Editing Exercise (section)

=== Skeletal muscle ===
{{main|Skeletal muscle}}
Resistance training and subsequent consumption of a protein-rich meal promotes [[muscle hypertrophy]] and gains in [[muscle strength]] by stimulating [[myofibrillar]] muscle protein synthesis (MPS) and inhibiting muscle protein breakdown (MPB).<ref name="Skeletal muscle homeostasis 2016 review" /><ref name="Muscle hypertrophy review">{{cite journal | vauthors = Phillips SM | title = A brief review of critical processes in exercise-induced muscular hypertrophy | journal = Sports Medicine | volume = 44 | issue = Suppl 1 | pages = S71–S77 | date = May 2014 | pmid = 24791918 | pmc = 4008813 | doi = 10.1007/s40279-014-0152-3 }}</ref> The stimulation of muscle protein synthesis by resistance training occurs via [[phosphorylation]] of the [[mechanistic target of rapamycin]] (mTOR) and subsequent activation of [[mTORC1]], which leads to [[protein biosynthesis]] in cellular [[ribosome]]s via phosphorylation of mTORC1's immediate targets (the [[p70S6 kinase]] and the [[protein translation|translation]] repressor protein [[4EBP1]]).<ref name="Skeletal muscle homeostasis 2016 review" /><ref name="Molecular Aspects of Medicine 2016 review">{{cite journal | vauthors = Brioche T, Pagano AF, Py G, Chopard A | title = Muscle wasting and aging: Experimental models, fatty infiltrations, and prevention | journal = Molecular Aspects of Medicine | volume = 50 | pages = 56–87 | date = August 2016 | pmid = 27106402 | doi = 10.1016/j.mam.2016.04.006 | s2cid = 29717535 | url = https://hal.archives-ouvertes.fr/hal-01837630/file/2016_Brioche_MAM_1.pdf }}</ref> The suppression of muscle protein breakdown following food consumption occurs primarily via increases in [[blood plasma|plasma]] [[insulin]].<ref name="Skeletal muscle homeostasis 2016 review" /><ref name="HMB in vivo human pharmacodynamics" /><ref name="Pharmacodynamics and pharmacokinetics of HMB-CA in humans in vivo" /> Similarly, increased muscle protein synthesis (via activation of mTORC1) and suppressed muscle protein breakdown (via insulin-independent mechanisms) has also been shown to occur following ingestion of [[β-hydroxy β-methylbutyric acid]].<ref name="Skeletal muscle homeostasis 2016 review" /><ref name="HMB in vivo human pharmacodynamics">{{cite journal | vauthors = Wilkinson DJ, Hossain T, Hill DS, Phillips BE, Crossland H, Williams J, Loughna P, Churchward-Venne TA, Breen L, Phillips SM, Etheridge T, Rathmacher JA, Smith K, Szewczyk NJ, Atherton PJ | display-authors = 3 | title = Effects of leucine and its metabolite β-hydroxy-β-methylbutyrate on human skeletal muscle protein metabolism | journal = The Journal of Physiology | volume = 591 | issue = 11 | pages = 2911–2923 | date = June 2013 | pmid = 23551944 | pmc = 3690694 | doi = 10.1113/jphysiol.2013.253203 }}</ref><ref name="Pharmacodynamics and pharmacokinetics of HMB-CA in humans in vivo">{{cite journal | vauthors = Wilkinson DJ, Hossain T, Limb MC, Phillips BE, Lund J, Williams JP, Brook MS, Cegielski J, Philp A, Ashcroft S, Rathmacher JA, Szewczyk NJ, Smith K, Atherton PJ | display-authors = 3 | title = Impact of the calcium form of β-hydroxy-β-methylbutyrate upon human skeletal muscle protein metabolism | journal = Clinical Nutrition | volume = 37 | issue = 6 Pt A | pages = 2068–2075 | date = December 2018 | pmid = 29097038 | pmc = 6295980 | doi = 10.1016/j.clnu.2017.09.024 | quote =}}</ref><ref name="Sarcopenia July 2015 review">{{cite journal | vauthors = Phillips SM | title = Nutritional supplements in support of resistance exercise to counter age-related sarcopenia | journal = Advances in Nutrition | volume = 6 | issue = 4 | pages = 452–460 | date = July 2015 | pmid = 26178029 | pmc = 4496741 | doi = 10.3945/an.115.008367 }}</ref>

Aerobic exercise induces [[mitochondrial biogenesis]] and an increased capacity for [[oxidative phosphorylation]] in the [[mitochondria]] of skeletal muscle, which is one mechanism by which aerobic exercise enhances submaximal endurance performance.<ref>{{cite journal | vauthors = Wibom R, Hultman E, Johansson M, Matherei K, Constantin-Teodosiu D, Schantz PG | title = Adaptation of mitochondrial ATP production in human skeletal muscle to endurance training and detraining | journal = Journal of Applied Physiology | volume = 73 | issue = 5 | pages = 2004–2010 | date = November 1992 | pmid = 1474078 | doi = 10.1152/jappl.1992.73.5.2004 | url = http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-184 }}</ref><ref name="Skeletal muscle homeostasis 2016 review" /><ref name="Aerobic exercise – mitochondrial biogenesis and OXPHOS capacity" /> These effects occur via an exercise-induced increase in the intracellular [[adenosine monophosphate|AMP]]:[[adenosine triphosphate|ATP]] ratio, thereby triggering the activation of [[AMP-activated protein kinase]] (AMPK) which subsequently phosphorylates [[PGC-1α|peroxisome proliferator-activated receptor gamma coactivator-1α]] (PGC-1α), the [[master regulator]] of mitochondrial biogenesis.