The physics behind helmets

Our new constitution is now established, and has an appearance that promises permanency; but in this world nothing can be said to be certain but death and taxes

Benjamin Franklin

Everything you do in life either increases or decreases your probability of dying. Do you drink consistently? Your probability of liver damage goes up but maybe you benefit from a strong social circle. Do you ride a bike? Your probability of heart disease goes down but chances of being run over by a car go up. Cram 5kg of Kale up your ass? Who the fuck knows.

The one thing that most cyclists do to tip probability in their favor is putting on a helmet. Riding gives your body’s systems a huge amount of health benefits but we’re kind of throwing ourselves into the world on two wheels. Any number of things can tip probability the other way: sticks, deer, cell phones attached to idiots in 2 ton metal cages. You probably know that the helmet is supposed to protect your head but do you know how it works to prevent damage?

If you don’t, I have goods news: an engineer is here to explain it to you.

Momentum is a term used for generic corporate bullshit and to explain what’s going on in football but it actually has a specific definition in physics. Momentum is a quantity that defines the motion of an object by its mass multiplied by its velocity and it has units of kilogram meters per second. When you begin to fall, your head has a certain amount of momentum and it gains velocity and therefore, momentum as you fall. Then, your head hits the ground and stops very rapidly.

It’s not the fall that kills you, it’s the sudden stop.

Douglas Adams

However, momentum is conserved in a closed system (which your head usually is) and it can’t just go away, it can only be transferred into another form. For that, there’s another lesser-known term in physics called impulse. Impulse is the result of a force applied over some period of time like when an object with momentum hits a hard surface. It is expressed as force (Newtons or kilogram meters per second squared) times time (in seconds). So, impulse has the same units as momentum.


Cat picture to break up boring physics

The amount of momentum, and therefore impulse of the impact, is a fixed value. The sudden stop means that your head has no momentum left and all of it is transferred to impulse. So, your head is guaranteed to get a certain amount of impulse but that is split into time and force. The force has a light side and a dark side and it binds the whole universe together. If we can increase the amount of time the impulse is imparted on your head and make it more light side (small number) force then there is less force and less injury.

And that, my friends, is where helmets come in. Helmets are made of foam which has a young’s modulus (measure of how much force is required to deform the material a certain amount) much lower than asphalt. So, a helmet deforms and spreads the force of impact over more time.  Same impulse, more time means less force *insert jar jar binks joke* and less injury.

So, wear your damn helmet.


The stages of being a concussed cyclist

Wear a damn helmet. Seriously, just do it.

Having a concussion sucks but it’s so much better than brain damage. You might looks a little bit less cool than when you have your hair flapping in the breeze but seriously: brain damage is not worth it. So while I’m off the bike, I’d like to present the stages I’ve gone through and you probably will too.


This is the stage that you should skip if you think you have a concussion. After my crash and getting home, I felt fine for a couple hours and I continued studying for my final exams. I was supposed to graduate exactly a week from the day of my concussion and had a lot of work to get through. As I was studying, my head started feeling a little foggy but I clocked it up to extended focus time and dehydration.

I went home for mother’s day the next morning and felt fine but when I returned to studying, it quickly came back. I confirmed it with my university’s health center the next morning and got that sweet, sweet doctor’s note. When you have a concussion, there’s not much the doctor can do for you aside from tell you to go lay in bed and stare at the ceiling for a few days.


Unfortunately, this concussion came at the worst possible time for me: right before my last ever finals week. I needed to be able to rest but had an incredibly important final mid-week and a capstone project that needed to be finished. I pushed my head really far that week and made it through the other side a bit worse for wear since I was supposed to be resting during that time.

It was really frustrating not to have the capabilities of concentration that I usually do. Trying to think through the issues with my capstone project and the problems on my exams were more difficult than they should have been. I had to have a couple tests moved back in order to finish what I needed to get done. I had to sleep more than usual. It was all uncharted territory and it was really frustrating. But I got through it and made it across the stage last Saturday.


At this point, you realize how good you actually have it. My head isn’t nearly as bad as it could have been. I’m able to go home to a bed to sleep in every night and food to eat. I have been able to ride and race my bike in places across this country and a couple others. Overall, my life is good aside from the fact that my head hurts. It just needs rest and I am grateful that I will be able to continue living my normal life eventually.


In this phase, you’re still grateful for what you have and the fact that your head is still on your shoulders but want to be riding again. We wouldn’t be bike racers or riders even if we didn’t love it and want to do it all the time. But you can’t really do anything when you have a concussion. The recommended guidelines for someone who has a concussion are: don’t do anything too mentally taxing, don’t look at screens and don’t exert yourself physically. And don’t drink alcohol. The Doctor basically tells you to just lay in bed and stare at the ceiling without actually saying that. They just eliminate all the other possibilities.

I tried to do that, I really did. But you just get antsy because you’re used to moving around all the time and doing things. So, you start doing things and get headaches and more symptoms. It’s impossible to sit and stare at a wall forever because biologically, we want to do things. So, take it easy at first before trying to get back into your routine and gradually build into it.

