Improved glucose tolerance and insulin sensitivity after electrical stimulation-assisted cycling in people with spinal cord injury.

DESIGN: Longitudinal training. OBJECTIVES: The purpose was to determine the effect of electrical stimulation (ES)-assisted cycling (30 min/day, 3 days/week for 8 weeks) on glucose tolerance and insulin sensitivity in people with spinal cord injury (SCI). SETTING: The Steadward Centre, Alberta, Canada. METHODS: Seven participants with motor complete SCI (five males and two females aged 30 to 53 years, injured 3-40 years, C5-T10) underwent 2-h oral glucose tolerance tests (OGTT, n=7) and hyperglycaemic clamp tests (n=3) before and after 8 weeks of training with ES-assisted cycling. RESULTS: Results indicated that subjects' glucose level were significantly lower at 2 h OGTT following 8 weeks of training (122.4+/-10 vs 139.9+/-16, P=0.014). Two-hour hyperglycaemic clamps tests showed improvement in all three people for glucose utilisation and in two of three people for insulin sensitivity. CONCLUSIONS: These results suggested that exercise with ES-assisted cycling is beneficial for the prevention and treatment of Type 2 diabetes mellitus in people with SCI. SPONSORSHIP: Supported by Alberta Paraplegic Foundation, Therapeutic Alliance.

Quadriceps muscle deoxygenation during functional electrical stimulation in adults with spinal cord injury.

STUDY DESIGN: Cross-sectional study comparing healthy subjects with age and gender matched subjects with spinal cord injury (SCI, injury levels from C5 to T12). OBJECTIVES: To compare the acute cardiorespiratory responses and muscle oxygenation trends during functional electrical stimulation (FES) cycle exercise and recovery in the SCI and healthy subjects exercising on a mechanical cycle ergometer. SETTING: Seven volunteers in each group participated in one exercise test at the Rick Hansen Center, University of Alberta, Edmonton, Canada. METHODS: Both groups completed a stagewise incremental test to voluntary fatigue followed by 2 min each of active and passive recovery. Cardiorespiratory responses were continuously monitored using an automated metabolic cart and a wireless heart rate monitor. Tissue absorbency, an index of muscle oxygenation, was monitored non-invasively from the vastus lateralis using near infrared spectroscopy. RESULTS: The healthy subjects showed significant (P<0.05) increases in the oxygen uptake (VO2), heart rate (HR) and ventilation rate (VE) from rest to maximal exercise. The SCI subjects showed a twofold increase in VO2 (P>0.05), a threefold increase in VE (P<0.05) and a 5 beats/min increase in HR (P>0.05) from the resting value. The SCI subjects demonstrated a lesser degree (P<0.05) of muscle deoxygenation than the healthy subjects during the transition from rest to exercise. Regression analysis indicated that the rate of decline in muscle deoxygenation with respect to the VO2 was significantly (P<0.05) faster in the SCI subjects compared to healthy subjects. CONCLUSIONS: FES exercise in SCI subjects elicits: (a) modest increases in the cardiorespiratory responses when compared to resting levels; (b) lower degree of muscle deoxygenation during maximal exercise, and (c) faster changes in muscle deoxygenation with respect to the VO2 during exercise when compared to healthy subjects.

Functional electrical stimulation effect on orthostatic hypotension after spinal cord injury.

OBJECTIVE: To investigate the possibility of using functional electrical stimulation (FES) to control orthostatic hypotension in patients with spinal cord injury (SCI) and to clarify the mechanism of the response. DESIGN: Subjects were tilted by 10 degree increments with varying intensities of lower-extremity FES. Stimulation over muscles was compared to stimulation over noncontractile sites. SETTING: Physical therapy department of a major rehabilitation center. PATIENTS: Six patients with SCI above T6 (3 with recent injury recruited consecutively from an inpatient spinal cord rehabilitation unit, and 3 from the community with longstanding injury, recruited as volunteers). MAIN OUTCOME MEASURES: Blood pressure, heart rate, and perceived presyncope score recorded at each tilt angle and analyzed using a multivariate analysis of variance statistical methodology. RESULTS: Systolic and diastolic blood pressure increased with increasing stimulation intensities (systolic, p = .001; diastolic, p = .0019) and decreased with increasing angle of tilt (p < .001) regardless of the site of stimulation. Subjects tolerated higher angles of incline with electrical stimulation than without (p = .03). CONCLUSIONS: FES causes a dose-dependent increase in blood pressure independent of stimulation site that may be useful in treating orthostatic hypotension.