<ref name="Skeletal muscle homeostasis 2016 review" /><ref name="Aerobic exercise – mitochondrial biogenesis and OXPHOS capacity">{{cite journal | vauthors = Boushel R, Lundby C, Qvortrup K, Sahlin K | title = Mitochondrial plasticity with exercise training and extreme environments | journal = Exercise and Sport Sciences Reviews | volume = 42 | issue = 4 | pages = 169–174 | date = October 2014 | pmid = 25062000 | doi = 10.1249/JES.0000000000000025 | s2cid = 39267910 | doi-access = free }}</ref><ref name="Mitochondrial biogenesis">{{cite journal | vauthors = Valero T | title = Mitochondrial biogenesis: pharmacological approaches | journal = Current Pharmaceutical Design | volume = 20 | issue = 35 | pages = 5507–5509 |year = 2014 | pmid = 24606795 | doi = 10.2174/138161282035140911142118 | hdl-access = free | hdl = 10454/13341 }}</ref>
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 | image1 = Muscle protein synthesis signaling cascades.jpg
 | alt1 = Signaling cascade diagram
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 | caption1 = Diagram of the molecular [[signaling cascade]]s that are involved in [[myofibrillar]] muscle protein synthesis and [[mitochondrial biogenesis]] in response to physical exercise and specific [[amino acid]]s or their derivatives (primarily [[leucine|{{nowrap|{{smallcaps all|L}}-leucine}}]] and [[Beta-Hydroxy beta-methylbutyric acid|HMB]]).<ref name="Skeletal muscle homeostasis 2016 review">{{cite journal | vauthors = Brook MS, Wilkinson DJ, Phillips BE, Perez-Schindler J, Philp A, Smith K, Atherton PJ | title = Skeletal muscle homeostasis and plasticity in youth and ageing: impact of nutrition and exercise | journal = Acta Physiologica | volume = 216 | issue = 1 | pages = 15–41 | date = January 2016 | pmid = 26010896 | pmc = 4843955 | doi = 10.1111/apha.12532 }}</ref> Many amino acids derived from food protein promote the activation of [[mTORC1]] and increase [[protein translation|protein synthesis]] by [[signal transduction|signaling]] through [[Rag GTPase]]s.<ref name="Skeletal muscle homeostasis 2016 review" /><ref name="The neurology of mTOR">{{cite journal | vauthors = Lipton JO, Sahin M | title = The neurology of mTOR | journal = Neuron | volume = 84 | issue = 2 | pages = 275–291 | date = October 2014 | pmid = 25374355 | pmc = 4223653 | doi = 10.1016/j.neuron.2014.09.034 }}<br />[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4223653/figure/F2/ Figure 2: The mTOR Signaling Pathway]</ref><br />{{hidden|Abbreviations and representations|{{bull}}PLD: [[phospholipase D]]<br />{{bull}}PA: [[phosphatidic acid]]<br />{{bull}}mTOR: [[mechanistic target of rapamycin]]<br />{{bull}}AMP: [[adenosine monophosphate]]<br />{{bull}}ATP: [[adenosine triphosphate]]<br />{{bull}}AMPK: [[AMP-activated protein kinase]]<br />{{bull}}PGC-1α: [[PGC-1α|peroxisome proliferator-activated receptor gamma coactivator-1α]]<br />{{bull}}S6K1: [[p70S6 kinase]]<br />{{bull}}4EBP1: [[EIF4EBP1|eukaryotic translation initiation factor 4E-binding protein 1]]<br />{{bull}}eIF4E: [[eukaryotic translation initiation factor 4E]]<br />{{bull}}RPS6: [[ribosomal protein S6]]<br />{{bull}}eEF2: [[eukaryotic elongation factor 2]]<br />{{bull}}RE: resistance exercise; EE: endurance exercise<br />{{bull}}Myo: [[myofibrillar]]; Mito: [[mitochondria]]l<br />{{bull}}AA: [[amino acid]]s<br />{{bull}}HMB: [[β-hydroxy β-methylbutyric acid]]<br />{{bull}}↑ represents activation<br />{{bull}}Τ represents inhibition | headerstyle=background:#ccccff | style=text-align:center; }}
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 | image2 = Resistance exercise-induced muscle protein synthesis.jpg
 | alt2 = Graph of muscle protein synthesis vs time
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 | caption2 = Resistance training stimulates muscle protein synthesis (MPS) for a period of up to 48&nbsp;hours following exercise (shown by dotted line).<ref name="Muscle hypertrophy review" /> Ingestion of a protein-rich meal at any point during this period will augment the exercise-induced increase in muscle protein synthesis (shown by solid lines).<ref name="Muscle hypertrophy review" />
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