Vicarious living

Most cyclists probably already do the thing where you check out pictures from races you couldn’t go to and follow results (don’t deny it). Thankfully, my new team, District Velocity Racing p/b Bicycle Pro Shop, has a slack stream and a relatively active listserv that allow me to follow what’s going on. So, I’ve been able to keep up a little bit with the racing that’s been going on since then. In addition, strava stalking is a crucial part of being a real cyclist. If you don’t spend at least an hour a day on strava, you’re not living. It feels so weird to be sitting on the sidelines of races like Greenbelt that are literally two feet away from where I’m living this summer but it’s what needs to happen for recovery.


This is the stage that I’m currently in. I know how lucky I am to live the life that I do. I was able to graduate and am lucky that my head doesn’t need surgery or extended care. But goddamn do I want to ride my bike again. I want it with every fiber of my body and yet, I know how devastating it would be to come back and crash again. Second impact syndrome, which is what happens when you get a concussion when the prior one hasn’t already healed, has an incredibly high fatality rate and for those who don’t die, permanent brain damage is common.

So, I’m impatiently waiting it out until I can ride again. It’ll be soon but it won’t come soon enough and I am trying to use my time to develop my other skills like writing (which I didn’t do nearly enough of in the past year). Studying Spanish for my departure in September is still a little out of reach but that will come around soon. Staying optimistic is also really important since incidences of depression are very high for people who have concussions.

Return to riding

Eventually, we all get back to this point. I’ve been to this point way too many times thanks to injury and illness but I always get there. It always seems like it takes forever because we miss it so much. Cycling is a habit; it’s like a drug. But in the end, it’s important to be sure to give your body the time that it needs in order to heal. Nothing is worth permanent damage. You have your whole life to ride, just give yourself the few days or weeks it takes. And enjoy it with every cell of your body when you get back because we never know how much time we have to do so.

The Hangover Spin

I’m not known amongst my friends for being a big drinker – more as someone with a low alcohol tolerance. But after four weeks of hard racing and training leading up to App State, our last collegiate race before nationals, I needed some morale training. A couple months ago, my friend Terri convinced me to buy a ticket to a seniors reception under the guise of an open bar. Apparently, too many people signed up and ‘open bar’ switched to ‘2 free drinks do the first 150 people and the rest of you pay $6 for cocktails.’ The organizers clearly hadn’t learned the lesson of not getting between college students and their alcohol.

This seemingly classy event complete with hors d’oeuvres turned out to be more of an awkward middle school dance style affair. There was a dance floor and a DJ who I will henceforth refer to as DJ Lame. I will refer to him as this for the following reasons:

1.DJ Lame was 30 minutes late

2.DJ Lame was unable to get the speakers working for another 25 minutes

3.DJ Lame had a MacBook and no other equipment

4. DJ Lame was actually 4 guys, 3 of whom were snapchatting while one snapchatted and picked through a poorly orchestrated playlist with awkward pauses

We tolerated DJ Lame for a while since we were fresh but when the music is bad, it’s hard to keep that high level of energy. So, one group of friends bailed to play drunk poker. I elected to split with a different group of friends and go to the bars. I was not going to have my one night in a blue moon out ruined by DJ Lame. During race season, a social life takes the backseat to everything else because my schedule is like this:

Monday-Thursday: be sore and tired while trying to ride, go to class, work with clients (I do private swim instruction now), and do homework

Friday-Sunday: be sore and tired while at a race, maybe get an hour of work done

The bars were infinitely better than #calvcott (the reception’s designated hash tag which I definitely didn’t use to be sarcastic to people :roll:). Drinks were less overpriced and the DJ played an excellent selection of music including those middle school classics that induce a little bit of bad flashbacks. I ended my night at 1:30 and after a small diversion to maybe or maybe not borrow this balloon, I came home to a Trader Joe’s Pad Thai (available at your local Trader Joe’s for 1.99).

I was awakened by my 7:30 alarm the next morning as a nice reminder of the class I have at 9 on Fridays. The snooze button was far too close to my bed and the alarm was no match. I woke up next at 9:35 with 15 minutes left in class and a nice headache. Breakfast was made (aka I opened some poptarts) and I donned my kit to depart on the slowest ride of my life: 10 MPH (proof here). 

In the middle of my ride, I stopped at my favorite coffee shop to buy the elixir that would prepare me for the rest of my day. The young woman taking my order commented “great day for a bike ride” while applying the 10% bike discount on my $2.89 coffee and asked “are you out training?”

“No,” I replied, “just spinning off a hangover,”which elicited a piteous chuckle.

I arrived home 15 minutes later with my hangover gone and my mind ready to take on the next challenge of the day: designing a filament spooler for my engineering capstone class. There are so many remedies out there for hangovers but I like the cyclists’ version the best: black coffee and the hangover spin.

