Every spring brings the same story into the clinic. Someone picks up running again, gets back to the gym, or spends the first warm Saturday in the garden, and a knee, a heel or a back that was fine in September is suddenly not. Nothing dramatic happened. The body spent the winter being asked for less, and in April it was asked for more than it had left.
This is the long version of Issue 5 of The ONE80 Turnaround, our newsletter. It covers what capacity is, why the winter quietly drains it, and what the research says about the four things that build it back: Sleep, Nutrition, Mindset and Movement.
What this post covers
Capacity: the idea underneath most of what we treat
Start with the idea that sits underneath almost everything we treat. Your body, and every tissue in it, can handle a certain amount right now. Your knee has a limit. So does your Achilles, your lower back, your nervous system. That limit is what we mean by capacity. Pain usually shows up when what you ask of a tissue goes past what it can currently handle. Not because something is broken. Because you asked for more than it was ready to give that day. We call this the load and capacity model, and it runs through everything we do at ONE80.
The part most people have never been told is that capacity moves. Tendon, bone, muscle, even your nervous system, all adjust to what you regularly ask of them. Ask a little more, steadily, and they give you more. Ask less for long enough and they give you less. That is also why rest makes such a poor long-term plan. Rest takes the load off, but it takes capacity with it, so the moment you go back to normal life the same problem is waiting for you.
Which brings us to winter. Between November and March, most of us ask less of our bodies without ever deciding to. The days get shorter, the weather turns, the calendar fills up, and the walk gets shorter, the gym gets skipped, the sleep gets cut. Your body notices, even if you don't. By March it has less to give than it had in September, and April is usually when you find out.
Why winter lowers capacity
When we work out why a problem started, we use the Five Stressors: the five kinds of load that either ask more of your body or lower what it can give. For most single problems, two or three of them are doing the work. Winter is unusual. All five are busy at once, which is why the season has such a predictable effect on how people feel by March.
The Five Stressors in winter
None of these is a problem on its own. They matter because they add up quietly over four months, and because every one of them has an answer.
What lost capacity feels like
You don't lose capacity in a day, and the early signs are easy to blame on the season. By late winter, most people notice some mix of these:
- Stiffer mornings that take longer to ease, especially in the knees, hips and low back.
- Being more out of breath on a flight of stairs than you were in the fall.
- Soreness for two days after something that used to be easy.
- Slower recovery from a cold, a late night or a hard week.
- An energy slump in the middle of the afternoon, and a shorter fuse in the evening.
- Then, in spring, a knee, a heel, a shin or a back that starts to complain two to four weeks after activity picks up.
If you recognize yourself in that list, you are not injured. You are under-loaded, and that is a much better problem to have, because it responds to exactly the four things below.
How we assess it
You don't need to be hurt to come in. A capacity assessment starts with a conversation about load: what you were doing in the summer, what has changed since, and what you want to be able to do in April. Then we measure, and the tests are simpler than you might expect, because a few basic strength and endurance tests predict how a tissue will cope with load far better than any scan. How many single-leg heel raises can you do? How many times can you stand up from a chair in thirty seconds? How long can you balance on one leg? What does your single-leg squat look like? We ask about sleep and recovery, because they decide how much load you can absorb, and we work out which of the Five Stressors actually apply to you rather than reciting all five.
From there we build a winter plan around the pillars. If something already hurts, we also set your entry point into our four-phase program of care, so the plan deals with the problem you have as well as the capacity you want.
How to build it: the Four Pillars
If the Five Stressors are how capacity falls behind, the Four Pillars are how you build it back. They are deliberately broad; each one does several jobs at once. And winter is when a little attention to them pays off most, because spring rewards whatever you have built by then.
The Four Pillars
Sleep: let daylight set the clock
Your body keeps time by light. It is the main signal your internal clock uses to set itself, and the same light does opposite things depending on when it arrives: in the morning it pulls your clock earlier, in the evening it pushes it later.[1] That is why timing matters more than brightness. Your clock's response to light is already half of its maximum at around 100 lux, and it tops out near 1,000 lux.[2] An overcast Toronto morning gives you several thousand lux outdoors. You don't need direct sun. You need to be outside.
