Glen M. Davis

Cardiorespiratory fitness and walking ability in subacute stroke patients.

OBJECTIVES To evaluate the cardiorespiratory fitness of subacute stroke patients and to determine whether reduced fitness is associated with gait performance. DESIGN Descriptive, cross-sectional study. SETTING Rehabilitation hospital. PARTICIPANTS Seventeen patients in an inpatient rehabilitation unit who had mild to moderate gait impairments after a recent (< or =7wk) stroke. All subjects could walk at least 3m alone or with an aid but with no standby assistance. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Peak and submaximal cardiorespiratory responses were measured during semirecumbent leg cycling exercise. Walking velocity and endurance were assessed with 10-m and 6-minute walk tests, respectively. RESULTS Peak oxygen uptake (Vo(2)peak) was 1.15+/-0.36L/min, which was only 50% of the Vo(2)peak reported in the literature for a healthy, age-matched group. Maximal walking velocity (1.02+/-0.28m/s) and endurance (294.1+/-120.2m) were also approximately 50% of an aged-matched healthy group. Pearson product-moment correlations revealed that 6-minute walking endurance was strongly associated with self-selected walking velocity (R=.91) and measures of peak cardiorespiratory fitness (R=.84). CONCLUSIONS Cardiorespiratory fitness was markedly impaired within 7 weeks after a stroke. Although muscle weakness and loss of coordination are the primary impairments that affect gait after a stroke, impaired cardiorespiratory fitness may secondarily affect gait performance by limiting walking endurance. To address this secondary impairment, current rehabilitation interventions can incorporate assessment of cardiorespiratory fitness status and aerobic exercise training for persons after stroke.

Exercise capacity of individuals with paraplegia

Spinal cord injury below the first thoracic vertebra defines the condition of paraplegia, with common medical sequelae including impaired motor function, bone and muscle atrophy, poor myocardial function, and a general decline of physical fitness. Recently, there has been renewed interest in the role of exercise for improving the physical fitness, health, and rehabilitation potential of individuals rendered wheelchair dependent following spinal cord injury. This brief review examines the pathophysiology of paraplegia, outlines useful strategies for cardiorespiratory fitness assessment, discusses the current levels of cardiorespiratory fitness in individuals with paraplegia, and highlights a few unique responses to acute exercise in this population.

Effects of electrical stimulation-induced leg training on skeletal muscle adaptability in spinal cord injury

Neuromuscular electrical stimulation has grown in popularity as a therapeutic device for training and an ambulation aid to human paralyzed muscle. Despite its current clinical use, few studies have attempted to concurrently investigate the functional and intramuscular adaptations which occur after electrical stimulation training. Six individuals with a spinal cord injury performed 10 weeks of electrical stimulation leg cycle training (30 min d−1, 3 d week−1). The paralyzed vastus lateralis muscle showed significant alterations in skeletal muscle characteristics after the training, indicated by an improvement in total work output (52–112 kJ; P < 0.05), an increase in fiber cross‐sectional area (18 to 41 × 102 µm2; P < 0.05), a reduction in the percentage of type IIX fibers (75% to 12%; P < 0.05), a decrease in myosin heavy chain IIx (68% to 44%; P < 0.05), an increase in capillary density (2–3.5 capillaries around fiber; P < 0.05) and increases in activity levels of citrate synthase (7–16 mU mg−1 protein) and hexokinase (1.2–2.4 mU mg−1 protein). This study showed that 10 weeks of electrical stimulation training of human paralyzed muscle induces concurrent improvements in functional capacity and oxidative metabolism.

Comparison of Effect of Aerobic Cycle Training and Progressive Resistance Training on Walking Ability After Stroke: A Randomized Sham Exercise–Controlled Study

OBJECTIVES: To determine whether changes in strength or cardiorespiratory fitness after exercise training improve walking ability in individuals who have had a stroke.

Cardiorespiratory, metabolic, and biomechanical responses during functional electrical stimulation leg exercise: health and fitness benefits.

