Understanding What Causes Your Pain
For years, exercise gurus and other scientists thought that people felt pain after exercising because of a buildup of lactic acid in the muscles. They thought that soreness was a sign that you'd worked the muscles well, the idea being that a "wimpy" workout wouldn't produce as much acid. Now they know that, although tough activity does form lactic acid, the body flushes most of it from the muscles within approximately 24 hours after you finish working out, meaning that lactic acid likely isn't the main reason you hurt after exercise.
With more research, researchers discovered that muscles that have been worked hard usually have a large number of microscopic tears. The current theory is that pain after a workout is mainly from these microscopic rips. The harder you work, the more rips you create and the more sore you feel later. The inflammation that happens from the tissue damage adds to your discomfort to some degree, but it also helps speed recovery, delivering healing white blood cells to the injured area.
The Repeat Bout Effect
When scientists studied exercise and muscle development more closely, they discovered what they now call the repeat bout effect (RBE). In this phenomenon, muscles that experience chemical or mechanical stress adapt quickly so that they don't continue to get hurt. Experts poorly understand the exact processes involved, but they recognize RBE as a basic protective mechanism.
What the Repeat Bout Effect Means for Your Training
RBE means that, if you gradually increase the amount of weight you use or number of reps you do, you'll be less sore than if you jumped right into the tough stuff. If you utilize the repeat bout effect correctly, you might even gain muscle or endurance without being sore at all. (Did you catch that?) Muscle soreness is a very poor indicator of progress for this reason, and in fact, most experienced body builders rarely experience pain. Some trainers even say that if you're sore after exercise, you haven't exercised properly, going too long or too heavy all at once.
So why is being pain free through your training so important? The most obvious answer is that pain can impede your performance, preventing you from concentrating well and making you want to pull back from what you're doing. The second and perhaps less obvious reason you need to keep pain at bay is because it's so mentally destructive. The more pain you experience, the less likely you are to see exercise as enjoyable and the more likely it is that you'll quit.
RBE also runs contrary to most of the workout videos currently on the market. These productions often feature trainers who send the old school message: "If you're not pushing until you drop, you won't see results." Even when they offer modifications, they label them as being for "beginners" or "less advanced" athletes, failing to mention that using the modifications to ease into the program can yield great improvements with none of the pain. With this in mind, any time you look into a fitness DVD, you shouldn't assume that it's best to follow the instructor to the letter on the advanced versions the first few times around.
For years, people thought that pain was a necessary part of improving fitness. Scientists have discredited this idea, revealing RBE as a way to advance without discomfort. It's a good idea to let RBE guide your workout planning and keep your activities enjoyable.