Exercise can reduce the impact of secondary health conditions due to the injury. Functional electrical stimulation has shown promising results in adults with a spinal cord injury, but additional considerations are needed to realise the method for the child with spinal cord injury, partly owing to their limited force producing capacity. An electric motor provides a practical means of performing cycling at controlled cadences, exercising for longer durations and can also be used for recreational outdoor cycling. Here, a novel real-time control technique is developed for cadence regulation during cycling. A feedback control structure is developed based on an empirical model derived from separate identification tests and pole placement and then verified in a series of reference-tracking tests. The system produced cadence responses in close agreement with reference values in all cases and demonstrated satisfactory robustness of stability characteristics. This approach moves towards the practical application of the technology as a training tool for paediatric spinal cord injured subjects. [Copyright &y& Elsevier]

Abstract: Cervical spinal cord injury (SCI) leads to tetraplegia, with paralysis and loss of sensation in the upper and lower limbs. The associated sedentary lifestyle results in an increased risk of cardiovascular disease. To address this, we require the design of exercise modalities aimed specifically at tetraplegia and methods to assess their efficacy. This paper describes methods for arm-crank ergometry (ACE) assisted by Functional Electrical Stimulation (FES) applied to the biceps and triceps. The instrumented ergometer enables work-rate control during exercise, implemented here for incremental exercise testing during FES-ACE. Detailed protocols for the tests are given. Experimental data collected during exercise tests with tetraplegic volunteers are provided to illustrate the feasibility of the proposed approach to testing and data analysis. Incremental tests enabled calculation of peak power output and peak oxygen uptake. We propose that the high-precision exercise testing protocols described here are appropriate to assess the efficacy of the novel exercise modality, FES-ACE, in tetraplegia. [Copyright &y& Elsevier]

Abstract: Treadmill training and testing applications combine changes in speed and angle to achieve a target work rate profile. Here we derive new methods which increase the flexibility available in the design of such protocols. Current methods of computing speed and angle are first reformulated in terms of work rate, rather than time, so that the existing limitation to work rate ramps is removed: the new methods allow arbitrary changes in work rate over time. New solutions are derived which allow the speed and angle functions to be positioned arbitrarily within the available speed and angle envelopes. It is shown that the methods can be easily specialised to the particular case of an incremental exercise test where work rate is defined to increase linearly with respect to time. The new methods facilitate the definition of arbitrary, possibly discontinuous, work rate profiles while permitting complete flexibility in the design of speed and angle profiles for treadmill training and testing applications. [Copyright &y& Elsevier]

In the San Antonio Heart Study (SAHS) we investigated the effects of exposure to parental smoking on diabetes, hypertension and the metabolic syndrome in adult offspring aged 25–64 years. In a retrospective cohort study the parental smoking status during childhood, obtained through a postal questionnaire, determined a person’s exposure status. Logistic regression models were used to calculate odds ratios for diabetes, hypertension and the metabolic syndrome at the baseline SAHS examination in relation to parental smoking status. All models were adjusted for age, sex, ethnicity, education years, personal smoking status (current, former or never-smoker), BMI and, in the case of diabetes, a family history of diabetes. Of the 2,371 participants who returned the mailing, 44.5, 5.4, 20.0 and 30.1% reported that their father, mother, both or neither parent smoked, respectively. Participants reporting that both parents smoked were 1.60 (95% CI: 0.95–2.69) times more likely to have diabetes, 1.55 (95% CI: 1.05–2.28) times more likely to have hypertension, and 1.46 (95% CI: 1.01–2.10) times more likely to have the metabolic syndrome than participants reporting that neither parent smoked during their childhood. Odds ratios, after limiting the population to younger participants (i.e. ≤50 years) to reduce survivor bias, were 2.53 (95% CI: 1.21–5.31), 1.29 (95% CI: 0.78–2.16), and 1.41 (95% CI: 0.89–2.22) for diabetes, hypertension and the metabolic syndrome, respectively. These results provide evidence that early exposure to parental smoking may be associated with an increased risk of diabetes and perhaps hypertension and the metabolic syndrome. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The energy efficiency of FES-cycling in spinal cord injured subjects is very much lower than that of normal cycling, and efficiency is dependent upon the parameters of muscle stimulation. We investigated measures which can be used to evaluate the effect on cycling performance of changes in stimulation parameters, and which might therefore be used to optimise them. We aimed to determine whether oxygen cost and stimulation cost measurements are sensitive enough to allow discrimination between the efficacy of different activation ranges for stimulation of each muscle group during constant-power cycling. Methods: We employed a custom FES-cycling ergometer system, with accurate control of cadence and stimulated exercise workrate. Two sets of muscle activation angles (“stimulation patterns”), denoted “P1” and “P2”, were applied repeatedly (eight times each) during constant-power cycling, in a repeated measures design with a single paraplegic subject. Pulmonary oxygen uptake was measured in real time and used to determine the oxygen cost of the exercise. A new measure of stimulation cost of the exercise is proposed, which represents the total rate of stimulation charge applied to the stimulated muscle groups during cycling. A number of energy-efficiency measures were also estimated. Results: Average oxygen cost and stimulation cost of P1 were found to be significantly lower than those for P2 (paired t-test, p <0.05): oxygen costs were 0.56±0.03lmin−1 and 0.61±0.04lmin−1 (mean±S.D.), respectively; stimulation costs were 74.91±12.15mCmin−1 and 100.30±14.78mCmin−1 (mean±S.D.), respectively. Correspondingly, all efficiency estimates for P1 were greater than those for P2. Conclusion: Oxygen cost and stimulation cost measures both allow discrimination between the efficacy of different muscle activation patterns during constant-power FES-cycling. However, stimulation cost is more easily determined in real time, and responds more rapidly and with greatly improved signal-to-noise properties than the ventilatory oxygen uptake measurements required for estimation of oxygen cost. These measures may find utility in the adjustment of stimulation patterns for achievement of optimal cycling performance. [Copyright &y& Elsevier]

Presents information on a study that investigated the role of Kupffer cells in CCl...-induced fibrosis. Methodology of the study; Results and discussion on the study.

The paper gives an introduction to and comparison of the four recursive identification algorithms most commonly used in self-tuning control. The paper demonstrates that the algorithms are very similar, and a simple simulation example is used to compare the algorithms and to give some insight into the suitability of each method for a particular problem. Choice of algorithm is seen to depend on four factors: model complexity, noise/signal ratio, convergence rate, and computational expense. [ABSTRACT FROM PUBLISHER]