Muscles. We have over 600 of them. They make up between 1/3 and 1/2 of our body weight, and along with connective tissue, they bind us together, hold us up, and help us move. And whether or not body building is your hobby, muscles need your constant attention because the way you treat them on a daily basis determines whether they will wither or grow. Say you're standing in front of a door, ready to pull it open. Your brain and muscles are perfectly poised to help you achieve this goal. First, your brain sends a signal to motor neurons inside your arm. When they receive this message, they fire, causing muscles to contract and relax, which pull on the bones in your arm and generate the needed movement. The bigger the challenge becomes, the bigger the brain's signal grows, and the more motor units it rallies to help you achieve your task. But what if the door is made of solid iron? At this point, your arm muscles alone won't be able to generate enough tension to pull it open, so your brain appeals to other muscles for help. You plant your feet, tighten your belly, and tense your back, generating enough force to yank it open. Your nervous system has just leveraged the resources you already have, other muscles, to meet the demand. While all this is happening, your muscle fibers undergo another kind of cellular change. As you expose them to stress, they experience microscopic damage, which, in this context, is a good thing. In response, the injured cells release inflammatory molecules called cytokines that activate the immune system to repair the injury. This is when the muscle-building magic happens. The greater the damage to the muscle tissue, the more your body will need to repair itself. The resulting cycle of damage and repair eventually makes muscles bigger and stronger as they adapt to progressively greater demands. Since our bodies have already adapted to most everyday activities, those generally don't produce enough stress to stimulate new muscle growth. So, to build new muscle, a process called hypertrophy, our cells need to be exposed to higher workloads than they are used to. In fact, if you don't continuously expose your muscles to some resistance, they will shrink, a process known as muscular atrophy. In contrast, exposing the muscle to a high-degree of tension, especially while the muscle is lengthening, also called an eccentric contraction, generates effective conditions for new growth. However, muscles rely on more than just activity to grow. Without proper nutrition, hormones, and rest, your body would never be able to repair damaged muscle fibers. Protein in our diet preserves muscle mass by providing the building blocks for new tissue in the form of amino acids. Adequate protein intake, along with naturally occurring hormones, like insulin-like growth factor and testosterone, help shift the body into a state where tissue is repaired and grown. This vital repair process mainly occurs when we're resting, especially at night while sleeping. Gender and age affect this repair mechanism, which is why young men with more testosterone have a leg up in the muscle building game. Genetic factors also play a role in one's ability to grow muscle. Some people have more robust immune reactions to muscle damage, and are better able to repair and replace damaged muscle fibers, increasing their muscle-building potential. The body responds to the demands you place on it. If you tear your muscles up, eat right, rest and repeat, you'll create the conditions to make your muscles as big and strong as possible. It is with muscles as it is with life: Meaningful growth requires challenge and stress.
Mišići. Imamo ih više od 600. Oni čine između 1/3 i 1/2 naše tjelesne težine, a uz vezivnog tkiva , oni nas vežu zajedno, drže nas uspravnima, i pomažu nam da se pokrečemo. I bez obzira na to da li je body building vaš hobi, mišići trebaju vašu stalnu pažnju jer način na koji s njima svakodnevno postupate utječe na njihovo slabljenje ili rast. Recimo da stojite ispred vrata, spremni da ih otvorite. Vaš mozak i mišići su savršeno spremni pomoći vam u postizanju tog cilja. Prvo, vaš mozak šalje signal motornim neuronima u vašim rukama. Nakon što prime ovu poruku, oni se bore, uzrokujući kontrakcije i opuštanje mišića, to povlaći kosti u vašoj ruci i stvara potreban pokret. Što izazov postaje veći, to je signal u mozgu veći, i više motornih jedinica se udruže da vam pomognu ostvariti taj zadatak. Ali što ako su vrata izrađena od čvrstog željeza? U tom slučaju sami mišići vaše ruke neće moći proizvesti dovoljno napetosti da ih otvore, pa vaš mozak apelira na druge mišiće za pomoć. Zabijete svoje noge čvrsto u pod, zategnete trbuh i napnete leđa, proizvodeći tako dovoljno snage ih povučete i otvorite. Vaš živčani sustav je jednostavno iskoristio sredstva koja već posjedujete, ostale mišiće, da bi došao do cilja. Dok se sve ovo događa, vaša mišićna vlakna prolaze drugu vrstu staničnih promjena. Nakon što ste ih izložili stresu, doživljavaju mikroskopsu štetu, koja je u ovom kontekstu pozitivna. Kao odgovor na to, ozlijeđene stanice otpuštaju upalne molekule citokine koje aktiviraju imunološki sustav da bi popravio ozljede. Tako se događa čarolija izgradnje mišića. Što je veća šteta u mišićnom tkivu, to je potrebno više vremena za oporavak. Rezultat ciklusa štete i popravaka su naposlijetku veći i jači mišići koji se postupno prilagođavaju većim zahtjevima. Budući da su se naša tijela prilagodila većini svakodnevnih aktivnosti, obično ne proizvode dovoljno stresa da bi stimulirala novi rast mišića. Za izgradnju mišića, ili hipertrofiju, opterećenje stanica se mora povečati. U stvari, ako stalno ne izlažete mišiće nekom otporu, oni će se smanjiti, taj proces je poznat kao mišićna atrofija. Nasuprot tome, izlažući mišiće visokom stupnju napetosti, pogotovo kad se oni produljuju, tijekom takozvane ekscentrične kontrakcije, stvaraju se učinkoviti uvjete za njihov novi rast. Međutim, mišićima je potrebno više od same aktivnost rasta. Bez pravilne prehrane , hormona i ostalog, vaše tijelo nikada ne bi bio u stanju popraviti oštećena mišićna vlakna. Proteini u našoj prehrani čuvaju mišićnu masu dajući joj materijal za izgradnju novog tkiva u obliku aminokiselina. Adekvatan unos proteina, zajedno s prirodnim hormonima, poput somatomedina i testosterona, pomažu dovesti naše tijelo u stanje u kojem se tkivo popravlja i raste. Ovaj vitalan proces popravka se uglavnom događa kad se odmaramo, osobito noću dok spavamo. Spol i dob utječu na ovaj mehanizam popravka, zato su mladi ljudi s više testosterona u prednosti kad se radi o izgradnji mišića. Genetski čimbenici su jako bitni kod nečije sposobnosti rasta mišića. Neki ljudi imaju jače imunološke reakcije na oštećenja mišića, i u mogućnosti su bolje popraviti i zamijeniti oštećena mišićna vlakna, povećavajuci njihov potencijal izgradnje mišića. Tijelo reagira na zahtjeve pred kojima se nalazi. Ako koristite vaše mišiće, pravilno jedete, odmarate se, stvoriti čete uvjete za maksimalan rast i snagu vaših mišića. S mišićima je kao i sa životom: Izazov i stres čini ih jačima.