Do not miss the first week with your Compex

Do not miss the first week: how to use your Compex at home

September 2026 · Patient Resource

The first week is the one that counts

The first week after the operation is the most important.

The studies that compared starting times are unambiguous: starting electrical stimulation in the first week gives three times more effect on quadriceps strength than starting later.¹ In the reference trial after knee replacement, stimulation started 48 hours after the operation.²

It is during these first days that the muscle is most “cut off” from its signal, and therefore the moment when a contraction triggered by the device brings what nothing else can. Waiting to feel better before starting means missing the window.

What a session looks like

A strengthening session is a series of alternating contractions and rests. The muscle tightens for a few seconds, then releases for longer, often around 10 seconds of contraction for 50 seconds of rest.⁴ The rest is not wasted time: a stimulated muscle tires faster than a muscle you contract yourself, and the rest lets it give a real contraction every time.

A session usually lasts 15 to 20 minutes, with ten to fifteen strong contractions. It is not long. What counts is the intensity of each contraction, not the total duration.

You settle in leg straight, knee in extension, sitting or lying down, with the leg wedged so it does not move. The muscle contracts, the leg does not move, that is intended.

How many times a day, a week

What the studies that worked show.

• The first two weeks: several sessions a day. That is when the effect is strongest. In the trial after knee replacement, it was twice a day.²
• Then: regularly, for as long as your thigh has not regained its strength. The duration recommended by the guidelines after ACL reconstruction is 6 to 8 weeks,³ and some protocols go up to 12 weeks, at two or three sessions a week.⁴

This framework adjusts to the operation and the speed of recovery. What must not be done is the opposite: little at the start, then catching up later.

The right time of day

If you also have a cryocompression device, the order matters:

And never place electrodes on skin that is still cold and numb: wait for it to warm up.

How to know it is working

Do not look for a visible change in three days. What you will see coming, in order:

• From the first sessions: you see the thigh contract, while you cannot yet do it voluntarily. That is already the muscle working.
• Within one to two weeks: you manage to tighten the thigh yourself more clearly, and to straighten the knee more easily.
• Within a few weeks: the intensity you can tolerate has risen noticeably, a sign that the muscle is responding and getting stronger.

Studies show that the strength gain is most marked in the first month, and that it is still measurable one year later.⁵

Three mistakes that waste a rental

Starting too late. Every day of the first week without stimulation is a day the muscle stays silent for nothing.

Staying at a comfortable intensity. A session that does not clearly tighten the muscle does not strengthen it. Raise the intensity at every session up to the strongest contraction you accept.

Skipping the days on which you feel better. Consistency over several weeks makes the result, not a few good sessions here and there.

In short

• Start early, ideally in the first week.
• Short sessions, strong contractions, leg straight and wedged.
• Several times a day at the start, then regularly for as long as the thigh has not regained its strength.
• Electrical stimulation before cold, never on numb skin.