When you work out vigorously, you place your body under considerable stress and it adapts to this stress by changing. If you always stay in your “comfort zone” and never challenge your body beyond what it’s used to you won’t get the change you’re looking for. This is the principle behind overload, a fundamental tenant behind change.
Overload is important but there’s another principle to consider when you plan your fitness training – the principle of specificity. Training specificity simply means if you want your body to adapt to the demands of a particular activity, focus your training around that activity. For example, if you want to become a faster sprinter, jogging long distances at a low or moderate intensity won’t bring you closer to your goal. A better option is to sprint and do power exercises like plyometrics that develop the fast-twitch muscle fibers – the fibers you use when you sprint.
Working out at a moderate intensity leads to a different set of training adaptations. Moderate-intensity exercise causes adaptations to occur in slow-twitch muscle fibers, those geared towards endurance exercise. When you target slow-twitch fibers, changes occur in the mitochondria inside these fibers that make them more efficient at using oxygen to produce ATP. Plus, capillary density increases to deliver more blood flow and oxygen to slow-twitch muscle fibers. This helps to fuel long periods of endurance activity. Little change occurs in fast-twitch muscle fibers, the ones you use for high-intensity exercise and sprinting. So a certain specificity applies to intensity. What does this mean? If you want to develop more power, be a faster sprinter, jump higher or do short bursts of intense activity, train at high intensity for short periods of time using interval training.
Training Specificity and Sports
Specificity and adaptation extend beyond fast-twitch versus slow-twitch muscle fibers. You’ll get the most improvement if you focus on the specific activity you want to get better at. Pedaling at a high intensity on an exercise bike targets fast-twitch muscle fibers but it won’t necessarily make you a better sprinter. It’ll only make you faster “cycle sprinter.” To improve sprint running times, the most effective way is to sprint. That’s the power of sports specificity. To get better at something, do that activity. Training adaptations are sport and activity specific.
Training Specificity: Resistance Training
Training specificity also applies to resistance training. Lifting light weights for a high number of reps gives a different type of adaptation than if you use heavy weights you can only lift a few times. High-rep workouts target slow-twitch muscle fibers. Over time, this increases muscle endurance, the ability to lift a lighter weight longer without becoming fatigued. Low rep workouts using heavy weight causes fast-twitch muscle adaptations. The muscle fibers become larger and neurological adaptations take place that lead to strength gains. Specificity is at work here too. On the other hand, recent research shows it’s possible to increase muscle size to some degree using lighter weights if you train to fatigue but it’s not the optimal way to build definition or strength.
What Does This Mean?
Make sure you’re training in a manner consistent with your goals. If you’re not getting the results you want, look at how you’re training. If strength is your goal and you’re using three-pound dumbbells, your training isn’t compatible with your goals. The same applies to building power. Target fast-twitch muscle fibers with high-intensity power drills, sprints, and plyometrics. Don’t take a comfortable jog and expect to be a better powerful athlete.
One word of caution. Even though training should be goal specific, that doesn’t mean you need to train that way every day. Too much high-intensity exercise without rest and recovery time can lead to overtraining or an injury. Scale back the intensity of your training some days to give your body time to recover and add more variety to your routine. Workout variety is important for keeping your body guessing and avoiding plateaus. If your workouts are geared towards strength and power, treat your body to a low-impact workout or a yoga DVD once or twice a week. This can actually help you stay more focused on your ultimate goal without risking burnout by helping you avoid fatigue and psychological staleness. It’s all about listening to your body.
References:
Journal of Physiology. 2008 January 1: 586: 1-2.
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