How long is enough? The trials that moved the clock used anywhere from thirty minutes to a few hours of morning light, and thirty minutes still did real work.[6] The fifteen minutes you'll hear quoted elsewhere is a sensible floor, not a tested dose. So: at least fifteen minutes outside within an hour of waking, thirty if you can manage it, no sunglasses. In the weeks after the clocks go back in early November the sun is up around ten to seven, so that light is there before work. By late December sunrise is closer to eight, and a walk at lunch does the same job.
What natural light does. More than most people think. A week of camping, with four times the daytime light and no electric light after dark, moved people's melatonin onset about two hours earlier.[3] A single winter weekend outdoors shifted the clock more than a summer one did.[4] In more than 400,000 UK adults, every extra hour spent outdoors in daylight went with lower odds of depression, fewer insomnia symptoms and easier waking.[5] And daylight protects your evening: a bright day makes your clock less sensitive to light later on, so the lamps and screens after dinner do less to push your sleep back.[19]
Why sleep comes first. One night without it raises your pain sensitivity the next day and measurably changes how your brain handles pain.[7] Follow people over years and a decline in sleep predicts new pain and worse pain, more reliably than pain predicts poor sleep.[8] Tissue repair, your nervous system's control of pain, hormonal recovery, and the judgment you need to pace yourself all run on sleep. No other pillar reaches as far.
In practice. Of all the sleep habits, a fixed wake time matters most. Get up at the same time every day, weekends included, because your body sets its rhythm from when you wake, not from when you go to bed. Get your daylight early. Dim the lights after dinner, have your last coffee by early afternoon, and keep the bedroom cool and dark.
Nutrition: the raw materials for repair
Vitamin D. From November to February the sun over Toronto never gets high enough for your skin to make vitamin D. That was shown decades ago for cities at our latitude.[9] By late winter a lot of people are running low, and the signs are easy to blame on the season: tired, flat, muscles that ache or feel weak, a deep ache in the low back, hips or legs, slow recovery from training, one cold after another. None of those point clearly to vitamin D on their own, which is exactly why testing beats guessing.
On dose, the evidence has moved, and not in the direction most people expect. The Endocrine Society's 2024 guideline tells healthy adults under 75 to take the standard daily allowance rather than more, and advises against routine blood testing.[10] That came after large trials in which 2,000 IU a day, given to adults who mostly had enough already, did not reduce cancer or heart disease[11] or fractures.[12] Our position for a Toronto winter: 1,000 to 2,000 IU a day with food is safe for nearly every adult and a sensible default at this latitude. More is not better. If a test shows you are deficient, the dose that corrects it is often higher, somewhere in the range of 5,000 to 10,000 IU a day for a period, and that is a decision to make with your physician, with the result in hand and a follow-up booked, because vitamin D is stored in the body and builds up. OHIP does not cover the test for most people. It is inexpensive at a private lab, and your physician can order it.
A word on vitamin K2, since many products now pair it with D. The mechanism is real: vitamin K switches on the proteins that steer calcium into bone. The evidence for adding it is not there yet. Trials show it moves bone markers, by amounts of uncertain clinical meaning, and no large trial has shown that adding K2 to vitamin D prevents fractures or heart problems. You don't need it at the doses above. And if you take warfarin, do not add it without talking to your physician.
Protein. When it is cold and dark, appetite drifts toward bread and sugar, and tendon, muscle and bone cannot repair without enough protein. In a meta-analysis of adults doing strength training, the benefit of extra protein levelled off at about 1.6 grams per kilogram of body weight a day.[13] For most adults, 1.2 to 1.6 grams per kilogram, spread across meals rather than piled onto dinner, is a reasonable target. If you weigh 80 kg, that is roughly 95 to 130 grams a day.
Energy. Skipping meals to make room for the evening starves your tissues of the energy they need to adapt. The 2023 International Olympic Committee consensus names low energy availability as a driver of bone stress injury and poor recovery, and it is not only an elite-athlete problem.[14] Busy, active adults who under-eat on weekdays are the common version.
Water. Cold blunts thirst and indoor heating dries you out. Mild dehydration shows up as fatigue and stiffness long before it shows up as thirst.
The holidays. In a prospective study, adults gained a modest amount over the holiday weeks and most never lost it; that one stretch accounted for much of the year's weight gain.[18] One dinner is nothing. Eight weeks of them is something. Keep the weekdays steady and enjoy the occasions.
