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Mechanics14 Sept 20266 min read

The head is part of the training

Attention, sleep and mental rehearsal — three large reviews of the research, with charts.

In short
  • Across 73 studies, focusing on the effect of a movement beat focusing on your own body — and the gap was about twice as large for learning.
  • In a 2023 review of 25 studies in athletes, sleeping longer and napping were the most effective sleep strategies.
  • Across 13 studies, imagining a movement increased maximal strength compared with no training — but less than real training.

Training is usually measured in things you can see: kilos, metres, minutes. But part of what decides a performance happens where nobody can see it — in attention, in sleep and in the mind.

This is not about motivation. It is about three things researchers have measured again and again, and that have since been pulled together in systematic reviews.

Why reviews, not single studies. One study can be lucky. A systematic review collects every study that fits a clear set of rules and looks at them together. A meta-analysis goes a step further and combines their results into one number.

Focus on the target, not on yourself

Where should your attention go during a movement? Researchers separate two kinds of focus. An internal focus is on the movements of your own body parts — for example your arm or your hips. An external focus is on the intended effect of the movement — for example the ball or the target.

In 2021, Chua and colleagues combined the studies that compared the two in a meta-analysis published in Psychological Bulletin. For performance they had 73 studies with 1,824 participants. For learning — how well a skill is kept and carried into a new situation later — they had 40 studies with 1,274 participants.

An external focus came out ahead in every comparison. The advantage for performance in the moment was small. The advantage for learning was more than twice as large, both for keeping the skill and for transferring it.

Figure 1

An external focus beat an internal focus — most clearly for learning

Dot: average effect size (Hedges' g). Shaded band: 95% confidence interval. Further right means a bigger advantage for an external focus.

Source: Chua et al., Psychological Bulletin 2021. Labels small / medium / large follow the common rule of thumb for effect sizes.
How to read an effect size. Hedges' g shows how far apart two conditions are, measured in standard deviations. As a common rule of thumb, 0.2 is a small difference, 0.5 medium and 0.8 large. The confidence interval shows the range the true value most likely falls in.

Two more findings from the same analysis. In 12 studies with 216 participants that measured muscle activity, an external focus was linked to more efficient neuromuscular processing (g = 0.83). And in 9 studies with 272 participants, a more distant external focus did slightly better than a closer one (g = 0.22).

The part that matters most for anyone reading this: the advantage did not depend on age, health or skill level. It held for beginners and for experienced performers alike.

Sleep is part of the session

Cunha and colleagues searched three research databases in May 2022 and found 1,584 records. Only 25 studies met their rules: the participants were athletes, the study tested a way to improve sleep, and it measured at least one objective outcome for performance or recovery. All 25 were published between 2011 and 2021.

Figure 2

25 studies, eight strategies — and what the review concluded

Number of studies for each strategy. Colour shows the authors' conclusion.

Most effectivePromising, needs more studiesNo effect found (few studies)Combined strategies
Source: Cunha et al., Sports Medicine – Open 2023, Table 1 and conclusions. None of the 25 studies was judged to be at low risk of bias.

Two strategies stood out. Sleep extension — simply sleeping longer at night — was tested in four studies, and all of them reported a positive effect on performance, such as reaction time or sport-specific skills. In those studies, athletes who usually slept about seven hours added 46 to 113 minutes a night (11–27% more) over 3 to 49 nights. To get there, they needed 9 to 10 hours in bed.

Naps were the most studied strategy, with nine studies. Most showed a benefit for cognitive performance, such as attention and reaction, while the results for physical performance and recovery were mixed. The authors conclude that a 20–90-minute nap can improve performance after a normal night, and bring it back to baseline after a night of shortened sleep.

The rest did less. Mindfulness and light interventions looked promising, but rest on very few studies. Sleep hygiene routines, removing phones and other devices at night, and cold water immersion showed no effect on sleep or on the performance that followed — again, based on only a few studies.

The authors are open about the limits: none of the 25 studies was judged to be at low risk of bias. The direction is consistent, but the evidence is not yet strong.

Training in your head still counts

Motor imagery means rehearsing a movement in your mind without actually contracting the muscles. Paravlic and colleagues collected 13 studies with 370 healthy adults to see whether it can build maximal strength.

Figure 3

Imagery builds strength — but real training builds more

Effect on maximal voluntary strength in each comparison.

Imagery vs no trainingModerate gain with imagery
Imagery vs physical trainingSmall benefit for physical training
Imagery + physical vs physical aloneUnclear
Source: Paravlic et al., Sports Medicine 2018 — 13 studies, 370 healthy adults.

Compared with no training, imagery practice moderately improved maximal voluntary strength, in both the upper and the lower body. Compared with real physical training, the difference was small and in favour of physical training. Adding imagery to physical training, compared with physical training alone, gave unclear results.

The authors also looked at how much imagery was linked to the best results.

Figure 4

The imagery dose linked to bigger strength gains

What the studies with larger improvements had in common.

4weeks
3×per week
2–3sets per session
25repetitions per set
15minutes per session
Source: Paravlic et al., Sports Medicine 2018, meta-regression. These are associations across studies, not a tested programme.

Their conclusion is careful: imagery could be used as a substitute or an additional tool to preserve muscle function when athletes are not exposed to maximal training intensities.

The limits

  • None of this replaces training. Imagery gave less than real practice, and none of these strategies is a shortcut.
  • These are averages. What holds across dozens of studies can work differently for one person.
  • The sleep evidence is still weak in quality. The direction is consistent; the certainty is not high.
  • This is not medical advice. If sleep problems persist or you have a health condition, talk to a professional.

Read the research

  1. Chua LK, Jimenez-Diaz J, Lewthwaite R, Kim T, Wulf G. Superiority of external attentional focus for motor performance and learning: systematic reviews and meta-analyses. Psychological Bulletin. 2021;147(6):618–645. doi:10.1037/bul0000335
  2. Cunha LA, Costa JA, Marques EA, Brito J, Lastella M, Figueiredo P. The impact of sleep interventions on athletic performance: a systematic review. Sports Medicine – Open. 2023;9:58. doi:10.1186/s40798-023-00599-z
  3. Paravlic AH, Slimani M, Tod D, Marusic U, Milanovic Z, Pisot R. Effects and dose-response relationships of motor imagery practice on strength development in healthy adult populations: a systematic review and meta-analysis. Sports Medicine. 2018;48(5):1165–1187. doi:10.1007/s40279-018-0874-8

Checked against the original papers, 14 September 2026. Educational content — not medical advice.

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