Do you get tired after swimming a few laps?🥶 You can be a very proficient long-distance runner but still get tired after a few laps in a pool. Why does it happen? 👉 Running and cycling heavily rely on leg muscles, while swimming primarily focuses on arm muscles. ⛔️ Even if your heart can efficiently pump blood and you have good stamina, it may not be enough if your arms and shoulders are not well-trained. 🧬 Let’s dive a bit more into science.  Human muscles contain a genetically determined mixture of both slow and fast fiber types. On average, people have about 50% slow-twitch and 50% fast-twitch fibers in most of the muscles used for movement. 👉 Fast-twitch muscle fibers provide bigger and more powerful forces, but for shorter durations and fatigue quickly and slow-twitch muscles fibers use energy slowly and consistently to sustain activity over a long period. 🔬 The research found that endurance athletes can have anywhere from 60 to 95 percent slow-twitch muscle fibers, ...