Paradigms of Lower Extremity Electrical Stimulation Training After Spinal Cord Injury.

Skeletal muscle atrophy, increased adiposity and reduced physical activity are key changes observed after spinal cord injury (SCI) and are associated with numerous cardiometabolic health consequences. These changes are likely to increase the risk of developing chronic secondary conditions and impact the quality of life in persons with SCI. Surface neuromuscular electrical stimulation evoked resistance training (NMES-RT) was developed as a strategy to attenuate the process of skeletal muscle atrophy, decrease ectopic adiposity, improve insulin sensitivity and enhance mitochondrial capacity.

Effects of electrical stimulation parameters on fatigue in skeletal muscle.

Study Design: Experimental laboratory study.

Objectives: The primary purpose was to investigate the independent effects of current amplitude, pulse duration, and current frequency on muscle fatigue during neuromuscular electrical stimulation (NMES). A second purpose was to determine if the ratio of the evoked torque to the activated area could explain muscle fatigue.

The role of pulse duration and stimulation duration in maximizing the normalized torque during neuromuscular electrical stimulation.

Study Design: Controlled laboratory study

Objectives: To determine the effects of pulse duration and stimulation duration on the evoked torque after controlling for the activated area by using magnetic resonance imaging (MRI).

Background: Neuromuscular electrical stimulation (NMES) is commonly used in the clinic without considering the physiological implications of its parameters.

Methods And Measures: Seven able-bodied, college students (mean +/- SD age, 28 +/- 4 years) participated in this study.

Low-frequency fatigue in individuals with spinal cord injury.

Background/objective: This study examined magnitude and recovery of low-frequency fatigue (LFF) in the quadriceps after electrically stimulated contractions in spinal cord-injured (SCI) and able-bodied subjects.

Subjects: Nine SCI (ASIA A-C, levels C5-T9, injured 13.6 +/- 12.

High specific torque is related to lengthening contraction-induced skeletal muscle injury.

Animal models implicate multiple mechanical factors in the initiation of exercise-induced muscle injury. Muscle injury has been widely studied in humans, but few data exist regarding the underlying cause of muscle injury. This study sought to examine the role of torque per active muscle volume in muscle injury.

Caffeine attenuates delayed-onset muscle pain and force loss following eccentric exercise.

Unlabelled: This double-blind, placebo-controlled, repeated-measures experiment examined the effects of a 5 mg . kg(-1) body weight dose of caffeine on delayed-onset muscle pain intensity and force loss in response to 64 eccentric actions of the dominant quadriceps induced by electrical stimulation. Low caffeine-consuming college-aged females (n = 9) ingested caffeine or placebo 24 and 48 hours following electrically stimulated eccentric exercise of the quadriceps.

Oxygen cost of dynamic or isometric exercise relative to recruited muscle mass.

Background: Oxygen cost of different muscle actions may be influenced by different recruitment and rate coding strategies. The purpose of this study was to account for these strategies by comparing the oxygen cost of dynamic and isometric muscle actions relative to the muscle mass recruited via surface electrical stimulation of the knee extensors.

Methods: Comparisons of whole body pulmonary delta VO2 were made in seven young healthy adults (1 female) during 3 minutes of dynamic or isometric knee extensions, both induced by surface electrical stimulation.

Determining the extent of neural activation during maximal effort.

Purpose: The purpose of this study was to compare the extent of neural activation assessed by the central activation ratio (CAR) versus activation estimated from T2 magnetic resonance imaging (MRI) and neuromuscular electrical stimulation (NMES).

Methods: Seven college-age individuals volunteered for this study. CAR was determined by manually superimposing a train of NMES (50 Hz, 450-mus biphasic pulses) for 1 s during a maximal voluntary effort.

Effects of neuromuscular electrical stimulation parameters on specific tension.

