|If you want to practice "vorschlafen" you may have to set your alarm-clock to tell you when to go to bed.|
Against that background it's good that in a new study from the Université de Lyon, Instead of testing cognitive performance markers such as the attention span of an individual, the researchers set out to "assess the effect of 6 nights of sleep extension on neuromuscular function and motor performance before and after [total sleep deprivation] TSD" (Arnal. 2016).
So what did the scientists do? Well, the subjects, twelve healthy men (age: 32.2 ± 3.9 years, weight: 75.2 ± 6.2 kg, height: 176.9 ± 6.2 cm, body mass index: 23.7 ± 1.7 kg/m², physical activity: < 4 h per week) participated in two counterbalanced experimental conditions (cross-over design):
- extended sleep aka EXT - mean (SE) h = 9.8 (0.1) time in bed and
- habitual sleep aka HAB - mean (SE) h = 8.2 (0.1) time in bed.
The second phase was conducted in the laboratory and started at 17:00 after the 5th night at home
"Two weeks before the first phase, a familiarization night was spent in the laboratory to avoid any first-night laboratory effects. Moreover, a control week where subjects spent 8 h in bed each night was realized before the first phase to avoid starting the experiment with the subjects in sleep debt. Time in bed during the control week was checked with actigraphy (Actiwatch TM, Cambridge Neurotechnology, Cambridgeshire, UK). The first phase consisted in 5 nights at home (N1 to N5) with sleep recorded by polysomnography. In HAB, subjects were instructed to maintain their habitual sleep time and spend at least 8 h in bed (bedtime between 22:30 and 23:00 and wake up at 07:00).
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In EXT, they spent 10 h in bed between 21:00 and 07:00. In both conditions, volunteers maintained a wake time of 07:00 to accustom themselves to the waking time of 07:00 used during the second laboratory phase. Volunteers were allowed to maintain their usual lifestyles but needed to return the polysomnography equipment to the laboratory every morning" (Arnal. 2016).
(standardized to be on Saturday for everyone for each condition). Subjects were familiarized
with the experimental protocol between 17:00 and 20:00. The day after was considered as the
baseline day during which neuromuscular testing was performed between 17:00 and 20:00 (D0).
Neuromuscular testing was repeated at the same time of day the following day, i.e. after 34-37 h
of continuous wakefulness (D1).
|Figure 1: Overview of the two phases of the experimental protocol (Arnal. 2016).|
|Figure 2: The fact that the effect size was individual should not surprise you and could be due to the fact that the extra 2h in bed may not have been spent sleeping in all subjects (Arnal. 2016).|
Accordingly, they are quite confident to conclude that the small, but for some of the subjects highly significant inter-treatment difference they observed, namely...
- a longer time to exhaustion in EXT compared to HAB (+3.9 ± 7.7% and +8.1 ± 12.3% at D0 and D1, respectively), as well as
- a lower rating of perceived exertion during exercise at D2 in the EXT compared to HAB (-7.2 ± 7.5%) group
- Arnal, et al. "Sleep Extension before Sleep Loss: Effects on Performance and Neuromuscular Function." Medicine & Science in Sports & Exercise (2016): Publish Ahead of Print - DOI: 10.1249/MSS.0000000000000925
- Schwartz, Jennifer, and Richard D. Simon. "Sleep extension improves serving accuracy: A study with college varsity tennis players." Physiology & behavior 151 (2015): 541-544.