So I am running behind a bit on studies, so this post will be a bit longer than normal and my comments are included at the start instead of after each one
Endurnace vs Strength Training Adaptations
The first study is looking at the signals from endurance training. There is a resurgence of sorts in the literature now of how the body adapts to training, both for endurance and strength performance.
Dr. Hawley's lab in the "Land Down Under" has done some very cool work in this area. I was able to see a great talk from Dr. Coffey at ACSM last year about this topic. The plasticity of the human body is just amazing!
MD Research Podcast
What do we know?
We know that strength athletes are not going to be the first ones to finish a marathon race since exterme endurance training (marathon) and extreme strength (1 rep max in say olympic lifting or a powerlifting event) are on the polar opposites of the spectrum.
The SAID (specific adaptation to imposed demand) states that "your body will ALWAYS adapt to EXACTLY what you are doing, whether you are aware or not" (special thanks to Dr. Cobb and Frankie Faires for reminding me about that one a few years back).
If you want to improve your marathon times, you need to go run! You want to get stronger, you need to lift heavy things!
How much overlap can exist between the two will be a hot topic in the future and there are some very cool studies that should be out later this year looking at this topic.
What to do now?
In the meantime, while there is little data on it, if you are doing some endurance work in addition to strength training; you may want to split out your sessions. An example is below
Mon: AM low intensity bike work
Mon: PM high intensity strength work
How much time you need between sessions is debateable. Even more debateable is what about high intensity sprint work? Again, there is not tons of data behind this currently.
Hence the science AND art to coaching!
The other abstracts below discuss molecular signalling needed for protein synthasiss (aka building muscle).
Any comments, let me know!
Mike T Nelson
Skeletal muscle eEF2 and 4EBP1 phosphorylation during endurance exercise is dependent on intensity and muscle fiber type.
Rose AJ, Bisiani B, Vistisen B, Kiens B, Richter EA. Molecular Physiology Group, Copenhagen Muscle Research Centre, Dept. of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Universitetsparken 13, Copenhagen, Denmark, 2100. firstname.lastname@example.org
Protein synthesis in skeletal muscle is known to decrease during exercise, and it has been suggested that this may depend on the magnitude of the relative metabolic stress within the contracting muscle. To examine the mechanisms behind this, the effect of exercise intensity on skeletal muscle eukaryotic elongation factor 2 (eEF2) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) phosphorylation, key components in the mRNA translation machinery, were examined together with AMP-activated protein kinase (AMPK) in healthy young men. Skeletal muscle eEF2 phosphorylation at Thr56 increased during exercise but was not influenced by exercise intensity, and was lower than rest 30 min after exercise.
On the other hand, 4EBP1 phosphorylation at Thr37/46 decreased during exercise, and this decrease was greater at higher exercise intensities and was similar to rest 30 min after exercise. AMPK activity, as indexed by AMPK alpha-subunit phosphorylation at Thr172 and phosphorylation of the AMPK substrate ACCbeta at Ser221, was higher with higher exercise intensities, and these indices were higher than rest after high-intensity exercise only. Using immunohistochemistry, it was shown that the increase in skeletal muscle eEF2 Thr56 phosphorylation was restricted to type I myofibers.
CONCLUSION: Taken together, these data suggest that the depression of skeletal muscle protein synthesis with endurance-type exercise may be regulated at both initiation (i.e., 4E binding protein 1) and elongation (i.e., eukaryotic elongation factor 2) steps, with eukaryotic elongation factor 2 phosphorylation contributing at all exercise intensities but 4E binding protein 1dephosphorylation contributing to a greater extent at high vs. low exercise intensities.
Intracellular signalling pathways regulating the adaptation of skeletal muscle to exercise and nutritional changes.
Matsakas A, Patel K. School of Biological Sciences, University of Reading, Whiteknights campus, Reading, UK. A.Matsakas@gmail.com
The focus of the present review is to assimilate current knowledge concerning the differing signalling transduction cascades that control muscle mass development and affect skeletal muscle phenotype following exercise or nutritional uptake. Effects of mechanical loading on protein synthesis are discussed. Muscle growth control is regulated by the interplay of growth promoting and growth suppressing factors, which act in concert. Much emphasis has been placed on understanding how increases in the rate of protein synthesis are induced in skeletal muscle during the adaptive process.
One key point to emerge is that protein synthesis following resistance exercise or increased nutrient availability is mediated through changes in signal transduction involving the phosphorylation of mTOR and sequential activation of downstream targets. On the other hand, AMPK activation plays an important role in the inhibition of protein synthesis by suppressing the function of multiple translation regulators of the mTOR signalling pathway in response to cellular energy depletion and low metabolic conditions.