This study examined the effects of altering surface neuromuscular electrical stimulation (SNMES) parameters on the specific tension of the quadriceps femoris muscle. Seven able-bodied subjects had magnetic resonance images taken of both thighs prior to and immediately after four SNMES protocols to determine the activated muscle cross-sectional area (CSA). The four protocols were: (1) research (RES, 100 Hz, 450 micros, and amplitude set to evoke 75% of maximal voluntary isometric torque, MVIT); (2) pulse duration (PD, 100 Hz, 150 micros, same current as in RES); (3) frequency (FREQ, 25 Hz, 450 micros, and same current as in RES); (4) amplitude (AMP, 100 Hz, 450 mus, and current set to evoke the average of the initial torques of PD and FREQ, 45 +/- 9% of MVIT).

Lower-extremity muscle cross-sectional area after incomplete spinal cord injury.

Objectives: (1) To quantify skeletal muscle size in lower-extremity muscles of people after incomplete spinal cord injury (SCI), (2) to assess differences in muscle size between involved lower limbs, (3) to determine the impact of ambulatory status (using wheelchair for community mobility vs not using a wheelchair for community mobility) on muscle size after incomplete SCI, and (4) to determine if differential atrophy occurs among individual muscles after incomplete SCI.

Design: Case-control study.

Setting: University research setting.

Exercise responses and adaptations in rowers and spinal cord injury individuals.

Elite rowers (ROWERS) and those who have had a spinal cord injury (SCI) are different physically in many realms. Both have physical activity histories that affect their lower-extremity extensor muscles in a dramatically different fashion. ROWERS can sustain a 500-W power output during their 5- to 6-min race.

Metabolic and phenotypic characteristics of human skeletal muscle fibers as predictors of glycogen utilization during electrical stimulation.

Characteristics of skeletal muscle such as fiber type composition and activities of key metabolic enzymes have been purported to affect glycogen utilization. However, the relative importance individual factors may have in predicting glycogen utilization of individual muscle fibers has not been addressed. Thus, we sought to determine the relative importance that metabolic characteristics and phenotypic expression of individual fibers have in predicting fiber specific glycogen utilization during neuromuscular electrical stimulation (NMES) exercise.

Changes in skeletal muscle size and glucose tolerance with electrically stimulated resistance training in subjects with chronic spinal cord injury.

Objective: To determine the effect of residence-based, resistance exercise training (RET) on affected skeletal muscle size and glucose tolerance after long-standing, complete spinal cord injury (SCI).

Design: Before-after trial.

Setting: University laboratory trial.

Time course of molecular responses of human skeletal muscle to acute bouts of resistance exercise.

Resistance exercise (RE) training, designed to induce hypertrophy, strives for optimal activation of anabolic and myogenic mechanisms to increase myofiber size. Clearly, activation of these mechanisms must precede skeletal muscle growth. Most mechanistic studies of RE have involved analysis of outcome variables after many training sessions.

Trabecular bone is more deteriorated in spinal cord injured versus estrogen-free postmenopausal women.

The prevalence of osteoporosis is high among postmenopausal women and individuals sustaining a spinal cord injury (SCI). We assessed the effects of estrogen loss and unloading on the trabecular bone of the knee in women. Pre- and postmenopausal ambulatory women (n=17) were compared to pre- and postmenopausal women with SCI (n=20).

Variable-frequency-train stimulation of skeletal muscle after spinal cord injury.

Skeletal muscle, after spinal cord injury (SCI), becomes highly susceptible to fatigue. Variable-frequency trains (VFTs) enhance force in fatigued human skeletal muscle of able-bodied (AB) individuals. VFTs do this by taking advantage of the "catch-like" property of skeletal muscle.

Trabecular bone microarchitecture is deteriorated in men with spinal cord injury.

Unlabelled: Using magnetic resonance imaging, men with spinal cord injury (n = 10) were found to have fewer trabeculae that were spaced further apart in the knee than able-bodied controls of similar age, height, and weight (n = 8). The deteriorated trabecular bone microarchitecture may contribute to the increased fracture incidence after injury.

