Electrical stimulation-evoked resistance exercise therapy improves arterial health after chronic spinal cord injury

A Primer on Repeated Sitting Exposure and the Cardiovascular System: Considerations for Study Design, Analysis, Interpretation, and Translation

Sedentary behavior, particularly sitting, is ubiquitous in many contemporary societies. This is a major societal concern considering the evidence for a strong association between sitting behavior and cardiovascular disease morbidity and mortality. Unsurprisingly, leading public health agencies have begun to advocate “reduction” in sitting behavior. Though, the guidelines are typically vague and non-specific. The lack of specific guidelines for prolonged sitting is attributable to the absence of available evidence to facilitate guideline development. To inform policy, well-designed randomized controlled trials are required to test the efficacy of specific and translatable sitting reduction strategies. To guide the design of randomized controlled trials, this review postulates that several gaps in the literature first need to be filled. Following a general discussion of the importance of sitting behavior to contemporary societies, each of the following are discussed: (i) acute sitting exposure and systems physiology; (ii) recommendations for a systems physiology toolbox; (iii) study design considerations for acute sitting exposure; and (iv) translation of sitting-focused research.

Does aerobic exercise benefit persons with tetraplegia from spinal cord injury? A systematic review

CONTEXT

This review synthesizes the findings of previous research studies on the cardiovascular and metabolic benefits of aerobic exercise for individuals with tetraplegia secondary to spinal cord injury. They are often less active due to muscular paralysis, sensory loss, and sympathetic nervous system dysfunction that result from injury. Consequently, these persons are at higher risk for exercise intolerance and secondary health conditions.

OBJECTIVE

To evaluate the evidence concerning efficacy of aerobic exercise training for improving health and exercise performance in persons with tetraplegia from cervical injury.

METHODS

The search engines PubMed and Google Scholar were used to locate published research. The final 75 papers were selected on the basis of inclusion criteria. The studies were then rank-ordered using Physiotherapy Evidence Database.

RESULTS

Studies combining individuals with tetraplegia and paraplegia show that voluntary arm-crank training can increase mean peak power output by 33%. Functional electrical stimulation leg cycling was shown to induce higher peak cardiac output and stroke volume than arm-crank exercise. A range of peak oxygen uptake (VO_2peak) values have been reported (0.57-1.32 L/min). Both VO_2peak and cardiac output may be enhanced via increased muscle pump in the legs and venous return to the heart. Hybrid exercise (arm-crank and functional electrical stimulation leg cycling) can result in greater peak oxygen uptake and cardiovascular responses.

CONCLUSION

Evidence gathered from this systematic review of literature is inconclusive due to the lack of research focusing on those with tetraplegia. Higher power studies (level 1-3) are needed with the focus on those with tetraplegia.

Safety and preliminary efficacy of functional electrical stimulation cycling in an individual with cervical cord injury, autonomic dysreflexia, and a pacemaker: Case report

Context: Functional electric stimulation (FES) cycling is a commonly used therapeutic exercise modality after spinal cord injury (SCI); however, additional precautions must be taken in certain situations. The purpose of this study was to develop and apply a safety monitoring protocol for autonomic dysreflexia (AD) during FES cycling and to determine if an interval-FES cycling program can be safe and beneficial to an individual with cervical SCI, a history of AD, and a non-dependent cardiac pacemaker.The participant was a 36-year-old male with C6 AIS-C SCI sustained 9 years earlier, intermittent AD, and implanted cardiac pacemaker. Ten sessions of interval-FES cycling were performed twice weekly for 5 weeks. Rating of perceived exertion (RPE), blood pressure (BP), oxygen saturation (O2sat), and heart rate (HR) were monitored before, after, and every 5 min during cycling. ECG and cardiac pacemaker were evaluated by a cardiologist after ending the program.Findings: The participant reported self-limited chills 27 times over 10 sessions (19 "light", 3 "moderate", 5 "sharp"). Chills coincided with BP increases 59% of the time and their magnitudes moderately correlated (r = 0.32). The ECG was determined to be normal and the pacemaker fully functional at the end of the study, while blood glucose decreased (111-105 mg/dl), HbA1c levels increased (5.5-5.9%), and resting BP decreased (118/84-108/66 mmHg).Conclusion/Clinical Relevance: A person with cervical SCI, symptomatic AD, and a non-dependent pacemaker can safely participate and benefit from the interval-FES cycling program provided adequate monitoring of symptoms and vital signs.

