The science of coaching feedback.
Coach Sidekick is built on decades of research into how people learn, and one stubborn finding: the most valuable thing a coach does is give feedback, and most of it fades before a player can use it.
Feedback is one of the strongest influences on learning.
When researchers pooled 435 studies and more than 61,000 learners, feedback had one of the larger measurable effects on how people learn. The most rigorous recent estimate puts it at d = 0.48; earlier work reported higher, up to around 0.79.
But the average hides the real lesson. Feedback only works when it carries real information. Detailed, specific feedback is worth roughly four times a simple “good job.”
How we apply it
Coach Sidekick turns what a coach actually says into specific notes for each player, not generic encouragement.
Wisniewski, Zierer & Hattie (2020): effect d = 0.48 across 435 studies; high-information feedback d = 0.99 versus simple reinforcement d = 0.24.
Most of what a coach says never fully lands.
In a study of 342 youth soccer players, athletes could completely reproduce only about a third of the feedback their coach had just given them. On average, 57% of the content was retained, and that was measured immediately, before anyone left the field.
Watch what coaches actually say and the problem compounds: the single most common kind of feedback is general praise, the kind with the least to act on.
How we apply it
Coach Sidekick keeps what was said as a written record each player can come back to, so specific coaching doesn't have to be remembered to be used.
57%
of feedback retained, measured immediately after it was given.
1 in 3
pieces of feedback were reproduced completely.
19 of 31
studies found general praise the most common feedback coaches give.
Retention: Januário et al. (2016), Journal of Human Kinetics. Feedback mix: Corbett, Partington, Ryan & Cope (2024), International Journal of Sports Science & Coaching.
The right practice beats more practice.
The “10,000 hours” story oversold practice. When researchers pooled 88 studies, practice volume explained only about 18% of the difference in performance between athletes.
What the evidence does support is specificity: the practice that carries over to the game is the practice that resembles the exact thing you're trying to improve.
How we apply it
Drills are matched to what the coach actually said to each player, up to three each time the coach sends notes, so practice at home targets the skill behind the note.
18%
of the difference in athletic performance is explained by practice volume.
Practice volume: Macnamara, Hambrick & Oswald (2014), Psychological Science (18% in sport; ~14% overall). Specificity of transfer: Oppici & Panchuk (2021), Psychology of Sport and Exercise.
A player is a shape, not a score.
No single number describes a developing player. Each player's map spans four domains of the game, technical, tactical, physical and psychological, showing how often the coaching touched each skill and what the coach has assessed. It stays a shape, never a rank. See the map.
The evidence, in full.
- Wisniewski, B., Zierer, K., & Hattie, J. (2020). The Power of Feedback Revisited: A Meta-Analysis of Educational Feedback Research. Frontiers in Psychology, 10, 3087. doi.org/10.3389/fpsyg.2019.03087
- Januário, N., Rosado, A., Mesquita, I., Gallego, J., & Aguilar-Parra, J. M. (2016). Determinants of feedback retention in soccer players. Journal of Human Kinetics, 51.
- Corbett, J., Partington, M., Ryan, J., & Cope, E. (2024). A systematic review of coach augmented verbal feedback during practice and competition in team sports. International Journal of Sports Science & Coaching, 19(2), 864–881. doi.org/10.1177/17479541231218665
- Macnamara, B. N., Hambrick, D. Z., & Oswald, F. L. (2014). Deliberate Practice and Performance in Music, Games, Sports, Education, and Professions: A Meta-Analysis. Psychological Science, 25(8), 1608–1618. doi.org/10.1177/0956797614535810
- Oppici, L., & Panchuk, D. (2021). Specific and general transfer of perceptual-motor skills and learning between sports: A systematic review. Psychology of Sport and Exercise, 59, 102118. doi.org/10.1016/j.psychsport.2021.102118