Achilles Tendinopathy in Runners: Managing the Morning Stiffness

The Achilles tendon absorbs forces of up to eight times body weight with each running stride. For recreational runners in Singapore, the number is harder to pin down, but the clinical pattern is consistent: a tendon that manages the run but protests the following morning. Understanding what that stiffness actually represents changes how you approach it.

What is Achilles Tendinopathy?

The shift from ‘tendinitis’ to ‘tendinopathy’ reflects a more accurate understanding of what happens inside an overloaded tendon[1]. Tendinitis implies acute inflammation; tendinopathy describes structural changes to the tendon itself: disorganised collagen fibres, increased water content, and reduced tensile capacity. The problem is structural, not simply inflammatory. Approaches that target inflammation alone, such as prolonged rest or anti-inflammatories, address symptoms without rebuilding the tendon’s capacity to handle load.

Two locations are clinically relevant. Mid-portion tendinopathy[2] affects the Achilles tendon two to six centimetres above the heel bone and is more common in runners. Insertional tendinopathy[3] occurs at the heel bone attachment and responds differently: deep sustained calf stretching, which helps mid-portion cases, can aggravate insertional symptoms by compressing the tendon at its attachment site. Identifying which type you have matters before beginning any exercise programme[4].

Why Morning Stiffness Occurs

When the Achilles tendon becomes irritated, changes in its internal collagen matrix allow fluid to accumulate within the tendon during periods of inactivity. Overnight, as the ankle rests in a slightly plantarflexed position, this fluid builds up and sensitises local nerve endings. The first steps of the morning stretch and load a tendon that has stiffened around that accumulated fluid, producing the characteristic discomfort most runners know well.

The warm-up effect, in which pain eases after several minutes of walking, reflects temporary fluid redistribution rather than structural improvement. It is not a reliable indicator that the run is safe to continue at full intensity.

There is also a pain-rest-pain cycle worth recognising. Prolonged complete rest further reduces the tendon’s load tolerance, making it more reactive when training resumes. Running through significant pain is not the answer; neither is stopping entirely.

Clinical Management of Achilles Tendinopathy

Effective management rests on finding the right amount of load: enough to drive tendon adaptation, not so much that symptoms escalate. A physiotherapy assessment is the most reliable way to establish where your Achilles tendinopathy sits on that continuum.

A study suggests that Heavy Slow Resistance (HSR) training promotes tendon remodelling[5]. Slow, heavy calf raises targeting both the gastrocnemius and soleus create the mechanical stimulus needed to reorganise collagen and rebuild capacity. High-repetition, low-load stretching does not produce the same structural response and should not be the primary approach.

Isometric holds are useful as a pre-run pain management tool. Stationary single-leg calf holds (five sets of 45 seconds) have a well-documented analgesic effect on tendon pain, reducing sensitivity before impact occurs without requiring full-range-of-motion loading.

For presentations that have persisted beyond three months without adequate improvement, shockwave therapy delivers acoustic energy to stimulate tissue repair within the tendon. At a physiotherapy centre in Singapore, shockwave is integrated into a broader sports injury physiotherapy programme rather than used in isolation.

Practical Tips for Daily Relief

Here are three practical habits that may help reduce day-to-day symptom flare-ups:

• Ankle pumps before standing: Ten to fifteen slow ankle pumps before getting out of bed disperses overnight fluid accumulation before the tendon takes its first load.

• Heel-to-toe drop: Temporarily switching to a running shoe with a higher heel-to-toe drop (10mm or above) reduces the stretch placed on the Achilles with each footfall, lowering irritability during a flare.

• Calf massage, not tendon massage: Self-massage should target the gastrocnemius and soleus muscles, not the tendon itself. Reducing mechanical pull from the calf decreases the load transmitted to the tendon without aggravating already sensitised tissue.

With consistent rehabilitation, the healing time typically ranges from eight to twelve weeks for mid-portion cases. Insertional presentations and those with longer histories tend to take longer.

Running with Achilles tendinopathy during rehabilitation is often possible, but symptom response is the guide: discomfort during a run should stay below 3/10 and return to baseline within 24 hours. If symptoms are escalating between sessions, that is the signal to reassess the load with a foot physiotherapy before continuing.

The Earlier, the Better

Morning stiffness that warms up after a few minutes is easy to train through when everything else feels fine. Clinically, it is one of the earliest indicators that the tendon’s load tolerance is being exceeded. Addressing it at that stage keeps rehabilitation short. Evaluate your tendon load tolerance, movement patterns, and training structure, and build a plan that keeps you running while the tendon recovers.

References

1. Williams, B., & Gyer, G. (2025). Tendons under load: Understanding pathology and progression. Journal of Musculoskeletal Surgery and Research, 9, 393–402. https://doi.org/10.25259/jmsr_86_2025
2. van Sterkenburg, M. N., & van Dijk, C. N. (2011). Mid-portion Achilles tendinopathy: why painful? An evidence-based philosophy. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 19(8), 1367–1375. https://doi.org/10.1007/s00167-011-1535-8
3. Matsui, T., & Tanaka, Y. (2025). Pathophysiology and healing of insertional Achilles tendinopathy: Current concepts. Journal of ISAKOS Joint Disorders & Orthopaedic Sports Medicine, 12, 100867. https://doi.org/10.1016/j.jisako.2025.100867
4. Yu, C., Deng, L., Li, L., Zhang, X., & Fu, W. (2022). Exercise Effects on the Biomechanical Properties of the Achilles Tendon-A Narrative Review. Biology, 11(2), 172. https://doi.org/10.3390/biology11020172
5. Morrison, S., & Cook, J. (2022). Putting “Heavy” into Heavy Slow Resistance. Sports Medicine, 52(6), 1219–1222. https://doi.org/10.1007/s40279-022-01641-y