Muscle: Interesting Facts, Names, and Function

Interesting Facts About Voluntary Muscles

• The human body has over 600 voluntary/skeletal muscles. This means muscles which we can control, as opposed to muscles of the heart and intestines which we can not voluntarily control.
• Muscles are made of microscopic filaments which contract and slide over each other causing the the muscles to shorten and therefore contract.
• No matter how much you exercise you can not increase the number of muscle cells you have. By getting bigger, via strength training, you are simply increasing the size of each muscle cell. The quantity of muscle cells remain the same.
• Muscles can only contract, they do not lengthen unless an opposing muscles contracts and causes lengthening of the first muscle.
• Muscles are metabolically active and are responsible for a large amount of our caloric requirements.
• There are fast-twitch and slow-twitch muscles. Although the type of exercise you do may develop one over the other, the quantity of each is determined by genetics and can not be changed. This is why some people are ‘natural' sprinters while other are ‘naturally' better at long distance running.
• The largest muscle is the Gluteus Maximus, the muscles of the buttocks.
• The strongest muscles are:
  • The Soleus, part of the calf muscle, below the calf muscles, as it can apply the most force.
  • The Masseter, also known as the jaw muscles.
  • The tongue. Yes, the tongue is a muscle! And for its size it's very strong.
• More muscle information.

Major Muscle Groups

• Head, face, and neck:
  • Temporalis: temples.
  • Frontalis: forehead.
  • Orbicularis (Oculi): around the eyes.
  • Masseter: jaw muscles.
  • Orbicularis Oris: lips.
  • Sternocleidomastoid: long muscle running vertically at the side of the neck.
• Deltoids: shoulders. Used to lift arms over head. Developed via standing flies, lateral arm raises. Can be divided into anterior, posterior, and medial.
• Trapezius: just behind the deltoids. Used to lift the arms up and towards the back.
• Pectorialis Major (superficial) and Minor (deeper): chest. Used for any movement which the arms are brought to the front of the body. Used in swimming, push-ups.
• Latissimus Dorsi: mid back. Used to pull something closer, e.g. opening a door. Developed by doing bent over, or sitting, rows.
• Rhomboids: between the shoulder blades. Used for pulling the arms back. Developed by doing bent over flies.
• Erector Spinae: very long back muscles that run up and down, around the vertebrae. Used mostly in walking, but these are core muscles so they are always contracting when a person is moving.
• Spinalis: closest to the vertebrae.
• Longissimus: just lateral to the Spinalis.
• Iliocostalis: just lateral to the Longissimus.
• Gluteus Maximus: buttocks. Used for climbing stairs, walking, standing from a sitting position. Doing squats is the best way to develop this group of muscles.
• Quadriceps: front of the upper leg. Used for knee extension, cycling, climbing stairs. Squats or leg extensions on a machine will develop this muscle.
  • Rectus Femoris: most anterior and is the part you can see. Attaches onto the patella (knee cap).
  • Vastus Intermedius: just below (deeper) than the Rectus.
  • Vastus Lateralis: to the outside of the leg.
  • Vastus Medialis: to the inside of the leg.
• Hamstrings: posterior (back) of upper leg. Used for knee flexion. Lying down leg flexion will develop this group.
  • Biceps Femoris: in the center
  • Semitendinosus: just medial to the Bicep Femoris.
  • Semimembranosus: medial to the Semitendinosus, almost to the inside of the leg.
  • Vastus Lateralis: to the outside of the leg.
  • Gracilis: inside of the leg.
  • Adductor Magnus: inside of the leg. Brings the legs together.
  • Abductor: outside of the legs. Brings the legs apart.
• Triceps: back of the arm. Used for elbow extension. Tricep extensions, or push-ups, will develop the Triceps.
• Forearm flexors: consists of many small muscles used for bending the fingers. Squeezing something like a tennis ball is a good way to strengthen these muscles.
• Forearm extensors: consists of many small muscles used for straightening the fingers.
• Gastrocnemius: the calf muscle you can see. Used for walking and standing on toes. Standing toe raises is the best way to strengthen these muscles. But they are very strong so you will need to hold a dumbbell to increase resistance.
• Soleus: deeper than the Gastrocnemius. Similar function as Gastrocnemius.
• Plantaris: deeper than the Soleus.
• Tibalis (anterior & posterior): front of the lower leg. Used to pull toes upwards.
• Abdominals:
  • External oblique: on the surface.
  • Internal Oblique. deeper.
  • Transverse Abdominis: fibers run horizontal.
  • Rectus Abdominis: fibers run vertical.

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