- A non-restricted group (8 h time in bed (TIB) each night, 7.4h actual sleeping time), a sleep restriction group (4 h TIB, 3.7h actual sleeping time), and an exercising sleep restriction group (4 h TIB, with three sessions of High Intensity Interval Exercise (HIIE) – similar effect as weight training for the legs).
- They did not include a group that performed HIIE while sleeping sufficiently.
- Very objective measurement methods: a special sleep watch detected sleeping duration.
- Measured “muscle protein synthesis” (MPS; a muscle growth indicator) with highly valid D2O method that measures MPS over longer periods [A].
- After 5 nights of cutting sleep by 3.5 actual sleeping hours per night, MPS was 19% lower compared to the normal sleep and exercising sleep restriction group.
- Limitation: The study only lasted 8 days (luckily, for the participants!).
A: Want more info? Please read Jorn Trommelen’s “The ultimate guide to muscle protein synthesis”
- 13 young and healthy participants, in a cross-over design (all participants underwent the sleep and non-sleep restricted interventions).
- Limitation: One day of 0h of sleep: not resembling a real life context.
- Sleep recorded highly objectively using an actigraphy device.
- Normal sleep time of participants was ~6h (already quite low)
- Measuring of muscle growth not as accurate as Saner 2020’s D2O method.
- After a nice breakfast, From 10 am to 4 pm on the next day, muscle growth was 18% lower when participants had 0 hours of sleep instead of 6 hours.
- Participants were 8 men (15% bodyfat) and 4 women (29% bodyfat), all physically active.
- For 10 days, men ate 2350 (-16.8% energy deficit, -450 kcal) and women 1650 (-24.2% energy deficit, -500 kcal) per day, compared to their 2800 and 2150 kcal energy expenditure.
- They did not weight train during the study and ate 1.5 g/kg protein per day.
- After these 10 days of dieting they achieved 1 kg weight loss on average.
- After an overnight fast, between 5:00 and 6:30 am in the morning, they used amino acid tracers to measure “muscle protein synthesis” (MPS by Fractional Synthetic Rate (FSR)), the main indicator of muscle growth, for 5 hours thereafter.
- There was a 19% reduction in this FSR (main muscle growth indicator) compared to eating at calorie maintenance.
The measure used to assess actual muscle growth in Saner et al. (2020) was “FSR of Myofribrillar Protein with deuterium oxide (D2O)-tracer techniques”, which according to Brook et al. (2015) is very much aligned with actual muscle growth”
Strength of evidence explanation: