Every week, we’re bringing you a roundup of the latest health and wellness news to hit the wire. This week, we look at a new study that uncovers how big an interval you need in high-intensity training to yield aerobic gains, how marathon running actually helps rebuild some parts of the middle-aged knee, and why vaping might not be much better than smoking for your lungs.

HIIT it for this long to build fitness

High-intensity interval training is an efficient way to build your fitness, but all intervals aren’t created equal, according to new research from Liverpool John Moores University in the Daily Mail.

Those doing four to eight body-weight exercise intervals of 30 seconds with 120 seconds of rest yielded no increase in aerobic capacity (the ability of the heart and lungs to get oxygen to the muscles) for previously sedentary study participants taking part in three weekly workouts over six weeks. The rest periods, researchers found, were simply too long.

However, those who paired six to 10 intervals of 60 seconds of these intense exercises such as squats, push-ups and lunges, paired with 60-second rest periods, improved their aerobic capacity. This is important, researchers said, because the higher this aerobic threshold is, the longer a person can exercise without fatigue, helping them to propel their fitness.

The bottom line: While most exercise is healthy, to really see changes in your health, experts say, it’s important to get your heart rate up and keep it there for at least 20 minutes.

Forget what you heard, marathon running is good for aging knees

Many starting a marathon training program later in life will hear warnings from friends and relatives that they’re ruining their knees.

But new research shows just the opposite: Taking up distance running in middle age can actually rebuild the health of certain components of the knees, even if the joints are somewhat worn and tattered to begin with, according to this story in The New York Times.

Research conducted by Dr. Alister Hart, an orthopedic surgeon and research professor at University College London, published in BMJ Open Sport & Exercise Medicine, studied a pool of 80 first-time marathon runners training for the London Marathon.

High-resolution MRIs were taken of the group’s knees that would reveal even minor damage in the joint’s tissues.

A few months later, the men and women began a four-month marathon training program. Eventually, 71 of them finished the race in an average time of five hours and 20 minutes. Two weeks later, they were back to the lab to have their knees scanned.

Comparing the before-and-after scans turned up a few surprises. Many of the pre-training knee images showed frayed or torn cartilage and lesions in the joint’s bone marrow. Hart expected to see additional damage. Instead, many of the bone-marrow lesions had shrunk, as had some of the damage in the runners’ cartilage and other tissues at the front of the knees around the kneecap.

Researchers speculate that the strengthening of muscles surrounding the joint may have helped stabilize it, helping to reduce or reverse tissue damage.

Vaping no better than cigarettes for your lungs?

While e-cigarettes have been touted as a safer alternative to smoking tobacco, evidence is growing that both are damaging to your airways, U.K. researchers report in U.S. News & World Report.

A team from the School of Pharmacy at Queen’s University Belfast compared cigarette smoke and e-cigarette vapor on bacteria associated with smoking-related lung disease.

When exposed to either smoke or vapor, the bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus made more biofilms or microbes involved in infections, thus demonstrating that vaping and smoking both increase the harmfulness of common lung germs and can cause persistent infection.

In another experiment, researchers showed that human lung cells exposed to bacteria that had been exposed to smoke or vapor responded with increased production of interleukin-8, a key factor tied to inflammation.

These findings show that the effects of vaping on common lung pathogens may be similar to those of smoking, said researcher Deirdre Gilpin.

Photo credit: Mikolette, Getty Images