Effects of a Tailored Physical Activity Intervention on Cardiovascular Structure and Function in Individuals With Spinal Cord Injury

Background

Spinal cord injury (SCI) leads to a loss of descending motor and sympathetic control below the level of injury (LOI), which ultimately results in chronically altered cardiovascular function and remodeling. While supervised, laboratory-based exercise training can generate cardiovascular adaptations in people with SCI, it is unknown whether behavioral community-based interventions effectively generate such adaptations for individuals with SCI.

Objective

Examine the effects of a tailored behavioral physical activity (PA) intervention on cardiac and vascular structure and function in individuals with SCI.

Methods

In this randomized controlled trial, 32 participants with SCI (18-65 years, SCI >1 year) were assigned to PA (8-week behavioral intervention) or control (CON) groups. At baseline and postintervention, measures of resting left ventricular (LV) structure and function, carotid intima-media thickness and pulse-wave velocity were assessed with ultrasound and tonometry.

Results

Twenty-eight participants completed the study (n = 14/group). Across the full study cohort there were no significant changes in indices of LV or vascular structure and function, despite notable improvements in peak power and oxygen uptake in the PA group. However, in a subanalysis for LOI, individuals in the PA group with LOIs below T6 had evidence of altered LV geometry (ie, increased LV internal diameter, reduced sphericity index and relative wall thickness; group × time P < 0.05 for all), which was not seen in individuals with higher LOIs at or above T6.

Conclusion

An 8-week behavioral PA intervention appears to promote adaptations in cardiac geometry more readily in individuals with lower level SCI than those with higher-level SCI.

Effects of robotic-assisted gait training on the central vascular health of individuals with spinal cord injury: A pilot study

Objective: To investigate the effect of a short-term, robotic-assisted (exoskeleton) gait training (RGT) program on central and peripheral hemodynamic measures in patients with spinal cord injury (SCI).Design: Parallel group, non-randomized trial with before (baseline) and after (follow-up) assessments.Setting: Single-center, community-based neuro-physiotherapy practice.Participants: Twelve individuals with SCI (ASI A to C).Interventions: Participants completed either a 5-day RGT program plus physiotherapy (n = 6), or a usual care physiotherapy only program (control group; n = 6). The RGT program consisted of daily 60-min physiotherapy and 90-min of RGT. Outcome measures were measured before and after the rehabilitation program.Main outcome measure(s): The primary outcome measure was arterial wave reflection (Augmentation index [AIx]), with central and peripheral blood pressures also reported. Data are presented as mean (SD) and effect sizes (partial eta squared; η2p).Results: There was a significant reduction in AIx (30 ± 18-21 ± 15%; η2p=0.75) and mean arterial pressure (89 ± 11-82 ± 10 mmHg; η2p=0.47) following completion of the RGT program (both P < 0.05). There were no changes in these measures for the control group. Although not significantly different, medium to large effects were observed in favor of RGT for all other central and peripheral measures (η2p=0.06-0.21), except for heart rate and pulse pressure (η2p<0.04).Conclusions: RGT using an exoskeleton is a promising therapy for improving cardiovascular health in patients with SCI. Specifically, this study indicates decreased arterial wave reflection and supports the need for larger randomized controlled trials.Trial Registration: Clinical trials Registry (https://clinicaltrials.gov/; NCT03611803).