Introduction: Spinal cord injury results in a dramatic decline in areal bone mineral density (aBMD) and a marked increase in lower extremity fracture; however, its effect on trabecular bone microarchitecture is unknown.

Long-term spinal cord injury increases susceptibility to isometric contraction-induced muscle injury.

Complete spinal cord injury (SCI) results in inactivation and unloading of affected skeletal muscles. Unloading causes an increased susceptibility of muscle to contraction-induced injury. This study used magnetic resonance imaging (MRI) to test the hypothesis that isometric contractions would evoke greater muscle damage to the quadriceps femoris muscle (mQF) of SCI subjects than that of able-bodied (AB) controls.

Assessment of skeletal muscle mass in men with spinal cord injury using dual-energy X-ray absorptiometry and magnetic resonance imaging.

The purpose of this study was to determine whether the proportion of skeletal muscle in the fat-free soft tissue mass (FFST) is the same in men with spinal cord injury (SCI) and able-bodied controls. Skeletal muscle mass and FFST of the midthigh were determined by using magnetic resonance imaging and dual-energy X-ray absorptiometry, respectively, in men with long-term (>2 yr) complete SCI (n = 8) and able-bodied controls of similar age, height, and weight (n = 8). Muscle mass (1.

Increasing blood flow before exercise in spinal cord-injured individuals does not alter muscle fatigue.

Previous studies have shown increased fatigue in paralyzed muscle of spinal cord-injured (SCI) patients (Castro M, Apple D Jr, Hillegass E, and Dudley GA. Eur J Appl Physiol 80: 373-378, 1999; Gerrits H, Hopman MTE, Sargeant A, and de Haan A. Clin Physiol 21: 105-113, 2001).

Human diaphragm remodeling associated with chronic obstructive pulmonary disease: clinical implications.

Diaphragm remodeling associated with chronic obstructive pulmonary disease (COPD) consists of a fast-to-slow fiber type transformation as well as adaptations within each fiber type. To try to explain disparate findings in the literature regarding the relationship between fiber type proportions and FEV1, we obtained costal diaphragm biopsies on 40 subjects whose FEV1 ranged from 118 to 16% of the predicted normal value. First, we noted that our exponential regression model indicated that changes in FEV1 can account for 72% of the variation in the proportion of Type I fibers.

Vascular remodeling after spinal cord injury.

Purpose: Our purpose was to determine whether spinal cord injured (SCI) subjects have decreased femoral artery diameter and maximal hyperemic blood flow when expressed per unit of muscle volume compared with able-bodied (AB) individuals. A secondary purpose was to determine whether blood flow recovery rates were similar between groups.

Methods: Blood flow was measured in the femoral artery using Doppler ultrasound after distal thigh cuff occlusion of 4 and 10 min.

Fatigability and variable-frequency train stimulation of human skeletal muscles.

Background And Purpose: The quadriceps femoris (QF) and tibialis anterior (TA) muscles are often activated through the use of electrical stimulation by physical therapists. These 2 muscles are fundamentally different in regard to their fiber-type composition. Whether protocols developed using a given muscle can be applied to another muscle has seldom been questioned, even if they differ in fiber type.

Acute molecular responses of skeletal muscle to resistance exercise in able-bodied and spinal cord-injured subjects.

Spinal cord injury (SCI) results in muscle atrophy, which contributes to a number of health problems, such as cardiovascular deconditioning, metabolic derangement, and osteoporosis. Electromyostimulation (EMS) holds the promise of ameliorating SCI-related muscle atrophy and, therefore, improving general health. To date, EMS training of long-term SCI subjects has resulted in some muscle hypertrophy but has fallen short of normalizing muscle mass.

Blood flow and muscle fatigue in SCI individuals during electrical stimulation.

Our purpose was to measure blood flow and muscle fatigue in chronic, complete, spinal cord-injured (SCI) and able-bodied (AB) individuals during electrical stimulation. Electrical stimulation of the quadriceps muscles was used to elicit similar activated muscle mass. Blood flow was measured in the femoral artery by Doppler ultrasound.