[0:00] hi everybody dr. Mike here in this video
[0:02] we're gonna take a look at skeletal
[0:03] muscle hypertrophy now we all know that
[0:15] going into the gym lifting weights
[0:17] undergoing resistance training increases
[0:19] our muscle mass muscle volume muscle
[0:21] size and muscle cross-sectional area all
[0:24] of which we term skeletal muscle
[0:26] hypertrophy but the question is how does
[0:29] this occur so in this video I'm going to
[0:30] go through the mechanisms that promote
[0:32] skeletal muscle hypertrophy but the
[0:34] first thing we need to go through is the
[0:36] skeletal muscle itself so let's just say
[0:39] we have a whole muscle like a bicep for
[0:41] example now we know that this whole
[0:42] muscle is surrounded by connective
[0:44] tissue that we term fashio and if you
[0:46] have a look inside of that whole muscle
[0:48] you'll find that there's these discrete
[0:50] areas called fascicles they themselves
[0:53] are surrounded by connective tissue
[0:55] which we call perimysium now you can see
[0:57] within each fascicle are gonna we're
[1:01] gonna have skeletal muscle cells known
[1:03] as muscle fibers and you can see these
[1:05] fibers now if I would have take one of
[1:07] these fascicles and pull out one of
[1:09] these muscle fibers which we call a
[1:11] muscle cell you're gonna see a couple of
[1:13] things firstly it's surrounded by
[1:15] connective tissue as well so the whole
[1:16] muscle connective tissue right the
[1:20] fascicle connective tissue and then the
[1:22] muscle fiber connective tissue now this
[1:25] is called the endomysium that connective
[1:26] tissue around the muscle fiber and
[1:28] underneath that you've got the cell
[1:30] membrane cuz all cells have a cell
[1:32] membrane and we called this four muscle
[1:34] cells the Sarco lemma alright now you
[1:37] can see that I've drawn up a couple
[1:38] things first of which these little blue
[1:40] things here are called satellite cells
[1:42] they're going to be very important when
[1:43] it comes to hypertrophy sunlight cells
[1:46] are sitting between the sarcolemma so
[1:48] the cell membrane and a connective
[1:50] tissue the basal lamina okay and they're
[1:52] sitting there in the quiescent which
[1:54] means they're asleep and they're waiting
[1:55] to be stimulated and do something very
[1:57] specific in order first skeletal muscle
[1:59] hypertrophy to occur the other thing you
[2:01] can see is the nuclei of skeletal muscle
[2:04] they have more than one and again this
[2:07] is important when it comes to sunlight
[2:08] cells remember the nucleus is where DNA
[2:11] is transcribed we make more DNA
[2:13] now remember proteins come from amino
[2:15] acids which come from DNA that's
[2:17] important you can also see that if we
[2:20] were to take out one muscle fiber that
[2:22] inside they're filled they're really
[2:24] filled up with these things could
[2:26] myofibrillar
[2:27] tubes now these myofibrils are made up
[2:31] of proteins two major types of proteins
[2:34] there's more but two major types you
[2:36] need to know called actin and myosin now
[2:39] what you're going to find is that these
[2:40] proteins inside the myofibrils their
[2:42] contractile proteins because not all
[2:44] proteins are contractile right but these
[2:46] are contractile proteins now you'll see
[2:49] that dispersed between the myofibrillar
[2:51] have some organelles some sub cellular
[2:54] components things like mitochondria
[2:56] right mitochondria is important for
[2:58] producing ATP energy which we need for
[3:00] skeletal muscle contraction we also have
[3:02] things like sarcoplasmic reticulum
[3:05] now the sarcoplasmic reticulum is the
[3:07] endoplasmic reticulum but for skeletal
[3:09] muscle and their important role is that
[3:11] they are the storage unit for calcium we
[3:14] also need calcium for muscle contraction
[3:15] actual fact calcium and ATP are two of
[3:18] the major things that we need for muscle
[3:20] contraction there's other organelles as
