1 Everyone has fatigued legs at first. This is very normal because snowboarding uses a lot of stabilizing muscles that you don't ordinarily utilize in everyday life. These muscles are often very tight, which can lead to fatigue. 2 Excessive sweating is also to be expected when snowboarding because the activity is hot enough to cause this problem without applying any external pressure to your skin. The more muscle tension you hold in your body, the more sweat you will produce. When you come off the mountain, it's important to stay hydrated and take time to re-hydrate after being on the slopes or in the cold weather. 3 Finally, long periods of inactivity can lead to muscle loss if you aren't using them. Your legs are part of your skeletal system and like all other muscles, need to be exercised or they will lose strength over time. The fact that snowboarding makes you tired comes as no surprise because it is a physically demanding sport. However, being aware of the reasons for this phenomenon will help you avoid overexerting yourself and causing injury instead.