Claudio Perret

High-volume FES-cycling partially reverses bone loss in people with chronic spinal cord injury

Spinal cord injury (SCI) leads to severe bone loss in the paralysed limbs and to a resulting increased fracture risk thereof. Since long bone fractures can lead to comorbidities and a reduction in quality of life, it is important to improve bone strength in people with chronic SCI. In this prospective longitudinal cohort study, we investigated whether functional electrical stimulation (FES) induced high-volume cycle training can partially reverse the loss of bone substance in the legs after chronic complete SCI. Eleven participants with motor-sensory complete SCI (mean age 41.9+/-7.5 years; 11.0+/-7.1 years post injury) were recruited. After an initial phase of 14+/-7 weeks of FES muscle conditioning, participants performed on average 3.7+/-0.6 FES-cycling sessions per week, of 58+/-5 min each, over 12 months at each individuals highest power output. Bone and muscle parameters were investigated in the legs by means of peripheral quantitative computed tomography before the muscle conditioning (t1), and after six (t2) and 12 months (t3) of high-volume FES-cycle training. After 12 months of FES-cycling, trabecular and total bone mineral density (BMD) as well as total cross-sectional area in the distal femoral epiphysis increased significantly by 14.4+/-21.1%, 7.0+/-10.8% and 1.2+/-1.5%, respectively. Bone parameters in the femoral shaft showed small but significant decreases, with a reduction of 0.4+/-0.4% in cortical BMD, 1.8+/-3.0% in bone mineral content, and 1.5+/-2.1% in cortical thickness. These decreases mainly occurred between t1 and t2. No significant changes were found in any of the measured bone parameters in the tibia. Muscle CSA at the thigh increased significantly by 35.5+/-18.3%, while fat CSA at the shank decreased by 16.7+/-12.3%. Our results indicate that high-volume FES-cycle training leads to site-specific skeletal changes in the paralysed limbs, with an increase in bone parameters at the actively loaded distal femur but not the passively loaded tibia. Thus, we conclude that high-volume FES-induced cycle training has clinical relevance as it can partially reverse bone loss and thus may reduce fracture risk at this fracture prone site.

Effect of detraining on bone and muscle tissue in subjects with chronic spinal cord injury after a period of electrically-stimulated cycling: a small cohort study

OBJECTIVE To investigate adaptive changes in bone and muscle parameters in the paralysed limbs after detraining or reduced functional electrical stimulation (FES) induced cycling following high-volume FES-cycling in chronic spinal cord injury. SUBJECTS Five subjects with motor-sensory complete spinal cord injury (age 38.6 years, lesion duration 11.4 years) were included. Four subjects stopped FES-cycling completely after the training phase whereas one continued reduced FES-cycling (2-3 times/week, for 30 min). METHODS Bone and muscle parameters were assessed in the legs using peripheral quantitative computed tomography at 6 and 12 months after cessation of high-volume FES-cycling. RESULTS Gains achieved in the distal femur by high-volume FES-cycling were partly maintained at one year of detraining: 73.0% in trabecular bone mineral density, 63.8% in total bone mineral density, 59.4% in bone mineral content and 22.1% in muscle cross-sectional area in the thigh. The subject who continued reduced FES-cycling maintained 96.2% and 95.0% of the previous gain in total and trabecular bone mineral density, and 98.5% in muscle cross-sectional area. CONCLUSION Bone and muscle benefits achieved by one year of high-volume FES-cycling are partly preserved after 12 months of detraining, whereas reduced cycling maintains bone and muscle mass gained. This suggests that high-volume FES-cycling has clinical relevance for at least one year after detraining.