Mindset: decide now what you will keep
Mindset, as we use the word, is not positive thinking. It is how you relate to load, to pain and to pace, and it can be measured. Self-efficacy, your confidence that you can do something about your own recovery, is one of the strongest predictors of how musculoskeletal pain turns out, whatever the tissue looks like on a scan.[16] Winter leans on it, because the season hands you reasons to stop.
Capacity is not a fixed trait. It builds over time, in the body and in life, and a difficult week tells you where you are today, not where you will end up. That matters, because the alternative, reading a stiff morning as proof that your body is failing, leads to protecting and avoiding, and that lowers capacity further still.
Decide in advance, in concrete terms. A plan like "if it is Tuesday at seven, then I am at the gym" gets kept far more often than a good intention. Across more than ninety studies, if-then plans of that kind had a medium to large effect on whether people actually did what they meant to.[17] Write down what you will keep this winter: the bedtime, the walk, the meal, the session, and when each one happens.
Keep commitments small enough to keep. Every commitment you keep is a small win, and small wins are how confidence gets built. Two sessions you do are worth more than five you plan.
Plan for the lapse. You will have off days. An off day is just that, one day. Don't let it become two.
Watch your mood. Shorter days flatten a lot of people, and low mood means less movement, which flattens mood further. Morning light and a daily walk are the two most reliable ways to break that loop,[5] which is why this pillar leans so heavily on the other three.
Movement: hold what you have built
Movement comes last because the other three make it possible, and because it is the pillar winter hits hardest.
You lose capacity faster than you build it. Strength starts to slip within a few weeks of stopping, and tendon and bone lose their tolerance for load when nothing is asked of them. So if you take the winter off and start again in March, you are not picking up where you left off. You are starting below it, loading a tissue that has lost some of what it had, and a sudden return to activity after a winter off is one of the most common ways an injury starts.
The good news is that holding on costs very little. In a trial where adults built strength over sixteen weeks and then cut back, young adults kept their gains on one third of the original training, and even one ninth held most of it; older adults needed about one third.[15] For most people that means two strength sessions a week, thirty to forty minutes each, heavy enough that the last few repetitions are hard. That is the minimum. Anything beyond it is a gain.
Keep walking. Step counts fall sharply through a Canadian winter, and a daily walk is still the most accessible capacity you can build. Use a treadmill, an indoor track or a mall when the sidewalks are bad.
If you run, keep running. Cold is not the risk; ice is. Shorter, more frequent runs beat long, rare ones. Give yourself ten minutes to warm up instead of five, because cold tissue is stiffer and takes longer to reach working temperature. If you can, run in the morning and collect your daylight at the same time.
Read your body accurately. Stiffness that eases as you move is tissue asking to be used. Pain that builds while you are active and is still there the next morning is the signal to adjust. Knowing which one you are dealing with is most of what keeps a stiff knee from becoming a sore one.
Whatever else has to give this winter, keep moving. Less is fine. The aim is simply not to stop.
Your winter numbers
General advice is easy to nod along to and hard to act on. So here is each pillar as a number you can work out from your own body weight, with the method beside it. These are starting points for healthy adults, not prescriptions. If you have a medical condition, talk to your physician before changing what you eat or take.
