Monthly Archives: March 2019

Just One Session of HIIT Might Help Stop Cancer Cells From Growing

New research provides further evidence that staying active could play a serious preventive role.

  • Exercise has been linked to a reduced risk of certain kinds of cancer. And now, new research suggests that high-intensity interval training, or HIIT, may help thwart the growth of cancer cells, too.
  • Researchers determined that even a single session of HIIT was effective at reducing the growth of colon cancer cells.
  • While the study was performed in cancer survivors, researchers believe the same findings may apply to others as well.

Consistent, long-term physical activity has been linked to reduced risk for several types of cancer, thanks to the way exercise reduces inflammation, improves immune system function, and lowers levels of certain hormones related to cancer development.

But you don’t need to log years of effort to get the cancer-fighting benefits: A new study published in the Journal of Physiology suggests that even a single session of high-intensity interval exercise may significantly slow the growth of colon cancer cells.

Researchers recruited male colorectal cancer survivors, and had them complete either one HIIT session or do HIIT training regularly. The single-session group did a 10-minute warmup before four rounds of cycling, each for four minutes, with three minutes of recovery time in between. The short-term training group did this protocol three times a week for a month.

Immediately before and after each exercise session, researchers collected blood samples. They replaced the serum—what’s left once red blood cells are removed—of cancer cells grown in a lab with the serum from the participants to see how exercise affected the cell growth.

Serum collected before exercise didn’t reduce colon cancer cell growth, but the serum taken after that single cycling session? That squashed the growth of the cancer cells immediately, suggesting that HIIT may change the environment of the cells, so they are less likely to grow unchecked.

The serum collected from the training group showed no significant differences, meaning they didn’t have more cancer-stopping power compared to the single-session group.

Researchers found there were elevations in some inflammatory markers, known as cytokines, immediately after exercise, and hypothesized that this is what played the biggest role in cell growth reduction, according to lead researcher James Devin, Ph.D., an exercise physiologist at the University of Queensland.

“During exercise, muscle becomes a primary source for releasing inflammatory cytokines markers, known as myokines,” he told Runner’s World. “We know that higher intensity exercise promotes a much greater myokine response compared to moderate intensity exercise.”

Although the recent study involved only colon cancer survivors, Devin said that the reduction in cancer cell growth is likely not specific only to those who’ve had cancer before. He noted that other research using similar techniques and serum from healthy individuals has found reductions in the growth of prostate cancer cells.

“There will always be subtle differences in how individuals respond to exercise,” he said. “And we are still a long way from understanding how these responses observed in the laboratory may influence human colorectal tumors. But the current results are very exciting, and suggest the acute effects following every single session of exercise are of great importance.”


How Timing Your Workout Can Help Calm Your Raging Appetite

It won’t mess with your sleep, either.
  • High-intensity interval exercise is known for a whole host of health benefits, but conventional wisdom has held that if you perform it too close to bedtime, it may mess with your sleep.
  • Now, a new study finds that HIIT will not hinder your sleep—and it may even help blunt your appetite after the session, too.
  • Because everyone’s body clock is different, the exact timing of when is best to exercise is hard to say.

You know that high-intensity interval training (HIIT) is great for your body. Not only does incorporating HIIT workouts into your routine help boost your running speed and power, but it has also been shown to help you lose weight and protect your heart, too.

Here’s one more to add to the list: HIIT may be able to curb your appetite, too. According to a new study published in the journal Experimental Physiology, HIIT—especially when done later in the day as opposed to in the morning—can also quell your cravings when it comes to food. 
The small study out of Charles Sturt University in Australia included 11 middle-aged men whose peak oxygen consumption (VO2peak) and sleeping and eating patterns were recorded a week before any experimental testing was done. Afterwards, they participated in three trials of 30 minutes of high-intensity interval exercise (HIIE), which involved six one-minute high-intensity cycling sprints at 100 percent of their VO2peak with four minutes of rest at 50 percent of their VO2peak in between each sprint. 

Each trial lasted three days each—the first was done in the morning, the second was done in the afternoon, and the third was done in the evening. There were five days of recovery between each trial. 

The results? Participants’ levels of the appetite-stimulating hormone ghrelin were actually reduced in the afternoon and evening trials.

One reason may be because peak power output was slightly higher during the afternoon and evening sprints than in the morning. The researchers believe that greater power output leads to a greater reduction in the signals governing your appetite.

Additionally, among the workout times, there were no significant differences in the total sleep duration of the participants or how well they slept. Translation: Those who sweated at night didn’t sleep any worse. So the age-old adage to avoid exercise—especially at a high intensity—in the hours before going to sleep might not be true.

In fact, the researchers believe that HIIT may actually help you sleep, since it triggers a larger release of the stress hormone norepinephrine, lead author Penelope Larsen, Ph.D.(c) of Charles Sturt University’s School of Exercise Science, Sport, and Health. That’s important, since it may aid in non-REM sleep—or deep sleep—and delay REM sleep, where your breathing becomes faster and irregular, and your heart rate and blood pressure increase to levels that are similar to when you’re awake. As a result, you’ll feel more well rested.

However, Larsen noted that while the evening portion of the experiment was done between 6 p.m. and 8 p.m., “the ‘ideal’ time [to work out] before bed would be different for everybody,” since no one’s body reacts exactly the same. Depending on your sleep-wake cycle, the best time for you may be slightly earlier or later. Just make sure your workout is not encroaching on your normal bedtime, so that you continue to get the same amount of sleep as you always do.

Another important note: Because study participants were exclusively middle-aged men, it’s hard for Larsen and her colleagues to say for sure whether or not other populations would respond the same way to evening HIIT.

“Previous research has shown that for young adults (predominantly men), evening high-intensity exercise can also be performed safely without detriment to subsequent sleep,” she said. “However, given hormonal changes experienced throughout the monthly cycle by women of a similar age group, or young adult women, sleep responses may be different to the findings of the current study.”

DANIELLE ZICKL Associate Health & Fitness EditorDanielle specializes in interpreting and reporting the latest health research and also writes and edits in-depth service pieces about fitness, training, and nutrition