By Randall Cooper, Sports & Exercise Physiotherapist
We’ve all heard it: “Sleep is important.” But for athletes and active people, it’s not just important, it’s essential.
In Episode 4 of Exercise Matters, Mick Hughes leads the discussion on what sleep actually does to your body, how it affects injury risk, illness, and performance, and what the science says about getting it right.
🎧 Listen to the full episode here
Injury Risk Goes Up When Sleep Goes Down
If you're getting less than 7–8 hours of sleep, you’re setting yourself up for problems. Studies on adolescent athletes show that sleeping less than 8 hours a night increases injury risk by 70%. That’s not a small number. It’s the biggest controllable variable in recovery that most people ignore.
Even in adults, the data shows a U-shaped curve. Too little or too much sleep both increase the chance of injury. The sweet spot? Around 7–9 hours.
Poor Sleep, More Colds
Lack of sleep doesn’t just affect your muscles. It affects your immune system. One study exposed people to a cold virus under controlled conditions. Those sleeping less than 6 hours per night were over 4 times more likely to get sick. If you’re training hard and not sleeping properly, don’t be surprised if you pick up every bug going around.
Sleep and Mental Health
There’s also a clear link between poor sleep and mental health - especially depression. Less than 7 hours of sleep increases depression risk by over 80%. More than 9 hours also increases risk. Again, the range that seems to protect mood and cognition is 7–9 hours.
Athletic Performance
Sleep improves reaction time, accuracy, and decision-making. We’ve seen it in basketball - players who sleep more score better, move faster, and get injured less.
Think of it this way: sleep is free. If it were a supplement, athletes would be spending hundreds of dollars a month on it.
What About Caffeine?
The short version: caffeine works, but the timing matters. If you’re having a strong coffee at 3 p.m., it’s likely still in your system at bedtime. The general rule is:
- Pre-workout supplements → before 9 a.m.
- Coffee → before 1 p.m.
- Tea → less of a problem, but still watch timing
Naps Work—If You Get Them Right
Short naps (20–30 minutes) help alertness. Longer naps (up to 90 minutes) can improve performance and mood. But avoid napping too late in the day or for too long, or it can mess with your night-time sleep.
Practical Sleep Tips
- Stick to a consistent sleep/wake schedule—even on weekends
- Make your room dark, cool (15–21°C), and quiet
- Avoid screens 1–2 hours before bed
- Get sunlight in the morning
- Avoid caffeine after lunch
- Don’t go to bed full—or starving
- If you’re not sleepy, get up and do something relaxing
If you’re training hard but not sleeping well, you’re leaving gains on the table - and increasing your risk of getting injured or sick. It’s the simplest performance fix available.
