Fitness is specific to the task at hand. When you see a great endurance cyclist, don’t automatically assume they’re a great marathoner. The physical qualities you build in one area may not carry over that well to others. If you have a specific goal in mind, you must practice specifically for that task. This sounds obvious, but it’s important to reiterate. To take it a step further, when you are strength training as an adjunct to a certain task(i.e. Strength training to help your marathon performance), understand that strength is a general quality, best trained as such. If you look at the range of motion of those running a marathon, they never come close to the knee/hip range of motion a squat puts you in. They run for multiple hours, and train a different adaptation than strength. Some take this line of thinking to mean they should only perform quarter range of motion squats, for very high repetitions (30+) in circuit format with other movements to mimic what they think the demands of running require. Training for strength should be general. Get stronger on the basic movements, use rep ranges that allow for heavier loads to be lifted, and don’t be worried if you’re not out of breath at the end. Then, go out and practice running. Make sure your training is systematic, rationale, and properly sequenced. I recommend Steve Magness’ book Science of Running). And while this example used marathon running, it can easily be applied to other sports or endeavors. As Coach Tsypkin writes, train general physical traits. Practice the task.