Functional electrical stimulation exercise increases GLUT-1 and GLUT-4 in paralyzed skeletal muscle.

The study purpose was to determine the effect of functional electrical stimulation (FES)-leg cycle ergometer training (30 minutes on 3 d/wk for 8 weeks) on the GLUT-1 and GLUT-4 content of paralyzed skeletal muscle. Biopsy samples of vastus lateralis muscle were obtained pre- and post-training from five individuals with motor-complete spinal cord injury ([SCI] four men and one woman aged 31 to 50 years, 3 to 25 years postinjury involving C5-T8). Western blot analysis indicated that GLUT-1 increased by 52% and GLUT-4 increased by 72% with training (P < .05). This coincided with an increase in the muscle oxidative capacity as indicated by a 56% increase in citrate synthase (CS) activity (P < .05) and an improvement in the insulin sensitivity index as determined from oral glucose tolerance tests (P < .05). It is concluded that FES endurance training is effective to increase glucose transporter protein levels in paralyzed skeletal muscle of individuals with SCI.

The effects of surface anaesthesia on the autonomic dysreflexia response during functional electrical stimulation.

Recently, increases in blood pressure (BP) and concomitant bradycardia, suggestive of autonomic dysreflexia (AD), have been documented during functional electrical stimulation (FES) in individuals with a high spinal cord injury (SCI). If uncontrolled, this response could preclude the safe use of FES among such individuals. FES induced pain is partly related to stimulation of skin nociceptors. Therefore, measures to reduce skin sensitivity may reduce the risk of AD during FES. The purpose of this study was to determine if topical anaesthetic applied over the site of electrical stimulation could minimize the AD cardiovascular and hormonal responses to FES in individuals with SCI above the T6 level. Seven subjects with a SCI above T6 received FES to the quadriceps muscle of each leg under two conditions on two different testing days. The two treatment conditions, topical anaesthetic and placebo creams, were double blinded and randomized. The cream was administered to an area the size of the electrode (10 x 10 cm) 1 h prior to stimulation. Stimulation began at 0 mAmps and increased by 16 mAmps every 2 min until an intensity of 160 mAmps was achieved. HR and BP were measured at each stimulation intensity level. Catecholamines were analyzed three times during the stimulation protocol (pre, mid and post stimulation intensities). At the end of the stimulation protocol, FES induced isometric quadriceps contraction force at 160 mAmps intensity was measured using a hand held dynamometer. As FES stimulation intensity increased, significant rises in systolic and diastolic BP were seen, with a concomitant progressive drop in HR. The AD response to stimulation was not significantly different between the topical anaesthetic and placebo conditions. Serum catecholamine (epinephrine and norepinephrine) levels tended to rise with increasing FES intensity levels but did not reach statistical significance. The two treatment conditions did not significantly affect serum catecholamine levels or FES-induced quadriceps contraction force. In summary, FES application to the quadriceps muscle in high level SCI subjects resulted in significant increases in BP, decreases in HR (AD-like response), a trend towards elevations in catecholamine levels, and no difference in quadriceps muscular strength. However, these responses were unaffected by the use of topical anaesthetic cream on the skin at the stimulation site. This suggests that other mechanisms than skin nociception are operative in FES-induced AD.

Hormonal responses to graded-resistance, FES-assisted strength training in spinal cord-injured.

Functional electrical stimulation (FES) assisted resistance training has been effective in increasing muscular strength and endurance in spinal cord injured men and women in preparation for FES-assisted cycle programs and for FES-assisted standing and walking. Increases in blood pressure and a concomitant bradycardia suggestive of autonomic dysreflexia have been reported during FES-assisted resistance training. Self-induced autonomic dysreflexia in athletes who use wheelchairs suppressed the normal exercise induced serum testosterone increase. We, therefore, examined the changes in hematocrit and circulating levels of testosterone, sex hormone binding globulin (SHBG), cortisol, prolactin, norepinephrine and epinephrine during FES assisted resistance exercise in five high spinal cord injured men (SCI) and comparable maximal exercise in five able bodied controls (AB). Mean serum testosterone levels significantly increased with FES-assisted resistance training in SCI and maximal resistance exercise in AB with no significant change in hematocrit or SHBG. Prolactin, cortisol and epinephrine levels were unchanged while norepinephrine levels were significantly increased in SCI and AB. These findings suggest that there is no concern over inadequate physiological androgen response to an exercise stimulus in SCI. The data do not support the previous findings that elevated levels of norepinephrine in autonomic dysreflexia suppress testosterone response to exercise.

Evidence of autonomic dysreflexia during functional electrical stimulation in individuals with spinal cord injuries.

The purpose of the investigation was to examine the safety and efficacy of functional electrical stimulation (FES)-assisted hydraulic resistance training in improving cardiovascular fitness in persons with spinal cord injuries. The cardiopulmonary responses of 10 high spinal cord injured (SCI) and five able bodied (AB) subjects were assessed during three bouts of FES-assisted leg extension exercise. The protocol involved three 30-minute tests: (1) unloaded leg extension, (2) hydraulically-resisted leg extension (loaded), and (3) a reproduction of the unloaded and loaded protocols to measure cardiac output (Q). Pre-measurements were made of body mass, mean limb weight, maximal force output and maximal oxygen uptake (incremental arm ergometry). Oxygen uptake (VO2), minute ventilation (Ve), respiratory exchange ratio (RER), heart rate (HR), blood pressure (BP) were recorded before, during and after tests. There was a significant difference in VO2 max between SCI and AB subjects. Cardiac output significantly increased between the loaded and unloaded tests. The significant increases from rest to unloaded and loaded exercise pointed to the potential value of adding resistance to a leg extension training regime. Heart rate and BP of the participants with SCI consistently demonstrated a response suggestive of autonomic dysreflexia. Upon stimulation an immediate increase in (predominantly systolic) BP was observed, followed by a fall in HR. On cessation of stimulation HR exhibited a substantial rebound effect and BP returned to normal levels. This response was highly reproducible and suggests caution be exercised in the use of FES for people with SCI with lesion levels above the major splanchnic outflow (T6).

Electrical stimulation-assisted rowing exercise in spinal cord injured people. A pilot study.

Recently a FES (functional electrical stimulation)-assisted rowing machine was developed to enhance cardiovascular training in people with spinal cord injuries. The machine was assessed in terms of its efficacy as a training tool. Six patients who were quadriplegic (C6-T1) and 2 who were paraplegic (T3-6) completed a series of three tests in succession: (1) leg stimulation only (quadriceps and hamstring groups)--'Stim', (2) arm row only--'Row' and (3) simultaneous row and stimulation--'R & S'. Measurements recorded included oxygen uptake (VO2), minute ventilation (Ve), respiratory exchange ratio (RER), heart rate (HR) and blood pressure (BP). In addition, 6 out of the 8 subjects took part in a qualitative assessment comprising a guided interview exploring the subject's perception of the machine and test. Significant increases in VO2 were demonstrated between the three tests with R & S producing mean steady-state values of 16.34 nm (+/- 0.74) ml/kg/min (83% of maximum). These values represented a 12% increase over Row alone. Of interest was the qualitative assessment which revealed that subjects perceived R & S to be easier than Row despite the higher levels of VO2 observed. The results suggest that the rowing machine represents a potentially valuable hybrid training device that may significantly reduce risk factors for cardiovascular disease and improve the quality of life of people with SCI.