Endocrine responses during overnight recovery from exercise: Impact of nutrition and relationships with muscle protein synthesis


Journal Title (Medline/Pubmed accepted abbreviation): Int. J. Sport. Nutr.Exerc.Metab.
Year: 2011
Volume: 21
Page Numbers: 398-409

Summary of background and research design:

Background: Muscle repair and hypertrophy (growth) after exercise are affected by hormone responses to exercise and are measured by rate of muscle synthesis. A large amount of recovery-based physiology occurs during sleep.  

Hypothesis: Consuming a beverage with carbohydrates + protein vs. a carbohydrate-only beverage will increase the levels of hormones that promote protein synthesis as well as the rate of protein synthesis during sleep in response to daytime exercise.

Subjects: Ten recreationally active males, age 20 ± 2 y.

Experimental design: randomized, double-blind, cross-over design 

Treatments:
C: carbohydrate- 50% glucose and 50% maltodextrin
C+P: carbohydrate + protein- C from above + casein protein hydrolysate
Both were vanilla flavored and artificially sweetened to yield similar tastes.

Protocol: Before the testing sessions, participants were evaluated for body composition and the exercise routine. One-repetition maxima were determined for chest press, shoulder press, lateral pull-down, leg press, and leg extension. The participants’ VO2max and workload capacity (Wmax) were determined on a stationary bicycle. On the testing days, they consumed standardized meals during the day and reported to the laboratory in the evening. They underwent a 2 hr exercise routine including both endurance (cycling) and resistance exercises. Participants consumed 1.5 mL/kg body mass of one of the test beverages every 15 min during exercise and 4 mL/kg 30 and 90 min after exercise. Blood samples were acquired at selected time points throughout exercise and recovery (including during sleep). Muscle biopsies were acquired from the vastus lateralis (quadriceps) before and after exercise and in the morning after exercise to assess fractional rate of protein synthesis.


Summary of research findings:
  • Growth hormone peaked during sleep with both recovery beverages (at about 2:00-3:00 am) with no difference between treatments.
  • Plasma cortisol concentrations peaked at mid-exercise and then again in the morning. There was a greater overall cortisol response to the C+P treatment compared to C.
  • Testosterone concentrations increased at the onset of exercise and continued throughout the recovery period with both beverages. The overall response was not different between treatments.
  • There was a trend for an overall greater insulin response for the C+P beverage compared to the C beverage (p = 0.07). Similarly, there was a trend for higher average glucose concentrations (p = 0.06). However, there were no statistically significant differences at any one time point.
  • There was no difference between treatments for mixed-muscle protein fractional synthetic rate (rate of protein synthesis) during overnight recovery.

Key practice applications:

There has been little research on the effects of nutrition on hormone response during sleep and the studies that do exist show conflicting results. This study showed few differences between recovery drinks on hormones and rate of protein synthesis in sleep immediately following evening exercise. Data from this studies and others suggest that athletes’ nutritional practices throughout the entire day can be important, since the next morning they are likely still recovering from the evening exercise.


 

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