Here's what happens when you push your body through an intense run, race, or workout: Your heart rate skyrockets and your oxygen-deprived respiratory system switches to anaerobic respiration. Low on oxygen, your muscles pump your arms and legs with lactic acid, which keeps you moving but turns your limbs into bricks. Micro-tears develop in your biceps and calves, and by the time you cross the finish line, your body’s nervous system is screaming that you've had enough.
This process is the reason your workout makes you stronger. In exchange for your suffering, you lose weight, improve your VO2 max, and bolster your insulin response. But odds are, you already knew that. What you might not know about are the smaller changes that researchers are just now discovering. So keep reading, and remember: Your best self is just beyond the finish line.
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Change #1: You become biologically younger
According to a Mayo Clinic study from March, high-intensity interval training (HIIT) fights the natural decline of mitochondria.
As a reminder, your mitochondria are the little engines that drive cellular respiration, which cells use to turn oxygen into energy. Over time, these engines lose their ability to keep up, and you find it increasingly more difficult to match your old PRs. You also experience symptoms that range from the visible (wrinkles) to the dangerous (increased insulin resistance, which can lead to type 2 diabetes).
In the Mayo Clinic study, younger participants—those between the ages 18 and 30—experienced a 49 percent increase in mitochondrial capacity after 12 weeks of HIIT training. Older volunteers—those between 65 and 80—saw an even greater improvement of 69 percent.
The phenomenon helps explain how in January, Robert Marchand, a 105-year-old Frenchman, set a world record for the most miles covered by a centenarian in one hour on an indoor cycling track. After two years of interval training, Marchand bested his previous record by three miles. (Let that be a reminder that you should never say “I’m too old.”)
Change #2: Your mental health improves
According to two studies from last year, regular exercise actually reduces your risk of depression. The first study, published in the journal Preventative Medicine, found that people with poor cardiorespiratory fitness were more likely to be depressed, and that by exercising, subjects could begin to shed the symptoms of depression.
The second study, conducted by University of Florida researchers, confirmed the result, but took it a step further. It found that people with genetic markers of depression actually stood to benefit the most. While all exercisers experienced a mental boost, theirs was the strongest.
Change #3: Your vision becomes better
In February, a team of researchers from UC Santa Barbara discovered that neurons related to vision were more active during workouts.
They put 18 adults on stationary bikes. While they pedaled, the subjects watched for visual cues on a computer monitor, and sensors followed their eye movement. Each person pedaled at high- and low-intensity intervals, and the researchers found that low-intensity exercise yielded a significant gain in vision sensitivity. (Oddly, high-intensity exercise didn’t have the same effect.)
The response was measured by looking at the arousal in neurons related to vision, so while more studies are needed to determine whether working out results in long-term sharper vision, the researchers are confident that important changes are taking place in the brain—changes that likely bolster your brain’s processing power.
“The benefits of brief bouts of exercise might provide a better and more tractable way to influence information processing—versus, say, brain training games or meditation,” says lead researcher Barry Giesbrecht in a release.
So if you needed another reason to go for a run right now, just remember: It's the smart thing to do.