What Rest Days Actually Do for Your Body
Yes, you need them. What a rest day does for your muscles, tendons and bones, what to do on one, and the signs you could use an extra one.
By Just5K
Key Takeaways
- Yes, beginners need rest days. The NHS Couch to 5K plan asks for a rest day between runs and calls rest days "just as important as the runs themselves".
- Each part of you recovers at its own speed. Soreness after something new peaks two or three days later. Tendons keep rebuilding for about three days after a hard session. Bone takes weeks to months.
- On a rest day, don't run. Walk, cycle, do a few strength exercises, or do nothing at all. Stretch if it feels good, but it won't stop soreness.
- Sleep is part of the rest. Adults need seven hours or more, and athletes who sleep that much tend to get hurt less often.
- Notice how you feel. Heavy legs, poor sleep or dreading a run are reasons to take an extra day. It costs you nothing.
Do You Need Rest Days When Running?
You've finally started, and now the plan tells you to stop. It feels wrong. You've built a bit of momentum, and a day off feels like losing it.
But the rest day is part of the training. The NHS Couch to 5K plan puts it plainly: "Rest days give your body time to recover, help prevent injury, and are just as important as the runs themselves." That's why it asks for three runs a week with a rest day between each one. Why three, and why not every day, is in how often beginners should run.
Why Are Rest Days Important for Runners?
A run is a small stress. Your body answers it by repairing and rebuilding, and that work happens after the run, over the following days. Different parts of you take very different amounts of time:
| Part of you | How long it takes to catch up |
|---|---|
| Muscles | Soreness after a new kind of exercise peaks 48 to 72 hours later, then fades |
| Tendons | After a hard session, the body keeps building new tendon tissue for about three days |
| Bones | Clearing out old bone takes about four weeks, and replacing it about three months |
| Energy stores | With normal meals, within a day |
Bone is the slow one. In military recruits who went from sitting to hard training, bone stress injuries tended to show up three to four weeks after the jump, not on the day. Running can feel fine for weeks while your bones are still catching up. That's why beginner plans add a little at a time and keep a day off between runs. It's also the answer to how long a beginner should run: not long at first, and longer only bit by bit.
Fuel is the fast one. Many articles say rest days are for refilling your energy stores. That matters for long, hard training. After a 30-minute walk-run, the sports nutrition guidelines say stores are back to normal within a day of normal eating, and fast refuelling only matters when two hard sessions are less than eight hours apart. For a beginner, the rest day is mostly for tendons and bones.
This is also why shin splints are so common in the first weeks of a plan. The pain usually comes from doing more than the bone and the tissue around it are ready for.
What to Do on Rest Days
A rest day means no running. It doesn't have to mean no moving.
- Walk. Mayo Clinic's beginner 5K plan puts 30-minute walks on two of its non-running days. Light movement may also ease soreness: a review of 99 studies found that light activity after exercise reduced it, though it didn't test walks on a rest day.
- Something easy that isn't running. The same plan suggests cycling, rowing or water running on the walking days.
- A little strength work. The World Health Organization recommends muscle-strengthening activity on two or more days a week. In a review of 25 trials across many sports, strength training cut injuries to less than a third. Squats, calf raises and a plank at home are enough to start.
- Stretch, if you like it. A Cochrane review found that stretching after exercise lowered next-day soreness by about one point on a 100-point scale, and another found it didn't prevent running injuries. So stretch because it feels nice.
- Or nothing at all. Mayo's plan keeps one day a week free of any exercise. A day on the sofa counts.
Tip: If a rest day leaves you restless, put a walk in your diary at the time you'd usually run. You keep the habit, and your legs get their day off.
Sleep Is Part of the Rest
Your body does a lot of its repair work while you sleep. In a lab study, one night without sleep cut the next day's muscle building by 18%. The CDC says adults need seven hours or more a night.
It seems to matter for injuries, too. In a year-long study of 95 endurance athletes, including runners, those who slept more than seven hours a night had about a third lower risk of a new injury. That's a link, not proof, and they weren't beginners. But if your runs are early and your nights are short, an earlier bedtime may do more for your running than an extra session.
Soreness or Pain?
Some soreness is normal, especially in the first weeks or after something new. It's often worst on the second or third day, then fades, and it eases as you move around. What's worth noticing is soreness that's still getting worse after that, or that builds from one run to the next.
Pain is different. A return-to-running programme from Berkshire Healthcare says to ease off if pain lasts more than two days, gets worse during a run, is sharp, or comes with swelling. If it doesn't settle with rest, see your GP or a physio.
Signs You Could Use an Extra Rest Day
There's no test that tells you you're tired. Even in elite sport, no marker can diagnose overtraining, and how athletes say they feel tracks their training better than measurements do. So pay attention to things like:
- Your legs feel heavy for the whole run, not just the first few minutes.
- You're sleeping badly, or waking up tired.
- You're dreading the next run in a way that feels like tiredness, not nerves.
- Soreness is building from one run to the next instead of fading.
If your watch shows your resting heart rate a few beats higher than usual, it could be a short night, stress or a drink the evening before, which all raise it, or a cold on the way. On its own it doesn't mean much. More on reading those numbers in what your Apple Watch heart rate means.
If a few of these sound familiar, take an extra rest day or make the next session a walk. An extra day off doesn't set you back; more on that in what to do after a missed running workout. And if you've been away for longer, here's how to start running again after a break.
Where Just5K Fits
Full disclosure: this is our app. Just5K builds the rest days in:
- Three sessions a week on the days you pick when you set it up: Monday, Wednesday and Friday unless you choose others. Pick two days in a row and it suggests a rest day between them. On rest days, Home just says "Rest day".
- An easy way to take an extra one. The morning check-in asks how you feel. Answer "Drained" on a session day and you can tap "Make today a rest day": the session waits for your next training day.
- Nothing to catch up. The plan moves on when you finish a session, not when the calendar does. Miss one, and "Run it today" on your next rest day lets you do it then, or you just pick up with the next session.
Just5K is in a free public beta on TestFlight now. After the App Store release, the whole road to your first 5K stays free: Gentle Start and all eight weeks of the 5K program. 5K → 10K after its first week needs Just5K Plus, a one-time $9.99, not a subscription.
FAQ
Do you need rest days when running?
Yes, especially as a beginner. Run three times a week with a day between runs. Your muscles settle within a few days, but tendons and bones need longer, and they're where new runners get hurt.
What should I do on a rest day from running?
Anything easy that isn't running: a walk, a bike ride, a swim or a few strength exercises. A day of doing nothing is fine too. Sleeping well matters more than any of them.
Is it bad to run on a rest day?
While you're on a beginner plan, yes. Running two days in a row gives your tendons and bones less time to adapt. If you feel great, go for a walk instead and save the energy for the next session.
Should I stretch on rest days?
If you enjoy it. Studies found stretching makes very little difference to soreness and doesn't prevent running injuries, so it's optional, not a must.
How many rest days a week do beginners need?
Three or four. Run on three days with a day between each, and walk or rest on the others. Keep at least one day a week completely easy.
Rest is when the running sinks in. Take the day off, go for a walk, get to bed a little earlier. Your tendons and bones are still at work.