With a lot of attention driven toward exercise selection, volume (sets x reps), and %weight to use, I realize exercise duration has been a bit overlooked. Exercise duration is a very important part of a workout because duration of activity affects hormone regulation, blood glucose levels, and many other important bodily functions.
I think that after about an hour long exercise session, your body is in a mostly catabolic state, meaning hormones made for breakdown are being released. Therefore, I don't really think you are getting much productive work done after about 60-75 minutes. Personally, I have never had a team in the weight room for more than 90 minutes including everything from warm-up to conditioning. In addition to hormone regulation, muscle glycogen levels are an easily exhaustable resource for quick, powerful movements directly embedded in the muscle. This energy is used for powerful actions or at the beginning of any exercise. This means, if we are exercising for over an hour, glycogen is depleted from the system and there is no longer any left for use in the muscle. To compensate for this, we use energy from other sources and are therefore less efficient.
The biggest mistake I am seeing is when teams hold a full practice session and then head into the weight room for a workout session. The team is not getting anything out of that workout and you are wasting their time. The message I want you all to have here is get your work done in the weight room or on the field and get out. Efficiency is the most important thing in an athletic practice. Set a couple goals for your practice sessions and adhere to the time frame you have laid out to accomplish these goals. In the weight room, you shouldn't be doing something if it takes more than an hour to complete, condense the program by asking questions about what is really important and what can be left out.