Missed a Week of Half Marathon Training? Do This

Illness has just taken a week out of your training plan, and you're bracing for the fitness loss you assume comes with it. A missed week of 7-10 days causes only modest, largely reversible fitness loss — blood plasma volume dips within days, but detraining research generally shows measurable endurance decline emerging around the two-week mark, not before. A missed week is mostly a scheduling problem, not a fitness problem. The decision tree below tells you exactly what to do next, based on how many days you've actually missed.

Where runners actually lose fitness isn't the missed week itself — it's the panic response afterward: bolting the skipped long run onto next week's, chasing lost mileage, or jumping straight back to full pace out of anxiety. That's the pattern that turns a manageable break into a real setback, and it's avoidable once you know which lever applies to your situation.

The Decision Tree: 2-3 Days, a Full Week, or 10+ Days

There's no single rule that covers every missed day the same way, so I use bands. Each one has a specific action attached — not a vague "ease back in."

My own heuristic: I rewind a training plan by one week for every five days missed beyond the first week — it's simple, but it stops athletes from bargaining their way back to full intensity too soon.

The "Above the Neck, Below the Neck" Rule

This is the fastest way to decide whether you should run at all while you're still unwell. It's not new advice, but it's worth stating precisely.

Above the neck only — runny nose, mild sore throat, no fever — and you're fine to run easy, skipping intensity. Below the neck or systemic — chest congestion, body aches, fever, fatigue — means rest completely until 24-48 hours symptom- and fever-free, then resume at easy pace only for the first two runs back.

What to Cut First When Compressing the Plan

When a week genuinely can't fit everything, cut in this order: protect the long run first — reduce its distance before you touch its existence. Cut easy-run volume second; those sessions are the most negotiable. Cut or skip the tempo/speed session only as a last resort, if time truly doesn't allow all three.

Never cut the long run entirely if you can avoid it. It's the hardest adaptation to make up later, and a smaller long run beats no long run every time.

Why This Matters More for a Half Marathon Than a Marathon

A marathon plan runs 16-20 weeks and has more runway to absorb a lost long run. A typical half marathon plan is 10-14 weeks, so you have proportionally less room to recover the same setback.

For anyone on a plan under 12 weeks, treat a 7-day miss like the marathon's 10-day threshold — move one band earlier in the decision tree above. I've watched an anonymised athlete on a 10-week plan try to "make up" a missed long run by combining it with the next week's session, and develop a knee niggle that cost two additional weeks. Compare that with the athlete who accepted a smaller long run and finished the block healthy — that's the trade-off every time.

Re-Entry Pacing: How Easy, For How Long

Your first run back should be 20-30% shorter than scheduled, run at the slow end of easy pace or by feel alone — leave the watch's pace alerts off if you need to. Your second run returns to the scheduled easy distance. Resume quality sessions on your third run, but only if the first two felt completely normal.

Should You Revise Your Goal Time?

A miss under 7 days needs no goal revision at all — don't touch the number. A miss of 10-14+ days inside the final 6 weeks of the plan should trigger a 3-5% pace revision, roughly 15-25 seconds per mile slower, rather than chasing the original number off a compressed build.

When a Missed Week Is Actually a Sign to See a Doctor

A few red flags override everything above: a fever over 38.5°C (101.3°F) lasting more than two days, chest pain, or any symptom that hasn't resolved after 10 days. See a doctor before resuming, regardless of where you are in the plan.

Frequently Asked Questions

How many days can I miss before it affects my fitness?

A missed week of 7-10 days causes only modest, largely reversible fitness loss. Blood plasma volume dips within days of stopping, but detraining research generally shows measurable endurance decline emerging around the two-week mark, not before. For most missed weeks, it's a scheduling problem more than a fitness problem.

Should I make up a missed long run?

No — don't bolt it onto the next week's long run or combine sessions to compensate. Resume the plan as written and let the missed run stay missed. Trying to make up lost ground in a single session is how niggles start.

Do I restart from an earlier week?

Only if you've missed 10 or more consecutive days. In that case, rewind the plan's progression by 1-2 weeks before resuming as written. For anything under 10 days, resume where you left off rather than repeating a week.

What's the above the neck, below the neck rule?

Symptoms above the neck only — runny nose, mild sore throat, no fever — are usually fine to run through at easy pace, skipping intensity. Symptoms below the neck or systemic mean complete rest until 24-48 hours symptom- and fever-free.

How long after a fever should I wait before running?

Wait until you've been fully fever-free for 24-48 hours, then resume at easy pace only for your first two runs back. Running too soon after a fever tends to extend the illness rather than shorten your time off.

Can I run through antibiotics?

It depends on what you're treating, not the antibiotics themselves. If the underlying infection is above the neck and mild, easy running is usually fine. If it's systemic, follow the below-the-neck rule and rest until genuinely recovered.

Will a missed week affect my goal time?

A miss under 7 days needs no goal revision at all. A miss of 10-14 or more days inside the final 6 weeks should trigger a 3-5% pace revision — roughly 15-25 seconds per mile slower.

Should I shorten my taper to compensate for lost training?

No. Cutting your taper short to squeeze in extra training trades a well-rested race day for a marginally longer build, and it's a poor trade. Adjust your goal pace instead if needed.

Should I resume at the same pace or the same volume?

Volume first, pace second. Rebuild your easy mileage back to normal over your first two runs back before reintroducing any quality session. Chasing your pre-break pace in run one is the most common re-entry mistake I see.

What if I feel fine but I'm still within the illness window?

Feeling fine is a reasonable sign for above-the-neck symptoms, but not for systemic illness. If you had a fever, wait out the full 24-48 symptom-free window regardless of how you feel on day one.

Some Other Pages You May Like