Missed Weeks of Training Before a Race: What to Do Next

Almost every training block has a hole in it somewhere.

The flu takes ten days. A work trip eats a fortnight. A calf needs a month. Then you look at the calendar and the race hasn’t moved. The question keeps coming up on r/Marathon_Training and every other training forum I read: the race is six weeks away, I’ve lost a month, can I still do this?

Most of the time, yes. How you spend the weeks you have left matters more than the weeks that are gone. Here’s what the research says you actually lost, and how I would use the time, depending on how much of it there is.

What a gap actually costs

The best-known numbers come from Coyle and colleagues in 1984. They followed seven endurance athletes who stopped training completely, and measured them at 12, 21, 56 and 84 days.

• VO2max fell 7 percent in the first 21 days.
• It levelled off after 56 days, 16 percent below where it started.
• At 84 days, those athletes still sat well above people who had never trained: 50.8 against 43.3 ml/kg/min.
• Capillaries in the muscle hadn’t dropped at all, and stayed about 50 percent above the untrained group.

The mechanism explains the shape of that curve. The early drop came with the heart pumping less blood per beat, and the later one with the muscles pulling less oxygen out of that blood. The structure you built in the muscle holds on much longer.

Seven people is a small study, and those athletes stopped everything. Most real gaps aren’t like that. You walked, you played with the kids, you got two short runs in during the work trip. So treat these as the upper end for a gap of that length, and notice what they say: the early losses are real, they slow down, and years of training don’t vanish in a month.

A little training holds more than you would expect

The more useful finding is how little it takes to hold on. A research group led by Robert Hickson ran a series of experiments in the 1980s. Young adults trained six days a week for 10 weeks, then cut one variable for the next 15 weeks.

• Fewer days: dropping to four or even two days a week held VO2max at trained levels.
• Shorter sessions: cutting from 40 minutes to 26 or 13 minutes also held VO2max. Endurance over two hours or more held in the 26-minute group, and fell 10 percent in the 13-minute group.
• Easier sessions: this is the one that bites. Cutting intensity by a third lost VO2max, and long endurance fell 21 percent.

These were recently trained young adults, not marathoners, so I wouldn’t lean on the exact numbers. The pattern is the useful part, and a later review landed in the same place: volume can drop a long way as long as intensity stays and frequency only eases a little.

Two things follow for anyone coming back with a race ahead:

• Short, reasonably hard sessions protect your engine cheaply. You don’t need many.
• Long-distance durability is what slips first, so that’s where the remaining time should go.

The one thing not to do

The urge is to catch the plan up. Find the long run on this week’s schedule, go and run it, and pretend the gap didn’t happen.

Frandsen and colleagues followed 5,205 runners on Garmin watches for 18 months and looked at more than 588,000 sessions. The thing that stood out was the single run. Compared with staying within 10 percent of the longest run of the previous 30 days:

• 10 to 30 percent longer: a 64 percent higher rate of overuse injury.
• 30 to 100 percent longer: 52 percent higher.
• More than double: 128 percent higher.

It’s an observational study with self-reported injuries, so it shows a link and doesn’t prove the cause. It’s still the clearest guide I know of for this exact moment. After a long gap, I would measure from the longest run since you came back, which is stricter than the study’s 30-day window. The long run on the old plan belongs to the person who did the previous four weeks.

The first week back should feel a little too easy. Pelaris has a full guide to returning after a break with the longer version. If the gap was illness, read the post on coming back after being sick first, and see a doctor before any hard training if you had a fever, chest symptoms or unusual breathlessness. If it was an injury, your physio’s timeline beats everything below.

How I would use the weeks you have left

These are my rules of thumb, not study results. Adjust them to your history: someone with ten years of running comes back faster than someone in their first block.

More than 8 weeks to go: keep the goal. There’s time. Take a week or two to ease back in, then rejoin the plan at the week that matches your current long run, not the week the calendar says. Drop the weeks in between. Nothing is owed.

4 to 8 weeks to go: rebuild the long run and trim the rest. Build the long run in steady steps. Keep one short quality session a week to hold the engine, and let the other runs stay easy. Accept that you may reach the start line with a shorter longest run than the plan wanted. Plenty of people finish well from there.

2 or 3 weeks to go: start tapering. The fitness you bring is mostly the fitness you have, and a big late session mostly adds fatigue. A meta-analysis of tapering studies found that a two-week taper cutting volume by 41 to 60 percent worked best. In data from more than 158,000 recreational marathoners, strict three-week tapers were linked to a median finish about 5 minutes 30 seconds faster than minimal ones. If the gap fell in this window, you have already had some of the rest, so keep moving and keep it short. The taper guide has the week-by-week.

The same logic holds for other races. For a triathlon, I would give the rebuilt time to the leg that takes longest on the day. For a Hyrox, the running base comes first and the stations come back quickly.

When to change the goal

A new goal keeps you racing.

Do a recent, honest effort and put it in the race time predictor. That gives you today’s number. Then you have good options:

• Keep the distance, change the target. Run for the finish, or plan run-walk from the start. Plenty of first marathons go best this way.
• Drop a distance. Many events let you move from the marathon to the half. A strong half beats a miserable marathon, and you keep the race day and the crowd.
• Move the race. If your longest run is still far off and the race is close, check your event’s transfer rules. The next race comes around, and you arrive with a whole block behind you.

All three are good calls. What I would avoid is holding the original time goal out of stubbornness and blowing up at 30 km.

How Pelaris handles this

How much to ease back depends on what you did during the gap, why it happened and what’s ahead, which is hard to write as a formula. So Pelaris gives that call to the coach instead of a fixed percentage. When it builds your coming weeks, the model sees the sessions that passed, along with what you actually did, including training logged by hand or from a connected app. A week of runs on Strava counts as training, even if it wasn’t on the plan. After a longer break you can also choose to pick up from a few weeks back.

Plenty of plans still assume nothing will go wrong. I wrote about why that fails intermediate athletes earlier this year.

What this means for your training

• A few weeks away costs less than it feels like. Expect about 7 percent of VO2max after three weeks of doing nothing at all, and less if you stayed active.
• Short sessions with some intensity hold your engine. Long-distance durability slips first, so rebuild the long run with the time you have.
• Don’t catch up. A single run more than 10 percent past your recent longest is linked to more overuse injuries, so build from where you are now.
• Let the weeks left decide: over 8, keep the goal; 4 to 8, rebuild the long run and trim the rest; 2 or 3, start the taper.
• A new target, a shorter distance or a later race are all good outcomes. Use a recent effort to pick.

The weeks you have left are enough to do something good with. Pick the next session and start there.