|Image 1: As a toddler you already knew - "Sleep is the most anabolic agent there is"; Sleep - Train - Eat, repeat! Remember that ;-)|
You got it, in those cosy (hopefully) ~8 hours you are snorkeling away in between your sheets (Cauter. 1998) - it is in these hours, that your GH levels spike at 600% of their daytime average and your cortisol levels plummet into the abyss. As studies show, this is yet not the only thing on which you are missing out if you do not get your share of quality sleep day in, day out: Even short-term (let alone chronic) sleep deprivation has been shown to significantly increase rates of perceived exertion in athletes and - and this may be even more detrimental - decrease insulin sensitivity and glucose tolerance (VanHelder. 1989). So that after nights and nights of low-quality or insufficient sleep, your secret weapon against tiredness, your pre-workout high-carb-get-me-going shake will no longer get you going in the gym, but rather out of the gym and right to your doctor to ask him for a script for some Metformin to get your blood sugar levels back to normal.
Assuming that I now got your full attention, I want to share the results of two very recent studies with you. One on the differential effect of strength and endurance training in the morning (10am) on sleep quality and duration in 15 healthy trained men (Roveda. 2011) and a second one on the beneficial effects even a single session of resistance training (at 60%RM) has on the sleep pattern of 22 65-85 year old men (Viana. 2011).
Always remember: Sleep is the most anabolic agent there is
One thing upfront: A reasonable amount of physical activity will - regardless of your age and fitness level - make it easier to fall asleep, lengthen the time you spent in bed actually sleeping and not tossing and turning, and contribute to an overall improvement in sleep quality.
|Figure 1: Relative changes (compared to baseline) in assumed and actual sleep on day 1 and day 2 after a 10am strength (bench press 4x80RM + 10 min warm up)or endurance training (10min warm-up, 30min 80%VO2max, 10min cool-down) session in 15 healthy young men (data calculated based on Roveda. 2011).|
|Figure 2: Relative changes in sleep efficiency and sleep latency on day 1 and day 2 after a 10am strength or endurance training session in 15 healthy young men (data calculated based on Roveda. 2011).|
Although there probably is no doubt that physical activity may benefit sleep quality and sleep quality in turn may benefit not only the performance during the former, but also its effects on your metabolic health and body composition (cf. image 1), it is still a matter of constant debate how much, is too much - after all, both forms of overtraining, the sympathetic form, which puts you into a chronic fight and flight mode and will wreak havoc on both your sleep quality and its duration (usually associated with higher intensity training than the bench pressing session 10min warm-up + 4x80%RM the Rovenda subjects performed) and the parasympathetic form, which is what people usually refer as "burnout syndrome" and will have you sleep hours after hours waking totally unrefreshed, produce quite distinct, yet of many athletes carelessly overlooked sleeping patterns, which - and here lies the culprit, still appear to be one of the best, yet by far not "objective" measures of whether you are "hitting your sweet spot" or are just digging a deep black hole by keep pushing and pushing, when your batteries have long run out of energy (Urhausen. 2002)... but this, my friends is a topic for another blog post ;-)