Principles of optimal practice duration from the expertise literature
The expertise literature and its discussion of deliberate practice provides substantial guidance on the question of optimal practice duration.
As Ericsson et al (2006) summarised:
elite performers search continuously for optimal training
activities, with the most effective duration and intensity, that will
appropriately strain the targeted physiological system to induce
further adaptation without causing overuse and injury.
With regards to optimal practice length, Ericsson et al (2006) stated (with key points bolded by me) that:
Although the detailed nature of deliberate practice will differ across
domains and as a function of attained skill, there appear to be limits
on the daily duration of deliberate practice, and this limit seems to
generalize across domains of expertise. Expert performers from many
domains engage in practice without rest for only around an hour, and
they prefer to practice early in the morning when their minds are
fresh (Ericsson et al., 1993 ). Elite musicians (Ericsson, 2002) and
athletes (Ericsson, 2001, 2003 c) report that the factor that limits
their deliberate practice is primarily an inability to sustain the
level of concentration that is necessary. Even more interestingly,
elite performers in many diverse domains have been found to practice,
on the average, roughly the same amount every day, including
weekends, and the amount of practice never consistently exceeds five
hours per day (Ericsson, 1996; Ericsson et al., 1993 ). The limit of
four to five hours of daily deliberate practice or similarly
demanding activities holds true for a wide range of elite performers
in different domains, such as writing by famous authors (Cowley, 195
9; Plimpton, 1977), as does their increased tendency to take
recuperative naps. Furthermore, unless the daily levels of practice
are restricted, such that subsequent rest and nighttime sleep
allow the individuals to restore their equilibrium, individuals
often encounter overtraining injuries and, eventually, incapacitating
“burnout.” In some domains of sports, such as gymnastics, sprinting,
and weight lifting, the max- imal effort necessary for representative
performance is so great that the amount of daily deliberate practice
is even further limited by factors constraining the duration of
produc- tion of maximal power and strength.
Implications for the specifics of your question
Thus, based on the expertise literature, four or five one-hour sessions of deliberate practice in a day with plenty of rest between and at night would be optimal if the aim is to maximise learning on the focal task in the shortest period of time.
In general, I wouldn't define optimal duration of practice in terms of amount of the task learnt.
Also, in the real-world, the optimality criterion can vary between people. The expertise literature assumes that the goal is to maximise learning on the focal skill. However, in the real-world, a person may be learning a number of things, and also need to accomplish tangible outcomes at the same time.
- Cowley, M. (Ed.) (195 9). Writers at work: The
Paris review interviews. New York: Viking.
- Ericsson, K. A. (1996). The acquisition of expert performance: An introduction to some of the issues. In K. A. Ericsson (Ed.), The road to excellence: The acquisition of expert performance in the arts and sciences, sports, and games (pp. 1–5 0). Mahwah, NJ: Erlbaum.
- Ericsson, K. A. (2001). The path to expert
performance: Insights from the masters on how
to improve performance by deliberate practice.
In P. Thomas (Ed.), Optimizing performance in
golf (pp. 1–5 7). Brisbane, Australia: Australian
- Ericsson, K. A. (2002). Attaining excellence through deliberate practice: Insights from the study of expert performance. In M. Ferrari (Ed.), The pursuit of excellence in education
(pp. 21–5 5 ). Hillsdale, NJ: Erlbaum.
- Ericsson, K. A. (2003c). The development of elite performance and deliberate practice: An
update from the perspective of the expert-performance approach. In J. Starkes & K. A.
Ericsson (Eds.), Expert performance in sport: Recent advances in research on sport exper-
tise (pp. 49–81). Champaign, IL: Human Kinetics.
- Ericsson, K. A., Krampe, R. Th., & Tesch-Romer, C. (1993 ). The role of deliberate practice in the acquisition of expert performance. Psychological Review, 100, 3 63 –406. PDF
- Ericsson, K. et al. (2006). The influence of experience and deliberate
practice on the development of superior expert performance. The
Cambridge handbook of expertise and expert performance, 10(3):683-703. PDF
- Plimpton, G. (Ed.) (1977). Writers at work: The Paris review. Interviews, Second Series. New York: Penguin.