Achilles Tendinopathy: Why Rest Is Making It Worse (Do This Instead)

Achilles pain is one of the conditions where the evidence is clearest and most counterintuitive: rest makes tendons weaker, not stronger. Here's what actually works.

Achilles tendinopathy — the term more accurately describes what's happening than "tendinitis" in most cases — is one of the most common overuse injuries in running and jumping sports. It's also one of the most mismanaged.

The standard advice is to rest, ice, and avoid the activity that caused it until the pain goes away. This provides temporary relief. And then you return to activity and the pain comes back within days or weeks, because nothing has changed about the tendon's capacity to handle load. You've just delayed the timeline.

The research on Achilles tendinopathy is actually unusually clear for musculoskeletal medicine. The effective treatment is progressive loading — not rest. The mechanism is well-understood. The protocol is well-defined. Here's what you need to know.

What's actually happening in the tendon

Tendons are made primarily of type I collagen in a highly organized, parallel structure. In tendinopathy, that structure breaks down — the collagen becomes disorganized, the tendon often thickens, and the pain-free load capacity decreases. This is a degenerative process, not a simple inflammatory one, which is why "tendinitis" (implying active inflammation) is a misnomer for most chronic cases.

Tendons remodel in response to mechanical load. Collagen synthesis and structural organization are stimulated by tensile loading. Without that stimulus, the degenerative changes persist and the tendon becomes progressively less capable of tolerating the demands placed on it. Rest removes the pain but also removes the only stimulus that drives real healing.

The Alfredson protocol — and why it works

In 1998, Dr. Hakan Alfredson published a landmark paper describing an eccentric loading protocol for Achilles tendinopathy that produced dramatically better outcomes than the rest-and-wait approach. The protocol is simple and brutal:

• –Stand on a step with your heel hanging off the edge.
• –Rise onto tiptoe using both feet.
• –Lower slowly and with control on the affected leg only — the eccentric phase, over 3 seconds.
• –Perform 3 sets of 15 repetitions with a straight knee, then 3 sets of 15 with a slightly bent knee (to target the soleus as well as gastrocnemius).
• –Do this twice daily, every day.
• –Progress load by adding weight (backpack, weight vest) as the exercise becomes comfortable.

Alfredson's protocol works through pain — mild to moderate discomfort during the exercise is expected and acceptable. This is counterintuitive but supported by the research. The loading stimulus is what drives tendon remodeling, and some discomfort during that process is normal.

The heavy slow resistance modification

More recent research suggests that heavy slow resistance (HSR) training — slow, heavy heel raises with both concentric and eccentric phases rather than pure eccentric-only work — produces equivalent or superior outcomes with better adherence. For people who find the pure eccentric protocol uncomfortable in ways that prevent them from following through, HSR training is a viable and well-supported alternative.

Managing load during rehab

You don't have to stop all activity during Achilles rehab. Guidelines suggest maintaining activity at a level that produces a pain rating of 5/10 or below during the activity, returning to baseline pain levels within 24 hours. If your pain is an 8/10 during a run and still elevated the next morning, the load is too high. If it's a 4/10 and you're back to baseline by the next day, that's within the manageable range.

Timeline and expectations

Meaningful improvement in 6–12 weeks with consistent loading. Full resolution in 3–6 months. Insertional tendinopathy and calcific cases take longer. The critical variable is consistency — the protocol needs to be done every day, not occasionally when it's convenient.

When to see someone

Get evaluated if: there's a sudden onset of severe pain after feeling a pop (possible Achilles rupture — urgent evaluation needed), pain that's severe and preventing normal walking, or swelling that's significant and doesn't improve within a few days. An Achilles rupture is a surgical emergency. Everything else can typically start the loading protocol, but getting confirmation of the diagnosis and ruling out rupture is worthwhile if you're unsure.