Lack of functional effects of neuromuscular electrical stimulation on skeletal muscle oxidative metabolism in healthy humans

Abstract

-A recent study has demonstrated that neuromuscular electrical stimulation (NMES) determines, in vitro, a fast-to-slow shift in the metabolic profile of muscle fibers. The aim of the present study was to evaluate if, in the same subjects, these changes would translate, in vivo, into an enhanced skeletal muscle oxidative metabolism. Seven young men were tested (cycle ergometer) during incremental exercises up to voluntary exhaustion and moderate and heavy constant-load exercises (CLE). Measurements were carried out before and after an 8-wk training program by isometric bilateral NMES (quadriceps muscles), which induced an ϳ25% increase in maximal isometric force. Breathby-breath pulmonary O2 uptake (V O2) and vastus lateralis oxygenation indexes (by near-infrared spectroscopy) were determined. Skeletal muscle fractional O2 extraction was estimated by near-infrared spectroscopy on the basis of changes in concentration of deoxygenated hemoglobin ϩ myoglobin. Values obtained at exhaustion were considered "peak" values. The following functional evaluation variables were unaffected by NMES: peak V O2; gas exchange threshold; the V O2 vs. work rate relationship (O2 cost of cycling); changes in concentration of deoxygenated hemoglobin ϩ myoglobin vs. work rate relationship (related to the matching between O2 delivery and V O2); peak fractional O2 extraction; V O2 kinetics (during moderate and heavy CLE) and the amplitude of its slow component (during heavy CLE). Thus NMES did not affect several variables of functional evaluation of skeletal muscle oxidative metabolism. Muscle hypertrophy induced by NMES could impair peripheral O2 diffusion, possibly counterbalancing, in vivo, the fast-to-slow phenotypic changes that were observed in vitro, in a previous work, in the same subjects of the present study. strength training; muscle hypertrophy; near-infrared spectroscopy; gas exchange kinetics NEUROMUSCULAR ELECTRICAL STIMULATION (NMES) (26, 28) is widely utilized as a complement to voluntary exercise in athletes (27) and in patients, such as those with heart failure (46), chronic obstructive pulmonary disease (34), or cancer (6). NMES represents an obligatory choice for training in patients who cannot perform voluntary contractions, such as those with spinal cord lesions (10), or in patients immobilized for fractures or following ligament reconstruction surgery (42). It is well established that NMES leads to significant increases in muscle mass and maximal voluntary strength (13,26,39).The effects of NMES on oxidative metabolism appear rather controversial. At molecular level, Perez et al. (36) reported a higher succinic dehydrogenase activity after NMES training, whereas both citrate synthase and phosphofructokinase activities were unchanged. Kim et al. (21) reported, after a NMES training program, no changes in citrate synthase activity and number of capillaries. Nuhr et al. (35) showed an increase in the activity of citrate synthase associated with a decrease in the activity of glyceraldehyde phosphate dehydrogenase. Int...

Oxygen delivery-utilization mismatch in contracting locomotor muscle in COPD: peripheral factors

“…Nevertheless, in healthy young subjects, chronic NMES has been found recently to produce no improvement in contracting muscle oxygenation despite increasing maximal isometric force (41). Whether similar adaptations (or lack thereof) in Q O 2 /V O 2 control occur in the lower limb muscle of COPD patients following NMES training remains to be determined.…”

PlanHab*: hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone

“…Data obtained during exercise were expressed as a percentage of the value of maximal muscle deoxygenation obtained in each subject by inflating a pressure cuff (at 300–350 mmHg) at the inguinal crease of the thigh for a few minutes, until the ∆[deoxy(Hb + Mb)] increase reached a plateau (Porcelli et al . ).…”

“…A 'physiological calibration' of [deoxy(Hb + Mb)] values was performed by inducing a transient ischaemia of the limb when the subject was sitting on the ergometer few minutes after the exercise. Data obtained during exercise were expressed as a percentage of the value of maximal muscle deoxygenation obtained in each subject by inflating a pressure cuff (at 300-350 mmHg) at the inguinal crease of the thigh for a few minutes, until the [deoxy(Hb + Mb)] increase reached a plateau (Porcelli et al 2012).…”

Effects of Neuromuscular Electrical Stimulation Training on Endurance Performance

“…High-frequency NMES training also appears to have a negligible influence on functional endurance, as illustrated for example by maximal oxygen consumption results (Figure 1A) (Pérez et al, 2002; Porcelli et al, 2012). These limited effects of high-frequency NMES training on endurance performance are somewhat surprising for different reasons.…”

“…For clarity purposes, we refer to muscle endurance as the exercise-induced decline in voluntary or electrically-evoked force (Duchateau and Hainaut, 1988; Gondin et al, 2006) or the endurance time of a sustained single-joint contraction (Gondin et al, 2006). In contrast, we refer to functional endurance as the maximal oxygen consumption or workload (Pérez et al, 2002; Porcelli et al, 2012), the distance covered in a given time (e.g., 6-minute walk test) or the endurance time (Kim et al, 1995) for whole-body exercises such as walking and cycling. In the last section, we will provide some recommendations for better clinical use of NMES, and suggest potential directions for future research.…”