Longevity

Can You Really Grow Muscle Effortlessly With Electricity?

Posted on 10 January 2023

One of the most effective things you can do to keep feeling young into old age is to keep your muscles strong. Age-related muscle wasting is a big contributor to frailty in old age and is strongly correlated with increased mortality from all causes. The most effective way to preserve strong muscles is through exercise, especially resistance training. While it’s never too late to start exercising, it can be very difficult for those who have already lost a substantial amount of muscle strength or cardiorespiratory fitness. Many older people would benefit from an intervention that could enhance muscle strength even slightly without requiring exercise. Enter electrical muscle stimulation (EMS), a technique that could be used to stimulate muscle development without the recipient having to lift a finger. What’s the evidence behind this intervention, and how far do its benefits extend? Can even young, healthy people benefit from it? Let’s take a look.

The decline in muscle strength with age. This graph shows the decrease in average dorsiflexor strength with age in males (black) and females (white).
Source

What is EMS and how does it work?

Electrical muscle stimulation (AKA neuromuscular electrical stimulation or electromyostimulation) is, as its name implies, about stimulating muscle tissue using electrical currents. During EMS, electrodes are placed on the skin over the muscles to be stimulated, and a small electric current is applied in weak pulses. These electrical pulses cause the nerves controlling muscle contraction to fire, which triggers the contraction of muscle fibres they control. By altering the amplitude and frequency of the pulses, the number and type of muscle fibres recruited can be controlled. This allows EMS to potentially activate nearly 100% of muscle fibres, which would normally require multiple high intensity exercises.

An athlete receiving EMS applied to the hamstrings
By Gciriani – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=36476961

Scientists still don’t fully understand how EMS benefits the muscle, but there are several likely mechanisms. EMS damages muscle tissue in a similar way to regular exercise, and seems to alter the production of proteins involved in muscle growth. EMS may also have neuromuscular benefits – that is to say, it may improve muscle strength through changes in the central nervous system. Scientists are increasingly realising that the deterioration of the synapses where motor nerves deliver signals to the muscle fibres (called neuromuscular junctions) is responsible for a large part of age-related loss of muscle strength. EMS may even promote beneficial changes in the brain by activating sensory neurons that deliver information about muscle movements back to the central nervous system. However, this might be more relevant to rehabilitation of people with a loss of motor control, such as following a spinal cord injury.

Who is EMS for?

As we’ve just mentioned, EMS has been used to help rehabilitate those who have suffered neurological injuries. Stimulations can be adapted to generate certain motions such as grasping or walking, which can help patients to regain control of their movements following an injury. This application of EMS is usually referred to as functional electrical stimulation (FES). Similarly, EMS has been used to help preserve muscle function during an extended period of disuse, such as during recovery following an operation.

When it comes to ageing healthily, we are more interested in using EMS to improve muscle strength in elderly people. EMS could be used either as a way to enhance muscle development when combined with exercise, or as an alternative to exercise in those who are already too unhealthy to exercise effectively.

EMS may be beneficial for healthy people who are looking to gain muscle through exercise. Since EMS doesn’t load the joints, it can be used while recovering from certain injuries. As already mentioned, EMS can be configured to recruit more ‘fast twitch’ or ‘slow twitch’ muscle fibres and can also recruit a greater proportion of one’s muscle fibres than would normally be used in a given exercise. As a result, EMS could be used in conjunction with regular exercise to more fully activate a muscle and achieve greater gains in strength.

There’s also interest in EMS as a weight loss strategy. EMS increases calorie expenditure in the short term by stimulating muscle contraction. EMS may also aid weight loss in the long term by raising muscle strength and allowing the recipient to exercise more.

What does the research say?

For untrained older adults:

Some clinical trials of EMS in elderly patients have shown promising results. Take this one for example, in which researchers found that 16 elderly participants had greater mobility, increased muscle fibre thickness and improved molecular markers of muscle function and growth after 24 sessions of EMS knee extension, which they performed themselves in their own homes. Other small trials have found similar improvements, but these studies taken together still aren’t really enough to draw any firm conclusions. One meta-analysis of 16 studies, whose participants were predominantly untrained adults in middle age or older, found a significant increase in muscle mass and strength with EMS, though the results of the different studies were very variable. In another more focussed meta analysis, published in 2020, researchers looked at only the EMS studies in which there was a control group in which elderly participants received a placebo or no intervention. They did not find a significant benefit for EMS, but concluded that the merits of the treatment were still unclear due to insufficient data.

