How serious are you about a sport you play or an activity you're passionate about? Are you serious enough to train for it, to work on building the major muscle groups used in that sport or activity? If so, and if you want to get even better at your passion, don't depend solely on practicing or on sessions at the gym. Pick a sport you can use for cross training.
Unlike the static, repetitive motions of working with weights or machines at the gym, cross training with a sport provides actual functional training.
Regardless of the sport or activity, the body is in constant motion. The ranges of motion (ROM) used will vary considerably. If it's a ball sport, the arms must be trained to reach up in the air, as well as out to your front, sides and even your back.
If mountain biking or cycling is your thing, your legs and hips have been made ready to absorb any terrain shock, and your spine has been trained to flex in extreme ranges of motion to help keep you upright.
One reason cross training with a sport is terrific is because ROM is somewhat unpredictable when in action. In a cross-training sport, your core may be forced to use more strength in different muscles than it does normally. That means that if you get into a position where you have to avoid an obstacle or reach out more with your legs or arms to make a move, your core will be ready.
While the core is used in nearly every human movement, it is less a "driver" of movement than it is a stabilizer. Having a strong core has also been scientifically proven to help protect athletes from injury. If you start to go down, your core can pull you back into balance if it's strong enough to do so, and it can also stabilize your body so that you don't start to go down in the first place.
So in choosing a cross-training sport, start by picking one where the activity of the core is similar to the way the core is used in your passion. For example, if you're a skier, cycling and mountain biking are perfect cross-training sports. If you're a runner, soccer is a great way to cross train because it will help your foot placement to be faster and more accurate.
You can find more information by asking a key word question on a search engine: "What is a good cross-training sport for (your main passion)."
One other thing: If your passion is an activity that demands repeated foot strikes on a hard surface such as a road, purchase actual cross-training shoes. These may need to be bought in specialized stores that sell running shoes. You can also find many different kinds online. Do some online research to find out what kind of shoe will work the best for both your passion and your cross training sport.
You don't need to spend equal time on both activities. However, at least half of the time devoted to your passion should be spent cross training. It's also important to find time to work out at the gym — if you're truly serious about becoming a better athlete.
Fitting all of this into your regular daily schedule will be demanding. You may even have to become a lot more organized. That, in itself, will be a good thing for the other parts of your daily life.