Microvascular responses during reactive hyperemia assessed by near-infrared spectroscopy and arterial stiffness in young, middle-aged, and older women

We investigated the effects of age on microvascular responses during reactive hyperemia and arterial stiffness in 13 young (22 ± 1 years), 12 middle-aged (42 ± 5 years), and 15 older (63 ± 2 years) women. During the vascular occlusion test (VOT), forearm tissue oxygen saturation (StO₂) was measured using near-infrared spectroscopy (NIRS). During reperfusion, the area under the curve (AUC) during hyperemia in young women (1123 ± 208% s) was significantly greater than that in middle-aged (771 ± 445% s, P = 0.024) and older women (619 ± 356% s, P = 0.001) with no differences between middle-aged and older women (P = 0.265). Cardio-ankle vascular index (CAVI) as an indicator of arterial stiffness was assessed using four-limb oscillometry. CAVI significantly increased with age (8.1 ± 0.7 in the older group, 6.0 ± 0.8 in the middle-aged group, and 5.8 ± 0.4 in the young group), with significant differences between older women and women in the other groups (P < 0.001); however, no differences in CAVI between young and middle-aged women (P = 0.484) were found. When the data of all groups were pooled, the AUC or upslope was associated with CAVI or body mass index or mean arterial pressure (all P < 0.05). To conclude, the AUC derived by NIRS measures of StO₂ during the reperfusion phase can be used as one of the evaluations of microvascular function, followed by the development of atherosclerosis in middle-aged and older women.

Effects of Intermittent Pneumatic Compression on Leg Vascular Function in People with Spinal Cord Injury: A Pilot Study

Objective: The purpose of this pilot study was to determine whether 60 mins of intermittent pneumatic compression therapy (IPC) could acutely increase leg blood flow-induced shear stress and enhance vascular endothelial function in persons with spinal cord injury (SCI). Design: Pretest with multiple posttests, within subject randomized control design. Setting: University of Southern Mississippi, Spinal Cord Injury Research Program within the School of Kinesiology, recruiting from the local community in Hattiesburg, Jackson, and Gulfport, MS. Participants: Eight adults with SCI (injury level: T3 and below; ASIA class A-C; age: 41±17 yrs). Interventions: A 60-min IPC session was performed in one leg (experimental leg; EXP), with the other leg serving as a control (CON). Outcomes Measures: Posterior-tibial artery shear rate (Doppler-ultrasound) was examined at rest, and at 15 and 45 mins during IPC. Endothelial function was assessed using the flow-mediated dilation (FMD) technique, before and after IPC. Results: Resting FMD (mm) was similar between legs at rest. A two-way repeated measures ANOVA (leg x time) revealed that during IPC, peak shear rate increased in the EXP leg (215±137 to 285±164 s^-1 at 15 mins; +39±29%, P = 0.03), with no change occurring in the CON. In addition, FMD significantly increased in the EXP leg (Pre IPC: 0.36±0.14 vs. Post IPC: 0.47±0.17 mm; P = 0.011, d = 0.66), with no change occurring in the CON leg. Conclusion: These preliminary findings suggests that IPC therapy may acutely increase leg shear stress within 15 mins, with a resultant moderate-large improvement in vascular endothelial function after 60 mins in people with SCI.

Endurance neuromuscular electrical stimulation training improves skeletal muscle oxidative capacity in individuals with motor-complete spinal cord injury

INTRODUCTION

Spinal cord injury (SCI) results in skeletal muscle atrophy, increases in intramuscular fat, and reductions in skeletal muscle oxidative capacity. Endurance training elicited with neuromuscular electrical stimulation (NMES) may reverse these changes and lead to improvement in muscle metabolic health.

METHODS

Fourteen participants with complete SCI performed 16 weeks of home-based endurance NMES training of knee extensor muscles. Skeletal muscle oxidative capacity, muscle composition, and blood metabolic and lipid profiles were assessed pre- and post-training.

RESULTS

There was an increase in number of contractions performed throughout the duration of training. The average improvement in skeletal muscle oxidative capacity was 119%, ranging from -14% to 387% (P = 0.019). There were no changes in muscle composition or blood metabolic and lipid profiles.

CONCLUSION

Endurance training improved skeletal muscle oxidative capacity, but endurance NMES of knee extensor muscles did not change blood metabolic and lipid profiles. Muscle Nerve 55: 669-675, 2017.

