Authors: Berry, H.R. | Kakebeeke, T.H. | Donaldson, N. | Perret, C. | Hunt, K.J.
Article Type: Research Article
Abstract: 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 × 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. Show more
Keywords: Metabolic cost, efficiency, exercise physiology, spinal cord injury, rehabilitation, electrical stimulation
DOI: 10.3233/THC-2011-0656
Citation: Technology and Health Care, vol. 20, no. 2, pp. 73-84, 2012
Authors: Hunt, K.J. | Fang, J. | Saengsuwan, J. | Grob, M. | Laubacher, M.
Article Type: Research Article
Abstract: 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. Show more
Keywords: Functional electrical stimulation, cycling, efficiency, rehabilitation, spinal cord injury, exercise physiology
DOI: 10.3233/THC-2012-0689
Citation: Technology and Health Care, vol. 20, no. 5, pp. 395-422, 2012
Authors: Jack, L.P. | Purcell, M. | Allan, D.B. | Hunt, K.J.
Article Type: Research Article
Abstract: Background: We are investigating the potential of robotics-assisted treadmill technology as a mode of exercise in people with spinal cord injury (SCI). People with incomplete SCI can actively contribute to this form of exercise, but in the clinical setting they often walk passively in the system. It is not known whether in doing so they are meeting the recommended guidelines for increasing cardiopulmonary fitness. Objective: The aims of this study were twofold: to characterise the intensity of passive walking during robotics-assisted treadmill exercise (RATE) in incomplete SCI; and to determine if this intensity meets the recommended guidelines for cardiopulmonary training …in this population. Methods: 10 subjects with incomplete SCI twice performed an exercise test on a robotics-assisted treadmill. The test comprised a period of passive walking and a ramp phase to the limit of tolerance. Oxygen uptake (V̇O2 ) and heart rate (HR) were continuously measured. Results: V̇O2 during passive exercise was on average 1.4 times higher than resting V̇O2 (V̇O2R ), but this was only 29% of peak V̇O2 (V̇O2peak ) (range 16–43%). Relative to rest, passive V̇O2 (V̇O2P ) was only 12% of V̇O2 (V̇O2peak ). HR did not increase from rest to passive walking (81 ± 10 bpm to 81 ± 13 bpm respectively). The HR associated with passive walking was on average 50% of peak HR (HRpeak ) (161 ± 13 bpm). Test-retest reliability was moderate for V̇O2R (R=0.62) and resting HR (HRR ) (R=0.68), high for V̇O2P (R=0.81), passive HR (HRP ) (R=0.87) and HRpeak (R=0.88), and very high (R=0.95) for V̇O2peak . Only HRP differed significantly between tests (p=0.029). Conclusions: The intensity of passive walking during RATE is low and is insufficient to increase cardiopulmonary fitness in people with SCI. Subjects must actively contribute to the exercise in order to achieve the recommended training intensity. Show more
DOI: 10.3233/THC-2011-0608
Citation: Technology and Health Care, vol. 19, no. 1, pp. 21-27, 2011
Authors: Gollee, H. | Hunt, K.J. | Allan, D.B. | Fraser, M.H. | McLean, A.N.
Article Type: Research Article
Abstract: Paralysis of the respiratory muscles in people with tetraplegia affects their ability to breathe and contributes to respiratory complications. Surface functional electrical stimulation (FES) of abdominal wall muscles can be used to increase tidal volume (VT ) and improve cough peak flow (CPF) in tetraplegic subjects who are able to breathe spontaneously. This study aims to evaluate the feasibility and effectiveness of a novel abdominal FES system which generates stimulation automatically, synchronised with the subjects' voluntary breathing activity. Four subjects with complete tetraplegia (C4-C6), breathing spontaneously, were recruited. The automatic stimulation system ensured that consistent stimulation was achieved. We compared …spirometry during unassisted and FES-assisted quiet breathing and coughing, and measured the effect of stimulation on end-tidal CO2 (EtCO2 ) during quiet breathing. The system dependably recognised spontaneous respiratory effort, stimulating appropriately, and was well tolerated by patients. Significant increases in VT during quiet breathing (range 0.05–0.23 L) and in CPF (range 0.04–0.49 L/s) were observed. Respiratory rate during quiet breathing decreased in all subjects when stimulated, whereas minute ventilation increased by 1.05–2.07 L/min. The changes in EtCO2 were inconclusive. The automatic stimulation system augmented spontaneous breathing and coughing in tetraplegic patients and may provide a potential means of respiratory support for tetraplegic patients with reduced respiratory capacity. Show more
Keywords: Tetraplegia, pulmonary function, electrical stimulation, automatic control system
DOI: 10.3233/THC-2008-16405
Citation: Technology and Health Care, vol. 16, no. 4, pp. 273-281, 2008
Authors: Hunt, K.J. | Gollee, H. | Jaime, R. | Donaldson, N.
