Training Over Christmas: Keep Your Form, Skip the Guilt

Between the first Sunday of Advent and the first week of January, most endurance athletes face three weeks in which almost nothing goes to plan: celebrations in the evening, cookies in the kitchen, relatives in the living room, minus two degrees outside and darkness by half past four. This stretch produces two classic mistakes. Some athletes stubbornly continue their December programme and arrive in January with a cold and a performance dip. Others let everything slide and start the new season off six weeks of nothing. Both are avoidable — and the middle path is far more relaxed than most training literature suggests.

The good news: two weeks off destroys nothing

Detraining is real, but it moves far more slowly than your guilty conscience suggests. Oxygen uptake falls by roughly three to six percent in the first two weeks without training, then the curve flattens. Muscle strength persists considerably longer than endurance, and capillarisation and mitochondrial density only decline measurably after four to six weeks. In practice: ten days off between Christmas and New Year costs you no form at all, it builds recovery — provided the weeks before were reasonably structured.

The real damage comes not from the break but from the return. Anyone who tries to make up three weeks of lost stimulus in the first January week produces exactly the overload that leads to shin splints, Achilles irritation or an infection. The details are in Detraining and training breaks.

The December problem in numbers

December has genuinely less available time than any other month — and more calories. One celebration with mulled wine, cookies and dinner easily adds up to 1,200 to 1,800 kilocalories, and the next morning's session does not change that. An average runner burns roughly 450 to 550 kilocalories in a 45-minute easy run. You cannot out-train the holidays, and trying usually leads to a cycle of guilt and even worse sleep.

The smarter inversion: don't train more so you can eat more, but place training so the holidays are easier to handle. Two sessions a week with a clear purpose beat five joyless runs done out of obligation.

The minimum programme: two sessions, two jobs

For three to four weeks in December, two sessions per week are enough — provided they serve different purposes. The first preserves intensity, the second preserves endurance.

• Session A — the sharp stimulus (30–40 minutes): 10 minutes easy, then 4 × 4 minutes hard with 3 minutes jogging recovery, 5 minutes easy to finish. That is 16 minutes around anaerobic threshold and just above VO2max — enough to hold oxygen uptake without leaving you fatigued for days. Short on time? 20 minutes of fartlek with 6 × 60 seconds brisk.
• Session B — the long easy run (60–90 minutes): Steady base work in zone 2. This is where volume adaptation happens: fat metabolism, capillarisation, tendon and bone loading. If it is too cold for that long outdoors, split it — 45 minutes running plus 30 minutes on the trainer or elliptical.

On top of that, ten minutes of bodyweight strength once a week is worth the effort: squats, lunges, calf raises, single-leg crossovers, plank. No gym, no equipment, no changing rooms — it fits between two appointments in the living room. How much strength work really delivers for runners is covered in Strength training for runners.

A sample week between the holidays

The week between 24 and 31 December is the hardest — here is a framework that survives family commitments:

• Christmas Eve: 30 minutes easy in the morning, then the day is free. No hard training, the night will be short.
• Christmas Day: Rest. A 45-minute walk after dinner is active recovery, not training.
• Boxing Day: Session A — 35 minutes with 4 × 4 minutes. Early, before visitors arrive.
• 27 December: Rest or 20 minutes of mobility.
• 28 December: Session B — 75 minutes easy. Use daylight, between 10 am and 2 pm.
• 29–30 December: Repeat one of the two sessions, depending on how you feel and what is on the calendar. Two sessions is the target, three is a bonus.
• 31 December: 30 minutes easy in the morning — or nothing at all. Both are fine.

That totals around 2.5 hours of training this week instead of the usual six to eight. It sounds like little, but it is precisely the dose that maintains the stimulus without blocking recovery.

What mulled wine, cookies and fondue actually do

The nutrition side is less dramatic than its reputation, as long as two things are right: timing and dose.

• Alcohol: One or two glasses cost about three to five percent of performance the next day and measurably impair recovery, because alcohol suppresses muscle protein synthesis by 20 to 30 percent and fragments deep sleep. The rule is simple: at least eight hours between the last glass and a hard session, and no session the morning after a celebration with more than two glasses.
• Carbohydrates: Cookies and cake are not a training error, they are simply additional energy. An easy run the next morning still makes sense — not to burn it off, but because it stabilises blood sugar and gives the day structure.
• Protein: Over the holidays protein intake often drops below 1.2 grams per kilogram of bodyweight, because meat, cheese and fish get displaced by sweets. One egg at breakfast, skyr as a snack and a portion of meat or legumes at the main meal is enough to prevent that. More on dosing in Protein for endurance athletes.
• Fluids: Mulled wine and punch do not count as hydration. After an evening with alcohol, deliberately drink 500 millilitres of water before the first coffee the next morning — it takes the edge off both the headache and the heavy legs.

Cold, darkness and the question of when

Two boundary conditions matter in December: daylight and temperature. The body needs light to regulate the sleep-wake rhythm, and in December the usable daylight window shrinks to a few hours. Placing the session between 10 am and 2 pm gives you both: daylight and the warmest part of the day.

Around freezing point, the onion rule applies — two thin layers instead of one thick one, so you can shed something after ten minutes. Gloves, a hat and reflective elements once it gets dark are non-negotiable. What else matters in cold and darkness is covered in Winter running.

The January plan: returning without overload

The first January week is not a catch-up week. If you did two sessions a week in December, come back at 70 to 80 percent of your old volume and increase only in the second week. If you stopped entirely, start at 50 percent and build by no more than ten percent per week. The rule stands: the body loses slowly and builds slowly — impatience is the actual injury factor.

For athletes targeting a spring marathon, December is not a wasted month anyway: a 16-week plan for an April marathon starts in early January, a 12-week plan at the end of January. Everything that happens in December is preparation for the preparation. If you already have the marathon build in mind, you can treat the holidays as part of the build rather than an interruption.

Common mistakes

• Trying to make it all up. 24 December is not a training debt to be settled on the 27th. Catching up produces fatigue without adaptation.
• Clinging to the plan. When a session does not fit the day, the right answer is to move it or skip it — not to shorten it and then rush.
• Declaring every celebration an exception. Three celebrations a week justified with "it's Christmas" are no longer an exception, they are the new normal. Two deliberate celebrations and two normal days work better than seven half-compromises.
• Training while ill. In December every virus circulates at once. A sore throat with a fever means rest, not an easy session. The rule: symptoms above the neck permit light movement, fever and aching limbs do not.
• Ignoring the watch. If resting heart rate sits five to seven beats above normal for several days, that is not a sign of too little training but of too little recovery.

How Peakora plans the holidays

The Peakora engine has no "holiday logic" — and it does not need one. The plan works with availability and load: if you enter only two sessions in a week, the engine distributes the stimulus across those two slots and automatically prioritises the session with the higher training value. If a session is missed, the plan moves it rather than deleting it and adjusts the following week so no load jump occurs. The recovery monitor shows transparently how form (TSB), sleep and recovery breaks interact — after two evenings with little sleep the recommended intensity drops without you having to judge it yourself. The underlying system is explained in the Peakora lexicon under training stress and supercompensation.