Helping Muscles Recover with Electrical Stimulation
Watching the ESPN CrossFit games last summer, it was interesting how many television advertisements were for home electrical stimulation units being marketed for “recovery.” Electrical stimulation machines have been used for decades in collegiate, professional, and Olympic training rooms facilities for decades. Over the past few years it has become increasingly apparent that small, portable devices are making their way into individual athletes’ homes and travel bags.
Neuromuscular electrical stimulation (NMES) involves the use of a device that transmits an electrical impulse through the skin via electrodes placed over selected muscle groups. In sports medicine rehabilitation, electrical stimulation is often applied to induce muscle contraction and increase blood flow through tissues. NMES intensity needs to be high enough to induce adequate muscle contraction (muscle pump function) yet not uncomfortable and not so high as to cause increased muscle fatigue.
In order to determine if electrical stimulation can improve recovery, there are a couple things to consider. First your physician or physical therapist must define recovery. In its most basic context, it involves getting the “good stuff in” and the “bad stuff out.” Inadequate muscle recovery may impair athletic performance. Recovery can be a passive process (= rest) or an active process (= movement). Passive recovery and factors that reduce blood flow, like muscle swelling after a workout, may lead to the buildup of metabolic waste and decrease the inflow of oxygen and other necessary nutrients effectively slowing recovery. In contrast, active recovery, often involving mechanical means such as external massage, riding a stationary bike on the sideline, or standing between periods in a match, may facilitate recovery through increasing or maintaining circulation. NMES causes muscles to twitch and may similarly help as an internal massage, increasing blood flow with the bodies’ “muscle pump.”
Electrical stimulation has proven to enhance blood flow. However, there is a lot of variability between people regarding how much current it takes to stimulate the muscle. This is partly due to variations in fatty and soft tissue between individuals, as well as differences in pain perception. Bodies are different, with differing amounts of muscle. Too little current and it doesn’t help. Too much and you risk muscle activation that is counter productive and painful. Published scientific studies remain unable to show that NMES was more effective when compared to more typical active or passive recovery methods. Future research may shed light on how NMES can best be used. Athletes are always looking for a way to enhance recovery in between competitions or training days in order to improve performance, and as with many aspects of sport—faster can be better. For now however, more research is needed to prove if these machines truly enhance recovery.