When you do hip exercises, how hard your gluteus medius muscle is working can only be partly guessed by measuring its electrical activity — it explains just under 1 in 5 parts of the actual force, so the signal doesn’t tell the whole story.

What we've found so far is that EMG readings only partly reflect how much force the gluteus medius muscle produces during hip exercises [1]. The evidence we've reviewed suggests that electrical activity measured by EMG explains just under 1 in 5 parts — or less than 20% — of the actual muscle force generated [1]. This means that while EMG can give some indication of muscle activity, it doesn’t capture most of what’s happening in terms of force output. Our analysis of the available research shows that relying solely on EMG to estimate gluteus medius force may be misleading [1]. Even if the muscle shows electrical activity, that signal alone doesn’t tell us how strong or effective the muscle contraction really is. There are likely other factors — like muscle fatigue, fiber type, or movement mechanics — that influence force in ways EMG can’t fully detect. The evidence we’ve reviewed leans toward the idea that EMG is an incomplete tool for predicting actual muscle force in the gluteus medius during hip exercises [1]. While it provides some useful data, it only captures a small piece of the puzzle. We don’t yet know how much other factors contribute or how they might change across different people or types of movements — the current evidence doesn’t address those questions. Based on what we’ve reviewed so far, it’s clear that EMG should not be used as the sole measure of how hard the gluteus medius is working. Other methods may be needed to get a fuller picture of muscle performance. Practical takeaway: If you're using EMG feedback during hip exercises — whether in rehab or training — keep in mind it only shows part of the story. A muscle might be working hard even if the EMG signal is low, so how you feel and move matters too.