This is an excerpt from Triathlon Anatomy-2nd Edition by Mark Klion & Jonathan Cane.
Development of functional strength is very popular in the fitness industry. It can be defined as training to enhance the coordinated working relationship between the nervous and muscular systems. Functional training exercises use everyday movement patterns, such as standing, twisting, bending, lifting, jumping, walking, and running, in contrast to exercises that isolate joints. An example is the walking lunge versus the leg extension. Whereas the leg extension effectively isolates the muscles of the quadriceps and makes them stronger, it does so in a way that the muscles will likely never be used in any athletic activity. In contrast, the walking lunge also uses the quadriceps, but it also targets all the other muscles associated with the fluid movement patterns of standing, walking, and running. A balanced resistance training program will typically have both types of movements as part of the routine since one is most effective at strengthening a specific muscle, whereas the other uses that muscle in a more practical way.
Earlier we referred to the importance of understanding why you're doing certain training. In the case of strength work, that's particularly important. Many athletes envision a linear relationship between strength and speed. In other words, they believe that if their muscles are stronger, they will be faster. In truth, the fastest runner isn't necessarily the athlete with the strongest hamstrings or quadriceps, but rather the one who addresses complementary muscles like the abductors and adductors that help stabilize the hip and minimize wasted energy. Similarly, the swimmer with the strongest lats might not be the fastest in the water; instead, someone who has strengthened the small muscles in her rotator cuff, thereby avoiding injury, might be faster. And most certainly, the athlete who compromises form or safety in the weight room and ends up injured isn't going to be a fast one. In other words, check your ego at the door. Don't be overly attentive to “show” muscles. Don't compete with anyone but yourself in the weight room. The goal of your resistance training should be to gain strength, not demonstrate it.