Control of work rate-driven exercise facilitates cardiopulmonary training and assessment during robot-assisted gait in incomplete spinal cord injury

Abstract Treadmill training is used for gait rehabilitation in various neurological conditions. Robot-assisted treadmill training automates repetition of the gait cycle and can reduce the load on therapists. Here we investigate the use of robot-assisted treadmill technology in cardiopulmonary rehabilitation and assessment. Using a new approach to exercise work rate estimation and volitional control, we propose cardiopulmonary assessment protocols for robot-assisted gait exercise, designed for estimation of cardiopulmonary performance parameters. Feasibility was explored in three subjects with incomplete spinal cord injury using the Lokomat system. Estimation and visual feedback of exercise work rate allowed all subjects to accurately follow specified work rate profiles in real time by means of volitional control. We were able to estimate the main cardiopulmonary performance parameters from constant work rate and incremental tests. “Passive” walking elicited a substantial metabolic response: on average, oxygen uptake ( V ˙ O 2 ) was a factor of 1.8 higher than during rest. The magnitude of peak V ˙ O 2 above rest, obtained from incremental tests, was a factor of 4–6 higher than the increment in V ˙ O 2 for passive walking, thus emphasising the importance of the subjects’ active participation in the exercise. Visual feedback and volitional control of estimated exercise work rate facilitates the imposition of work rate profiles for estimation of cardiopulmonary performance parameters in robot-assisted gait. This new approach could be used to guide a patient’s training regime during a cardiopulmonary rehabilitation programme, and for periodic assessment of cardiopulmonary status.

Cardiorespiratory and power adaptations to stimulated cycle training in paraplegia

PURPOSE The extent to which cardiorespiratory fitness and cycling power can be improved in individuals with paraplegia by progressive, high-volume, home-based, electrically stimulated (ES) cycle training was investigated using a novel, sensitive method and protocol that allowed high-resolution power output analyses to be performed for the first time in ES cycling. METHODS Nine male and two female individuals with paraplegia trained progressively at home for up to five 60-min sessions x wk(-1) for 12 months. Peak power and cardiorespiratory parameters were estimated during quarterly feedback-controlled incremental work rate tests in the laboratory. RESULTS Cycle training endurance increased from 10 to 60 min of continuous pedaling for all subjects. Peak power output (POpeak) increased by 132% (P = 0.001), peak oxygen uptake (VO2peak) increased by 56% (P < 0.001), and oxygen pulse increased by 34% (P = 0.002). All significant adaptations occurred during the first 6 months of training when training load was progressive and duration compliance (90%) and frequency compliance (88%) were at their highest. A strong positive relationship between the total training duration and the magnitude of improvements in both POpeak (r2 = 0.84, P < 0.001) and VO2peak (r2 = 0.52, P= 0.012) was found during the first 6 months only. CONCLUSIONS High-volume, home-based ES cycle training using the current training and the ES strategies can significantly improve cardiorespiratory fitness and cycling power output in paraplegia but only while training is progressive. The training plateau reached by 6 months may be physiological in nature or due to the ES strategy used.

Training and detraining of a tetraplegic subject: high-volume FES cycle training.

Objective:To test the effect of high-volume FES cycle training on cardiopulmonary fitness and bone parameters in a tetraplegic subject. Design:Case study of 1 yr of functional electrical stimulated (FES) cycle training with the highest possible power output in a tetraplegic subject. Results:Depending on the training compliance (varying from 22.9 to 82.9%) maximal power output and peak oxygen uptake increased by 113 and 103%, respectively. After reduction in training intensity, these parameters reduced correspondingly. Bone mineral density of the distal femoral epiphysis showed an increase of 3.9% after 12 mos of cycle training. Conclusions:It is possible to increase maximal power output, cardiopulmonary fitness, and bone parameters of the paralyzed limbs in tetraplegia by high-volume cycle training. However, if training is not maintained, these improvements are lost. In tetraplegic subjects, it may be difficult to maintain the high level of training required to achieve benefits.