Functional electrical stimulation (FES)-induced leg exercise offers the potential for individuals with lower-limb paralysis to otherwise gain some benefits conferred by leg exercise. Although its original intent is to reactivate the leg muscles to produce functional upright mobility, as a rehabilitation therapy, FES-evoked exercise increases the whole-body metabolism of individuals with spinal cord injury (SCI) so that they may gain general and localized health and fitness benefits. The physiological and psychosocial responses during FES-evoked cycling, standing, rowing, leg extension, or stepping have been extensively explored for over 20 years. Some of the advantages of such exercise include augmented cardiorespiratory fitness, promotion of leg blood circulation, increased activity of specific metabolic enzymes or hormones, greater muscle volume and fiber size, enhanced functional exercise capacity such as strength and endurance, and altered bone mineral density. Positive psychosocial adaptations have also been reported among SCI individuals who undergo FES exercise. This article presents a position review of the available literature on the effects of FES-evoked exercise since the earliest date until 2007, to warrant a conclusion about the current status and potential of FES-evoked exercise for paralyzed people.

Benefits of FES gait in a spinal cord injured population.

Study design:Review.Objectives:This review article investigated the objective evidence of benefits derived from functional electrical stimulation (FES)-assisted gait for people with spinal cord injury (SCI). Both FES and gait have been proposed to promote not only augmented health and fitness, but specific ambulatory outcomes for individuals with neurological disabilities. However, due to small sample sizes and the lack of functionality of the intervention, it has not been widely used in clinical practice. This review assessed whether there is sufficient evidence to encourage a more widespread deployment of FES gait within the rehabilitation community.Methods:Hand searches and online data collection were performed in Medline and Science Direct. Specific search terms used included SCI/paralysis/paraplegia and tetraplegia with electrical stimulation/FES, gait and walking.Results:The searches generated 532 papers. Of these papers, 496 were excluded and 36 papers were included in the review. Many reported benefits were not carefully investigated, and small sample sizes or different methodologies resulted in insufficient evidence to draw definitive conclusions.Conclusions:FES gait can enhance gait, muscle strength and cardiorespiratory fitness for people with SCI. However, these benefits are dependent on the nature of the injury and further research is required to generalize these results to the widespread population of SCI individuals. Proof of the functionality and further evidence of the benefits of FES gait will assist in FES gait gaining clinical acceptance.

Effects of electrical stimulation leg training during the acute phase of spinal cord injury: a pilot study

Abstract Four individuals with a spinal cord injury underwent 16 weeks of isometric electrical stimulation training to both legs for 60 min, five times per week during the first 5 months after injury, while two SCI individuals remained untrained. A baseline biopsy sample of the vastus lateralis muscle was obtained within 1 month of injury, and another biopsy sample was taken after a further 16 weeks. The untrained, paralyzed skeletal muscle displayed a reduction in (1) type I fibers (from 50% to 9%), (2) myosin heavy chain (MHC) I (from 27% to 6%), and (3) fiber cross-sectional area of type I, type IIA and type IIX fibers (−62%, −68%, and −55%, respectively) when compared to the baseline sample of muscle taken within 1 month of injury. In contrast, the trained group showed smaller alterations in type I fibers (from 49% to 40%) and MHC I composition (from 39% to 25%), while fiber cross-sectional area was similar to baseline levels for type I, type IIA and type IIX fibers (−3%, −8%, and −4%, respectively). In conclusion, electrical stimulation training can largely prevent the adverse effects of a spinal cord injury upon paralyzed human skeletal muscle if applied soon after the injury.