| Pillar | The minimum between now and March | How to work out your number |
|---|---|---|
| Sleep | Seven to nine hours a night for adults.[20] Same wake time every day. At least fifteen minutes of daylight before 9 am. Lights down after dinner. | Count back from your fixed wake time. If you need to be up at 6:30, lights out by 11 gives you seven and a half hours in bed, which is about the minimum that delivers seven hours of sleep. |
| Nutrition: protein | 1.2 to 1.6 grams per kilogram of body weight per day, spread over three or four meals.[13] | Weight in kilograms multiplied by 1.2 and by 1.6 gives your daily range. Divide by the number of meals: about 0.4 grams per kilogram per meal is the amount that fully switches on muscle repair.[21] Weight in pounds divided by 2.2 gives kilograms. |
| Nutrition: energy | Enough that your weight stays stable through the winter while you keep training. Do not skip meals to bank calories for the evening. | Quick estimate: weight in kilograms multiplied by 25 (mostly sitting), 30 (two to four sessions a week) or 35 (training most days) gives a rough daily calorie need. For a more precise figure use the Mifflin-St Jeor equation: 10 times weight in kg, plus 6.25 times height in cm, minus 5 times age, plus 5 for men or minus 161 for women, then multiply by 1.4 to 1.7 depending on activity.[22] If your weight is stable, your intake is about right. |
| Nutrition: vitamin D and water | Vitamin D 1,000 to 2,000 IU a day with food. Water through the day. | Vitamin D does not scale with weight at these doses; the range covers nearly every adult. For fluid, a reasonable starting point is 30 to 35 millilitres per kilogram per day from all sources, including food, tea and coffee, and more on training days or in very dry indoor air.[23] |
| Mindset | Write down what you will keep, with days and times. Never miss two in a row. Treat stiffness as a reason to move. | Pick the smallest version of each commitment you are confident you can keep for twelve weeks, then write it as an if-then plan: "If it is Tuesday at seven, then I am at the gym." Review the list on Sunday night. |
| Movement | Two strength sessions a week of thirty to forty minutes. A daily walk. Ten-minute warm-ups before you run. | Strength: the last two or three repetitions of each set should be hard. Walking: around 7,000 steps a day is where the health benefit is largely captured in middle-aged adults; more is fine, but 7,000 is a realistic winter target.[24] |
Worked example: an 80 kg adult training three times a week
Where our treatments fit
The pillars are your work. Ours is different. If a tendon or a joint has stopped responding to what you can do on your own, that is where our treatments come in. Focused and radial shockwave and EMTT get repair going again in a tendon that has stalled. FSM, photobiomodulation and medical acupuncture settle a nervous system that has turned the pain up too high. ART restores the glide that lets a tissue take load again. None of this replaces the pillars. The point is to get the tissue ready so that the work you do takes hold. Each treatment, and what it does for which tissue, is explained on our treatments page.
Common questions
Is fifteen minutes of daylight really enough on a grey day?
Yes, as a floor. Your clock's response to light tops out near 1,000 lux, and an overcast sky outdoors is several times brighter than that, so what limits you is minutes, not brightness. Thirty minutes is better than fifteen, and the trials that moved the clock most used longer exposures, but fifteen minutes outdoors beats an hour at a window.
I eat well. Do I still need vitamin D in winter?
Almost certainly, at this latitude. Food gives you very little vitamin D and the sun gives you none from November to February. A daily 1,000 to 2,000 IU with food is safe and sensible. If you think you might be low, ask your physician for a test before taking more.
Should I take vitamin K2 with vitamin D?
You don't need to. The mechanism is plausible, but no trial has shown that adding K2 improves fracture or heart outcomes, and at 1,000 to 2,000 IU vitamin D does not raise blood calcium in healthy adults. If you take warfarin, do not add K2 without speaking to your physician.
Can I keep running outside through a Toronto winter?
Yes, with two adjustments. Treat ice as the risk, not cold, and move indoors or to a cleared track on the days the sidewalks are bad. Warm up for ten minutes rather than five. Shorter, more frequent runs hold your capacity better than one long weekend run.
I took last winter off and spent the spring injured. How do I avoid repeating it?
Hold the minimum through the winter: two strength sessions a week and a daily walk. If you do lose ground, rebuild in March the way you would after any layoff, with a gradual increase rather than a return to last summer's volume in the first week. An assessment before you ramp up will tell you where your capacity actually is.
When to see someone
Lower capacity is a normal, reversible winter pattern. But see a clinician promptly if any of the following apply, because they point to something that needs its own assessment:
- Loud snoring with pauses in breathing, or waking unrefreshed and fighting sleep during the day, which may be sleep apnea.
- Low mood or loss of interest most days for more than two weeks, or any thoughts of harming yourself.
- Persistent fatigue with unexplained weight change, fever, night sweats or bruising.
- Pain that is present at rest or wakes you at night and is unrelated to activity.
- Chest pain, pressure or unusual breathlessness with exertion.
- Numbness, weakness, or a change in bladder or bowel control.
Want a plan for the winter?
If something is not settling, or you would simply like to arrive in spring stronger than you left summer, book an assessment. We will work out where your body is being asked for more than it can currently give, and build a plan around the pillars that will change that. Same-day and next-day appointments are often available.
Book an Assessment at ONE80 →References
References link to PubMed, PubMed Central or the publisher. In-text numbers correspond to the gold superscripts throughout the post.
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