The Winter Half or Marathon: Useful Training Race or Spring Setback?

Every autumn, a lot of triathletes sign up for a winter road race. Some choose a half marathon in December or January, others a spring marathon in February or March. The reasons are good ones: the off-season can feel aimless, a race date keeps you running through the dark months, and many triathletes see the run as their weakest leg.

The risk is that a winter race becomes the season. The build-up takes over the week, swim and bike training shrink, the race leaves your legs damaged, and a niggle picked up in January is still there when the triathlon season starts. This article covers what research shows about muscle damage and recovery after a marathon, injury risk in the build-up, illness around race day, and how to decide whether a winter race helps your triathlon season. TriForward's "After the Finish Line" covers recovery after an Ironman, which is a different and larger problem.

What a winter race can give you

Before looking at the costs, it's worth being clear about the possible benefits. None of these has been tested in triathletes, so they're reasoned rather than proven:

• A run-specific block. Several weeks of consistent running can build run fitness and running durability at a time of year when the bike often takes a back seat.
• Motivation and structure. A fixed date makes it easier to train consistently through winter.
• A benchmark. A half marathon time gives you a clear measure of run fitness for setting training zones and race targets.
• Race practice. Pacing, fuelling and pre-race routines all get rehearsed.

The question isn't whether these are useful. It's whether they're worth what the race costs in recovery, injury risk and lost swim and bike time.

What a marathon does to your muscles

A marathon causes measurable muscle damage, even in well-trained runners. It shows up in blood markers that leak from damaged muscle fibres, such as creatine kinase (CK), lactate dehydrogenase (LDH) and myoglobin, and in reduced muscle function.

How long the markers stay raised

A 2021 study by Bernat-Adell and colleagues in the Journal of Strength and Conditioning Research followed 86 marathon runners, taking blood the day before the race, straight after it, and at 24, 48, 96 and 144 hours afterwards, with a later sample at 192 hours.

• Creatine kinase rose sharply and stayed raised for up to 96 hours. It was back to baseline after 144 hours.
• LDH was raised at every time point and returned to baseline only after 192 hours, about eight days.
• High-sensitivity troponin T, a heart muscle marker, was raised at 24 and 48 hours and back to baseline after 96 hours.
• C-reactive protein, an inflammation marker, was still raised at 192 hours.

Different markers recovered at different speeds, and runners who expended more energy in the race had higher levels. The abstract didn't report the sex split or ages of the runners.

Inference: by day three most runners feel almost normal walking downstairs, but the markers suggest the muscles are still recovering for about a week, and some inflammation persists beyond that.

Slowing down and muscle damage

A 2013 study by Del Coso and colleagues in PLoS ONE looked at 40 amateur marathon runners (34 men, 6 women) in a warm race at 27 °C. Average pace fell from 3.5 m/s in the first 5 km to 2.9 m/s in the last 5 km.

• Runners who slowed by more than 15% had higher post-race myoglobin (1,318 versus 623 µg/L) and LDH than those who slowed less.
• CK was higher too (564 versus 363 U/L), though this didn't reach statistical significance.
• Body-mass loss and core temperature were similar in both groups.

This is an association, not proof that muscle damage caused the slowing. But it suggests that the runners who struggled most late in the race were also those with the most muscle damage afterwards. Inference: a marathon that goes badly is likely to need a longer recovery than one that goes to plan.

What about a half marathon?

There's far less research on recovery after a half marathon, and none of the studies here compared the two distances directly. Inference: a half marathon is about half the duration, usually run at a higher intensity, and likely to cause less total muscle damage than a full marathon. Most triathletes who have done both would recognise that the half recovers faster, but that's experience rather than measured evidence.

Running in the week after

A common question is whether to rest completely after a marathon or keep moving. A 2021 study by Martínez-Navarro and colleagues in the European Journal of Sport Science tested this in 64 marathon finishers (54 men, 10 women), average age 39, who had run about 3 hours 35 minutes.

The runners were split into three groups at the finish line:

• Running: 40 minutes of easy running at 48, 96 and 144 hours after the race.
• Elliptical: the same sessions on an elliptical trainer.
• Rest: no exercise.

The exercise sessions were easy, at a heart rate around the first ventilatory threshold.

