Originally Posted by
mcours2006
The only issue with that analogy I have is that all three activities are very aerobic. You stress your cardio vascular system with an intense swim, you wouldn't do it again with either ride or run. Weight training is anaerobic.
But weight training doesn't just stress the muscles, it also taxes your CNS. So even working different muscles on subsequent days, CNS fatigue from previous workouts can be a factor if volume is too high.