The clocks went back on Sunday 25 October, and most of us have already felt the result: an alarm that rings in the dark, a session that feels heavier than it should, and a flat sense that the legs are not quite there. Searches for daylight saving UK fitness spike every autumn for good reason. The hour you gained in bed is quickly lost to a body clock still set to the old light. Here is what is really happening, which adjustments hold up, and where people waste effort.
Key Insight |
Explanation |
|---|---|
Expect a slow first week |
Circadian realignment typically takes around three to seven days, so judge your progress over a week rather than a single session. |
Cut intensity, not consistency |
For the first few days, reduce target intensity by roughly 10 to 20 percent and keep showing up for every planned session. |
Get daylight before you train |
Outdoor light in the morning helps set your body clock, so a short walk or outdoor warm-up before a session pays off. |
Shift hard sessions later |
If you feel flat early, move key sessions to mid-morning or afternoon rather than forcing a 6am interval set. |
Protect sleep before adding load |
Sleep is the cheapest recovery tool you have, so protect your bedtime for the first week before adding volume. |
Recheck hydration and electrolytes |
Shorter, darker days shift meals, drinks and training times, so review your fluid and electrolyte intake rather than assuming it is fine. |
Plan indoor backups now |
Dark evenings make outdoor sessions less appealing, so pick two indoor sessions you can do without thinking. |
The clock change does not alter daylight by itself. What it changes is when light arrives relative to your body clock. Your circadian rhythm, the roughly 24-hour cycle that governs sleep, hormones and metabolism, is tied closely to light, so an hour moved on the wall becomes an hour of mismatch in the body.
Aaptiv's guide to adjusting workouts, written about the spring change, describes the effect as a mild case of jet lag without leaving home, and that comparison holds up for the autumn change too. You are not ill, you are out of step. The trouble is that the symptoms look like a motivation problem: a session that felt easy last week now feels like work, and most people assume they have lost discipline.
In practice, the first sign in most training logs is not a drop in strength but a rise in how hard the same pace feels. Heart rate may look normal on a watch while the effort feels a full notch harder. That gap is the clock, not the programme.
A study indexed on PubMed used American Time Use Survey data from adults aged 18 to 64 in Arizona, Colorado, New Mexico and Utah, covering 2003 to 2009. It asked whether daylight saving time was associated with more time spent in moderate physical activity. The authors noted that little research has addressed this question, which tells you how much we still assume rather than know.
Sleep experts cited by Runner's World note that daylight saving time may be linked to cardiovascular events, hospital admissions and mood disturbances. You do not need to be in a clinical group to feel the edge of that. For an athlete, the practical takeaway is narrower: the days right after the change are when your recovery margin is thinnest.
In autumn the change does not take an hour of sleep away, so it is easy to assume nothing much happens. The effect is subtler. Mornings get darker, the light that signals wakefulness arrives later, and evenings feel like bedtime came early. Many people keep their old bedtime and wake at their old alarm, and sleep quality suffers in the process.
Chrissy Lawler, a licensed marriage and family therapist and sleep specialist, is quoted in Aaptiv's guide making the link between disrupted timing and training output:
“When sleep and circadian timing are disrupted, perceived exertion tends to increase and recovery can take longer.”
That is the mechanism behind the flat sessions. Recovery is where you see it first, because repair and hormonal recovery depend on sleep. When sleep is shortened or badly timed, sessions feel heavier and soreness lingers longer than usual.
A physician quoted in the same guide notes that night owls and people already short on sleep struggle more, because their internal clocks run later than the social schedule requires. If you are already training at 6am on five hours a night, the change is not a minor inconvenience. It is the week your training quality drops.
Pro tip: Move your bedtime earlier by about 15 minutes a night for the first few days, rather than trying to recover an entire hour in one go. Your body responds better to gradual steps than to a single abrupt change.
Light is the strongest signal your body clock responds to, and exercise is one of the few things you can do to reinforce it. Aaptiv's guide suggests that physical activity, especially outdoors in natural light, tells your circadian rhythm that it is time to be awake and alert. For UK athletes in late October, that means rethinking when and where you train.
Sunrise now arrives after many people's alarms, and by mid-afternoon the light is already fading. Training indoors at your usual time can mean missing the morning light entirely. The fix is not to train harder in the dark. It is to put yourself in daylight at the right moment.
If your schedule allows, take a short walk or an easy outdoor warm-up in whatever daylight is available before a key session. Even on overcast days, outdoor light is far brighter than most indoor lighting. The point is to give your body a clear signal that the day has started.
Pro tip: Set a reminder to step outside for ten minutes within an hour of waking, then do your warm-up there. It costs nothing, and it is the most reliable change to make during the first week.
Nike's guidance on regulating your body clock is built around working out the best time of day to train and eat, which can improve both sleep and performance. During the first week of adjustment, moving one hard session from first thing to mid-morning or early afternoon is a sensible test. Keep easier sessions early, while the body is still finding its rhythm.
Here is the adjustment I recommend for the first five to seven days after the change. Keep the number of sessions you planned, but reduce the target intensity of each, and swap one heavy day for a technique or easy aerobic session. The aim is to finish the week feeling sharper, not to set a personal best on a Tuesday.
