General physical preparedness is one of the least utilized aspects of training for athletes. When I was growing up it was important that you ran around, moved things from one place to another and had fun doing things that were nothing specific. Training to be an athlete is far more than just doing things that improve your sport directly. There are reasons for all athletes to push up their GPP.
Any and all athletes who compete in a sport need to increase their general physical preparedness. Simple.
There are a variety of ways in which you can increase your GPP. It would all depend on what your sport is but here are a few suggestions for powerful athletes that even endurance athletes can take advantage of.
Adding these for longer distances and changing the load will add variety to your training and simply make you a better athlete overall.
You can do general physical preparedness anywhere. I personally love to get outside and get it done. That way you can get the fresh air and get into all those weighted walking movements.
Now, this is an interesting question to ask. I believe that general physical preparedness needs to be attacked all year round in some aspects. If you are in the middle of the season then, of course, you should adjust the loads to fit or match what you are doing but, doing GPP is a good way to keep everything working right. When you are in the off-season though you should be doing it as often as possible. It needs to be attacked in a correct way though. Do not just go out there throwing way to much weight on the implements and expecting to increase your GPP. Find a load that you can do multiple 60 yards walks.
I believe athletes put far too much emphasis on SPP (specific physical preparedness) and let GPP fall off to the wayside for whatever reason. Many new athletes are completely missing the ability to work for long periods of time. The work capacity is limited and needs to be increased in order to really maximize the effectiveness of SPP. So Adding in more GPP at the beginning of an off-season is important in my opinion.
Work capacity. That is the reason why you should be adding in significant amounts of general physical preparedness into your training regimen. Your ability to perform for longer periods of time. Your ability to add more volume into your training will determine your performance on the field ultimately.
Adding in non-specific movements that challenge you in a variety of different ways is going to be the key to unlocking all of your potential in the sport. If you can be an athlete first that is a good way to keep the mindset of increasing your fitness as opposed to being married to the label of whatever your sport is. For example, powerlifters who are married to the title of powerlifter tend to only want to do the movements in powerlifting. But if they believe that they are athletes first then they are going to be more inclined to do movements that sit outside the platform.