Article Type: Research Article
Abstract: This paper presents the results of continuing work on feedback control of unsupported standing in paraplegia. Our experimental setup considers a situation in which all joints above the ankle are braced, and stabilising torque at the ankle is generated by stimulation of the plantarflexors. A previous study showed that short periods of unsupported standing with paraplegic subjects could be achieved. In order to improve consistency and reliability of unsupported standing we are currently investigating several modifications to the control strategy. The paper reports progress towards this goal.
DOI: 10.3233/THC-1999-7610
Citation: Technology and Health Care, vol. 7, no. 6, pp. 443-447, 1999
Authors: Saengsuwan, J. | Laubacher, M. | Nef, T. | Hunt, K.J.
Article Type: Research Article
Abstract: 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 (V̇O2 ) was 4.6 ± 0.7 mL/min/kg and V̇O2 peak was 32.4 ± 5.1 mL/min/kg; this mean V̇O2 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 V̇O2 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. Show more
Keywords: Rehabilitation, cardiopulmonary performance testing, rehabilitation robotics, tilt table
DOI: 10.3233/THC-140783
Citation: Technology and Health Care, vol. 22, no. 2, pp. 179-187, 2014
Arm-cranking exercise assisted by Functional Electrical Stimulation in C6 tetraplegia: A pilot study
Authors: Coupaud, S. | Gollee, H. | Hunt, K.J. | Fraser, M.H. | Allan, D.B. | McLean, A.N.
Article Type: Research Article
Abstract: Tetraplegic volunteers undertook progressive exercise training, using novel systems for arm-cranking exercise assisted by Functional Electrical Stimulation (FES). The main aim was to determine potential training effects of FES-assisted arm-crank ergometry (FES-ACE) on upper limb strength and cardiopulmonary {fitness} in tetraplegia. Surface FES was applied to the biceps and triceps during exercise on an instrumented ergometer. Two tetraplegic volunteers with C6 Spinal Cord Injury (SCI) went through muscle strengthening, baseline exercise testing and three months of progressive FES-ACE training. Repeat exercise tests were carried out every four weeks during training, and post-training, to monitor upper-limb strength and cardiopulmonary fitness. At …each test point, an incremental test was carried out to determine peak work rate, peak oxygen uptake, gas exchange threshold and oxygen uptake-work rate relationship during FES-ACE. Peak oxygen uptake for Subject A increased from 0.7 l/min to 1.1 l/min, and peak power output increased from 7 W to 38 W after FES-ACE training. For Subject B, peak oxygen uptake was unchanged, but peak power output increased from 3 W to 8 W. These case studies illustrate potential benefits of FES-ACE in tetraplegia, but also the differences in exercise responses between individuals. Show more
Keywords: Electrical stimulation, spinal cord injury, cardiopulmonary fitness, rehabilitation, tetraplegia
DOI: 10.3233/THC-2008-16602
Citation: Technology and Health Care, vol. 16, no. 6, pp. 415-427, 2008
Authors: Stoller, O. | de Bruin, E.D. | Schindelholz, M | Schuster, C | de Bie, R.A. | Hunt, K.J.
Article Type: Research Article
Abstract: 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. Show more
Keywords: Stroke, exercise testing, severe motor impairment, aerobic capacity, robotics-assisted treadmill exercise
DOI: 10.3233/THC-130730
Citation: Technology and Health Care, vol. 21, no. 2, pp. 157-166, 2013