[3:22] well but let's just focus on those two
[3:24] all right now let's take a myofibrillar
[3:26] out have a look at this right we've got
[3:28] the Maya febrile sitting within the
[3:30] muscle fiber sitting within the fascicle
[3:31] sitting within the whole muscle each
[3:33] component is surrounded by connective
[3:35] tissue we take a my fibrillate and we
[3:37] looked at look at the actin and myosin
[3:39] contractile proteins within and you'll
[3:41] see they have a particular arrangement
[3:43] what I've drawn up here is something
[3:45] called a sarcomere now you keep hearing
[3:47] this word Sarco as a prefix when we talk
[3:49] about scalar muscle because it means
[3:51] flesh all right so you can see the two
[3:53] major types actin which we call the thin
[3:55] filament and myosin that we call the
[3:58] thick filament now in order for muscle
[4:00] to contract muscle its job is to
[4:03] contract so that force can be generated
[4:05] usually things can move and you've got
[4:07] cardiac muscle to pump blood smooth
[4:09] muscle to push things through the hollow
[4:11] insides of those of that lumen and we've
[4:13] got skeletal muscle attached to the
[4:15] skeleton so things can move right so
[4:17] what we need to do is that this thick
[4:20] myosin filament needs to bind to the
[4:22] thin actin filament and these little
[4:24] myosin heads need to walk their way
[4:26] along the actin filament and it pulls it
[4:28] in what this does is it shortens the
[4:30] skeletal muscle in actual fact it
[4:32] shortens this thing called the sarcomere
[4:34] now you're gonna have sarcomeres lined
[4:36] up in series like this or or I should
[4:39] say and lined up in parallel okay and
[4:42] this is going to be important when it
[4:43] comes to skeletal muscle hypertrophy as
[4:45] well now remember the myosin can't bind
[4:48] to the actin unless calcium is present
[4:50] calcium frees the actin so it can bind
[4:52] and calcium sits within the sarcoplasmic
[4:55] reticulum and we need ATP the thing with
[4:58] ATP is we don't actually have a lot of
[5:00] it just freely floating around you think
[5:02] we would but we don't we need to
[5:03] generate ATP and so skeletal muscle
[5:06] needs to generate ATP fast and we'll
[5:08] talk about that with skeletal muscle
[5:09] hypertrophy soon all right
[5:11] couple things now when we talk about
[5:13] hypertrophy I told you increasing the
[5:16] size increasing the volume increase in
[5:17] the mass increasing the cross-sectional
[5:19] area what do you think is increasing
[5:22] here is it the whole muscle is that the
[5:24] fascicle is it the muscle fiber or is it
[5:26] the sarcomere or is it the protein
[5:28] subunits of the sarcomere well it's not
[5:31] just these individual things so for
[5:34] example a lot of people rely on scooter
[5:36] muscle hypertrophy has just been an
[5:38] abundance of the proteins that
[5:39] contractile proteins and their
[5:41] arrangement within the sarcomere people
[5:43] think that scooter muscle hypertrophy is
[5:45] only more sarcomeres lined up in series
[5:49] or lineup in parallel but that's only
[5:51] one type of skeletal muscle hypertrophy
[5:53] right called myofibrillar hypertrophy I
[5:56] think we should write this down right so
[5:59] you can have myofibrillar hypertrophy
[6:04] and like I said what that is is an
[6:09] increase in the protein subunits for
[6:12] contraction and an increase in the
[6:14] amount of sarcomeres we have either in
[6:17] series or in parallel but we know that
[6:21] up to 20% of the whole muscle is
[6:23] connective tissue like I stated before
[6:25] right so you've got that fashion you've
[6:28] got the Paramecium you got the
[6:30] endomysium you have the epimysium on the
[6:32] outside here so up to 20% is connective
[6:36] tissue so in connective tissue is
[6:38] dynamic it doesn't
[6:39] sit there connective tissue can grow and
[6:41] it can contribute to strength so you can
[6:44] have connective tissue hypertrophy now
[6:53] the last or third type of hypertrophy
