Sequential Segmental Neuromuscular Stimulation: An Effective Approach to Enhance Fatigue Resistance

Abstract

Electrical stimulation of skeletal muscle flaps is used clinically in applications that require contraction of muscle and force generation at the recipient site, for example, to assist a failing myocardium (cardiomyoplasty) or to reestablish urinary or fecal continence as a neo-sphincter (dynamic graciloplasty). A major problem in these applications (muscle fatigue) results from the nonphysiologic manner in which most of the fibers within the muscle are recruited in a single burst-like contraction. To circumvent this problem, current protocols call for the muscle to be put through a rigorous training regimen to transform it from a fatigue-prone to a fatigue-resistant state. This process takes several weeks during which, aside from becoming fatigue-resistant, the muscle loses power and contraction speed. This study tested the feasibility of electrically stimulating a muscle flap in a more physiologic way; namely, by stimulating different anatomical parts of the muscle sequentially rather than the entire muscle all at once. Sequential segmental neuromuscular stimulation (SSNS) allows parts of the muscle to rest while other parts are contracting. In a paired designed study in dogs (n = 7), the effects of SSNS on muscle fatigability and muscle blood perfusion in gracilis muscles were compared with conventional stimulation: SSNS on one side and whole muscle stimulation on the other. In SSNS, electrodes were implanted in the muscles in such a way that four separate segments of each muscle could be stimulated separately. Then, each segment was stimulated so that part of the muscle was always contracted while part was always resting. This type of stimulation permitted sequential yet continuous force generation. Muscles in both groups maintained an equal amount of continuous force. In SSNS muscles, separate segments were stimulated so that the duty cycle for any one segment was 25, 50, 75, or 100 percent, thus varying the amount of work and rest that any segment experienced at any one time. With duty cycles of 25, 50, and 75 percent, SSNS produced significantly (p < 0.01) enhanced resistance to fatigue. In addition, muscle perfusion was significantly (p < 0.01) increased in these sequentially stimulated muscles compared with the controls receiving whole muscle stimulation. It was concluded that SSNS reduces muscle fatigue and enhances muscle blood flow during stimulation. These findings suggest that using SSNS in clinical myoplasty procedures could obviate the need for prolonged training protocols and minimize problems associated with muscle training.

Reducing muscle fatigue during transcutaneous neuromuscular electrical stimulation by spatially and sequentially distributing electrical stimulation sources

“…This type of spatially distributed and sequentially applied stimulation is referred to as ‘sequential stimulation’ (Nguyen et al 2011). Fatigue was reduced with such stimulation in animal experimental models using spinal stimulation (Petrofsky 1978, 1979; Mushahwar and Horch 1997), intrafascicular stimulation (McDonnall et al 2004; Yoshida and Horch 1993), interfascicular stimulation (Thomsen and Veltink 1997), epineural stimulation (Petrofsky 1979), and intramuscular stimulation (Lau et al 1995; Zonnevijlle et al 2000; Lau et al 2007). …”

Minimizing muscle fatigue through optimization of electrical stimulation parameters

“…[18,38] Nevertheless, other researchers have also used a threshold of 50%. [34,39,40] Because In the present results, at lower levels of injected PA×PD, a low signal-to-noise ratio combined with low security in torque production resulted in low bilateral symmetry (see Table 1) and higher sensitivity to measurement error (e.g., when low torque levels [< 10 Nm] are generated in Figure 3). However, our measurement precision was sufficiently high at higher levels of injected PA×PD, where both torque production and fatigue were substantial that has higher clinical relevance.…”

Closed-Loop Asynchronous Neuromuscular Electrical Stimulation Prolongs Functional Movements in the Lower Body

“…However, studies comparing asynchronous to conventional stimulation have primarily focused on isometric contractions with fixed stimulation parameters [21]- [25], [28]- [32], [34], due to the fact that it is easier to control for variation in the data. Sequential stimulation has also been shown to be advantageous over conventional stimulation as a method to reduce fatigue in isometric contractions [36], [37]. However, one study [36] found that a shorter on-time (i.e., the time to keep one stimulation channel activated before switching to the next channel) resulted in less fatigue, motivating the use of asynchronous stimulation over sequential stimulation.…”

“…focused on isometric contractions with fixed stimulation parameters (i.e., open-loop stimulation) [21]- [25], [28]- [32], [34], [36], [37]. Therefore, it is presently unclear if the fatigue benefits reported for open-loop stimulation similarly applies to feedback control of NMES in man.…”