This is interesting.
Evolution doesn't just pertain to humans over the course of thousands of years, we have micro-evolution going on everyday. Since the day we are born, we are evolve, physically and mentally.
My daughter, Eva, who is 1 1/2, makes dramatic changes over the course of weeks. First, she learned to hold her head up, then roll-over, then sit-up, then crawl, and walk and so on. Now she squats, does snatches, power cleans, and even does flips. My wife, the know-it-all occupationl therapist, tells me she's just picking things up off the floor; and that flip she did the other day, wasn't a flip she claims, it was because she tripped and fell. Whatever, I know what Eva's really doing. ;)
The old adage "use it or lose it" could be as wise a quote there is. Kids use it, adults lose it. We need to just get out and move everyday. The more we do so the more we regain back those previously easy movement skills.
For example, I have done a fair job of keeping myself in shape since my college football days, which was only 4 years ago. Most of my activity has been centered around weightlifting and strength training. This has been great for maintaining a decent body composition, and I have actually become stronger than when I was playing college football.
Lately, I have gotten back into doing sprint work. Mainly because now I have access to plenty of space to run indoors. Especially because it is tough to do in the winter in the upper midwest without shrivelling the "boys" up into tiny little raisins.
When I first started sprinting again, I started off slow with just doing tempo runs of about 60 yards. The first few sprints sessions really reinforced "use it or lose it". Everything felt tight and I was slow. These first few times are enough for most people to come up with the excuse that I am just too old, or my body's to worn out to do this. However, after each subsequent sprint session my body has started to feel better. Now I am up to doing all-out sprints of 40 to 50 yards and my body has been feeling better than it has in a long time. I definately feel a lot more "spring" in my legs now. Just walking feels easier.
I think often times we, referring to those of us that lift heavy weights and possibly sprinkle some light cardio in on the side, forget what it feels like to have true power or speed, and for our bodies to feel fresh again. I think getting back to what we used to do as kids, sprinting, we can regain that youthful feeling.
If you have the space to do it, add some sprinting into your exercise routine. It's a lot easier on your body than traditional cardio (treadmills, bikes, etc.), and develops great total body power, and re-awakens the nervous systems. Power is what we lose the fastest as we get older. Use it or lose it.
The key is to start slow and progress even slower. Start with light tempo runs, to get the range of motion back in the hips. Anything from 40 to 100 yards would do. Work on your feet striking right below you on each step, concentrate on moving your arms quickly through the shoulders, and keep your face relaxed. Start out with just 1 to 2 times a week.
As you become more comfortable with your technique and conditioning, slowly integrate some acceleration work of 10 to 20 yards (or meters, doesn't really matter), while just pacing the final 20 to 80 yards. You can also start to incorporate some "ins and outs" where you jog the first 10 yards, accelerate as fast as possible for the next 20 yards, then decelerate for the final 20 meters.
These are just some ideas to incorporate speed work into your routine. Be sure to keep a good balance of hip and knee dominant work in the weight room, focusing primarily on single-leg work. Continue to work on good movement patterns and focus on recovery and regeneration, with good nutrition and plenty of soft tissue work.
Use it or lose it. Re-evolve your ability to move fast and explosively again.