Sore tendon, sore heel? Resting it is probably why it is still sore

You have had it for months. An Achilles, a tennis elbow, a knee that is fine until you actually use it, or the heel that hurts on the first step in the morning, eases once you are moving, and comes back after a day on your feet.

It settles if you do nothing. Then you try to get on with things and it is straight back. Someone told you to rest it, you did, and it is still there.

That is not you failing at recovery. A muscle can feel better in a couple of weeks. A tendon is often still earning your trust a few months later. Rest felt sensible. For a grumble that has outstayed its welcome, rest is often why it stays weak.

If the pain is under the heel, it is usually the plantar fascia. Not a tendon, a thick band under the arch, and it behaves in a similar way. This is not for a fresh tear, a pop, something hot and swollen, or pain that wakes you and is getting worse. Get those looked at. This is for the one that has just been hanging around.

A patch, not a sprain

A tendon that has been sore for months is often thicker, and unhappy when you load it. Jill Cook’s work treats that as a patch of repair tissue, weaker and less tidy than what was there. I describe it like the rough concrete poured into a pothole. It gets you over the hole. It is not the road.

I cannot see that patch from the treatment room. Nobody can. That takes a biopsy, so the pattern is a working explanation, not a fact about your tendon.

Laying the patch down attracts water, which is why it looks thicker and everyone calls it inflamed. It is not a sprained ankle. There can be some immune cells in there, but not the flood you would see in a fresh injury. The swelling is mostly water from the repair. Ice or heat, if one of them helps for an hour, use that. Neither turns the patch back into the original tissue.

The useful point is capacity. At some point the tendon was asked to do more than it could tolerate, or it was rested and then asked to work again before it had the capacity back.

Rest does not give that patch, tendon or fascia, a reason to change. Load does, if you get the amount wrong less often than you get it right. Not so little that nothing happens, and not so much that you knock the new concrete out. Under the foot, that load is the heel and the calf. Insoles can help with the day. They rarely finish the job on their own.

Why rest keeps it sore

Once a patch is sore, the load prefers the tissue that still feels sturdy. The stronger bit takes the step, and the sore bit hides behind it, protected from the very pull that would give it a reason to change. That hiding is called shielding. Rest does the same thing to the whole heel. Nothing is asked, so nothing remodels.

The evidence has leaned toward loading for years. It takes a while to filter into practice, and protection is still what a lot of people are given first. Rest, a firmer shoe, an orthotic. Those can help with the day. They do not ask the fascia to tolerate a step.

A hold is a start, not the job

You have probably seen the posts. Forget ice, hold still, take collagen, fixed. Some of that is fair. I use a hold. I do not treat it as the cure.

The pain-relief finding comes from Ebonie Rio in Melbourne, in 2015. A small group of volleyballers with sore kneecap tendons did a heavy hold, and the pain dropped for a short while afterwards. Useful before training if the tendon is under the kneecap. I may try a hold at a shoulder, a forearm, foot or a hip if it suits that person. That is a trial of one, not a finding from her study.

A 2018 trial in people with plantar fasciopathy tested the same idea, and an isometric heel-raise hold did not beat an ordinary heel raise, or a walk. Pain did not drop.

Keith Baar prefers a shorter hold. The study is from UC Davis, my old hometown, and it comes from the lab rather than from sore patients. Hold the length still and the tension falls, because the collagen fibres slowly give. In his lab work most of that give happens by about 30 seconds, long enough for the stronger fibres to ease off and a share of the load to reach the patch that was hiding. A fair reason to use a short hold early, when a normal rep stings. The heel trial used a long hold and still got nothing, so the mechanism is not the same as a result.

The collagen powder claim is Shaw, Baar and colleagues, in 2017. Gelatin and vitamin C before a few minutes of skipping, and a blood marker went up. That is not evidence a tub of powder heals a sore tendon, or a sore heel.

What I actually trust

A hold can take the edge off a kneecap tendon for a short while. It has not been shown to do that job for a heel. The trial that changed morning steps used a slow heel raise with the toes bent back, load added over the weeks. Better than stretching at three months. By a year they had ended up in the same place.

Everywhere else, slow heavy loading beats rest, and holds have not beaten that loading over the following weeks. Collagen is optional if you already take it and it sits well. Skip it if you are pregnant, have kidney trouble, or have been told to go easy on protein supplements.

If the exercise feels easier than last time, that is a good sign.

If rest has not fixed it, you are not failing. It was waiting for a load it could use, matched to that tissue, not copied from a graphic.

Disclaimer. General information, not a plan for your tendon or your foot. A pop, sudden weakness, heat, swelling, or night pain that is getting worse needs checking.