The Rundown

For The Love of Exercise. Does exercise boost the “love hormone” oxytocin? So called because of its role in human behaviors including recognition, trust, romantic attachment and mother-infant bonding, oxytocin, as it relates to a good workout, has been a subject of debate for years. A few recent studies suggest exercise may raise its levels.

As Alex Hutchinson discusses in a recent article for Outside magazine, a study from researchers in Iran used mice to test if exercise boosted oxytocin levels and if the elevated levels were responsible for exercise’s antidepressant effects.

Before and after an eight week swim training period, the team assessed social behavior and levels of depression-like symptoms in the mice. The mice that swam were more sociable and had less anhedonia (a lack of interest in or pleasure from life’s experiences) than the non-swim trained mice.

The results also found that oxytocin levels were raised in both the brains and bloodstream of the mice that exercised. To find out if the oxytocin caused the behavioral changes, the scientists gave the mice an oxytocin antagonist to block its effects and the observed social and antidepressant benefits seemed to disappear.

In people, the results are less clear. In one study, researchers in Japan and Denmark had male volunteers complete a pair of high-intensity interval cycling workouts while catheters were inserted in their brachial artery (in the arm) and jugular vein. Their aim was to find out how much oxytocin is in the blood as it enters and exits the brain in order to figure out whether levels in the brain are changing during exercise.

The workouts increased oxytocin levels in the blood but the increase was the same in the artery going into the brain and the vein coming out of it. As Hutchinson notes, it could be that oxytocin production in the brain didn’t increase or it increased a lot and raised levels in the entire body.

So is oxytocin the secret behind the positive mood we typically feel after exercise? The research has a way to go but the “love hormone” does have a place among the many ways that exercise boosts our health.

High/Low. When it comes to working out, there are often different views on what benefits us the most. Should we do hard, high-intensity interval workouts? Or is it better to do relatively easy, longer workouts? This is otherwise known as the zone 2 vs. HIIT debate. One recent meta-analysis looked at the impact of each on the cardiorespiratory fitness of older adults.

The review included 23 randomized controlled trials with over 1300 older adults divided into a moderate intensity group and a high-intensity group.

Meta-regression analysis showed a moderate but not significant relationship between exercise intensity and improvements in VO2 max. Comparing moderate versus high-intensity revealed a small but not significant effect in favor of high-intensity.

The researchers say the findings “challenge the notion that high-intensity exercise is inherently superior and indicate that regular aerobic exercise, irrespective of the specific approach and intensity, provides the primary benefits to cardiorespiratory fitness in older adults.”

Commenting on the study, Steve Magness, performance coach and co-founder of The Growth Equation, says that when it comes to general fitness the most important rule is to perform the exercise that you can sustain. “Long and slow, short and fast, everything in between works!” He adds that if you are training for an event, you need to tailor that training to meet its demands but most elite athletes have a mix of high/low in their workout regimen and the same goes for general health.

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