This morning I missed my swim.
This happens occasionally, and usually I manage to slip in a walk on those days, but today our team was at Stanford MedX by 8:30 am and with Bay Area traffic from San Francisco, that left no time to work out. While I am serious about exercise in my life, I also value sleep in equal measure.
All day I felt off.
I gave an interview where I was not as articulate and quick on my feet as usual. All day, I noticed differences and I know it is because I missed my swim. As a regular runner from age 20-38 and a swimmer for the past 7 years, I notice a distinct difference in mood, performance and cognition on days I am unable to get in the water.
While I have previously written about the general benefits of exercise for cognition and a healthy life, I wanted to delve deeper into the immediate benefits we feel when we exercise.
And yes, before we get started, in case you’re wondering – the photo up top is me open-water swimming in Hawaii.
For almost two decades, I was a regular runner, often covering 30-40 miles a week, but I was unprepared for how swimming changed my life. At 38, my knees and hips pushed back on almost 20 years of impact, and I found myself in the pool.
It was a bit embarrassing at first, as I was a great swimmer in my teens, and here I was taking starfish level lessons with kids. I finally decided to save what was left of my dignity, and shell out for individual lessons. Within two weeks, I was cutting through the water again, gaining speed on my lap times weekly.
My resting pulse was always an impressive 65 or so — but when I started swimming, it dropped into the high 50s and I experienced a level of reduced stress that running never delivered. I was not out of shape – in fact I ran around a 8.5 to 9 minute mile — so what was happening?
It turns out that while all exercise is good, water-based sports deliver a little extra kick for our health. One study suggests that water immersion, up to heart level, has cardiovascular benefits contributing to more blood flow to the brain. Exercise leads to angiogenesis, synaptogenesis, and neurogenesis.
Physical activity also increases population of neurotrophic factors. IGF1, VEGF, and BDNF are noted neurotrophic factors that are upregulated with exercise.
Another study out of the University of Poitiers noted a positive correlation (in older adults) between swimming and three axes of cognition: behavioral inhibition, working memory, and cognitive flexibility. A possible cognitive benefit derived from swimming is stress-relief. A core component of the activity is rhythmic breathing—stroke, stroke, breath—which is a commonly cited stress-reducing component of yoga and other meditative activities.
Several animal studies have described neurogenesis in certain parts of the brain due to swimming exercises. After 8 weeks of swimming exercises, an experimental group of rats had increased neurogenesis in the subventricular zone of their brain and increased levels of nerve growth factor and synapsin I in the olfactory bulb compared to the control group.
Another animal study tested whether swimming could be used to reverse long-term memory impairment associated with pregnancy. Researchers found that swimming reversed the memory impairment and hypothesized that this was due to an increase in cell proliferation.
So there is the answer to why I don’t feel as good on days I miss my swim. It’s my down-regulated BDNF. Ok — maybe not because I missed one day, but I know that the meditative results are real.
The rhythmic back and forth of laps and breathing in a slow, regulated count against swim strokes (in my case 3 to 1 and 5 to 1) that provide a “check out” from the incessant stress of running a startup company. The fact is that I am “sharper” when I swim and I feel better, I’m happier and more energetic.
Every time someone tells me they can’t set aside the time for regular exercise, I want to say – you cannot afford not to do this. It is something you can do to improve your life today and for the long run.
Humans were not built to be sedentary. Sitting around doesn’t just pack on the pounds – but it makes us arguably a little “stir crazy” as our cortisol levels spike and BDNF, IGF1, and VEGF are down regulated.
I don’t swim for my waistline – I swim to stay centered, grounded, energetic, happy and focused to lead Savonix and guide our team through the myriad of ever-changing and evolving healthcare landscape to help improve patient lives, one day at a time.