Mind. Memory. Mood. Motivation. Meth.  Reflections titles the last few weeks have had a common thread.  The words not only begin with the letter "M," but they all express our deeper understanding of the remarkable link between physical activity with mental and emotional health.  A natural question emerges from that discussion: how much and what kind of physical activity is needed to reap the benefits we have been talking about?  While science does not yet provide a definitive answer to that question, it can tell us in general terms what we can expect to gain from different levels of intensity. 

 Walking, and other low-intensity exercise generates a neuro-chemical environment conducive to patience, optimism, focus, and motivation.  It triggers the production of serotonin and dopamine, and moderates the chemicals of unhealthy stress.

Jogging is considered moderate-intensity exercise. Moderate exertion generates microtears in the muscles, a mild stressor that then triggers the proliferation of capillaries, nerve cells, and neurological connections. Moderate exercise benefits the learning process and strengthens the immune system.

Running takes us to a higher level of intensity, simulating a full-blown state of emergency.  It switches on human growth hormone, burns belly fat, adds muscle, and increases brain volume.

In Spark, Dr. Ratey recommends that we exercise aerobically at least 30-45 minutes per day, 5-6 days a week.  He suggests that we spend most of that time in low and moderate intensity zones, but that we periodically push the limits to gain the benefits of intense effort.

It seems that everything we hear and read points to exercise as the fountain of physical health.  Spark considers it the source of mental health and happiness as well.  There are so many reasons to get up, get out, and get moving.  There are also many obstacles to carving out time and energy from otherwise busy schedules.  Establishing a regular program of activity doesn't just "happen."