Neuro-Muscular Electrical Stimulation

Fun Fact! No active contraction is occurring during this video! Yep, you read that right – this bicep curl is happening completely passively via a nifty machine called Neuromuscular Electrical Stimulation.

But, how? Well, muscles of the body are comprised of different types of fibres. “Slow-twitch Type 1 Muscle Fibres” produce low-force muscle contractions. They tend to have good endurance, thus fatiguing and atrophying less readily. These fibres are activated during endurance activities such as jogging, biking, walking, and postural control.

“Fast-Twitch Type 2 Muscle Fibres” are recruited when your body requires more powerful muscle contractions, and are often followed by muscle fatigue. These fibres are activated during power/strength activities such as powerlifting, jumping, sprinting, and strength training.

When we voluntarily contract a muscle, the order of recruitment is progressive: Type 1, followed by Type 2 as necessary.

Think of moving your hand to your mouth as you eat a bag of popcorn. This involves repetitive low-force bicep contractions, and your arm generally won’t feel too fatigued after performing this activity. In this example, the Slow-Twitch Type 1 Muscle Fibres are recruited. However, as more weight is placed on the bicep muscle, we start to recruit type 2 muscle fibres to meet this increased demand. For example, if we replace the popcorn with a dumbbell, we are now recruiting both Type 1 and Type 2 fibres. Finally, as we perform a 1 Rep Max exercise, we must recruit even more Type 2 muscle fibres to meet increased demand on the muscle.

NMES uses electrical impulses to cause passive stimulation of muscles in a reverse order of recruitment: Type 2, followed by type 1. What good is this? Well, when coupled with an active exercise, NMES allows for a fuller contraction of the muscle than would be possible without, by recruiting as many muscle fibres as possible – thus speeding up the strengthening process!