Intermittent stimulation enhances function of conditioned muscle

Effect of patterned electrical neuromuscular stimulation on vertical jump in collegiate athletes

Background:

Patterned electrical neuromuscular stimulation (PENS) uses the electrical stimulation of sensory and motor nerves to achieve a skeletal muscle contraction using an electromyogram-derived functional pattern. PENS is used extensively for neuromuscular reeducation and treatment of muscle disuse atrophy.

Purpose:

To explore the effectiveness of PENS as applied to the quadriceps muscles on the vertical jump of an athletic population.

Study Design:

Experimental with control and repeated measures over time.

Methods:

Healthy college athletes (54 women, 75 men) were divided into 3 groups (control, n = 30; jump, n = 33; and jump with PENS, n = 63). There was no difference among groups’ height and weight. Athletes performed a baseline standing vertical jump using a vertical jump system. The control group continued its normal daily activities with no jumping tasks included. The jump groups performed 3 sets of 12 repetitions with a 2-minute rest between sets at a frequency of 3 times per week. The PENS group did the jumping with the coordination of an electrical stimulation system. Vertical jump was retested after 6 weeks of intervention and 2 weeks after cessation.

Results:

A 3-way repeated measures analysis of variance for time (control, jump alone, jump with PENS) revealed a significant difference (P < 0.05) for time and an interaction between time and treatment, as well as a significant difference for the PENS group from baseline to posttest and for the jump group from posttest to follow-up jump. There was no significant difference between groups for the baseline vertical jump.

Conclusions:

This study demonstrated that 6 weeks of vertical jump training coordinated with PENS resulted in a greater increase than jumping only or control. This pattern of stimulation with PENS in combination with jump training may positively affect jumping.

Mechanical properties of the latissimus dorsi muscle after cyclic training

Cardiomyoplasty is a procedure developed to improve heart performance in patients suffering from congestive heart failure. The latissimus dorsi (LD) muscle is surgically wrapped around the failing ventricles and stimulated to contract in synchrony with the heart. The LD muscle is easily fatigued and as a result is unsuitable for cardiomyoplasty. For useful operation as a cardiac-assist device, the fatigue resistance of the LD muscle must be improved while retaining a high power output. The LD muscle of rabbits was subjected to a training regime in which cyclic work was performed. Training transformed the fiber-type composition from approximately equal proportions of fast oxidative glycolytic (FOG) and fast glycolytic (FG) fibers to one composed of almost entirely of FOG with no FG, which increased fatigue resistance while retaining rapid contraction kinetics. Muscle mass and cross-sectional area increased but power output decreased, relative to control muscles. This training regime represents a significant improvement in terms of preserving muscle mass and power compared with other training regimes, while enhancing fatigue resistance, although some fiber damage occurred. The power output of the trained LD muscle was calculated to be sufficient to deliver a significant level of assistance to a failing heart during cardiomyoplasty.