Why is fatigue a concern when using functional electrical stimulation (FES) for training?

• A. It reduces the specificity of muscle activation.
• B. Electrical stimulation can cause fatigue only in untrained individuals.
• C. Fatigue is only a concern if the user is not trained.
• D. Because electrical stimulation can cause rapid muscle fatigue during cyclical tasks like biking or rowing.

Answer: (D)

Fatigue with FES training shows up because electrical stimulation drives muscle contractions in a way that isn’t the same as voluntary effort. It tends to recruit many fibers quickly and in a more synchronized fashion, often engaging fast-fatigable fibers that tire faster. When these contractions are repeated in cyclical tasks like biking or rowing, there’s little time for recovery, so metabolite buildup and reduced muscle excitability accumulate rapidly. As a result, force output drops during a training session, making fatigue a key concern to manage through adjustments to stimulation, rest, and task pacing.