When you let college get in the way of riding

So I’ve known myself to procrastinate a bit; I think I’m pretty good at it at this point and this week was no performance slouch. My Spanish teacher assigned us a movie to watch and a worksheet to go along with it. Going along with the theme, I hadn’t watched it as of 8am this morning. But I wanted to go for a ride since the weather was beautiful and I thought I wouldn’t have time later in the day. So, my solution: watch a movie on the trainer and shut the blinds to block out the sun and ignore the nice weather outside.
I ate my standard breakfast these days of peanut butter on toast. And by standard I mean whatever I happen to have a lot of for snacks this week. Then I pulled the trainer out of the car since I hadn’t taken it out after Foothills this past weekend. As John Oliver explained why pennies suck to me, I finished setting up my bike and got prepped to ignore the outside world for an hour and a half.

The last movie we watched in spanish class was on youtube so I searched for today’s movie, “Juan de los Muertos.” The first listing was 3 hours and had no english subtitles, like what we usually do. “Interesting,” I thought as I prepared to half pay attention while trying to ride and translate rapid spanish in my head. Over the next hour and a half, I got enough of the gist to understand that zombies took over Cuba and many people flee on rafts to escape to the United States. In addition, there is a hilarious segment in which the main character, Juan, offers his service, Juan de los muertos, as a contract zombie killer in a style similar to Ghostbusters. He even answers the phone the same way and the only thing missing is an assistant with glasses.

The title is obviously a nod to “Dawn of the Dead” and “Shawn of the Dead.” However, this one is a metaphor for how th communists took over Cuba, as we discussed in class later that day.  When I got to class a little early, I asked my next door sitter, “Did you think it was weird that the movie was three hours?” “Three hours?” she replied, “I think it was only supposed to be an hour and a half.”

“Where did you watch it?”

“Vimeo, like he put in the syllabus”

Spokes Out.

Training isn’t hard

Maybe this is a revelation I’m coming to because I’m so far removed from the interval sets I’d usually be doing at this point. But after continuing knee issues for the past three months, I’m starting to believe it. Training isn’t the hard part of the sport that we do because the actual riding is the reason we got into it. We all started riding and fell in love with the sport and the way it made us feel. The endorphin highs and exhausted post-ride meals with friends or teammates brought us closer together. Then we started racing and the need for speed and enjoyment of competition pushed us to continue to improve. And while motivation can ebb and flow, we were always happy to get on the bike and get out there and ride because it seems like the thing we were born to do.

So, my hypothesis today: that’s not the hard part. No, the hard part is when you have to stop, look around and evaluate yourself. Sometimes you may find a problem, either mental or physical and you have to decide whether to take a rest or keep going. I’ve made that decision four times over the past year and each time, I’ve decided to take a rest before continuing on. And each time it’s been more difficult as the clock ticks on both my racing goals and the time available to spend riding with friends in College Park. But each time, I have not regretted it. I have been angry, frustrated and disappointed but I’ve never regretted it.

If you’ve been following this site for a while, you’ll know that I’ve had ongoing issues in my left leg related to muscle imbalance. Well, this time it was something even more stupid. See the chunk missing from my right pedal there? I rode like that for two months and apparently, that was enough to give me patellar tendonitis in my right knee as well. The decision to take a rest at this point is one of the hardest that I’ve made, especially since in November I was on track to have probably my best season yet.

The internal curvature of the pedal is not supposed to be jagged like that.

One of the common refrains that is heard when talking about any sport is “no pain, no gain” and while a certain amount of toughness is required to compete, it’s not the be all, end all. This is something that athletes will even repeat in interviews and it might give people an unhealthy perception of how to deal with pain. Obviously, muscle soreness and the burning sensation of a hard effort are necessary but we need to pay attention to pain in unexpected areas. If there is pain outside of what seems normal, it can be indication of dysfunction such as a muscle imbalance like I had or a poor movement pattern. Taking the time to either go to a professional or do some research yourself can yield important information in reducing any impact or even avoiding injury altogether.

Another aspect to consider stopping for is the mental side of the sport. This is an incredibly hard sport and sometimes things can get overbearing depending on your degree of seriousness and external stress. Even if you’re outside the elite ring (like myself), mental issues can crop up. Depression is something that impacts between a tenth and a fifth of adults in our society and it can cripple you if it’s not taken care of. Cycling is something that enables people to mask underlying issues even when those things become critical. And that’s something that can be very hard to admit due to the social stigma regarding mental health issues.

I don’t want to self-diagnose myself with depression because it’s a very serious condition but it definitely felt like after I stopped riding due to the ankle issue over the summer, some issues bubbled over. There was a strong unhappiness that would not go away until I actually paid it some mind. These issues can stem from environment, cultural influences and more but the underlying theme is that it does need to take time to heal, like any physical injury. The good news is that you don’t really have to take time off like with a physical injury, just make sure you’re listening to yourself and never be afraid to ask for help. Someone will be there for you.

So, to conclude: if you think you might need to take a rest, listen to your body or mind and should take it. You never know what you may be able to avoid.

Spokes out.

Update: In the middle of writing this blog, I started riding again and did a short set of steady state intervals. They sucked but I was so happy about being able to ride again that I barely felt it.