Weekly Blog

July 24

No one really knows for sure, but one reason "green exercise" - nature-based movement like walking, hiking, biking, trail running, etc. - is such a powerful driver of health is because it engages us fully. We experience sights, smells, sounds, and sensations "out there" that we just don't get in the gym. Adding a little extra focus to navigate the potential randomness of the terrain creates an activity profile that keeps us strong, fit, and moving well, as reviewed here in May.

Of course, one of the more interesting twists is that simply being in nature, even without much movement, can have a strong positive impact. Research on forest bathing - oversimplified as a mindfulness-in-nature practice of Japanese origin - is certainly intriguing, especially for stress modulation, immune function, and psychological well-being; evidence that not all sedentary time is negative. Understanding the line between healthy sedentary time - the kind that helps us RECOVER day to day and may actually improve our capacity to ENDURE - and the harmful kind has not been easy, but we're getting closer.
 

For a while there, it seemed "screens" were the root of the problem. For example, excessive screen time in adolescence has been linked to poorer cognitive development and early cardiovascular risk, which strongly supports limiting it. However, the research for adults is more nuanced. In 2023, this review showed a generally negative connection between screen time and mental health (with slight differences in studies done before and after the pandemic). Yet, one finding suggested that the *way* screens were used might carry more weight than originally thought. In a single sentence in the article summary, the authors stated: "Recreational screen time was associated with depression and screen time for schoolwork was not." How we interface with screens may matter more than "if" and "how long".

The thread was taken further in 2024 when a research team looked back at data on recreational and mindless screen time - in this case, TV time in the 1990s - a precursor to the "scrolling" tractor beam which pulls so many of us in today. Their findings were clear: as TV time increased, so did a variety of cardiovascular risks, including blood pressure, unhealthy blood markers, and metabolic risk. Then, last year another review highlighted the nuance, drawing a clear distinction between passive screen time - the kind where content is absorbed with low brain effort (scrolling) - and active screen time where we might be engaged in tasks like emailing, writing, searching or brain-games. Passive screen time dragged on health; one study showed more than 3.5 hours per day was particularly detrimental, but active screen time actually offered several benefits.

Then, earlier this month, the Alzheimer's Association published another study - the first of its kind - which showed actual structural changes in the brain associated with sedentary time by type. They looked back at data from a long-term and comprehensive heart-health study that began in the late 1980s. This study included data on total sedentary time, encompassing both passive (TV time) and active/engaged (work-related) sedentary time, and included brain MRIs. When the research team compared brain scans to sedentary time, the connection was clear. While passive sedentary time was associated with negative brain changes on MRI - some of which are linked to Alzheimer's disease - brain-engaged (active) sedentary time showed a generally positive correlation, a finding which was most pronounced in men.

Once again, our health risk sits on a spectrum. While getting plenty of brain-engaged movement is probably closer to ideal - see "Take a Hike", our June 19th blog - even when we're not moving, how we do it matters. Whether it's our senses (forest bathing) or our brain (active screen time, puzzles, etc), we thrive when challenged. Now is as good a time to find one as any.

Have a great weekend,
Mike E.