In order to improve your functional fitness you need to design exercises that will incorporate the movements you do in your sport. You will find a wide variety of home gym fitness equipment for different types of sports. A thousands bicep curls is not going to help you get the best time on a 100m sprint, you could rather spend that time you wasted on the bicep curls, and incorporate it on your core exercises and leg exercises.
Don't get me wrong here, doing a bit of upper body will definitely help, but training your upper body should not be the focus of your training program when you are a runner. And also thousands of leg extensions will not develop a boxer's optimal punching power. Although squats will help with your upper body strength... more on that subject later. With your own home gym fitness equipment you can achieve your fitness goals without wasting time.
I've been in a special operations unit for a couple of years, some of the urban training PT consisted of climbing a 4 story building up on drain pipes and climbing down on balconies, sometimes you do it with all your gear (bulletproof, ballistic helmet, weapons and ammo) on as well. That was without safety equipment. As you can imagine it developed great upper body strength. What did the rest of the PT consist of? Among other things, we did hundreds of pull-ups. We're training for functional strength, to handle your own body weight with ease. Since then I've build my own home gym and search the net for home gym fitness equipment and bought the necessary equipment for my goal.
Bruce Lee is a legend; some believe he was the greatest martial artist of all time. He didn't become that good in martial arts because he had good genes and talent. That will count for maybe 10%, but the rest came with hard work. He was committed to his goal and trained 8 hours a day. He lived his goal and it became real. One thing he said that sticks in my head is this: A 100m sprinter trains by doing lots of sprints with all out effort; the same should be for martial arts. When you training to punch and kick, you must punch and kick with all out effort.
The same mentality must be applied to anything you want to achieve. Set your goals and revise every couple of weeks. The most important thing you can do to start any training program is to decide what your goal is and stay focused on it. Build your own little home gym, and get all the home gym fitness equipment you will need to start a fitness program with your goal in mind. Don't wait; start your journey to a new you now! We have all the tools you need...