FloWave.US: validated, open-source, and flexible software for ultrasound blood flow analysis

Automated software improves the accuracy and reliability of blood velocity, vessel diameter, blood flow, and shear rate ultrasound measurements, but existing software offers limited flexibility to customize and validate analyses. We developed FloWave.US-open-source software to automate ultrasound blood flow analysis-and demonstrated the validity of its blood velocity (aggregate relative error, 4.32%) and vessel diameter (0.31%) measures with a skeletal muscle ultrasound flow phantom. Compared with a commercial, manual analysis software program, FloWave.US produced equivalent in vivo cardiac cycle time-averaged mean (TAMean) velocities at rest and following a 10-s muscle contraction (mean bias <1 pixel for both conditions). Automated analysis of ultrasound blood flow data was 9.8 times faster than the manual method. Finally, a case study of a lower extremity muscle contraction experiment highlighted the ability of FloWave.US to measure small fluctuations in TAMean velocity, vessel diameter, and mean blood flow at specific time points in the cardiac cycle. In summary, the collective features of our newly designed software-accuracy, reliability, reduced processing time, cost-effectiveness, and flexibility-offer advantages over existing proprietary options. Further, public distribution of FloWave.US allows researchers to easily access and customize code to adapt ultrasound blood flow analysis to a variety of vascular physiology applications.

Neuromuscular Electrical Stimulation-Induced Resistance Training After SCI: A Review of the Dudley Protocol

BACKGROUND

Neuromuscular electrical stimulation (NMES), often referred to as functional electrical stimulation (FES), has been used to activate paralyzed skeletal muscle in people with spinal cord injury (SCI). The goal of NMES has been to reverse some of the dramatic losses in skeletal muscle mass, to stimulate functional improvements in people with incomplete paralysis, and to produce some of the health benefits associated with exercise.

OBJECTIVE

The purpose of this brief review is to describe a quantifiable resistance training form of NMES developed by Gary A. Dudley.

METHODS

People with motor complete SCI were first tested to confirm that an NMES-induced muscle contraction of the quadriceps muscle could be achieved. The contraction stimulus consisted of biphasic pulses at 35 Hz performed with increasing current up to what was needed to produce full knee extension. Four sets of 10 knee extensions were elicited, if possible. Training occurred biweekly for 3 to 6 months, with ankle weights being increased up to an added weight of 9.1 kg if the 40 repetitions could be performed successfully for 2 sessions.

RESULTS

Many participants have performed this protocol without adverse events, and all participants showed progression in the number of repetitions and/or the amount of weight lifted. Large increases in muscle mass occur, averaging 30% to 40%. Additional physiological adaptations to stimulated muscle have also been reported.

CONCLUSIONS

These results demonstrate that the affected skeletal muscle after SCI responds robustly to progressive resistance training many years after injury. Future work with NMES should determine whether gains in lean mass translate to improved health, function, and quality of life.

Following the Physical Activity Guidelines for Adults With Spinal Cord Injury for 16 Weeks Does Not Improve Vascular Health: A Randomized Controlled Trial

OBJECTIVE

To evaluate the effects of following the physical activity guidelines (PAG) for adults with spinal cord injury (SCI) for 16 weeks.

DESIGN

Randomized controlled trial.

SETTING

Community exercise program.

PARTICIPANTS

Individuals with SCI (N=23; neurological level of injury, C3-T11; American Spinal Injury Association Impairment Scale A-C; time postinjury, 12.0±9.9 y; age, 41.4±11.6 y).

INTERVENTIONS

Participants were randomly assigned to PAG training (n=12) or active control (n=11) groups. PAG training involved ≥20 minutes of moderate-vigorous aerobic exercise (rating of perceived exertion 3-6 on 10-point scale) and 3×10 repetitions of upper-body strengthening exercises (50%-70% 1 repetition maximum) 2 times per week. The control group maintained existing physical activity levels with no guidance on training intensity.