• Muscle-damage markers (CK and LDH) recovered at the same rate in all three groups. Easy exercise didn't slow recovery.
• At 96 hours, the running group's squat jump was 108% of its pre-race level, compared with 101% in the rest group.

The authors concluded that returning to easy running at 48 hours didn't harm muscle-damage recovery up to eight days after the race and might help neuromuscular recovery. This was one small study, mostly in men, with easy sessions only. It says nothing about intervals, long runs or racing again soon.

Inference for triathletes: easy swimming and cycling, which put less eccentric load on the legs than running, are likely to be at least as safe as easy running in the days after a marathon. That hasn't been tested.

The build-up: where most of the risk sits

For many triathletes, the race itself is less risky than the preparation. A marathon block means more running than usual, longer long runs and often faster sessions, during winter, when surfaces are hard and many runs are in the dark.

Injury rates by runner type

A 2015 meta-analysis by Videbæk and colleagues in Sports Medicine pooled 13 studies of injury rates per 1000 hours of running:

• Novice runners had 17.8 injuries per 1000 hours.
• Recreational runners had 7.7 injuries per 1000 hours.
• Individual studies ranged from 2.5 to 33.0 injuries per 1000 hours.

Inference: a triathlete who runs only two or three times a week may be closer to a novice than a recreational runner in terms of running-specific tissue tolerance, even if their aerobic fitness is high. A rapid jump in running is where that gap shows. TriForward's "Forget the 10% Weekly Rule" covers why single-session jumps in distance matter, and "Heel Pain in the Winter Build" covers one of the injuries that a winter run build can trigger.

Training volume and long runs

A 2020 study by Fokkema and colleagues in the Scandinavian Journal of Medicine & Science in Sports followed 556 half-marathon and 441 marathon recreational runners through their preparation.

• Half-marathon runners who ran more than 32 km a week, or did a long run of more than 21 km, finished faster and slowed less during the race.
• Marathon runners who ran less than 40 km a week finished slower, and those who ran more than 65 km a week finished faster.
• A longest run under 25 km was linked to a marathon finish about 13 minutes slower.
• None of these training characteristics was associated with running injuries.

Inference: to get the most from a marathon, you need a substantial run build, which for most triathletes means cutting swim or bike time. A half marathon can be run well on much less, which is one reason it fits more easily into a triathlete's winter. TriForward's "How Long Does Your Ironman Long Run Really Need to Be?" uses the same study for Ironman preparation.

Illness around race day

A 2006 study by Ekblom and colleagues in the Scandinavian Journal of Medicine & Science in Sports surveyed 1,694 runners from the 2000 Stockholm Marathon, about 17% of finishers, about infections in the three weeks before and after the race.

• 17% reported an infection in the three weeks before the race.
• 19% reported an infection in the three weeks after.
• Among runners who had been ill beforehand, 33% also reported an infection afterwards, compared with 16% of those who hadn't been ill.
• Training volume over the previous six months wasn't related to infection.

The authors concluded that the study didn't support the idea that marathon running generally increases infection rates in recreational runners, but suggested that hard exercise too soon after an infection may cause problems. A winter race falls in cold and flu season. Inference: if you're ill in the run-up, the safest decision is often to drop down to a shorter race or skip it. TriForward's "Train Through a Cold?" covers when to rest.

How a winter race fits a triathlon season

No study has tested whether a winter marathon helps or hurts the following triathlon season. The following is inference from the evidence above.

Timing

• December or January half marathon: easy to fit. It sits at the end of the off-season, needs only a modest run build, and leaves months before spring racing.
• February or March marathon: harder. The build runs through the winter months when many triathletes would be building bike volume, and recovery takes up part of the early-season block.
• A marathon within eight weeks of a key triathlon: usually a poor trade. Recovery, a rebuild and a taper all have to fit into a short window.

What limits your triathlon?

• If the run is your clear weakness, and especially if you fade late in long-course runs, a run block can target it. TriForward's "Why the Ironman Marathon Falls Apart After 25 km" covers running durability.
• If the bike is your limiter, winter is often the best time to build it, and a marathon block takes time away from it.
• If your swim is weak, a winter swim block may give more race-day time back than a marathon. TriForward's "Where Should Your Next Training Hour Go?" covers this trade-off.

