Endurance athletes and coaches usually say that they perform long workouts for three key reasons: to build strength, boost endurance and add volume to the overall training load, presumably leading to significant gains in physiological fitness. VO2max, for example, is generally considered to increase directly and predictably in response to increased training mileage.
Unfortunately, these popular assumptions are slightly misleading. Taking the notion that long sessions build strength, for example, it is important to remember that strength is always speed-specific; that is, if you utilize slow movements in your effort to improve your strength, your strength will be improved during slow movements but not fast ones – and vice versa.
Of course, long workouts are almost always carried out at moderate-to-low intensities and so, while they do build strength, it is not the kind of strength needed at competitive intensities, which tend to be high. For endurance runners, for example, even a prolonged event like the marathon is usually completed at an intensity of 85% VO2max-or-so – well above a typical long-run intensity of 70-75% VO2max. Long sessions primarily build the strength needed to complete more long sessions, not the strength needed during competition.
A similar argument can be constructed against the belief that long efforts favor endurance. The problem is that endurance is also intensity-specific, and thus the building of endurance at prolonged-effort intensities does not ensure endurance at competitive intensities.
Do long workouts work any better in relation to their third presumed benefit – of enhancing fitness via the volume effect? It would be nice to give prolonged efforts a glowing review in this area, but my most truthful and accurate answer would have to be: it depends. The problem is that the relationship between fitness and training volume is a perfect example of the law of diminishing returns; specifically, as volume increases to higher levels, the gains in fitness become smaller and smaller. Eventually, in fact, fitness does not respond at all to advances in volume. Thus, adding a two-hour workout to an existing eight-hour week wouldn’t do much for VO2max. Worse still, long workouts do little for lactate threshold, since they are conducted at below-lactate-threshold intensity, and they probably improve economy primarily at the relatively low intensities chosen for the long workouts. In addition, they are poor producers of power, and they offer true specific preparation only for ultra-type events.
However, long workouts can work well if you are currently training well below your normal work load or a beginner to your sport. If you can add more to such a program without adding TOO much fatigue, you can probably upgrade your velocity at VO2max. Note, though, that there is no scientific evidence to support the idea that a two-hour workout is better than two separate one-hour sessions; in fact, one might argue that breaking a two-hour workout into one-hour chunks would actually be better, since it would permit higher average training intensities. To summarize, we can say that prolonged workouts are not actually necessary for optimizing VO2max; the process can occur without the need to have a ‘biggie’ in your workout bag. Perhaps the greatest benefit of long efforts is that they do steel the mind for exhausting exercise, and such preparation can be very useful in competitive situations. If during a long run you can keep on going at a reasonable pace when your mind and muscles are screaming ‘no’, your confidence in your toughness and ability will be enhanced, and you will be more likely to keep on going at the ends of tough races. This is done in the Specific Phase.