[6:56] that we need to talk about is
[6:57] hypertrophy of non contractile subunits
[7:00] and non connective tissue which has to
[7:02] do with the stuff sitting between the
[7:05] cells and in the cells for example which
[7:08] includes things like the organelles and
[7:10] the fluid and also the metabolic energy
[7:15] sources that are stored inside of these
[7:17] muscle cells so for example now we call
[7:20] this let's just write this down
[7:22] we call this sarcoplasmic hypertrophy so
[7:32] what we're referring to for sarcoplasmic
[7:34] hypertrophy is an increase in the size
[7:36] or abundance or volume of the organelle
[7:39] so it could be the mitochondria it could
[7:41] be the sarcoplasmic reticulum could be
[7:43] the T tubules that skeletal muscle needs
[7:45] to propagate that action potential to
[7:47] tell it to contract right it could be an
[7:50] accumulation of fluid inside and it
[7:52] could be an accumulation of the
[7:54] metabolic products needed to produce
[7:56] energy so up to three percent of
[8:00] skeletal muscle is made up of glycogen
[8:03] up to five percent is made up of
[8:05] triglycerides so you can increase the
[8:07] abundance of these and they're going to
[8:08] come back later when we talk about
[8:09] hypertrophy so these are the three major
[8:12] types and the thing is what causes these
[8:15] types of hypertrophy so doctor shown
[8:18] field dr. Brad shown field is the king
[8:21] of skeletal muscle hypertrophy and all
[8:23] the research that I've performed most of
[8:25] it has come from dr. Shawn field and so
[8:28] what dr. Schoenfield states is the three
[8:30] major causes or stimuli for hypertrophy
[8:33] include the following mechanical tension
[8:43] metabolic stress and muscle damage so
[8:53] these three stimuli are what can result
[8:59] in these three types of hypertrophy now
[9:02] your question may be well which of these
[9:03] hypertrophy is occurring usually all of
[9:05] them are going to be occurring to some
[9:07] degree you're probably going to think
[9:09] with resistance training probably the
[9:10] most common type of hypertrophy is Maya
[9:13] febrile hypertrophy but in saying that
[9:15] when you look at bodybuilders and
[9:16] compare them to power lifters their
[9:18] training regime is different but both of
[9:20] them exhibit quite significant
[9:22] musculature quite significant muscle
[9:24] growth and they train differently right
[9:26] so for example bodybuilders have a
[9:28] moderate load with shorter rest periods
[9:31] and you're going to find that power
[9:32] lifters have a higher load with longer
[9:35] rest periods and what you might find is
[9:38] that some bodybuilders may more so have
[9:40] a connective tissue based and
[9:42] sarcoplasmic based hypertrophy because
[9:44] they tend to have more stores of
[9:45] glycogen within their cells and they
[9:47] tend to have more connective tissue
[9:49] products as well compared to the power
[9:51] lifters so training type can be specific
[9:55] to the type of hypertrophy that you get
[9:58] all right so mechanical tension
[10:00] metabolic stress and muscle damage of
[10:03] these mechanical mechanical tension is
[10:06] king right and you'll find that
[10:08] metabolic stress and muscle damage are
[10:10] additive to this process because you
[10:12] really get skeletal muscle hypertrophy
[10:14] on metabolic stress alone and muscle
[10:17] damage alone now let's talk about some
[10:19] things let's talk about how this can
[10:22] result in this all right so when you've
[10:25] got mechanical tension on a muscle so
[10:27] you lifting a particular load over time
[10:30] and so we know that we have eccentric
[10:32] portions of a movement and concentric
[10:33] portions in the eccentric portions where
[10:36] you've got lengthening of the muscle but
[10:38] these sarcomeres are contracting you can
[10:41] have damage occurring to the
[10:43] myofibrillar units now damage promote
[10:46] some form of inflammatory response it
[10:48] can recruit cytokines and inflammatory