Cardiorespiratory responses to arm cranking and electrical stimulation leg cycling in people with paraplegia

PURPOSE The purpose of this study was to assess the cardiorespiratory responses during arm exercise with and without concurrent electrical stimulation-induced leg cycling in people with paraplegia. METHODS On separate days, 10 subjects with spinal cord injuries (T5-T12) performed either arm cranking (ACE), or simultaneous arm cranking + electrical stimulation-induced leg cycling (ACE+ES-LCE) graded exercise tests. RESULTS During submaximal, steady-state exercise, ACE+ES-LCE elicited significantly higher VO2, (by 0.25-0.28 L x min(-1)) stroke volume (by 13 mL), and VE(BTPS) (by 9.4 L x min(-1)) compared with ACE alone. In contrast, there were no significant differences of submaximal HR, cardiac output, or power output between the exercise modes. At maximal exercise, ACE+ES-LCE elicited significantly higher VO2 (by 0.23 L x min(-1)) compared with ACE alone, but there were no differences in power output, HR, or VE(BTPS). CONCLUSIONS These results demonstrate that during submaximal or maximal exercise there was a greater metabolic stress elicited during ACE+ES-LCE compared with during ACE alone. The higher stroke volume observed during submaximal ACE+ES-LCE, in the absence of any difference in HR, implied a reduced venous pooling and higher cardiac volume loading during ACE+ES-LCE. These results suggest that training incorporating ACE+ES-LCE may be more effective in improving aerobic fitness in people with paraplegia than ACE alone.

Effect of progressive resistance training on muscle performance after chronic stroke.

PURPOSE This study investigated the effects of high-intensity progressive resistance training (PRT) and high-intensity cycling (cycling) on muscle performance and the time course of strength gains in a chronic stroke population. METHODS Forty-eight individuals with chronic stroke sequelae (mean +/- SD; age = 63 +/- 9 yr, time since stroke = 57 +/- 54 months) were randomly allocated to one of four treatment groups: PRT + cycling, PRT + sham cycling, sham PRT + cycling, or sham PRT + sham cycling groups in a fully factorial clinical trial. Thirty exercise sessions were conducted over a 10- to 12-wk period. The main outcomes investigated were measures of unilateral muscle strength, peak power, and muscle endurance. RESULTS Those undergoing PRT improved their lower limb muscle strength, peak power, and endurance compared with participants receiving sham PRT or cycling only (P < 0.05), and combined exercise was not superior to PRT alone. Strength improvements occurred primarily during the first 6 to 8 wk (98%-100% of total gain) and then reached a plateau during the final 2 to 4 wk. CONCLUSION We have shown for the first time in a direct comparison study that high-intensity PRT, but not cycling or sham exercise, can improve muscle strength, peak power, and muscle endurance in both affected and unaffected lower limbs after chronic stroke by a significant and clinically meaningful amount. Although strength gains plateaued earlier than anticipated, adherence to the intended continuous high-intensity progressive overload protocol was largely achieved (average load of 84% +/- 4% of one repetition maximum).

Postural control during stance in paraplegia: Effects of medially linked versus unlinked knee-ankle-foot orthoses☆☆☆

OBJECTIVE To investigate the effect of medially linking knee-ankle-foot orthoses (KAFOs) on postural stability and sway during (1) quiet standing and (2) functional activities for persons with spinal cord injury (SCI). DESIGN A randomized, mixed design, with the factors being activity (quiet standing and two function-mimicking tasks), SCI (present or not), and type of orthosis used in SCI group (linked or unlinked KAFO). PARTICIPANTS Nine men with T5 to T12 paraplegia, 8 of whom had complete lesions and 1 with some sacral sparing (American Spinal Injury Association grade B) without proprioception, matched to 9 able-bodied men. MAIN OUTCOME MEASURES Mean amplitude of sway and sway path in anteroposterior and mediolateral directions, derived from center of pressure measurements on a force platform. RESULTS All men with SCI were able to stand unsupported and perform function-mimicking activities in medially linked KAFOs; however, when wearing unlinked KAFOs only 5 could maintain balance during quiet stance and 3 could maintain balance during activity. Significant differences were found between linked and unlinked KAFOs; side-to-side mean amplitude of sway was less and sway path was greater for SCI subjects when they wore the linked KAFOs. CONCLUSION Medial linkage of bilateral KAFOs provides an effective strategy to improve stability and increase postural control for persons with SCI, facilitating performance of functional activities during standing without upper limb support.