Your running history

• Experienced runners with several years of consistent running are better placed to handle a marathon build.
• Triathletes with a history of run injuries, especially bone stress injuries, tendon problems or plantar heel pain, should be more cautious. A half may be the better compromise.

A triathlon scenario

The following example is illustrative, not drawn from a study. A 42-year-old triathlete is targeting a half-distance race in mid-June. Her run has been her weakest leg for two seasons, and she's considering a marathon in late March.

Applying the evidence:

• Recovery: muscle-damage markers take about a week to settle. Allowing at least two weeks of easy training after the marathon, plus a gradual return to harder sessions, takes her to mid-April.
• Build-up: a marathon block from December to March means four or five runs a week, with a long run above 25 km. That's a big increase from her usual three runs a week, and most of her bike volume would shrink.
• Spring: that leaves about eight weeks to rebuild her bike before the June race.

An alternative is a half marathon in late January. It needs a smaller run build, gives her a benchmark and a run-focused block, and leaves February to June for a structured triathlon build with the bike restored. Given her goal, the half looks like the better fit, and she keeps a marathon for a year when she isn't targeting an early-summer triathlon.

Common mistakes

• Treating the winter race as the A-race and building the rest of the season around recovery from it.
• Racing a marathon off triathlon run volume. The Fokkema data link low weekly volume and short long runs to slower marathon times.
• Jumping run volume quickly in November and December to catch up.
• Racing hard while ill or straight after an illness.
• Doing hard sessions in the first week after a marathon because the legs feel fine.
• Dropping all bike and swim training during the marathon build, then trying to rebuild them in a rush.
• Booking a marathon too close to the first key triathlon, leaving no room for recovery and a taper.

What we don't know

• Whether a winter marathon helps a triathlon season. No study has compared triathletes who do one with those who don't.
• Recovery after a half marathon. There's much less data than for the full distance, and no direct comparison.
• Women. The recovery studies were mostly in men; in one, only 10 of 64 runners were women.
• Older athletes. Recovery may take longer with age, but the studies here didn't test that directly. TriForward's "The Masters Training Week" covers recovery after 50.
• Functional recovery. Blood markers don't map neatly onto when you can train hard again, and no study has measured when triathletes can safely resume hard bike or run sessions after a marathon.

References

• Bernat-Adell MD, Collado-Boira EJ, Moles-Julio P, Panizo-González N, Martínez-Navarro I, Hernando-Fuster B, Hernando-Domingo C. Recovery of inflammation, cardiac, and muscle damage biomarkers after running a marathon. Journal of Strength and Conditioning Research, 2021;35(3):626–632. doi:10.1519/JSC.0000000000003167
• Martínez-Navarro I, Montoya-Vieco A, Hernando C, Hernando B, Panizo N, Collado E. The week after running a marathon: effects of running vs elliptical training vs resting on neuromuscular performance and muscle damage recovery. European Journal of Sport Science, 2021;21(12):1668–1674. doi:10.1080/17461391.2020.1857441
• Del Coso J, Fernández D, Abián-Vicén J, Salinero JJ, González-Millán C, Areces F, Ruiz D, Gallo-Salazar C, Calleja-González J, Pérez-González B. Running pace decrease during a marathon is positively related to blood markers of muscle damage. PLoS ONE, 2013;8(2):e57602. doi:10.1371/journal.pone.0057602
• Fokkema T, van Damme AADN, Fornerod MWJ, de Vos RJ, Bierma-Zeinstra SMA, van Middelkoop M. Training for a (half-)marathon: training volume and longest endurance run related to performance and running injuries. Scandinavian Journal of Medicine & Science in Sports, 2020;30(9):1692–1704. doi:10.1111/sms.13725
• Videbæk S, Bueno AM, Nielsen RO, Rasmussen S. Incidence of running-related injuries per 1000 h of running in different types of runners: a systematic review and meta-analysis. Sports Medicine, 2015;45(7):1017–1026. doi:10.1007/s40279-015-0333-8
• Ekblom B, Ekblom O, Malm C. Infectious episodes before and after a marathon race. Scandinavian Journal of Medicine & Science in Sports, 2006;16(4):287–293. doi:10.1111/j.1600-0838.2005.00490.x