Well at least cycling and treadmill running are very well suited to multitasking. With enough motivation it is possible to squeeze in 4+ hours per day of cyclin

Well at least cycling and treadmill running are very well suited to multitasking. With enough motivation it is possible to squeeze in 4+ hours per day of cycling that you would be spending stationary while on your job or at home doing emails, at least some calls, reading, research, TV-shows/documentaries/online courses/hacker news. Throw in the "normal" 2 hours of exercise before or after work and voilá! It does take one 4-5 years to build up to that even from non-sedentary active lifestyles, otherwise maintaining energy for everything else will be impossible. And my (completely speculatory) hypothesis is that amateur sports (or some pro-sports) or serious goal-oriented strength/physique training will offer benefits down the line, as long as you quit "heavy" exercise after a reasonable amount of time and maintain a moderate amount of exercise for the rest of your life. After all, Tour de France riders of the past century outlive us by many years, despite most allegedly having been on quite a comprehensive cocktail of anabolic steroids, erythropoietin stimulating drugs, amphetamines, etc..