It appears extended working days, such as, 16 hours are counterproductive.
(1) Safe working hours - doctors in training a best practice issue examines the effects of extended working hours on performance for doctors. It is recommended that a 7-8 hour working day is more productive than extended days. One issue being the sleep deprivation that accompanies extended working days.
There is research on optimal work-break rhythms. It has been found that work performance is optimized in 90 minute time slots. This is improved by dividing this into 25 minute time slots, with short breaks. With relation to the type of work, it is suggested that breaks be taken away from the working environment, optimally, within an altogether different environment.
This is consistent with natural ultradian cycles:
Image taken from The origin of the 8 hour work day and why we should rethink it a blog by Leo Widrich
I have quoted extensively from the following article:
(2) Best Rest Practices for Optimal Productivity and Creativity.
This addresses your questions comprehensively and also confirms that an extended working day is counter productive.
Timing of natural working rythms
Rossi champions the 20-Minute Break in his book of the same name for
peak performance. And Anders et al studied in 1993 a group of
violinists and discovered that the best performers practiced in
90-minute intervals and learned not to over-practice.
We can break down that 90-minute rhythm even further into 25-minute
spurts. Most people can pay attention to a talk for 25 minutes (hence,
the brilliance of TED Talks’ 17-minute limit).
Hence, another client, a highly reputed novelist and short story
writer, wisely writes in three 25-minute periods—each divided with a
timer. At the end of the third period, she takes a walk or switches to
Breaks away from the workplace
I recommend to clients they remove themselves from the work
environment if possible.
For a corporate client, I recommended he schedule a walk to another
part of his vast office quarters, glance out a floor-to-ceiling
window, and then return to his office room, sit in a comfortable sofa
normally reserved for clients, and remember the last time he was
outdoors working on his ranch—one of his favorite activities.
Step outdoors if you can. I suggested that one client who gets
overwhelmed with multiple tasks in the afternoon to step outdoors and
sit in her garden for fifteen minutes and simply observes the colors,
textures, sounds, and smells. Ideally, she would weed for fifteen
minutes as the physical activity more likely will let her processor
mind incubate some of her creative problems.
Or step away from your work space, and read four pages from a book
that brings you delight.
If you can jog or bicycle for 20 minutes, even better—as you’re also
increasing the chances of your hippocampus forging new neurons in your
middle-aged gray matter, according to Fred Gage of the Salk Institute
and other researchers who’ve examined the benefits of intentional,
enjoyable cardiovascular exercise.
Techniques to combat fatigue
DISTRACTION CAN RE-BOOT LONG-TERM FOCUS. () Here’s a mind-twister:
Atsunori Ariga and Alejandro Lleras of University of Illinois at
Urbana-Champaign, United States questioned the assumption that loss of
focus came from, say, fatigue or lack of attention. In 2010, their
study published in Cognition concluded that a deliberate distraction
or introduction of a second task actually can increase vigilant
attention on the first task.
Utilising multi tasking to break mental fatigue.
Pay attention to when you need to introduce a quick second task. Maybe
sending off an email or text message will free up mental bandwidth and
get you re-committed to the high-thinking task. Do this in tandem with
the “Break with Rhythm” suggestions above.
The benefits of a daily nap
Some students took no naps. Some students took catnaps. And some
students took full-fledged 90-minute naps complete with REM
dreams...//... students who took the full REM-level naps showed
boosts in creative problem-solving performance.
The concept that a longer working day is counter-productive
Schedule non-digital time in the evenings, especially 45 minutes
before sleep. Set up a bi-weekly schedule of evening rhythms: One
Monday as “reading night,” One Tuesday as “date night,” et cetera. If
you must work some evenings, schedule work evenings. Make them the
exception instead of the rule.
(1) Safe working hours - doctors in training a best practice issue
Andrew Lewis is Senior Industrial Relations Adviser with the Australian Medical Association Victoria
(2) Best Rest Practices for Optimal Productivity and Creativity
How and when to break from creative work.
Published on April 30, 2012 by Jeffrey Davis, M.A. in Tracking Wonder
The Seattle Longitudinal Study K. Warner Schaie, Ph.D. and Sherry L. Willis, Ph.D. UW Medicine
Life In The Middle Life in the Middle: Psychological and Social Development in Middle Age
edited by Sherry L. Willis, James B. Reid
Recovering from Work: Interview with Sabine Sonnentag
Brief and rare mental ‘‘breaks’’ keep you focused: Deactivation
and reactivation of task goals preempt vigilance decrements
Atsunori Ariga, Alejandro Lleras
University of Illinois at Urbana-Champaign, United States
The Role of Deliberate Practice in the Acquisition of Expert Performance
K. Anders Ericsson, Ralf Th. Krampe, and Clemens Tesch-Romer
1993, Vol. 100. No. 3, 363-406
Copyright 1993 by the American Psychological Association, Inc.