MAIN OUTCOME MEASURES

Outcome measures were obtained pre- and postintervention. Vascular health indicators included arterial stiffness via carotid distensibility and pulse wave velocity, and endothelial function via flow-mediated-dilation. Fasted blood samples were analyzed for markers of cardiovascular disease (CVD) risk. Body composition was assessed via anthropometrics and with dual-energy x-ray absorptiometry.

RESULTS

Twenty-one individuals completed the intervention (PAG=12, control=9). Group-by-time interactions were observed for whole-body mass (P=.03), whole-body fat (P=.04), visceral adipose tissue (P=.04), and carotid artery distensibility (P=.05), suggesting maintained body composition and carotid stiffness in the PAG group concurrent with declines in the control group. No changes were found in any other outcome measure.

CONCLUSIONS

While 16 weeks of adherence to the PAG in adults with SCI is insufficient to improve many markers of CVD risk, it may prevent declines in others. The PAG should continue to be promoted as a means to increase physical fitness and maintain body composition in individuals with SCI, but changes may be needed to achieve other health outcomes.

The use of shear rate-diameter dose-response curves as an alternative to the flow-mediated dilation test

The brachial artery flow-mediated dilation test (FMD) is the non-invasive gold-standard used to test endothelial function. Reduced FMD precedes the development of atherosclerosis and provides an early marker for predicting future cardiovascular disease events. Although, this test is of high potential, it is somewhat limited by poor reproducibility. By utilizing hand warming and grip exercise combined with hierarchical linear modeling, shear rate-diameter dose-response curves may provide a novel and more accurate way to assess endothelial function in humans. Shear rate-diameter dose-response curves could potentially improve upon the traditional FMD measurement and serve as a superior clinical and research tool for assessing cardiovascular disease risk in a variety of populations. The current paper presents testable hypotheses and methodology for assessing the validity and reliability of an alternative to the current FMD test.

Altered resting hemodynamics in lower-extremity arteries of individuals with spinal cord injury

OBJECTIVE

To investigate lower-extremity arterial hemodynamics in individuals with spinal cord injury (SCI). We hypothesized that oscillatory shear index would be altered and resting mean shear would be higher in the lower-extremity arteries of SCI.

RESEARCH

Cross-sectional study of men and women with SCIs compared to able-bodied controls.

SUBJECTS

Subjects included 105 ages 18-72 years with American Spinal Injury Association (ASIA) Impairment Scale grades A, B, or C and injury duration at least 5 years. Subjects were matched for age and cardiovascular disease risk factors with 156 able-bodied controls.

METHODS

Diameter and blood velocity were determined with subject at rest via ultrasound in superficial femoral, popliteal, brachial, and carotid arteries. Mean shear, antegrade shear, retrograde shear, and oscillatory shear index were calculated.

RESULTS

Oscillatory shear index was lower in SCI compared to controls for superficial femoral (0.16 ± 0.10 vs. 0.26 ± 0.06, P < 0.01) and popliteal arteries (0.20 ± 0.11 vs. 0.26 ± 0.05, P < 0.01). Mean shear rate was higher in SCI compared to controls for superficial femoral (43.54 ± 28.0 vs. 20.48 ± 13.1/second, P < 0.01) and popliteal arteries (30.43 ± 28.1 vs. 11.68 ± 9.5/second, P < 0.01).

CONCLUSIONS

The altered resting hemodynamics in SCI are consistent with an atheroprotective hemodynamic environment.

Peak and time-integrated shear rates independently predict flow-mediated dilation

BACKGROUND

To determine whether peak and time-integrated shear rates independently predict flow-mediated dilation (FMD).

METHODS

Eleven physically active (25 ± 5 years old) male subjects were tested. FMD was defined as the shear rate-diameter relationship. Hierarchical linear modeling was used to estimate brachial artery diameter change with repeated measures of shear rate nested within each subject. Two models were tested: 1) FMD was induced using ischemia-induced hyperemia (2, 4, 6, and 10 minutes); and 2) FMD was induced following transient (ischemia) and steady-state (forearm heating and handgrip exercise) increases in shear rate. For both models we determined whether peak, in addition to time-integrated shear rates, explained a significant portion of variation for diameter change.

