Weight lifters use a variety of muscles in their body, from the shoulders to the feet. The muscular system is made up of two types of muscle fiber, and knowing how each plays into weight lifting can help you create workout routines that benefit your ultimate goals.
Muscle Fibers
Your body's muscles and muscle groups contain both fast-twitch and slow-twitch, or Type 1 and Type 2, muscle fiber. Most people have a relatively balanced ratio of fast-twitch to slow-twitch muscle fibers in the 60-to-40 or the 40-to-60 range, meaning your body's muscle fibers are divided evenly between the two. The ratio in which they're found in your body depends on your activities. For example, weight lifters may use more slow-twitch muscle fibers than a sprinter.
Function
All muscles in your body require adequate oxygen for optimal function. A fast-twitch muscle fiber, because it needs speed and power, requires a lot of glycogen and the enzyme adenosine triphosphate, or ATP, that transports fuel to it quickly for bursts of action or activity. These bursts of energy are consumed quickly by your muscle fibers, leading to fatigue in a short period. Slow-twitch muscles rely on oxygen as their main source of energy, which is in more plentiful supply through normal breathing.
Fast-Twitch
Fast-twitch muscle fibers are those that experience brief moments of contraction but tire quickly. The more active your sport or activity, the higher the ratio of fast-twitch to slow-twitch muscle fibers you may have. For example, a sprinter may have a very high ratio of fast-twitch muscles, upward of 80 percent. Fast-twitch muscle fibers allow for quick bursts of speed and power in activities such as sprinting, marathon running, bicycle racing and basketball.
Slow-Twitch
Muscle fibers that slowly contract but have stamina and endurance are slow-twitch, or ST. You find slow-twitch muscle fibers in greater ratios in muscles required for body support and stability, such as your back, buttocks and thighs.
Weight Lifting
Weight lifters uses both fast- and slow-twitch muscles. Lifting heavy poundage for only a few repetitions uses fast-twitch muscle fibers, as you tire or reach fatigue or muscle failure quickly. Using lighter poundage forces slow-twitch muscle fibers into play, as you're able to engage in more repetitions than you would lifting heavy poundage. Performing single sets with heavy weights encourages your body to use the speed and power of your fast-twitch fibers.
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