When you work out, sometimes it seems like your body has a mind of its own; all kinds of weird physical symptoms, irritants and annoyances can pop up for seemingly no reason. Maybe your body is putting up a fuss because it doesn't feel like doing everything you're telling it to do. Maybe it's reacting to the many physical changes that are taking place "behind the scenes" in the various parts of your body. Maybe it's just plain tired and needs a break. Whatever the reason, your body can respond to exercise in all kinds of weird ways; here are some of the most common "side effects" of working out, as well as some clues as to why they happen.
Itchy Legs - You've probably experienced this at the beginning of a jog or a treadmill workout - especially if you haven't moved like that in a while. What's this nagging itching all about? As you begin to get moving, your heart rate increases, which sends more blood to the capillaries and arteries in your muscles. As they begin to expand, they activate nearby nerves, which send messages to your brain that are "interpreted" as itching.
Runny Nose - When your nose starts to run while working out, you're probably experiencing a decongestion of your sinus cavities, which can happen due to increased blood flow during your workout. Doctors refer to this unpleasant phenomenon as exercise-induced rhinitis, with common symptoms ranging from a leaky or stuffy nose to frequent sneezing.
Nausea - If you've ever felt a little dizzy or like you might throw up after a hard workout session, more than likely you've pushed yourself a little too hard. When you're exercising close to your maximum aerobic output, your body will automatically redirect the flow of blood from the gastrointestinal tract to the most active muscles, which slows down the digestive process. This can make you feel like you need to vomit. Other potential culprits include dehydration and inadequate nutrition.
Hives - No, you're not allergic to working out. Cholinergic urticaria, a.k.a. hives, can actually come from activities that boost your body heat, such as exercise. The most common form of cholinergic urticaria are those small bumps that can appear on your skin, typically within the first few minutes after breaking a sweat. They normally last between 30 minutes to an hour (possibly more) before they recede as your body temperature returns back to normal.
Muscle Twitches - Part fascinating and part aggravating, muscle twitches often occur after you work out due to a buildup of lactic acid in your muscles. Most of the time, the twitching will stop if you just move the muscle a little bit. If your muscles constantly twitch while you're working out, it may be a sign of a neurological condition; consult your doctor if this is the case. The best way to prevent these annoying twitches is to warm up before you work out, and cool down after you're finished. In addition, be sure to get adequate hydration (via drinking water), and remember to replenish your electrolytes through sports drinks or electrolyte-enhanced water after you work out.
Numb Toes or Feet - Let's say you're about 5 minutes into your jog, and all of a sudden you can't feel your toes, or your feet feel like they've gone numb. What's up with that? When you're working out, your feet actually begin to swell due to repetitive impact, and your body temperature begins to rise as well. The combination of these two factors can actually affect the circulation of blood to your feet, especially if you're wearing thick socks, shoes that are too small, or shoes that have been tied too tight.
Headaches - Perhaps you just finished an intense workout, and now your head is pounding--what went wrong? This is known as a primary exercise headache, and it is usually caused by factors such as low blood sugar, inadequate warm-up time or changes in the flow of blood to the brain during and after your workout. Most of the time they will go away on their own anywhere between 5 minutes to 48 hours after your workout, but if you have a headache that lasts for several days or even a week, be sure to consult with your health professional.
Your body is a complex machine, and it can respond to exercise in a number of interesting and often weird ways. If you have experienced any of the above symptoms, at least you know now that you're not the only one!