Aaptiv's guide also works through daylight saving adjustments and recommends reducing training intensity by about 10 to 20 percent for the first few days. That range is sensible for most recreational athletes. Anyone training for a race or a competition should be more careful about what they call a 10 percent cut, because the margin for error is smaller.
On days one and two, keep easy runs or rides easy, skip maximal efforts, and go to bed earlier. On days three to five, reintroduce one moderate session at normal load and watch how it feels. By day seven most people feel the gap closing, though some will need a few more days.
Pro tip: Log your rating of perceived effort for the same session, at the same pace, each day. If that number keeps climbing, you are not ready for more load yet, whatever the watch says.
The most common mistake is treating a dip as a reason to skip training altogether. In most cases, a week off costs more fitness than a week of slightly lighter work, and it makes the return harder. Keep the habit and change the target.
A practical example: if your plan calls for six hard intervals, do four at the same pace with longer rests, then finish with a steady warm-down. You keep the stimulus and the routine without asking your body to chase the old schedule.
Hydration tends to slip when routines break, and the clock change is a routine break. Earlier darkness can move dinner earlier, shift training into a different part of the day, and leave drinks forgotten around work. Each change is small, but together they add up over a week.
If you are moving sessions to a different time of day, your fluid and electrolyte habits need the same review. An electrolyte drink is most useful when you are sweating through a hard session, not as a background habit, so match the product to the training you are actually doing. Many people only start drinking once they are already behind.
At Plusssz we formulate our electrolyte hydration range with no added sugar, so you can support training without the sugar load that some products bring. Check the label for the electrolytes each product contains and how much sugar it adds, rather than assuming all hydration products are the same.
Many people shift to indoor training when evenings darken, and heated gyms and living rooms can make it easy to underestimate fluid loss. Plan drinks before the session, not during it. A simple habit is to keep a bottle beside you during any indoor session and to check your urine colour when you wake.
Not every adjustment suits every athlete. Some people need to move their whole training block, while others only need a lighter week. The table below compares three approaches that come up most often, along with the situations where each one works best.
Reducing intensity for a few days works well for people with flexible plans and a clear recovery window. Moving sessions later suits those whose early mornings are the main problem. Keeping the full plan and relying on sleep alone works only if your sleep was already solid before the change.
Approach |
What It Involves |
Best For |
|---|---|---|
Short intensity reduction |
Cut target intensity by roughly 10 to 20 percent for three to five days, keeping the session count the same |
Recreational runners and gym users with flexible weekly plans |
Later session timing |
Move hard sessions to mid-morning or early afternoon and keep easy work early in the day |
People who feel flat at their usual early slot |
Full plan with sleep priority |
Keep the programme as written and protect bedtime with an earlier wind-down routine |
Athletes with strong sleep habits and tight race preparation |
The sleep-first approach is the least disruptive option, but it is also the weakest if your sleep was already poor before the clocks changed. If you are waking at 5am on five hours a night, no amount of bedtime discipline will make a full plan safe. In that case, reduce load first and rebuild sleep before anything else.
Moving sessions later works best for lifters and team athletes on fixed schedules, where a 2pm session is easier to fit than a shift in the whole week. Whichever approach you choose, review after a week. If the same session still feels harder at the same pace, the adjustment needs to run longer, not shorter.
Motivation dips in late autumn for a reason: the light goes early, the weather turns and the warm sofa wins. Treat that as a scheduling problem, not a character flaw. The fix is to build a plan that works in the dark before you need it.
Choose two indoor sessions you can do without thinking, and put them in the calendar now. Keep the kit by the door, and decide your warm-up before you leave the house. Decisions made in advance survive the first cold, wet Tuesday.
Warm-up matters more when the air is cold. A ten-minute indoor routine that raises your temperature before any hard work makes sessions feel easier and reduces the temptation to rush. Track each session in a simple log, because three weeks of steady entries is a strong argument when the sofa is calling.
Rather than chasing a seasonal peak, set a modest target for the months until the clocks go forward again next March. A realistic goal gives you a reason to keep showing up through the darkest weeks. Consistency through winter usually matters more than a strong October.
Most people settle within about three to seven days, according to the guidance Aaptiv published on daylight saving time, though your sleep habits and training load can change that window. If you are still flat after a week, reduce load further and check your sleep before adding more work.
Train at the time you can do consistently, but prioritise daylight exposure when you can. If mornings are dark and you are sleeping well, an early indoor session is fine. If you feel flat early, move the hardest work to mid-morning or afternoon for a week and compare.
There has been little research on this question. A PubMed-indexed study looked at adults in four US states to test whether daylight saving time was associated with more moderate physical activity. For your own training, the useful question is not what happens across a population but how your sessions feel this week.
Not for every session. Electrolytes matter most when you are sweating heavily or training for longer, and when your routine has shifted enough to affect your drinking habits. Choose a product with no added sugar, check what it contains, and use it when the session calls for it.
Get outside in daylight within an hour of waking, then keep at least one session per week at a manageable intensity until your energy settles. Those two changes address the body clock and the training load together, which is where most of the problem sits.
Tell us what changed in your training this week and which adjustment helped most.