Feasibility of functional electrical stimulated cycling in subjects with spinal cord injury: An energetic assessment

OBJECTIVE To determine the functional electrical stimulated (FES) cycling volume necessary to reach the recommended weekly exercise caloric expenditure of 1000-2200 kcal in FES-trained subjects with paraplegia. SUBJECTS Eight (7 males, 1 female) FES-trained subjects with traumatic motor and sensory complete paraplegia (AIS A, lesion level between Th3 and Th9) of at least 3 years duration were included. METHODS Subjects performed an FES-training session at the highest workload they were able to sustain for 60 min. During the training session respiratory gas exchange was measured, which allowed the calculation of mean fat and carbohydrate oxidation rates, and of total energy expenditure by means of indirect calorimetry. RESULTS Subjects revealed a mean energy expenditure of 288 (standard deviation 104) kcal/h. This corresponded to a mean oxidation rate of 49.5 (standard deviation 35.2) g/h for carbohydrate and 8.5 (standard deviation 8.4) g/hour for fat. Thus, 4-8 hours of FES-cycling are necessary to reach the recommended weekly exercise caloric expenditure of 1000-2200 kcal. CONCLUSION FES-cycling appears to be a feasible and promising training alternative to upper body exercise for subjects with spinal cord injury. Four to 8 h of FES-cycling are necessary to reach the recommended weekly exercise caloric expenditure that seems to be essential to induce persistent health benefits.

Work-rate-guided exercise testing in patients with incomplete spinal cord injury using a robotics-assisted tilt-table.

Abstract Purpose: Robotics-assisted tilt-table (RTT) technology allows neurological rehabilitation therapy to be started early thus alleviating some secondary complications of prolonged bed rest. This study assessed the feasibility of a novel work-rate-guided RTT approach for cardiopulmonary training and assessment in patients with incomplete spinal cord injury (iSCI). Methods: Three representative subjects with iSCI at three distinct stages of primary rehabilitation completed an incremental exercise test (IET) and a constant load test (CLT) on a RTT augmented with integrated leg-force and position measurement and visual work rate feedback. Feasibility assessment focused on: (i) implementation, (ii) limited efficacy testing, (iii) acceptability. Results: (i) All subjects were able follow the work rate target profile by adapting their volitional leg effort. (ii) During the IETs, peak oxygen uptake above rest was 304, 467 and 1378 ml/min and peak heart rate (HR) was 46, 32 and 65 beats/min above rest (subjects A, B and C, respectively). During the CLTs, steady-state oxygen uptake increased by 42%, 38% and 162% and HR by 12%, 20% and 29%. (iii) All exercise tests were tolerated well. Conclusion: The novel work-rate guided RTT intervention is deemed feasible for cardiopulmonary training and assessment in patients with iSCI: substantial cardiopulmonary responses were observed and the approach was found to be tolerable and implementable. Implications for Rehabilitation Work-rate guided robotics-assisted tilt-table technology is deemed feasible for cardiopulmonary assessment and training in patients with incomplete spinal cord injury. Robotics-assisted tilt-tables might be a good way to start with an active rehabilitation as early as possible after a spinal cord injury. During training with robotics-assisted devices the active participation of the patients is crucial to strain the cardiopulmonary system and hence gain from the training.

Energetics of paraplegic cycling: Adaptations to 12 months of high volume training

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.

Determination and possible application of the aerobic gas exchange threshold in aerobically untrained paraplegic subjects based on stimulated cycle ergometry

Purpose. To accurately characterise cardiopulmonary baseline performance in aerobically untrained paraplegic subjects by means of an incremental exercise test (IET) and to derive possible training recommendations based on these measurements. Methods. Twelve motor complete paraplegic subjects with no previous experience in stimulated leg-cycling participated in the study. Exercise testing was performed on a recumbent FES-tricycle by means of a work rate and cadence controlled IET until maximal work rate was reached. Heart rate (HR) and respiratory parameters were recorded continuously. Results. Peak oxygen uptake was 671 ± 192 mL min−1 (mean ± standard deviation), peak HR 90 ± 12 beats min−1, net peak power 8.4 ± 3.3 W and peak minute ventilation 23.6 ± 7.5 L min−1. Aerobic gas exchange threshold (GET) was found to be 51% ± 10% of peak oxygen uptake and corresponded to 41% ± 13% of peak power. Conclusions. A cadence and work rate controlled exercise test allows the determination of cardiopulmonary parameters during stimulated cycle ergometry even in aerobically untrained paraplegic subjects. The precise determination of GET allows an appropriate exercise intensity to be prescribed and thus provides a suitable method for exercise intensity calculation in the spinal cord injured population in the future.