In Part 1, we discussed – briefly – how the energy pathways work. But the beauty of these systems isn't that they're mutually exclusive; rather, that they're mutually enhanced through their overlap.
CrossFit's goal is to produce an athlete with skills that are 'broad, general, and inclusive.' However, it's often been opined that training in the glycolytic pathway can yield the most efficient use of an athlete's time, since it overlaps both the CP and the aerobic metabolic pathways.
In fact, the glycolytic system can provide up to 30 minutes of high-intensity anaerobic movement, if trained properly; it can also allow an athlete to put out up to 80% of their maximum power output, if trained properly.
That means that gains in both strength AND endurance can be had through CrossFit METCON, up to the point of specialization in a sport. Elite powerlifters and long-distance runners will still need to spend some of their training time in their specific energy domain, since demands that aren't energy-specific will eventually trump the abilities of the energy pathways used. For example, a powerlifter's output is limited more by Rate of Force Development – recruitment of muscle cells by the nervous system – before it's limited by his ability to metabolise energy. The output period is simply too short. A marathoner will have to develop secondary characteristics, like very low overall body mass (even a lack of total muscle,) low innervation thresholds, selective muscle recruitment to save energy, and increased vascularization. Her output period is simply TOO long to achieve 100% of her potential through the glycolytic pathway, though short-term, high-intensity exercise can replace a lot of her running time each week.
Our main point: skill development and energy metabolism are different things. While skill development is specific to the sport being played, energy metabolism is NOT. If you're exercising at a high-demand level for 30 minutes, it doesn't matter whether you're running or doing CrossFit METCON work.
Runners who spend hours running every week – using ONLY running to improve their speed, shorter-distance endurance, power, etc. – are missing out, and possibly overtraining in a specific movement. while the original goal of "cross-training" in the 1990s was to reduce injury and deliver the same results using movements that didn't involve running, it devolved to mean "lifting light weights for many reps" in the common parlance.
30 minutes of very hard exercise means 30 minutes of developing your anaerobic (glycolytic) capacity. Calisthenics will develop your glycolytic capacity as well as running can; combining weightlifting with gymnastics and calisthenics will do the same, or even better, than running. Consider that, by shifting exercises, your output can increase because specific muscular fatigue is shifted around during workouts, and it's more efficient to do a couplet or triplet (2 or 3 exercises) to develop anaerobic capacity than running, where one weak link can limit the ability to sustaina very high energy demand.
Science aside, we had several athletes – CrossFitters – achieve 5k personal bests on the weekend. Some were in a running group for the last few weeks, where they worked on form but never ran more than a few minutes at a time. Some, like me, had done close to ZERO running in the last few months (my longest run since March was a 600m sprint, and I took 2:40 off my 5k time.) Even our longer-distance runners are going faster on less running. How is this possible? They're training the same energy systems with METCON. Are they 'better runners?' It's possible, if they've improved their technique. But mostly, they're just better at operating at a high intensity over 25-30 minutes.
The really beautiful part: they're not dragging themselves out the door, daily, for yet another 30-minute jog over the same course as yesterday. They're checking the website at midnight; they're learning skills far more technical than running; they're doing Strongman events 12 hours later. And they're having a ball. They're faster runners – but they don't consider themselves "runners," because the term typically infers an athlete who practices one sport to the exclusion of all others.
In Part 3, we'll discuss our April experiment – The Enduro Project – and how its results make our case that the improvement of a broad trait – energy metabolism – will improve a specific outcome, like running.