perhaps exercise upregulates certain gene expression in the time following the workout, and immediate ingestion of food interferes with this process.
Exercise does change gene expression in muscle. The most significant recent discovery in this field is the shift in IGF-1 gene splicing towards the Mechano Growth Factor (MGF) splice variant that occurs post-exercise in muscle tissue. This field has many questions that remain to be answered however…
I wouldn’t expect nutrient ingestion to really interfere with any processes. However as I was eluting to, there may be a down-time shortly after you are done exercising (<1 hour PWO) when the majority of these changes in the genetic expression profile are taking place.
In these events, the muscle undergoes the final push of hypertrophy and prepares for rebuilding. Thus it would be irrelevant to take protein supplements immediately after you are done working out, as your body is not yet in the optimal state for muscle repair. So in deciding between a protein shake immediately post-workout or one/two hours post-workout, you might be better off one/two hours PWO.
I put up some article abstracts for those interested in this rapidly expanding field. I find it interesting in the 2nd article they say immediate PWO protein ingestion stimulates the best recovery, but in the third article they do the protein ingestion at 1 hour PWO and see an increase in muscle FSR at 2 hours whereas the control group has nothing. There appears to be a little disparity here… Hope this isn’t too off topic!
Signal transduction pathways that regulate muscle growth.
Wackerhage H, Ratkevicius A. (2008)
Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK. email@example.com
Progressive high-resistance exercise with 8-12 repetitions per set to near failure for beginners and 1-12 repetitions for athletes will increase muscle protein synthesis for up to 72 h; approx. 20 g of protein, especially when ingested directly after exercise, will promote high growth by elevating protein synthesis above breakdown.
Muscle growth is regulated by signal transduction pathways that sense and compute local and systemic signals and regulate various cellular functions. The main signalling mechanisms are the phosphorylation of serine, threonine and tyrosine residues by kinases and their dephosphorylation by phosphatases.
Muscle growth is stimulated by the mTOR (mammalian target of rapamycin) system, which senses (i) IGF-1 (insulin-like growth factor 1)/MGF (mechano-growth factor)/insulin and/or (ii) mechanical signals, (iii) amino acids and (iv) the energetic state of the muscle, and regulates protein synthesis accordingly. The action of the mTOR system is opposed by myostatin-Smad signalling which inhibits muscle growth via gene transcription.
Protein co-ingestion stimulates muscle protein synthesis during resistance type exercise.
Beelen M, Koopman R, Gijsen AP, Vandereyt H, Kies AK, Kuipers H, Saris WH, van Loon LJ. (2008)
Movement Sciences, Nutrition and Toxicology Research Institute Maastricht (NUTRIM Maastricht University, Maastricht, Netherlands; , Netherlands.
In contrast to the impact of nutritional intervention on post-exercise muscle protein synthesis, little is known about the potential to modulate protein synthesis during exercise. This study investigates the impact of protein co-ingestion with carbohydrate on muscle protein synthesis during resistance type exercise.
Ten healthy males were studied in the evening after consuming a standardized diet throughout the day. Subjects participated in 2 experiments, in which they ingested either carbohydrate or carbohydrate with protein during a 2h resistance exercise session. Subjects received a bolus of test drink prior to and every 15 min during exercise, providing 0.15 g.kg(-1).h(-1) carbohydrate with (CHO+PRO) or without (CHO) 0.15 g.kg(-1).h(-1) protein hydrolysate. Continuous intravenous infusions with L-[ring-(13)C6]phenylalanine and L-[ring-(2)H2] tyrosine were applied, and blood and muscle biopsies were collected to assess whole-body and muscle protein synthesis rates during exercise.
Protein co-ingestion lowered whole-body protein breakdown rates by 8.4+/-3.6% (P=0.066), compared to the ingestion of carbohydrate only, and augmented protein oxidation and synthesis rates by 77+/-17 and 33+/-3%, respectively (P<0.01). As a consequence, whole-body net protein balance was negative in CHO, whereas a positive net balance was achieved following the CHO+PRO treatment (-4.4+/-0.3 vs 16.3+/-0.4 micromol phe.kg(-1).h(-1), respectively; P<0.01).
In accordance, mixed muscle protein fractional synthetic rate (FSR) was 49+/-22% higher following protein co-ingestion (0.088+/-0.012 and 0.060+/-0.004 %.h(-1) in CHO+PRO vs CHO treatment, respectively; P<0.05). We conclude that, even in a fed state, protein co-ingestion stimulates whole-body and muscle protein synthesis rates during resistance type exercise. Key words: muscle, protein synthesis, exercise, nutrition.
Leucine-enriched essential amino acid and carbohydrate ingestion following resistance exercise enhances mTOR signaling and protein synthesis in human muscle.
Dreyer HC, Drummond MJ, Pennings B, Fujita S, Glynn EL, Chinkes DL, Dhanani S, Volpi E, Rasmussen BB. (2007)
Department of Physical Therapy, Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1144, USA.
We recently showed that resistance exercise and ingestion of essential amino acids with carbohydrate (EAA+CHO) can independently stimulate mammalian target of rapamycin (mTOR) signaling and muscle protein synthesis in humans. Providing an EAA+CHO solution postexercise can further increase muscle protein synthesis. Therefore, we hypothesized that enhanced mTOR signaling might be responsible for the greater muscle protein synthesis when leucine-enriched EAA+CHOs are ingested during postexercise recovery. Sixteen male subjects were randomized to one of two groups (control or EAA+CHO).
The EAA+CHO group ingested the nutrient solution 1 h after resistance exercise. mTOR signaling was assessed by immunoblotting from repeated muscle biopsy samples. Mixed muscle fractional synthetic rate (FSR) was measured using stable isotope techniques. Muscle protein synthesis and 4E-BP1 phosphorylation during exercise were significantly reduced (P < 0.05). Postexercise FSR was elevated above baseline in both groups at 1 h but was even further elevated in the EAA+CHO group at 2 h postexercise (P < 0.05).
Increased FSR was associated with enhanced phosphorylation of mTOR and S6K1 (P < 0.05). Akt phosphorylation was elevated at 1 h and returned to baseline by 2 h in the control group, but it remained elevated in the EAA+CHO group (P < 0.05). 4E-BP1 phosphorylation returned to baseline during recovery in control but became elevated when EAA+CHO was ingested (P < 0.05). eEF2 phosphorylation decreased at 1 and 2 h postexercise to a similar extent in both groups (P < 0.05).
Our data suggest that enhanced activation of the mTOR signaling pathway is playing a role in the greater synthesis of muscle proteins when resistance exercise is followed by EAA+CHO ingestion.