# thinlens

## Staying in shape

It's easy to stay in shape living in a city. As an undergrad at UChicago, I walked around the campus everyday, and took public transit downtown on the weekends and then walked some more. In Boston, I biked almost everywhere year round (1). From my apartment to Harvard to MIT to Back Bay to the MFA to Whole Foods and back home. Then I slept.

After graduating I took a job in Connecticut and got a car. A car spoils you. Getting groceries is easier. Getting to work is easier. You don't have to walk when it's cold...or hot...or rainy...or basically ever. Not being in the habit of working out, I started to get back pain after about a year of this.

I started PT and learned that my hamstrings, hip flexors, and lower back were tight. And my legs and abs were weak. So I started doing stretches before and after work and taking 20min walks mid afternoon. After 2-3 months, my back was feeling a lot less tense. After that experience I'm a believer in PT.

But I want to do more than just treat back pain: I want to have energy and be strong and be able to eat whatever I want. It's hard to stay in shape as a working adult. You have to plan when to work out and when to eat. When it it okay to be drenched with post workout sweat at work and when isn't it. I prefer outdoor activities because there is build in leverage to go some distance (you can't bike 4 miles out and call it quits in the next town!), but what if it's cold or hot or wet?

For the past few months, my workouts have been

• Swimming at the YMCA. I love swimming, and it's low impact and it's hard to overdo it. It's takes a big chunk of time though: I get heartburn unless I wait 2-3 hours after I eat, and of course it takes twice as long as running because I have to drive there, change, and shower before and after.
• Biking up East rock park. ￼This is usually a fun workout, but not when its 85 degrees outside.
• Running. Fun when it's cool. Unpleasant when it's hot. I make sure to drink water 20 minutes before working out instead of during the run in order to minimize GERD symptoms.
• Kayaking. Good upper body exercise, and it's definitely cooler on the lake than on land. But same complaints as swimming: lots of overhead.
Mythbusters was one of my favorite series growing up, and it was definitely one of my early inspirations to study experimental physics. But over the course of the show, Adam Savage and Jamie Hyneman did plenty of experiments that were basically unnecessary had they done a two line physics calculation. Yes, it was fun to see the guys make a football field-sized sheet of paper, and use a hydraulic press to fold it, but...well...you could just do the math instead. Standard printer paper is $t=0.1\text{mm}$ thick, and $d=25\text{cm}$ long. It gets twice as thick and half as long each time you fold it, so after $N$ folds it is $2^Nt$ thick and $d/2^N$ long. Roughly speaking, you can fold paper in half until it is as thick as it is long, i.e., $2^Nt = d/2^N$, which implies $N = \frac{1}{2}\log_2 d/t\approx 5.6$. So maybe if you really force it: 6 times. Because this result depends only logarithmically on the length and thickness, it is fairly insensitive to their values. For example, if the sheet of paper is as large as a football field, $d=100\text{m}$, 400 times bigger than standard printer paper, then $N=9.9$. So experiments are great, but sometimes a spherical cow is all you need.