Louis Crowe

Prolonged Electrical Muscle Stimulation Exercise Improves Strength, Peak VO2, and Exercise Capacity in Patients With Stable Chronic Heart Failure

BACKGROUND Exercise training can help patients with chronic heart failure but may be limited in its applicability due to age and other comorbidities. This investigation evaluated training responses to prolonged electrical muscle stimulation (EMS) in patients with stable chronic heart failure. METHODS AND RESULTS In a crossover designed study, 10 patients (age 66 +/- 6.5 years, 9 male) were randomized to 8 weeks of training or habitual activity before crossing over to the other limb after a washout period of 2 weeks. Training consisted of electrical muscle stimulation of the major leg muscles for a minimum of 1 hour, 5 days a week. Peak oxygen consumption, 6-minute walking distance test, body mass index, and quadriceps muscle strength were the end points. At baseline the mean values for peak oxygen consumption (VO(2)), 6-minute walking distance, quadriceps strength, and body mass index were 19.5 +/- 3.5 mL x kg x min, 415.1 +/- 56.6m, 377.9 +/- 110.4N, and 27.9 +/- 3.1 kg/m(2), respectively. After training, peak VO(2) increased to 21.2 +/- 5.1 mL x kg x min (P < .05), walking distance increased to 454.9 +/- 54.5M (P < .005), quadriceps strength increased to 404.9 +/- 108.6N (P < .005), whereas we did not observe a significant effect on body mass index (P > .05). CONCLUSIONS EMS can be used in sedentary adults with stable chronic heart failure to improve physical fitness and functional capacity. It may provide a viable alternative for patients unable to undertake more conventional forms of exercise.

Electrical stimulation of unloaded muscles causes cardiovascular exercise by increasing oxygen demand

Background The development of new strategies to encourage increased levels of physical activity can help to reduce the incidence of cardiovascular disease. A new system of electrical muscle stimulation (EMS) has been developed that attempts to cause an increase in energy expenditure by mimicking the action of shivering in the body. The purpose of this study was to show that this form of EMS is capable of eliciting a cardiovascular exercise response in healthy adults. Design An observational study. Methods Ten healthy volunteers completed a maximal treadmill test and four EMS sessions using a hand-held EMS device that delivered current to the body via five silicone rubber electrodes on each leg. At each session subjects completed 3 min stimulation at each of four stimulation outputs (10, 20, 30 and 40% of maximum output) while cardiopulmonary gas exchange and heart rate (HR) were measured. Physiological responses at increasing levels of stimulation were evaluated. Results Average (±SD) HR and oxygen consumption (VO2) levels of 67 ± 11 bpm and 4.7 ± 1.2 ml/kg per min at rest, respectively, were increased to 186 ± 10 bpm and 44.9 ± 9.8 ml/kg per min at peak exercise intensity on treadmill testing. The electrical stimulation was generally well tolerated by the subjects. Subjects demonstrated statistically significant increases in all physiological variables measured with successive increases in stimulation intensity. Peak HR and VO2 at 40% stimulation intensity were 101 ±12 bpm and 14.9 ± 4.3 ml/kg per min, respectively. Conclusions These results demonstrate that this form of EMS is capable of producing a physiological response consistent with cardiovascular exercise at mild to moderate intensities. It achieves this without producing gross movement of the limbs or loading of the joints. This EMS-induced cardiovascular exercise response could be used to promote increased levels of physical activity in populations unable to participate in voluntary exercise.

Neuromuscular electrical stimulation can elicit aerobic exercise response without undue discomfort in healthy physically active adults.

Abstract Crognale, D, De Vito, G, Grosset, J-F, Crowe, L, Minogue, C, and Caulfield, B. Neuromuscular electrical stimulation can elicit aerobic exercise response without undue discomfort in healthy physically active adults. J Strength Cond Res 27(1): 208–215, 2013—Recent studies have suggested that subtetanic neuromuscular electrical stimulation (NMES) protocols applied to the quadriceps and hamstrings may have potential as an alternative aerobic exercise modality. However, its tolerability and effectiveness in the physically active population has been questioned. The primary purpose of this study was to measure physiological and subjective responses to a modified subtetanic NMES protocol in a physically active adult population. Furthermore, the effect of habituation to stimulation on tolerability, the repeatability of response on separate days, and the differences in male and female responses to stimulation were assessed. Oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), blood lactate (BLa), rate of perceived exertion, and subjective discomfort were measured in 16 participants (8 men and 8 women) throughout a subtetanic NMES protocol performed at incremental intensities to subjective comfort threshold on 2 separate days, before and after 9 NMES habituation sessions. Peak physiological responses observed at subjective comfort threshold were consistent with therapeutic aerobic exercise intensities (51.5 ± 10.9% V[Combining Dot Above]O2max; 72.0 ± 10.9% HRmax; 4.7 ± 2.7 mMol BLa). Peak V[Combining Dot Above]O2 and current intensity achieved were significantly higher (p < 0.05), yet perceived discomfort was unchanged, after the period of habituation. However, physiological and subjective responses at equivalent stimulation intensities remained unchanged on different days. Male participants showed higher values than female participants. These results suggest that subtetanic NMES can elicit a consistent aerobic exercise response without undue discomfort and could be considered as an alternative exercise modality.

