Electro-myo-stimulation (EMS) training can have several side effects, particularly if not used appropriately or without proper supervision[2]. One of the most significant risks is muscle damage, including the elevation of creatine-kinase (CK) activity, which can indicate muscle breakdown or injury. Rare but severe cases of rhabdomyolysis—where muscle tissue breaks down rapidly and releases harmful proteins into the bloodstream—have been reported following EMS training[2].
Other potential side effects documented include:
- Muscle pain or soreness: Many individuals may experience soreness similar to delayed onset muscle soreness (DOMS) after intense sessions.
- Temporary fatigue or weakness: Fatigue in stimulated muscle groups is common, particularly after intensive or prolonged EMS sessions.
- Skin irritation or burns: Improper electrode placement or overly high intensities may lead to skin redness, irritation, or, in rare cases, minor burns[8].
- Inter-individual variability: The degree of muscle response and the risk of side effects can vary considerably between individuals, depending on factors such as fitness level and pre-existing medical conditions[2].
Research indicates that, in healthy subjects, EMS training typically does not significantly affect blood pressure, heart rate, or oxygen uptake; however, its safety profile in people with underlying conditions remains uncertain[2].
Experts recommend a thorough medical assessment before starting EMS training—especially to screen for risk factors for muscle injury (including rhabdomyolysis) and to identify contraindications, such as certain heart conditions or malignancy[2]. The training should always be supervised by properly trained professionals to minimize risks[2].