This graph shows how likely someone is to die from any cause based on their muscle characteristics. LMM stands for low muscle mass, and LMS for low muscle strength. You can see that for two people with adequate muscle mass, someone with low muscle strength has around twice the risk of death. An intervention that could improve muscle strength even by a small amount could greatly reduce mortality.
Source

For fit, active adults:

For people looking to use EMS to enhance their regular training routine, many studies appear to show beneficial effects when EMS is applied during a given exercise. Unfortunately, the results reported in these studies aren’t very consistent, probably because there are so many different ways of using EMS devices. The amplitude, frequency, and duration of the pulse delivered to the muscle can affect how the muscle contracts, such as by recruiting different types of muscle fibre. That’s before taking into consideration factors like the intensity and type of exercise, the frequency of sessions and so on. Furthermore, many studies looked at before-and-after effects of EMS rather than using a control group receiving ‘fake’ EMS. This means that there could have been a sizable placebo effect influencing the results.

One meta-analysis looked at 19 studies in which young, healthy participants receiving EMS and participants in the control group did equal volumes of strength training. They found no significant difference between the effectiveness of the two training methods. So while EMS might be helpful for those unable to train at full capacity (due to injury for example), it may not add anything on top of an already effective training routine. Once again, more evidence is needed to tease out the benefits of EMS with different settings for specific scenarios.

It’s worth mentioning here that using EMS for the purpose of muscle development isn’t without risk, as EMS damages muscle tissue in a similar way to regular training, meaning that it is possible to over-train. There have even been some cases of rhabdomyolysis, a potentially fatal condition in which proteins released by damaged muscle can cause kidney failure.

For weight loss:

Finally, we come to weight loss. While research in this area is limited, there are some reasons to believe that EMS could be useful here. As you might expect for an intervention that activates a large proportion of muscle fibres, EMS can significantly increase calorie expenditure both during and after the treatment has ended. One study found that EMS applied to the abs, glutes, quads and hamstrings resulted in subjects burning around 75 additional Calories per hour. While this isn’t negligible, it’s well below the rate of energy expenditure during moderate exercise: a brisk walk can burn upwards of 200 additional Calories per hour. A meta analysis of studies in non-athletic adults found that EMS was associated with a reduction in body fat, but this wasn’t statistically significant. However, many of the studies used EMS in addition to other weight loss strategies, so the effects of EMS were difficult to disentangle. On the whole, EMS could be valuable when used in conjunction with conventional weight loss strategies, but probably can’t replace them.

Photo by i yunmai on Unsplash

So, EMS seems like it could be very valuable in a range of applications, but we really need more research. We need to know which people specifically will benefit from EMS the most, and how it should be applied to yield maximum benefits.


References

Physical Exercise in Aging: Nine Weeks of Leg Press or Electrical Stimulation Training in 70 Years Old Sedentary Elderly People: https://doi.org/10.4081%2Fejtm.2015.5374

Neuromuscular Electrical Stimulation Training vs. Conventional Strength Training: A Systematic Review and Meta-Analysis of the Effect on Strength Development: https://doi.org/10.1519/jsc.0000000000004119

Post-operative electrical muscle stimulation attenuates loss of muscle mass and function following major abdominal surgery in older adults: a split body randomised control trial : https://doi.org/10.1093/ageing/afac234

Resistance Exercise, Electrical Muscle Stimulation, and Whole-Body Vibration in Older Adults: Systematic Review and Meta-Analysis of Randomized Controlled Trials: https://doi.org/10.3390%2Fjcm9092902

Effects of Whole-Body Electromyostimulation on the Energy-Restriction-Induced Reduction of Muscle Mass During Intended Weight Loss: https://doi.org/10.3389/fphys.2019.01012

Efficacy of Whole-Body Electromyostimulation (WB-EMS) on Body Composition and Muscle Strength in Non-athletic Adults. A Systematic Review and Meta-Analysis: https://doi.org/10.3389/fphys.2021.640657

Effect of Neuromuscular Electrical Muscle Stimulation on Energy Expenditure in Healthy Adults: https://doi.org/10.3390%2Fs110201932

Electrical Stimulation Counteracts Muscle Decline in Seniors: https://doi.org/10.3389%2Ffnagi.2014.00189

Resistance Exercise, Electrical Muscle Stimulation, and Whole-Body Vibration in Older Adults: Systematic Review and Meta-Analysis of Randomized Controlled Trials: https://doi.org/10.3390%2Fjcm9092902

Why brain-controlled neuroprosthetics matter: mechanisms underlying electrical stimulation of muscles and nerves in rehabilitation: https://doi.org/10.1186/s12938-020-00824-w

Two Cases of Rhabdomyolysis After Training With Electromyostimulation by 2 Young Male Professional Soccer Players: https://doi.org/10.1097/jsm.0000000000000153

Effect of Electromyostimulation Training on Muscle Strength and Sports Performance: http://dx.doi.org/10.1519/SSC.0b013e3182079f11

Neuromuscular electrical stimulation increases muscle protein synthesis in elderly type 2 diabetic men: https://doi.org/10.1152/ajpendo.00138.2012

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