RESULTS

Model 1: Time integrated shear rates explained most of the variation for diameter change. However, peak shear rate explained an additional significant portion of variation. Model 2: The transient condition resulted in significantly (p = 0.012) smaller diameter change per shear rate change than the steady-state condition. However, when specifying peak shear rate as a covariate, the difference between conditions became nonsignificant (p = 0.138).

CONCLUSIONS

Peak and time-integrated shear rates independently predict FMD. Future studies using the FMD test should consider both parameters.

Velocity acceleration as a determinant of flow-mediated dilation

Shear stress is the established stimulus for flow-mediated dilation (FMD). In vivo, shear stress is typically estimated using mean blood velocity. However, mean blood velocity may not adequately characterize the shear stimulus. Pulsatile flow results in large shear gradients (velocity acceleration) at the onset of flow. The purpose of this study was to determine the importance of velocity acceleration to FMD. We define FMD as the brachial artery shear rate-diameter slope. Fourteen physically active, young (26 ± 5 years), male subjects were tested. Progressive forearm heating and handgrip exercise elicited steady-state increases in shear rate. FMD was measured prior to and following induced increases in velocity acceleration. Velocity acceleration was increased by inflating a tourniquet around the forearm to 40 mm Hg. Hierarchical linear modeling was used to estimate change in diameter with repeated measures of shear stress nested within each subject. Averaged across conditions, the 40 mm Hg cuff resulted in a 14% increase in velocity acceleration (p = 0.001). FMD was attenuated by 11.0% (p = 0.015) for the acceleration vs. control condition. However, after specifying velocity acceleration as a covariate, FMD was no longer significantly (p = 0.619) different between acceleration and control conditions. This finding suggests that mean blood velocity alone may not adequately characterize the shear stimulus.

Use of ultrasound for non-invasive assessment of flow-mediated dilation

The pathological complications of atherosclerosis, namely heart attacks and strokes, remain the leading cause of mortality in the Western world. Preceding atherosclerosis is endothelial dysfunction. There is therefore interest in the application of non-invasive clinical tools to assess endothelial function. The flow-mediated dilation (FMD) test is the standard tool used to assess endothelial function. Reduced FMD is an early marker of atherosclerosis and has been noted for its capacity to predict future cardiovascular disease events. This review discusses the measurement of endothelial function using ultrasound, with a focus on the FMD technique.

The importance of velocity acceleration to flow-mediated dilation

The validity of the flow-mediated dilation test has been questioned due to the lack of normalization to the primary stimulus, shear stress. Shear stress can be calculated using Poiseuille's law. However, little attention has been given to the most appropriate blood velocity parameter(s) for calculating shear stress. The pulsatile nature of blood flow exposes the endothelial cells to two distinct shear stimuli during the cardiac cycle: a large rate of change in shear at the onset of flow (velocity acceleration), followed by a steady component. The parameter typically entered into the Poiseuille's law equation to determine shear stress is time-averaged blood velocity, with no regard for flow pulsatility. This paper will discuss (1) the limitations of using Posieuille's law to estimate shear stress and (2) the importance of the velocity profile-with emphasis on velocity acceleration-to endothelial function and vascular tone.

Evidence for greater burden of peripheral arterial disease in lower extremity arteries of spinal cord-injured individuals

