<ur body has, thanks to evolution, a number of remarkably sophisticated mechanisms that allow it to adapt to the challenges presented by the environment.
If your exercise routine involves submaximal exertion for extended periods of time, your body will adapt by increasing angiogenesis, oxygen utilization efficiency, and myocytic mitochondrial density. These sorts of changes are what allow long-distance runners, swimmers, and bikers to sustain activity by means of improved circulation, reduced respiratory stress and associated systemic pH homeostasis enhancement, and elevated energy output, respectively. While this kind of fitness is helpful, it comes at the cost of muscular power output, strength, and size.
The other extreme is a heavy lifting-oriented type of fitness that results from adaptations such as increased intramuscular fat storage, left ventricular cardiac hypertrophy, and vascular wall strengthening. These changes allow a lifter to perform by providing a readily accessible and dense source of energy, enabling the heart to pump blood throughout the body against pressure resulting from exertion-
related vascular impedance, and allowing the vasculature to handle the acute blood pressure spikes that accompany such exercise.
So why is all this stuff important? Because when your body adapts to either type of fitness, it specializes. Once you’re specialized toward one side of the fitness spectrum, the other side becomes difficult to manage. Most everyone, other than professional athletes, should try to keep a balanced fitness profile. The best way to do this is to not allow your body to specialize to either extreme.
In your workouts, try to keep your body guessing. One day, do high weight, low rep strength training to trigger the heavy lifting adaptive mechanisms. The next try some circuit training to build endurance. When you keep your body from adapting in a one-directional way, it is forced to become a jack-of-all trades. While this often means slower overall progress, the gains you make will reflect true balanced fitness, as you will get the best of both worlds.
