Compared to other types of exercise, high-intensity interval training is the most efficient way to boost cardiorespiratory fitness, rev metabolism, and maintain muscle. A new study from the Mayo Clinic reveals yet another reason HIIT outshines other workouts: It reverses aging at the cellular level.
To see which workout keeps us youngest, researchers randomly assigned 72 relatively healthy but sedentary adults — half were 18- to 30-year-olds; half were 65 to 80 — to one of three 12-week regimens. The first group did high-intensity interval cycling three days a week plus moderately tough treadmill walking twice a week. The second group did only resistance training twice a week, and the last group did five days of steady-state cycling plus four days of light strength training.
By the study’s end, everyone showed improvements in overall fitness. As expected, the strength-training-only group built the most muscle mass and strength, while both cardio groups gained more aerobic fitness. However, those who’d completed the HIIT program had markedly better insulin sensitivity, which decreases naturally as we age.
Additionally, the HIIT group scored the most benefits at the cellular level, where many age-related declines take place. It was significantly more effective at boosting mitochondrial capacity, meaning it prompts the cells to crank out more proteins to fuel the mitochondria, the body’s energy spark plugs. The younger participants saw a 49-percent jump in their mitochondrial capacity after 12 weeks, while the older folks had an astounding 69-percent increase.
“The mitochondria change all macronutrients [from food] to the chemical form of ATP, which is used for all cell functions,” says lead investigator Dr. Sreekumaran Nair. “A slowing of the body’s ability to produce ATP is a key factor leading to aging and physical decline. This was significantly improved by HIIT.”
HIIT also reinvigorated the participants’ ribosomes, tiny particles that are instrumental in protein synthesis and muscle building. Ribosome function is yet another common casualty of age. “Our study is a very clear demonstration that HIIT produces a remarkable reversal of all the age-related cellular changes that lead to physical decline,” Nair says.
Nair says any type of exercise is better than none, but if you’re going to zero in on one, HIIT should deliver the biggest anti-aging benefits, likely in the least amount of time. To aid in building muscle mass, he recommends peppering in strength training as well, if it’s not already part of your intervals.