Two problems that share a name
The Achilles tendon connects the calf muscles to the heel bone and handles enormous force in running, several times body weight with every stride. Pain along it is usually a tendinopathy: tendon tissue that has been loaded beyond its current capacity and has not kept up with repair. Location divides it into two problems that are managed differently.
- Mid-portion Achilles pain sits in the tendon itself, roughly 2 to 6 centimeters above the heel bone. The tendon may feel thickened or tender to a pinch, stiff in the morning, and sore at the start of runs.
- Insertional Achilles pain sits right where the tendon attaches to the back of the heel. It is often aggravated by anything that presses on the spot, including the heel counter of a shoe, and sometimes comes with a firm bump at the attachment.
The distinction matters because the classic rehab exercise for mid-portion pain, heel drops below the edge of a step, stretches the tendon into compression at the heel attachment and frequently makes insertional pain worse. The same program, done only to floor level, is the insertional-friendly version.
Why runners get it
- Sudden load changes: more hills, speed work, or mileage than the tendon was prepared for. Hills are a particularly common trigger because they increase tendon stretch and calf demand.
- Low-drop shoe switches: moving quickly from a traditional trainer to a low or zero-drop shoe increases Achilles and calf load with every step.
- Calf weakness or fatigue: the tendon and calf work as one unit; a weak calf hands its share of the work to the tendon.
- Training monotony: the same load, the same way, with too little recovery between hard days.
The heel-drop rule
A shoe's drop is the height difference between heel and forefoot. A higher drop (roughly 10 to 12 mm) tilts the foot so the Achilles works through a shorter range and stretches less at footstrike, reducing tendon strain. That is why a temporary move to a higher-drop trainer, and even a small heel lift inside the shoe, is a standard short-term strategy while the tendon calms down. The reverse also holds: during a symptomatic period, avoid racing flats, spikes, and zero-drop shoes, and reintroduce any lower-drop shoe gradually over weeks, not days.
The loading program
Tendons respond to progressive load, not complete rest. The best-known approach is the Alfredson eccentric protocol, developed for mid-portion pain:
- Stand on a step with the balls of your feet on the edge and heels free. Rise up on both feet.
- Shift your weight to the affected side and lower the heel slowly below the step edge, taking about three seconds, until you feel a stretch in the calf and tendon.
- Use the other foot (or both feet) to rise back up. The affected side only does the lowering.
- Perform 3 sets of 15 repetitions with the knee straight, then 3 sets of 15 with the knee slightly bent, twice a day. Add weight in a backpack as it gets easier.
Mild discomfort during the exercise is expected and generally acceptable; sharp pain is not. For insertional pain, lower only to floor level, never below the step edge, and stop the deep-stretch version entirely. Isometric holds (pushing against a wall with the heel down, holding 30 to 45 seconds) are a gentler entry point when the tendon is very irritable. Expect the program to run about twelve weeks before judging it; tendons adapt slowly, and morning stiffness is a practical daily scorecard.
Training while it heals
Many runners can keep some easy running during rehab if the pain stays mild during the run and, critically, the tendon is no stiffer the next morning than it was the day before. Hills and speed work come out first; flat, easy miles are the last thing to go and the first thing to rebuild. Cross-training that does not load the tendon hard, such as cycling with the pedal under the midfoot or pool running, maintains fitness in the meantime. When morning stiffness returns to baseline for a couple of weeks, reintroduce hills and faster work one at a time.
Red flags: stop and get seen
Stop running and seek prompt in-person care if you felt a pop or snap in the back of the ankle, cannot push off or rise onto your toes on that side, or develop rapid swelling, as these can indicate a partial or complete tendon rupture. Also book a visit if there is a growing bony bump with shoe pressure at the heel attachment, numbness, or no improvement after six to twelve weeks of a consistent loading program. Getting the diagnosis right matters here, because bursitis, stress injury of the heel bone, and tendon problems can overlap and are treated differently.
Related reading: our plantar fasciitis guide covers the other classic runner's heel complaint, and the max-cushion shoe guide lists higher-drop, cushioned options that suit a sore tendon.