The Week After a Marathon: What's Happening in Your Body (and How to Recover Fast)

Quick Symptom Checklist (Totally Normal)

What you might feel in the first week:

• Low energy / “battery drained”
• “Hollow” hunger (even after eating)
• Brain fog or mood dip
• Heavy legs + stiffness (especially stairs)
• Sniffles / scratchy throat
• Random twinges in ankles, knees, hips

What Happens to Your Body After a Marathon

1) Muscle damage peaks in the first 48 hours

A marathon creates thousands of microscopic tears in muscle fibers and connective tissue. Blood markers of muscle damage (like creatine kinase) often rise sharply and can stay elevated for several days. [1,2]

What you feel:

• Heavy legs
• Stiffness going downstairs
• Soreness that “moves around”

This is normal — it’s tissue repair in progress.

2) Glycogen stores are severely depleted

Even with great fueling, a marathon can leave muscle glycogen low. Your body prioritizes restoring it in the first 24 hours, and delaying carbs slows the refueling process. [3,4]

What you feel:

• Low energy
• “Hollow” hunger
• Brain fog

3) Your immune system takes a temporary hit

Hard endurance racing can temporarily shift immune function, including measurable drops in salivary IgA (a key “front-line” mucosal antibody). That’s one reason runners often feel more susceptible to colds shortly after a marathon. [5,6]

What you feel:

• Feeling run-down
• Scratchy throat or sniffles
• Fatigue that feels “deeper than soreness”

4) Tendons & joints may lag behind muscles

Muscle soreness can improve quickly, but tendon and connective-tissue remodeling is slower and responds differently to load. [7] And newer imaging work suggests that collagen within the Achilles tendon can show measurable structural changes after running, reinforcing why easing back matters. [8]

What you feel:

• Stiff ankles or knees
• Slight instability
• “Twinges” that come and go

5) Hormones & sleep can be disrupted

A marathon is a major stressor: cortisol can spike and then normalize over the next day, but sleep disruption is still common in the immediate post-race window (especially when soreness, travel, nerves, or inflammation are in the mix). [9,10]

6) The emotional dip is real

Many runners experience a “post-race emotional paradox”: pride + relief, but also anxiety, flatness, or loss of routine. That’s a documented, common post-endurance experience. [11]

What Runners Should Do the Week After a Marathon

Day 0–2: Full reset mode

• Walk, don’t run. Gentle movement increases circulation without adding damage.
• Carbs + protein at every meal. (See targets below.)
• Hydrate + sodium. You’re still catching up from race-day losses.
• Compression + elevation if swelling is noticeable.
• Avoid “just in case” NSAIDs. Some evidence suggests common NSAIDs can blunt muscle protein synthesis and satellite-cell activity after exercise, and endurance events plus NSAIDs can raise kidney-risk in some settings. [12–14]

Day 3–4: Active recovery begins

• Light bike / swim / elliptical (20–30 min, truly easy).
• Mobility + gentle yoga (hips, glutes, calves, lower back).
• Sleep is the assignment.

Day 5–7: Slow return to running

• Optional: 15–20 min EASY on soft surfaces (conversation pace).
• Run/walk is fine.
• Light strength only if pain-free (core + glute activation).
• Watch for red flags: sharp pain, worsening limp, swelling, unusual fatigue → stop and reassess.

Most runners feel noticeably better by days 7–14. The biggest recovery “hack” is not rushing days 1–4.

What to Eat to Speed Recovery

Carbs Prioritize carbs early to refill glycogen efficiently. [3,4]

Protein Aim for steady protein to support repair.

Color + omega-3s Fruits/veg and omega-3-rich foods support overall recovery (and make it easier to eat enough when appetite is weird).

The Bottom Line

Your body just did something extraordinary. The fastest way to recover isn’t pushing through — it’s respecting the repair process.

Walk for 2–3 days, eat intentionally, sleep deeply, and ease back slowly. You’ll return stronger — and you’ll actually enjoy your next start line.

References

[1] Baird MF, Graham SM, Baker JS, Bickerstaff GF. Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery. J Nutr Metab. 2012;2012:960363. doi:10.1155/2012/960363.

[2] Totsuka M, Nakaji S, Suzuki K, Sugawara K, Sato K. Break point of serum creatine kinase release after endurance exercise. J Appl Physiol. 2002;93(4):1280–1286. doi:10.1152/japplphysiol.01270.2001.

[3] Ivy JL, Katz AL, Cutler CL, Sherman WM, Coyle EF. Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. J Appl Physiol. 1988.

[4] Burke LM, van Loon LJC, Hawley JA. Postexercise muscle glycogen resynthesis in humans. J Appl Physiol. 2017;122(5):1055–1067. doi:10.1152/japplphysiol.00860.2016.

[5] Nieman DC, et al. Change in salivary IgA following a competitive marathon race. Int J Sports Med. 2002;23:69–75. doi:10.1055/s-2002-19375.

[6] Nieman DC. Exercise, upper respiratory tract infection, and the immune system. Med Sci Sports Exerc. 1994/1995 (review).

[7] Kjaer M. Role of extracellular matrix in adaptation of tendon and skeletal muscle to mechanical loading. Physiol Rev. 2004;84(2):649–698. doi:10.1152/physrev.00031.2003.

[8] Fang Y, et al. Running induces Achilles tendon collagen denaturation in humans. Sci Adv. 2024;10:eado2015. doi:10.1126/sciadv.ado2015.

[9] Nikolaidis PT, Weiss K, Knechtle B, Trakada G. Sleep in marathon and ultramarathon runners: a brief narrative review. Front Neurol. 2023;14:1217788. doi:10.3389/fneur.2023.1217788.

[10] Leers MPG, Schepers R, Baumgarten R. Effects of a long-distance run on cardiac markers in healthy athletes. Clin Chem Lab Med. 2006;44(8):999–1003. doi:10.1515/CCLM.2006.179.

[11] Augustsson SR, et al. Post-race reactions: The emotional paradox of high performance and anxiety. BMC Sports Sci Med Rehabil. 2024. doi:10.1186/s13102-024-00968-5.

[12] Trappe TA, et al. Ibuprofen and acetaminophen: effect on postexercise muscle protein synthesis. J Appl Physiol. 2002. doi:10.1152/japplphysiol.00672.2002.

[13] Mikkelsen UR, et al. Inhibition of cyclooxygenase-2 reduces satellite cell proliferation following eccentric exercise in humans. Eur J Appl Physiol. 2009. doi:10.1007/s00421-009-1100-8.

[14] Lipman GS, et al. Ibuprofen versus placebo effect on acute kidney injury in ultramarathon runners (observational study). PLoS One. 2017. doi:10.1371/journal.pone.0170615.