Humans have both in their bodies.
There are basically two types of muscle fibers in our bodies that we have voluntary control over. One is called "red" muscle, and the other is called "white". Red muscle fibers have the ability to perform work over longer periods of time without fatigue. White muscle fibers are able to work hard, but for a shorter period of time than red fibers. An endurance athlete will have exercised his or her red muscle fibers (through long exercise sessions), so that they grow stronger and bigger. This means that their body will have the ability to do work for much longer than a person who only exercises for shorter periods (and exercises their white muscle fibers).
Basically the time under stress brings in red muscle or the slow twitch fibers into action. If the movement is controlled and the set goes longer the red fibers are used.. If the movement is explosive and heavy then the white fibers are used. For example squatting for 15 rep range incorporates red fibers of the thighs very well
The strength of joints limits the size of red muscle fibers.
Presence of myoglobin
Type I (red) muscle fibers, which have slow oxidative characteristics, are those primarily called on for long-distance running. These are more commonly referred to as 'slow-twitch' muscle fibers.
Because muscles need a lot of ATP for muscle contraction and it needs oxygen to make ATP, it has its own form of hemoglobin called myoglobin. The binding of oxygen to hemo(myo)globin is what gives the characteristic red color in both RBCs and muscle tissue.
weight lifting uses white muscle. Red muscle is used for longer sustained, repetitive movements, like long distance running.
White muscle and red muscle differ in their structure and function. White muscle is pale in color, has fewer blood vessels and mitochondria, and is used for short bursts of activity. Red muscle is darker in color, has more blood vessels and mitochondria, and is used for sustained activity. White muscle is better suited for strength and power, while red muscle is better suited for endurance and stamina.
if you use a wieghted bat before u hit then u are actually doing more harm than good. because the weighted bat has to use the red muscle fibers in your arm ur bat speed is actually slower. In your muscle u have to types of fibers white and red, red is for endurance and white is for quik and fast motions. In a baseball swing u have to swing quik rather than many times so swinging a weighted bat trains the wrong muscles and then when u get to the plate u use the wrong muscle fibers. Although it only effects about 1 mph on ur swing speed it still makes a difference
It is not the muscle but the muscle fiber which works for when recruited for long duration. The red muscle fiber or the slow twitch fiber gets recruited for long term stress on the muscle for example if you do bench press on heavy weight explosively for 5 reps you extensively use fast twitch fibers but if you do bench flys for 15 reps in controlled fashion, you extensively use red fibers.
Myoclonic epilepsy with ragged-red fibers, also known as MERRF is a mitochondrial disorder (therefore, it is maternally inherited) which affects many parts of the body but in particular, muscle and the nervous system. MERRF is usually characterized by muscle twitches (hence, myoclonus), muscle weakness and generally patients experience progressive stiffness or spasticity.
ofcourse not; slow twitch muscle fibers are: * smaller in diameter * red in color * depend on oxidative phosphorylation for their ATP supply * are highly vascularized (better blood supply) * have more mitochondria * more myoglobin fast twitch muscle fibers * larger * white * glycolysis is the source of ATP * less vascularized * less mitochondria * less myoglobin