CONCLUSION: The effects of exercise and/or nutritional uptake on the activation of signalling molecules that regulate protein synthesis are highlighted, providing a better understanding of the molecular changes in the cell.
Rapamycin administration in humans blocks the contraction-induced increase in skeletal muscle protein synthesis.
Drummond MJ, Fry CS, Glynn EL, Dreyer HC, Dhanani S, Timmerman KL, Volpi E, Rasmussen BB. University of Texas Medical Branch.
Muscle protein synthesis and mTORC1 signalling are concurrently stimulated following muscle contraction in humans. In an effort to determine whether mTORC1 signalling is essential for regulating muscle protein synthesis in humans, we treated subjects with a potent mTORC1 inhibitor (rapamycin) prior to performing a series of high-intensity muscle contractions. Here we show that rapamycin treatment blocks the early (1-2h) acute contraction-induced increase (~40%) in human muscle protein synthesis. In addition, several downstream components of the mTORC1 signalling pathway were also blunted or blocked by rapamycin. For instance, S6K1 phosphorylation (Thr421/Ser424) was increased post-exercise by 6 fold in the Control group while being unchanged with rapamycin treatment.
Furthermore, eEF2 phosphorylation (Thr56) was reduced by ~25% post-exercise in the Control group but phosphorylation following rapamycin treatment was unaltered indicating that translation elongation was inhibited. Rapamycin administration prior to exercise also reduced the ability of raptor to associate with mTORC1 during post-exercise recovery. Surprisingly, rapamycin treatment prior to resistance exercise completely blocked the contraction-induced increase in the phosphorylation of ERK1/2 (Thr202/Tyr204) and blunted the increase in MNK1 (Thr197/202) phosphorylation. However, the phosphorylation of a known target of MNK1, eIF4E (Ser208), was similar in both groups (P>0.05) which is consistent with the notion that rapamycin does not directly inhibit MAPK signalling.
CONCLUSION: We conclude that mTORC1 signalling is, in part, playing a key role in regulating the contraction-induced stimulation of muscle protein synthesis in humans, while dual activation of mTORC1 and ERK1/2 stimulation may be required for full stimulation of human skeletal muscle protein synthesis.
A Ca2+-calmodulin-eEF2K-eEF2 signalling cascade, but not AMPK, contributes to the suppression of skeletal muscle protein synthesis during contractions.
Rose AJ, Alsted TJ, Jensen TE, Kobber JB, Maarbjerg SJ, Jensen JR, Richter EA. University of Copenhagen.
Skeletal muscle protein synthesis rate decreases during contractions but the underlying regulatory mechanisms are poorly understood. It was hypothesised that there would be a coordinated regulation of eukaryotic elongation factor 2 (eEF2) and eukaryotic initiation factor 4E-binding protein 1 (4EBP1) phosphorylation by signalling cascades downstream of rises in intracellular [Ca(2+)] and decreased energy charge via AMP activated protein kinase (AMPK) in contracting skeletal muscle. When fast-twitch skeletal muscles were contracted ex vivo using different protocols, the suppression of protein synthesis correlated more closely with changes in eEF2 rather than 4EBP1 phosphorylation. Using a combination of Ca(2+) release agents and ATPase inhibitors it was shown that the 60-70% suppression of fast-twitch skeletal muscle protein synthesis during contraction was equally distributed between Ca(2+) and energy-turnover related mechanisms.
Furthermore, eEF2 kinase inhibition completely blunted increases in eEF2 phosphorylation and partially blunted (i.e. 30-40%) the suppression of protein synthesis during contractions. The 3-5 fold increase in skeletal muscle eEF2 phosphorylation during contractions in situ was rapid and sustained and restricted to working muscle. The increase in eEF2 phosphorylation and eEF2 kinase activation were downstream of Ca(2+)/calmodulin but not other putative activating factors such as a fall in intracellular pH or phosphorylation by protein kinases. Furthermore, blunted protein synthesis and 4EBP1 dephosphorylation were unrelated to AMPK activity during contractions, which was exemplified by normal blunting of protein synthesis during contractions in muscles overexpressing kinase dead AMPK.
CONCLUSION: In summary, in fast-twitch skeletal muscle, the inhibition of eukaryotic elongation factor 2 activity by phosphorylation downstream of Ca(2+)-CaM-eEF2K signalling partially contributes to the suppression of protein synthesis during exercise/contractions.