Spinal cord injury leads to increased risk for cardiovascular disease and results in greater risk of death. Subclinical markers of atherosclerosis have been reported in carotid arteries of spinal cord-injured individuals (SCI), but the development of lower extremity peripheral arterial disease (PAD) has not been investigated in this population. The purpose of this study was to determine the effect of spinal cord injury on ankle-brachial index (ABI) and intima-media thickness (IMT) of upper-body and lower-extremity arteries. We hypothesized that the aforementioned measures of lower-extremity PAD would be worsened in SCI compared with controls and that regular participation in endurance exercise would improve these in both groups. To test these hypotheses, ABI and IMT were determined in 105 SCI and compared with 156 able-bodied controls with groups further subdivided into physically active and sedentary. ABIs were significantly lower in SCI versus controls (0.96 ± 0.12 vs. 1.06 ± 0.07, P < 0.001), indicating a greater burden of lower-extremity PAD. Upper-body IMTs were similar for brachial and carotid arteries in controls versus SCI. Lower extremity IMTs revealed similar thicknesses for both superficial femoral and popliteal arteries, but when normalized for artery diameter, individuals with SCI had greater IMT than controls in the superficial femoral (0.094 ± 0.03 vs. 0.073 ± 0.02 mm/mm lumen diameter, P < 0.01) and popliteal (0.117 ± 0.04 vs. 0.091 ± 0.02 mm/mm lumen diameter, P < 0.01) arteries. The ABI and normalized IMT of SCI compared with controls indicate that subclinical measures of lower-extremity PAD are worsened in individuals with SCI. These findings should prompt physicians to consider using the ABI as a screening method to detect lower-extremity PAD in SCI.

Assessment of flow-mediated dilation in humans: a methodological and physiological guideline

Endothelial dysfunction is now considered an important early event in the development of atherosclerosis, which precedes gross morphological signs and clinical symptoms. The assessment of flow-mediated dilation (FMD) was introduced almost 20 years ago as a noninvasive approach to examine vasodilator function in vivo. FMD is widely believed to reflect endothelium-dependent and largely nitric oxide-mediated arterial function and has been used as a surrogate marker of vascular health. This noninvasive technique has been used to compare groups of subjects and to evaluate the impact of interventions within individuals. Despite its widespread adoption, there is considerable variability between studies with respect to the protocols applied, methods of analysis, and interpretation of results. Moreover, differences in methodological approaches have important impacts on the response magnitude, can result in spurious data interpretation, and limit the comparability of outcomes between studies. This review results from a collegial discussion between physiologists with the purpose of developing considered guidelines. The contributors represent several distinct research groups that have independently worked to advance the evidence base for improvement of the technical approaches to FMD measurement and analysis. The outcome is a series of recommendations on the basis of review and critical appraisal of recent physiological studies, pertaining to the most appropriate methods to assess FMD in humans.

Low-frequency electric muscle stimulation combined with physical therapy after total hip arthroplasty for hip osteoarthritis in elderly patients: a randomized controlled trial

OBJECTIVE

To assess the effects of low-frequency electric muscle stimulation associated with usual physiotherapy on functional outcome after total hip arthroplasty (THA) for hip osteoarthritis (OA) in elderly subjects.

DESIGN

Randomized controlled trial; pre- and posttreatment measurements.

SETTING

Hospital rehabilitation department.

PARTICIPANTS

Subjects (N=29) referred to the rehabilitation department after THA for hip OA.

INTERVENTIONS

The intervention group (n=16; 78+/-8 y) received simultaneous low-frequency electric muscle stimulation of bilateral quadriceps and calf muscles (highest tolerated intensity, 1h session, 5 d/wk, for 5 weeks) associated with conventional physical therapy including resistance training. The control group (n=13; 76+/-10 y) received conventional physical therapy alone (25 sessions).

MAIN OUTCOME MEASURES

Maximal isometric strength of knee extensors, FIM instrument, before and after; a six-minute walk test and a 200 m fast walk test, after; length of stay (LOS).

RESULTS

Low-frequency electric muscle stimulation was well tolerated. It resulted in a greater improvement in strength of knee extensors on the operated side (77% vs 23%; P<.01), leading to a better balance of muscle strength between the operated and nonoperated limb. The low-frequency electric muscle stimulation group also showed a greater improvement in FIM scores, though improvements in the walk tests were similar for the 2 groups, as was LOS.

CONCLUSIONS

Low-frequency electric muscle stimulation is a safe, well-tolerated therapy after THA for hip OA. It improves knee extensor strength, which is one of the factors leading to greater functional independence after THA.

