Electrical stimulation of muscles is used by some athletes to increase strength. This is the type of training you see sometimes where electrodes are placed on the skin and the muscles twitch from the current. Theoretically, this method can be used as a means of improving recovery too, but research in this area has been limited. In a study this month in the Journal of Strength and Conditioning Research, investigators took a look at the available evidence to see if there was a scientific consensus on its use as a recovery aid.
You may have noticed some combat athletes stand in between rounds of fighting, or have their legs massaged. They do this to improve blood flow, and theoretically, electrical stimulation works in the same way. Some of your capillaries, which are the blood vessels between arteries and veins, are so small that blood cells have to travel through single-file. When you exercise the muscle tissues start to swell, and when this happens, blood flow to these tiny blood vessels can be cut off.
These effects on blood flow can reduce both acute recovery and between-workout recovery. Metabolic waste products can back up in the muscles and valuable nutrients can’t get in. Besides simply waiting it out, athletes can alleviate these issues in a few ways. Treatments that reduce inflammation, like ice baths and other cold temperature treatments, might help, as can the use of mechanical action.
Mechanical action treatment assists the heart in getting blood through trouble areas. The aforementioned standing in between rounds allows the muscles themselves to help, whereas massage uses an outside force to move blood through. Myofascial release is another common mechanical action treatment. Electrical stimulation would function like a combination of external and internal mechanical action. The stimulation causes the muscles to lightly twitch, and the researchers in the Journal study wondered if that would be enough to assist in recovery.
To find out, the researchers performed a literature review, examining the studies they found relevant to the topic from 1970 up to 2012. During that time period they found only thirteen studies used on humans that tested recovery variables such as soreness, muscle damage indicators, and performance.
On the subjective scales, like perceived soreness, the electrical stimulation actually did the trick. Compared to passive recovery, meaning doing nothing specific to recover except relaxing, the electrical stimulation showed evidence of working better to lower blood lactate levels, a metabolic byproduct of exercise. However, electrical stimulation performed about as well as traditional recovery methods (like a jog or a massage) when it came to improving performance or clearing metabolic waste products.
Electrical stimulation does seem to work at enhancing blood flow through activation of the muscles. In fact, it works about as well as many other recovery methods. The major problem is that there is a great degree of variability between people when it comes to the exact level of electrical stimulation required. It is possible to make it too intense, creating either pain or further muscle fatigue. While electrical stimulation may work pretty well in studies, it doesn’t work well enough to offset its potential downsides. Stick with the old standards for recovery.
References:
1. John Malone, et. al., “Neuromuscular electrical stimulation (NMES) during recovery from exercise: A systematic review,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000426
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