So why is two days of hi intensity high volume better then 3, 4, or even 5 days of lower volume?
From my own experience doing heavy construction work, after reading lyle's thoughts on training I've switched up from 3 days hitting it hard to 5 days of lower volume hi intensity and have much more energy to do the work that needs to be done on both off days and training days with no more joint pains or DOMS at all.
More like adequate intensity (I would define adequate intensity as keeping within 5-10% of your typical working weights, but that is not backed with research or anything just something to give a little context to the discussion) and low'ish volume.
And some say its better because if you are doing some kind of high intensity work everyday then when does your body get to recover? Say you squat heavy on monday, tuesday your body is shitting a brick trying to repair all the damage from monday's workout but then you hit it with sprint training. Now you just added more stress to the Neuromusculoskeletal system. Then comes wednesday and its time to play a soccer game...even more stress. Now its thursday, time for another heavy training session and so on and so forth. A natural, non elite level athlete, even with the best nutrition cannot hope to recover from such frequent, intense bouts of exercise. You gotta remember the pros and such, that is all they do, they sleep enough, go train, eat, get a massage, rest, eat some more, go train again, sit in the hot tub etc. Their job in essence is to train and recover, normal people don't have that luxury nor the genetics, or drugs in many instances, for that type of stress.
The changes will really depend on what the level of conditioning is/was prior to beginning the competitive season. So if someone was doing some sort of 5x5, 3x/week, I'd scale it down to 2-3x5, 2x/week but being sure try and maintain the weight on the bar during the season. After the competitive season ends and you can concentrate on GPP stuff, strength, power, etc then you can bump everything up and try to really increase those parameters.
And lastly, heavy construction work is not really intense activity from an objective point of view. If it were truly intense (defined as % of 1RM or Vo2Max or whatever), you wouldn't be able to do it 5 days/week, 8 hours a day. But it works for you because you probably lowered volume down to a level where, even if the w/o's are intense, you are allowing recovery. Or maybe not and you are screwing yourself up lol. There is grey area in all of this stuff no matter what certain gurus would have people believe.
End of the day though, the take home point is that you need to let something go and make room because having too many things on your plate at once will lead to some, or all, of them suffering.