Well-meaning people look at an example of a metabolic disaster, and say, “at least she’s getting fit.” No. Fitness is not hours of cardio. Fitness is capability to perform all physical tasks. Health and fitness professionals define fitness very clearly, and none of it involves just doing tons of cardio and starvation.
Jogging and cycling are great and all, but during a basic athletic screen I and almost every other tenured fitness professional follow science-based guidelines to check fitness as primarily a product of neuromuscular health and type II muscle fiber development. Cardiovascular endurance training governs NONE of this. And I have seen many advanced endurance athletes abysmally fail on 5 out of 7 NSCA batteries.
Type II muscle development manages balance, risk of fall, ability to get in and out of a chair, keeping osteoporosis and sarcopenia at bay. Period. Take an elite endurance athlete and have him or her perform a BASIC balance drill or BASIC agility test and they may injure themselves irreparably. This isn’t hyperbole. Conversely, observe power athletes and good luck finding deficits in their capabilities. Take a few minutes to peruse sprinters, pole vaulters, long jumpers, high jumpers or triple jumpers, like the one pictured above. Now, I want you to dwell on the implications. Power athletes specialize in the type II muscle effort, type IIX to be specific. That is, they train and work exclusively with the phosphagen system whose duration lasts 5-8 seconds. THINK ABOUT THAT. LESS THAN TEN SECONDS. Look at their mobility, their overall capability, their bodies. This is what training effort in 5-8 seconds of intensity looks like.
Societally, yes, our problem is generally people don’t move much. But physiologically the miss is on strength development, not a need for hours of repetitive single-plane monotony.
An employee of mine was once working with a woman to stall her rapid wasting. She had lost a significant amount of bone density every year for 10 years in a row. Her husband has done almost every ultra and major distance endurance event in Minnesota history. She accompanied him for many runs. But this failed to rectify her chronic loss of bone density. Exercise WILL spike cortisol (which isn’t inherently bad): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315045/. Cortisol is catabolic. This isn't opinion. Without very solid nutrition and high resistance strength training, cortisol will not break down fat. It will only destroy bones, tendons, ligaments, organs, and muscles. Women are at a disadvantage in a cortisol-enriched environment, because they lack the testosterone, growth hormone, and IGF to offset the breaking-down effect. This can often become extremely problematic for people performing lengthy bouts of exercise.
Thus, the woman was strengthening with one of my coaches. No surprise: the strengthening stopped her bone-loss trend. Her husband, who was obviously a great fan of endurance training, was in disbelief. He believed, like many people who don’t understand exercise science, that endurance training ALONE suffices for health and fitness. Scoffing at her, he said, “show me something you do.” She demonstrated a static split stance lunge. No explosiveness. No added weight. No dynamism. Just control under load through a basic range of motion. The husband, continuing his dismissal, arrogantly proceeded to “show her up,” except as he descended into his very first rep he pulled his hamstring. This guy can run 100 miles at 5 degrees of hip flexion, 5 degrees of knee flexion, 2 degrees of ankle range; but the moment he performed not-even-a-full-range lunge, he practically ceased to exist. ZERO mobility. ZERO strength. ZERO frontal and transverse plane development. Even in the sagittal plane, he was a joke.
This isn’t a knock against endurance athletes. They do remarkable things. They have a mental toughness, to be sure. But NO fitness professionals considers endurance by itself a measure of a well-rounded, fit, or even healthy athlete.
Fitness isn’t long distance monotony. It’s capability in total human performance. One single little subset of cardiorespiratory endurance capability is NOT the answer for most Americans, most sedentary people, most struggling with supreme muscle imbalance. For people who are having a really hard time losing fat and managing lean tissue, long bouts of cardio are a very risky proposition, especially for older people or females. Fitness is not adding hours of cardio.