Increased Aerobic Fitness After Neuromuscular Electrical Stimulation Training in Adults With Spinal Cord Injury

OBJECTIVES To evaluate the efficacy of a novel neuromuscular electrical stimulation (NMES) system for improving aerobic fitness in individuals with spinal cord injury (SCI). It was hypothesized that training with this NMES system would increase peak oxygen consumption (Vo(2)peak) and peak heart rate (HRpeak) in a sedentary adult SCI population. DESIGN Prospective cohort study. SETTING All testing took place at a university human performance laboratory. PARTICIPANTS Volunteer participants with SCI (N=16; T4-11 American Spinal Injury Association Impairment Scale grades A and B) were recruited from the national SCI outpatient and outreach service databases. All completed the training program, but results from 2 participants were excluded because posttraining tests were invalid. Therefore, 14 participants (11 men, 3 women) completed the program and testing. INTERVENTIONS Four electrodes (175cm(2)) were placed bilaterally on the quadriceps and hamstrings muscle groups, and subtetanic contractions were elicited using an NMES device. Training was undertaken unsupervised at home for 1 hour, 5d/wk for 8 weeks. MAIN OUTCOME MEASURES An incremental treadmill wheelchair propulsion exercise test with simultaneous cardiopulmonary gas exchange analysis was used to determine Vo(2)peak and HRpeak. RESULTS A statistically significant increase in Vo(2)peak (P=.001) and HRpeak (P=.032) between baseline and follow-up was observed. CONCLUSIONS This novel form of NMES is an effective method of improving aerobic fitness in an SCI population. Results are comparable to those with current functional electrical stimulation exercise systems.

Electrical muscle stimulation for deep stabilizing muscles in abdominal wall

Low back pain is associated with dysfunction in recruitment of muscles in the lumbopelvic region. Effective rehabilitation requires preferential activation of deep stabilizing muscle groups. This study was carried out in order to quantify the response of deep stabilizing muscles (transverses abdominis) and superficial muscle in the abdominal wall (external oblique) to electrical muscle stimulation (EMS). Results demonstrate that EMS can preferentially stimulate contractions in the deep stabilizers and may have significant potential as a therapeutic intervention in this area, pending further refinements to the technology.

Alterations in body composition and spasticity following subtetanic neuromuscular electrical stimulation training in spinal cord injury

The objective of this prospective cohort study was to investigate alterations in body composition variables and spasticity following subtetanic neuromuscular electrical stimulation (NMES) training in an adult population with spinal cord injury (SCI). Fourteen sedentary adults with SCI (thoracic [T]4-T11; American Spinal Injury Association Impairment Scale A/B; time since injury: 10.17 +/- 11.17 yr) were recruited from the National SCI database. Four adhesive electrodes (175 cm2 each) were placed bilaterally on the proximal and distal quadriceps and hamstrings muscle groups and subtetanic contractions were elicited using a handheld NMES device. Lean body mass (LBM) and other body composition variables were measured using dual-energy X-ray absorptiometry. Spasticity was measured using the Spinal Cord Assessment Tool for Spastic Reflexes (SCATs) and visual analog scales. Verbal and written feedback was obtained to subjectively evaluate spasticity. LBM and spasticity measurements were taken before and after an 8 wk NMES training program in order to assess change. A statistically significant increase in lower-limb LBM, i.e., muscle tissue (p > 0.001), and a reduction in SCATs (p < 0.001) score, indicating reduced spasticity, was observed. Subjective responses were positive. Improvements in body composition and SCATs scores indicate that subtetanic NMES training elicits favorable responses and may have important clinical implications for an SCI population.