[10:50] cells and this promotes your repair
[10:52] that's great what also happens is this
[10:55] type of damage
[10:56] wakes up the sleeping satellite cells
[10:58] the quiescent satellite cells and they
[11:00] are myogenic cells that means they're
[11:03] basically muscle stem cells and what
[11:05] they can do is they fuse since they're
[11:06] sitting underneath the basal lamina
[11:08] right but above the sarcolemma they fuse
[11:10] with the muscle cell they're all muscle
[11:12] cells remember they fuse with them and
[11:14] they donate a nuclei that's why I've got
[11:17] more nuclear here donates a nuclei and
[11:20] what that means is there's now more
[11:21] nuclei more DNA more transcriptional
[11:25] activity more amino acids and proteins
[11:27] being produced in actual fact when you
[11:29] look at skeletal muscle the larger the
[11:31] muscle is correlated with more nuclei
[11:34] and this has to do with that satellite
[11:36] cell so the satellite cell is really
[11:38] important for donating the nuclear but
[11:39] in addition the satellite cell can call
[11:42] upon particular transcriptional
[11:43] activities right since it's got this
[11:45] additional nuclei transcribe more
[11:49] pathways associated with anabolic or
[11:51] growth pathways so for example mTOR map
[11:55] kinase calcium signaling pathways all of
[11:59] these can be recruited pathways for
[12:01] growth and ab ilysm alright so we'll
[12:05] focus on that now when you look at the e
[12:07] centric and you start to go into that
[12:09] pattern of moment eccentric stretching
[12:11] at the same time that it's contracting
[12:13] you can find that in some studies animal
[12:15] studies predominantly that the types of
[12:18] growth that you get at the sarcomere is
[12:21] an addition of sarcomeres in series and
[12:24] when you get more column centric
[12:27] movements the addition of sarcomeres is
[12:30] in parallel alright so again the type of
[12:33] that movement can change what type of
[12:35] hypertrophy you have at the sarcomere so
[12:37] talking about the my fibrillar
[12:39] hypertrophy if we actually take all them
[12:41] all the proteins within a skeletal
[12:43] muscle what you're gonna find is up to
[12:45] 70% of them are my fibrillar proteins
[12:48] right seventy percent twenty percent of
[12:50] them are sarcoplasmic proteins and
[12:53] around about 10% our mitochondrial
[12:56] proteins alright now a couple of other
[12:59] things is when so if we have a look at
[13:02] different types of loads so when we look
[13:04] at load lifting load it's usually going
[13:07] to be represented as a percentage of our
[13:08] one-hour
[13:09] and we usually equate that to how many
[13:11] reps we can perform other particular
[13:13] weight all right so you can have a low
[13:17] rep scheme a moderate rep skein and a
[13:19] high rep scheme
[13:20] all right low rep scheme zero to six
[13:21] reps mutter at six to twelve reps
[13:24] anything above 12 13 14 15 reps and
[13:26] above is going to be a high rep scheme
[13:28] so what they've found is that the low to
[13:30] moderate rep scheme seems to be more
[13:32] beneficial to hypertrophy compared to
[13:34] high rep skeins and the reason is a
[13:37] little bit complex but has to do with a
[13:39] couple of things has to do with
[13:40] mechanical tension and has to do with
[13:42] metabolic stress and muscle damage but
[13:44] let's look at metabolic stress now so
[13:46] when you lift a particular load we need
[13:50] ATP and I told you that ATP is needed
[13:52] for muscle contraction and I told you we
[13:54] don't have many reserves of ATP so we
[13:57] need to produce it now when we need to
[13:59] produce it immediately we use something
[14:01] called the Fausto creatine pathway
[14:03] creatine likes to hold onto phosphate
[14:05] called phosphor creatine and it donates
[14:07] that phosphate to an adp to basically
[14:10] turn it into ATP we have energy but that
[14:13] only lasts for like one two three
[14:14] seconds not very long at all so the low
