But what are these and how do they differ? They are distinguishable through the level of activity of the enzyme Myosin Adenosine Triphosphase ATPase as well as through other characteristics. Your Type I fibers are slow-twitch while both Type II fibers are classed under the term of fast-twitch. These muscle fibers are an endurance athlete's best friend. They are plentiful in mitochondria, myoglobin oxygen binding protein , and capillaries which allow for oxygen to be used to produce energy via oxidative phosphorylation.
The capillaries transport the oxygen bound to the myoglobin into the muscles where it can be used by the mitochondria to synthesize ATP; allowing you to exercise longer. Slow twitch muscle fibers are therefore highly fatigue-resistant which is why muscles such as your gastrocnemius calf contain more slow-twitch fibers innately; allowing you to keep walking, standing and doing all those everyday activities without fatiguing quickly.
The major fuel for slow twitch muscle fibers are triglycerides fats as this energy source can provide an abundance of ATP. Find out more about how your body uses fat for fuel here.
While slow twitch muscle fibers power you through long runs or rides, they won't be great for explosive lifting or sprints as they are slower to contract. The two types of fast-twitch muscle fibers differ from the slow-twitch fibers because they have the ability to produce energy in the absence of oxygen glycolytic oxidation. This allows them to produce energy quicker using phosphocreatine and glycogen read more on these energy systems here , to fuel those quick explosive movements such as jumping and sprinting.
This means they have faster contraction speeds than slow-twitch fibers. These two types of fast-twitch fibers also differ from each other, with Type IIa fibers displaying some similarities with the slow-twitch fibers. Type IIa fibers can produce energy through both glycolytic AND oxidative pathways which make them slightly more fatigue resistant than the Type IIb fibers. Type IIa also have more capillaries than IIb; aiding their ability to produce energy using oxygen.
Your Type I fibers are perfect for long duration exercise performed at a low to moderate intensity. If you enjoy marathons, half marathons, 10ks, long walks or cycles; these are the muscle fibers powering you through.
Type IIa fibers are for moderate duration exercise at a higher intensity. Events like the m and using moderately heavy weights in an rep range during your resistance training will predominantly use these fibers. Type IIb fibers are the experts at short exercise bouts at a high intensity that require that explosive production of force by the muscles. Sprinting the m or powerlifting are examples of the kind of sports these fibers thrive in.
Some exercise examples are, but not limited to box jumps, kettle-bell swings, squat jumps, sprinting. Since these fibers do fatigue much quicker, focusing on heavy weight or these previously mentioned exercises for a smaller amount of repetitions.
Additionally, you will want to allow your body to rest longer with seconds of rest after sets so that you give it enough time to replenish ATP levels. Resistance and weight training with heavy weight will recruit more muscle fibers. The heavier the weight, the more fibers will be used to help get you through that exercise.
Slow Twitch Muscle Fibers The slow twitch muscle fibers are able to withhold a longer duration of exercise at a steadier pace. They use oxygen for energy ATP to keep you going through the exercise. This means they fatigue less quickly. Slow twitch fibers are important for endurance athletes; long-distance runners, cyclists, or even ones who participate in triathlons.
This improves the muscle endurance within the muscle itself in order to give off energy. You can use bodyweight exercises for a higher amount of repetitions for engaging your slow twitch fibers, too.
Shorter periods of rest also help make it more of a challenge! Whether your main focus is on training your fast or slow twitch muscle fibers, you still need to focus on muscle recovery. This means you need to eat enough protein on a daily basis. The general rule is to eat 1 g of protein per lb of your bodyweight.
Impact Whey Protein. Age Age is also a factor for our muscle fibers. Glycolytic fast-twitch muscle fiber restoration counters adverse age-related changes in body composition and metabolism. Aging Cell Sarcopenia: characteristics, mechanisms and functional significance.
British Medical Bulletin Muscle fiber recruitment and the slow component of O2 uptake: constant work rate vs. Barh R Editor. Single muscle fiber adaptations with marathon training. Journal of Applied Physiology, , Next post Joint Hypermobility: The Shoulder. The Author. Related Posts. Concentric, Eccentric, and Isometric Muscles. Sign up to receive content, exclusive offers and so much more from NASM. Popular Recent.
By Brad Dieter. Fast-Twitch Vs. By Dr. Allison Brager. Slow-Twitch Type I. Muscle Fiber Size. Force Production. Very High. Resistance to Fatigue. Very Quick. Contraction Speed. ATPase Level.
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