Neuro-muscular electrical stimulation training enhances maximal aerobic capacity in healthy physically active adults

Previous research has shown that a novel form of neuro-muscular electrical stimulation (NMES) can be used to bring about aerobic training effects in sedentary adults and in patients with heart failure. However, it is not clear whether this form of NMES could induce a significantly strong cardiovascular exercise effect in a more active group where a greater stimulus is required for training. In this study we investigated the aerobic training effects of repeated exposure to low frequency NMES in a group of physically active healthy adults. Results demonstrated a clinically and statistically significant training response following 18 trainings sessions, suggesting that this form of NMES has a role to play in cardiovascular exercise training in a physically active healthy population.

Comparative effect of a 1 h session of electrical muscle stimulation and walking activity on energy expenditure and substrate oxidation in obese subjects

It has previously been shown that low-frequency neuromuscular electrical stimulation (NMES) techniques can induce increases in energy expenditure similar to those associated with exercise. This study investigated the metabolic and cardiovascular effects of a 1 h session of lower limb NMES and compared cardiovascular response with that observed during walking in nine obese subjects (three males) (age = 43.8 ± 3.0 years; body mass index (BMI) = 41.5 ± 1.8 kg/m(2)). The NMES protocol consisted of delivering a complex pulse pattern to the thigh muscles for 1 h. The walking test consisted of five 4-min bouts starting at 2 km/h with 1 km/h increments up to 6 km/h. In both tests, an open-circuit gas analyser was used to assess O(2) consumption ([Formula: see text]O(2)), CO(2) production ([Formula: see text]CO(2)), respiratory exchange ratio (RER), and heart rate (HR). Rates of fat oxidation (RFO) and carbohydrate oxidation (CHO) were estimated by indirect calorimetry. One hour of NMES significantly increased [Formula: see text]O(2), HR, RER, and mean energy expenditure compared with resting values, reaching 8.7 ± 1.3 mL·min(-2)·kg(-1) (47% of [Formula: see text]O(2peak)), 114.8 ± 7.5 bpm, 0.95, and 318.5 ± 64.3 kcal/h, respectively. CHO, but not RFO, increased during 1 h of NMES. With NMES, CHO was greater and RFO was less than at all walking speeds except 6 km/h. Lactate also increased more with NMES, to 3.5 ± 0.7 mmol versus a maximum of 1.5 ± 0.3 mmol with the walking protocol. These results suggest that NMES can be used in an obese population to induce an effective cardiovascular exercise response. In fact, the observed increase in energy expenditure induced by 1 h of NMES is clinically important and comparable with that recommended in weight management programs.

Pushing out the limits of electrical stimulation. A case study in the aggressive use of an alternative to voluntary exercise

Recent advances in neuromuscular electrical stimulation (NMES) suggest that sophisticated techniques can exercise and train people aerobically. However, the limits of this exercise modality would be of interest to sportspeople, trainers and rehabilitation experts. Additionally, there are physical and other barriers which prevent many from undertaking aggressive voluntary exercise. Maximum voluntary and peak NMES efforts were assessed for 1) maximal heart rate and oxygen consumption, 2) excess postexercise oxygen consumption (EPOC), 3) lactate and 4) time-to-fatigue while exercising at 65% of predicted maximal heart rate (maximum voluntary versus peak NMES efforts). Heart rates: 195 bpm and 194 bpm; Oxygen consumption: 52 ml/kg/min and 39 ml/kg/min. EPOC: 110.5 kcal and 96.5 kcal; Lactate: 15.0 mmol/l and 15.3 mmol/l; Time-to-fatigue: 4 h and over 6 h. Sophisticated NMES compares well to voluntary exercise with potential applications for sportspeople and some who cannot exercise due to disease or injury.

Clinical application of neuromuscular electrical stimulation induced cardiovascular exercise

We need to find novel ways of increasing exercise participation, particularly in those populations who find it difficult to participate in voluntary exercise. In recent years researchers have started to investigate the potential for using electrical stimulation to artificially stimulate a pattern of muscle activity that would induce a physiological response consistent with cardiovascular exercise. Work to date has indicated that this is best achieved by using a stimulation protocol that results in rapid rhythmical isometric contractions of the large leg muscle groups at sub tetanic frequencies. Studies completed by our group indicate that this technique can serve as a viable alternative to voluntary cardiovascular exercise. Apart from being able to induce a cardiovascular exercise effect in patient populations (e.g. heart failure, COPD, spinal cord injury, obesity), this approach may also have value in promotion of exercise activity in a microgravity environment.