If you have Achilles tendonitis, the exercises most likely to make it worse share a common trait: they load the tendon too fast, compress it against the heel bone, or push your ankle into extreme positions. Knowing which movements fall into these categories can mean the difference between steady recovery and a frustrating setback that adds weeks to your timeline.
The Achilles tendon responds well to load, but only the right kind. Heavy, slow resistance actually helps it heal. The problems start with speed, impact, and range of motion you’re not ready for.
High-Impact and Explosive Movements
Plyometrics, sprinting, box jumps, and jump rope top the list of exercises to avoid. These movements store and release energy through the tendon at high speed, and that rapid strain rate is precisely what damages tendon cells. Research using computational models of tendon stress shows that when the rate of loading increases, shear stress inside the tendon rises dramatically, even if the total force stays the same. That internal shearing helps explain why explosive movements are so much harder on a sore Achilles than a heavy but slow calf raise.
This also applies to sport-specific drills like cutting, bounding, shuttle runs, and any form of sprinting. These are classified as high-load tendon activities, meaning they can push pain levels to 4 or 5 out of 10 during the activity and even higher the next day. High-load activities need at least three full recovery days between sessions. During active tendonitis, they’re better left out entirely until you’ve rebuilt strength.
Uphill and Downhill Running
Running on hills changes how force travels through the tendon in ways that aren’t intuitive. Downhill running produces the largest peak vertical forces of any running grade, increasing your overall injury risk. Uphill running, while it generates less peak force, demands more work from the calf muscles and keeps the tendon under sustained tension through a greater range of ankle motion.
When researchers matched the metabolic cost of running across different grades, the Achilles tendon showed similar levels of swelling regardless of incline. In practical terms, no grade of hill running is gentler on the tendon than flat ground. If you’re going to run during recovery, flat surfaces at a moderate pace are the safest option, and even those should be monitored using the next-day pain rule described below.
Deep Calf Stretches and Full Dorsiflexion
Aggressive static calf stretching is one of the most common mistakes people make with Achilles tendonitis. It feels like you’re helping, but the mechanics tell a different story, especially if your pain is at or near the heel.
When you push your ankle into deep dorsiflexion (pulling your toes toward your shin as far as they’ll go), the tendon gets compressed against the back of the heel bone. This compression triggers changes in the tendon’s internal structure, encouraging the formation of fibrocartilage, a stiffer, less resilient tissue. Research confirms that the site where the tendon wraps around the calcaneus is a predominant location for pathology, making compression a direct contributor to insertional tendonitis.
Studies on stretching programs also show that static stretching doesn’t actually change Achilles tendon stiffness. It reduces resistance in the relaxed muscle tissue above, but the tendon itself remains unchanged. So you get the compressive risk without the structural benefit you’re hoping for. If you have insertional pain (right where the tendon meets the heel), avoid wall stretches, step stretches, and any exercise that drives your ankle past a neutral position. For mid-portion tendonitis (pain in the body of the tendon, a few centimeters above the heel), gentle stretching in a limited range is less risky but still not particularly helpful.
Exercises That Load the Tendon Too Fast
In the gym, it’s not just which exercises you do but how you do them. The speed of the movement matters enormously. Research on tendon rehabilitation shows that slow lifting tempos, around 6 to 8 seconds per repetition, protect the tendon while still providing enough stimulus to drive healing. Faster tempos, like 1 second up and 1 second down, dramatically increase the rate of loading and push the tendon closer to the strain patterns that cause damage.
Exercises to be cautious with in the gym include:
- Leg press with a low foot position: Places the ball of the foot on the platform’s lower edge, forcing the calf and Achilles to absorb most of the load through a large range of ankle motion.
- Deep barbell squats: At the bottom of a deep squat, the ankle reaches near-maximum dorsiflexion, compressing the tendon insertion. A parallel or slightly above-parallel depth is safer.
- Fast or bouncing calf raises: Calf raises are actually a key rehabilitation exercise when done slowly and with control. But performing them quickly, with a bounce at the bottom, converts a therapeutic movement into a damaging one.
- Seated calf raises with explosive reps: The bent-knee position isolates the soleus, but fast reps still generate high strain rates through the tendon.
The goal during recovery isn’t to avoid loading the tendon. It’s to load it slowly and heavily. Heavy slow resistance at 70% or more of your one-rep max, performed at a tempo of about 6 seconds per repetition, is one of the best-supported rehabilitation approaches. Some protocols use micro-sets of 3 reps at around 85% of max with short rest periods to keep intensity high without excessive repetitions.
Minimalist and Zero-Drop Shoes During Exercise
Switching to minimalist or zero-drop shoes while dealing with Achilles tendonitis significantly increases tendon loading. A 12-week study on runners transitioning to minimalist footwear found that peak Achilles tendon force increased by 10 to 20%, loading rate jumped by 25 to 37%, and peak tendon stress rose by 8 to 14%, depending on whether runners also changed their foot strike pattern. Runners who adopted a forefoot strike along with minimalist shoes saw the biggest increases.
These adaptations may be beneficial for a healthy tendon over time, but for a tendon already in a reactive or degenerative state, the added stress is counterproductive. Stick with shoes that have a moderate heel-to-toe drop (8 to 12 mm) during recovery. The small heel lift reduces the amount of dorsiflexion your ankle goes through with each step, taking some compressive load off the insertion.
How to Tell If an Exercise Is Too Much
The most reliable way to gauge whether a specific exercise is safe for your Achilles is the 24-hour pain rule. After any workout, monitor your tendon pain on a 0-to-10 scale both immediately after and the following morning. Clinicians use a simple classification system to guide decisions:
- Light activity (safe to repeat daily): Pain stays at 1 to 2 during the exercise and 1 to 2 the next day.
- Medium activity (needs 2 days of recovery): Pain reaches 2 to 3 during the exercise, 3 to 4 the next day.
- High activity (needs 3 days of recovery): Pain hits 4 to 5 during exercise, 5 to 6 the next day.
If your pain the morning after a workout is consistently above a 4, that exercise is too aggressive for your current stage of recovery. Morning stiffness that lasts more than a few minutes is another red flag. The tendon can tolerate more than most people think, but it communicates clearly through next-day symptoms. Pay attention to that signal rather than how the exercise feels in the moment, since adrenaline and warmth can mask strain during the session itself.
What to Do Instead
The exercises that help Achilles tendonitis share a pattern: heavy load, slow speed, controlled range. Eccentric calf raises (lowering slowly from a raised position) are the most widely studied option. For mid-portion tendonitis, these can be done off the edge of a step to allow a full range of motion. For insertional tendonitis, keep the heel at or above the level of the step to avoid compressing the tendon against the bone.
For cardio, cycling and swimming place minimal strain on the Achilles compared to running. If you need to run, flat ground at a conversational pace, wearing supportive shoes, is a reasonable starting point once you can do single-leg calf raises without significant pain. Gradually reintroduce higher-impact activities only when your next-day pain consistently stays in the light category across multiple sessions.