[14:16] rep scheme tends to favor the
[14:18] phosphocreatine pathway when we go into
[14:20] the moderate rep scheme right six to
[14:22] twelve reps we go past that and we start
[14:25] to go into glycolysis we start to use
[14:27] glucose for energy now if we're doing
[14:28] this quick and fast and remember when
[14:31] you have glycolysis and it jumps into
[14:32] the mitochondria a user's oxygen to
[14:35] produce heaps of ATP if we need more ATP
[14:37] than we have available oxygen has to go
[14:40] through another pathway which is
[14:41] producing lactate right and ATP as well
[14:45] another thing is lactate production is
[14:47] associated with hypertrophy in this
[14:49] sense lactate can pull water has a
[14:52] strong osmotic gradient right it pulls
[14:54] water into the cell and causes the
[14:56] muscle cell to swell this swelling of
[14:59] the muscle cell puts pressure on the
[15:00] sarcolemma sort of cell membrane and
[15:02] this actually stimulates a couple of
[15:04] things it stimulates amino acid
[15:06] transport and it stimulates anabolism or
[15:09] protein synthesis brilliant so this is
[15:12] something that lactate can do lactate
[15:15] production is also associated with
[15:18] testosterone levels and growth hormone
[15:20] levels as well alright so it seems to be
[15:22] this is
[15:23] why the moderate reps game seems to be
[15:25] represented as potentially the most
[15:27] beneficial when it comes to hypertrophy
[15:29] but let's not forget volume all right so
[15:32] that's load volume is adding up all your
[15:35] reps and sets in the single session and
[15:37] it seems to be the higher the volume the
[15:39] better it is for hypertrophy as well now
[15:42] let's talk about something that involves
[15:44] both metabolic stress and muscle damage
[15:46] which is hypoxia
[15:47] so hypoxia is a reduction in oxygen
[15:49] going to that tissue and feeding that
[15:51] tissue so often we call this vascular
[15:54] occlusion and the some sort there's some
[15:56] types of training where you occlude the
[15:58] vasculature with a cuff for example and
[16:01] it seems to be that this type of hypoxic
[16:03] or or banded vascular occlusion training
[16:05] can increase muscle hypertrophy if done
[16:09] in accordance with exercise and it
[16:10] doesn't even need to be under high load
[16:12] so what the found is that hypoxia
[16:15] training or vascular occlusion training
[16:17] without any exercise just the vascular
[16:19] occlusion can maintain muscle size and
[16:21] strength for individuals who are
[16:23] bedridden if you mix it in with exercise
[16:26] it seems to be an additive effects with
[16:28] hypoxia and exercise to promote
[16:32] hypertrophy as well so that's really
[16:34] interesting why why does this hypoxic
[16:37] event promote hypertrophy couple of
[16:39] theories one of which is that of lactate
[16:41] so when you've got no oxygen we're
[16:43] forced to use glucose to produce ATP and
[16:47] lactate and like I said lactate pulls
[16:49] water into the cell it swells promotes
[16:51] amino acids and protein synthesis and
[16:53] also promotes
[16:54] growth hormone and testosterone coming
[16:58] in the other thing is when you have a
[17:00] hypoxic environment low oxygen you get
[17:02] the production of reactive oxygen
[17:03] species one of which is nitric oxide
[17:06] nitric oxide tells blood vessels to
[17:08] dilate so after that training when you
[17:11] release the cuff or the band you get
[17:13] increased in nitric oxide tells blood
[17:15] vessels to dilate you get hyperemia
[17:17] which is more blood to that area
[17:18] carrying all the metabolites that you
[17:20] require for growth so maybe that is also
[17:23] another factor coming into play so what
[17:26] I've gone through here is the anatomy of
[17:28] the skeletal muscle and gone through the
[17:31] different types of hypertrophy and also
[17:33] the different causes of these particular
[17:36] high
[17:37] a hypertrophic events hopefully that
[17:40] helps them make sense