Paddle Science #15 - Smart Muscle Training

Some athletes are able to sprint paddle faster and are able to develop bigger muscles more easily whilst some athletes will be able to paddle for longer and further without fatigue. This is largely based upon which muscle fibres are recruited in your body. If you’re thinking of creating a SUP training programme for the summer then understanding what types of fibres you have in your muscles will greatly influence how you will adapt to any training programme.

- Kate Starling

Types of Muscle Fibres

Within our bodies, we have three different types of muscle fibers. Slow twitch or Type I fibers are identified by a slow contraction time and have a high resistance to fatigue. Functionally, slow twitch muscle fibers are used during aerobic activities which require low-level force production. This includes most daily activities such as walking and maintaining posture. Fast twitch or Type II fibers are identified by a quick contraction time and have a low resistance to fatigue. These fibers can be further divided into fast twitch A (or Type IIA) and fast twitch B (or Type II B) fibers. Fast Twitch A fibers have a moderate resistance to fatigue and are used for prolonged anaerobic activities with a relatively high force output. They could, for example, be used in a 400m SUP race. Meanwhile, fast twitch B fibers are very sensitive to fatigue and are used for short anaerobic, high force production activities, such as sprinting over a short distance.

During an isometric contraction where the muscle doesn’t change its length, both slow and fast twitch fibers produce the same level of force. However, as soon as you move, a dynamic contraction will lead to muscle shortening and lengthening. During dynamic contractions, fast twitch muscle fibers are capable of producing much more force and power when compared to slow twitch fibers.

Typically, endurance athletes have a greater proportion of slow twitch fibers whilst sprinters will have a greater proportion of fast twitch fibers. Research into identical twins has identified that muscle fiber composition is very much genetically determined. This means that genetically you’ll have either have a greater percentage of slow twitch fibers, making you better at endurance activities or you’ll have a greater percentage of fast twitch fibers making you better at shorter, faster activities.

What Muscle Fibres Do You Have?