You need this many hours of sleep for muscle growth, study says
There are few things worse than trying to make it to the gym after a rough night's sleep. You may think trying to bust through a HIIT class while bleary eyed and yawning isn't the best way to build muscle, but you may be mistaken - new evidence suggests that getting in a session on less sleep than usual might still elicit the same amount of muscle growth as a full night's kip. While we're not downplaying the importance of sleep or saying you should skip rest days, we might be suggesting that you review some of the excuses in your fitness repertoire.
The study
The study published in Sleep Science aimed to evaluate the effects of reducing between one and two hours of recommended sleep time (seven hours) on the response to resistance training sessions.
The methods
36 participants took part in the study, divided into three groups:
Less than 7 hours sleep group: Those who slept on average 6 hours per night (1-2 hours less than the recommended amount).
7 hours of sleep group: Those who slept the recommended seven hours per night.
Control group: Those who slept over seven hours but did not complete any resistance-training sessions.
Both the <7h and 7h groups completed 16 training sessions (three times a week for five weeks) using resistance bands. They had 48 hours rest between each session. These sessions included:
Lateral raises
Seated rows
Each exercise was done for max reps until failure, with rest intervals between exercises. Sleep quality, total sleep time, sleep efficiency (the percentage of time spent asleep while in bed) and sleep latency was measured. Body composition was measured using BMI, arm circumference, and triceps skinfold thickness. Muscle strength was assessed by the maximum number of reps for each exercise before and after the intervention.
The results
The researchers found:
Muscular strength: Both <7h and 7h groups showed significant increases in muscle strength after the intervention across all exercises. There was no statistical difference between the two groups, suggesting that the 1-2 hour sleep reduction didn't affect strength increases.
Body composition: Both <7h and 7h groups showed increases in arm circumference and arm muscle area, and a reduction in tricep skin-fold thickness after the intervention. The changes in these body-composition measures were similar between the <7h and 7h groups, showing that the 1-2 hour sleep reduction didn't affect body composition.
BMI and body mass: There were no significant changes in body mass or BMI in any of the groups.
The conclusion
The researchers concluded that: 'A habitual reduction of one to two hours in the daily period of sleep is not able to modify the effects of resistance training with elastic bands. In addition, 16 training sessions were able to increase strength and muscle mass in non-resistance-trained adult subjects.'
Commenting on the study, author and researcher Brad Schoenfeld PhD said in an Instagram post: 'The topic is difficult to investigate in a controlled fashion and the study had a number of limitations,' while noting the small sample size, quasi-experimental design, use of resistance bands as opposed to traditional resistance training exercises and relatively low training volumes. 'Thus, results need to be interpreted cautiously,' he said.
Schoenfeld continued, 'That said, the findings do suggest that there isn’t necessarily an "ideal" number of hours of sleep, and perhaps the required sleep time is specific to the individual. It also raises the possibility that when you habitually reduce sleep time by a couple of hours, the body may get used to subsisting on less sleep and adjust its function accordingly — the human body is highly resilient.' So, perhaps agonising over an hour or two less sleep is unwarranted, and in fact we could do well by still including a session.
The researcher adds that there still seems to be a lower threshold for sleep time, below which the body cannot subsist properly and training will be compromised, 'Exactly how much isn’t clear, and likely would be specific to the individual. Quality of sleep must also be considered, as there is a difference between light, deep and REM sleep'
He concludes that overall it still seems that what's most important is to take into account your own individual needs and lifestyle factors when it comes to the amount of hours sleep necessary for building muscle.
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