Low-frequency electromyostimulation and chronic heart failure

Low-frequency electromyostimulation (EMS) acts on the skeletal muscle abnormalities that aggravate intolerance to effort in patients with chronic heart failure (CHF). It improves the oxidative capacity of muscles and thus enhances aerobic performance and physical capacity to almost the same degree, as does conventional physical training. No local or hemodynamic intolerance has been reported, even in cases of severe CHF. However, the presence of a pacemaker is one of the relative contra-indications (prior evaluation of tolerance is required), while that of an implanted defibrillator is one of the absolute contra-indications. EMS is an alternative to physical effort training when the latter is impossible due to a high degree of deconditioning or because there is a contra-indication, which may be temporary, due to the risk of acute decompensation and/or rhythm troubles. EMS can also be used in patients waiting for a heart transplant or in CHF patients who are unwilling to engage in physical activities. As EMS is not expensive and easy to set up, its use is likely to develop in the future.

Endothelium-dependent and -independent vasodilation of the superficial femoral artery in spinal cord-injured subjects

Extreme inactivity of the legs in spinal cord-injured (SCI) individuals does not result in an impairment of the superficial femoral artery flow-mediated dilation (FMD). To gain insight into the underlying mechanism, the present study examined nitric oxide (NO) responsiveness of vascular smooth muscles in controls and SCI subjects. In eight healthy men (34 +/- 13 yr) and six SCI subjects (37 +/- 10 yr), superficial femoral artery FMD response was assessed by echo Doppler. Subsequently, infusion of incremental dosages of sodium nitroprusside (SNP) was used to assess NO responsiveness. Peak diameter was examined on a second day after 13 min of arterial occlusion in combination with sublingual administration of nitroglycerine. Resting and peak superficial femoral artery diameter in SCI subjects were smaller than in controls (P < 0.001). The FMD response in controls (4.2 +/- 0.9%) was lower than in SCI subjects (8.2 +/- 0.9%, P < 0.001), but not after correcting for area under the curve for shear rate (P = 0.35). When expressed as relative change from baseline, SCI subjects demonstrate a significantly larger diameter increase compared with controls at each dose of SNP. However, when expressed as a relative increase within the range of diameter changes [baseline (0%) - peak diameter (100%)], both groups demonstrate similar changes in response to SNP. Changes in diameter during SNP infusion and FMD response are larger in SCI subjects compared with controls. When these results are corrected, superficial femoral artery FMD and NO sensitivity in SCI subjects are not different from those in controls. This illustrates the importance of appropriate data presentation and suggests that, subsequent to structural inward remodeling of conduit arteries as a consequence of extreme physical inactivity, arterial function is normalized.

Neuromuscular electrical stimulation of completely paralyzed abdominal muscles in spinal cord-injured patients: a pilot study

STUDY DESIGN

Prospective placebo-controlled.

OBJECTIVE

The effect of abdominal neuromuscular electrical stimulation (NMES) in patients with spinal cord injury. The principal parameters observed in this study are lung capacity, colonic transit, patient satisfaction of used method and of aesthetics effect on abdominal wall.

SETTINGS

Centre de Traumatologie et de Réadaptation, Brussels, Belgium.

METHODS

A total of 10 volunteers participated in this study and were assigned to two groups-the effective electrical stimulation group (ESG) and the placebo-controlled group (PG). NMES of abdominal muscles was performed 25 min per day for 8 weeks.

RESULTS

NMES significantly decreased forced vital capacity (FVC) in ESG but not in PG. In ESG, colonic transit was accelerated in ascending, transverse and descending colon but transit in rectosigmoideum was not affected. In PG, no variations in colonic transit were observed. Satisfaction scale shows a better influence on aesthetics effect in ESG than in PG.

CONCLUSION

This pilot study shows that NMES of paralyzed abdominal muscles positively affects colonic transit except in rectosigmoideum segment and negatively affects FVC. It could be a simple self-used method to regulate colonic transfer with considerably good cosmetic effect on abdominal wall. However, regular verification of FVC will probably be necessary.