Sunday, April 28, 2013

The Bloodflow Hypothesis Rabbit Hole

A few weeks ago I injured myself while lifting weights—while putting them down, to be exact. The incident, though a bothersome interruption to my workout, served both as a reminder to observe good safety practices at the gym and as an opportunity to expand my knowledge about science, a loose goal I set back in July.

I was doing shoulder presses with 25-lb. weights, and I wasn’t very careful in replacing them in the weight rack. Instead of placing them properly, I managed to crush my fingers between the weights and the metal ridge of the rack. Within seconds blood started to stream out of my left and right ring fingers, so I headed to the front desk for some first aid.

As I sat there waiting for the desk attendant to put his gloves on, I watched the blood begin to roll down my hands. The cuts didn’t hurt much at all, so my thoughts freely drifted. Looking at the unexpectedly large amount of blood (it wasn’t a great deal more than expected, but enough to be noticeable), I began to wonder if the fact that I was lifting weights right before cutting myself—using hand and finger strength to grip the dumbbells—was making me bleed more than I normally would. Though I simultaneously felt like an idiot for being so careless, this hypothesis made me feel a little proud. I’m not very scientifically curious, as a rule, so it was nice to catch myself theorizing without being prompted by someone else. I decided to check into the increased bloodflow idea later that day.

Later that day turned into a few weeks later. Either I wasn’t that curious, or other matters took priority—probably both. Nevertheless, I finally began searching the internet for information, soon finding some answers from sources that appear credible:

"Blood flow through tissues is matched with the metabolic needs of the tissues. During exercise, blood flow through tissues is changed dramatically. Its rate of flow through exercising skeletal muscles can be 15 to 20 times greater than through resting muscles."1

Image by Chris Aldridge.

As science writer Craig Freudenrich explains,

"As you exercise, the blood vessels in your muscles dilate and the blood flow is greater, just as more water flows through a fire hose than through a garden hose. . . . As [the chemical compound] ATP gets used up in working muscle, the muscle produces several metabolic byproducts. . . These byproducts leave the muscle cells and cause the capillaries. . . within the muscle to expand or dilate. The increased blood flow delivers more oxygenated blood to the working muscle."2

Next I decided to learn a bit more about specific muscles in the hand and fingers, but I quickly discovered that in fact there are no muscles in the fingers.3 When I first read this I wondered if it might be one of the many “crazy facts” lurking on the internet that are just crazy, not factual. Further investigation, however, confirmed that the muscles that help move the fingers are located on the hand and forearm.

This makes me doubt my original hypothesis, because I was bleeding from the fingers. It was the lower part of the finger, so it makes sense that increased bloodflow to my hand muscles resulted in abnormally high bleeding nearby. But for all I know, what seems like proximity to me is actually remoteness on the level of capillaries, and the increased bleeding was simply illusory. Or caused by something else entirely.

What other factors cause bloodflow to increase? Do any other body parts besides fingers operate in a remote control-like way? I use the phrase “rabbit hole” in this post’s title because one empirical observation can create a never-ending chain of questions. I like that. The humanities scholar Barbara Herrnstein Smith (who at first studied chemistry in college, actually) has written about literature, “The completed work is thus always, in a sense, a temporary truce among contending forces, achieved at the point of exhaustion...”4 With scientific inquiry, too, one eventually has to stop somewhere, at least for the moment.

This can be frustrating when the desire to know, to understand, persists beyond our energies. But the idea that there’s always another question to be asked is bracing. None of us will ever reach the final answer of any line of inquiry. There will always be another question. And because we’re human, we’ll always make mistakes—like smashing our fingers with dumbbells—that set off the whole process.

1. Rod Seeley, Trent Stephens, and Philip Tate, “Blood Flow Through Tissues During Exercise,” Anatomy and Physiology, 5th ed., McGraw-Hill, accessed April 27 2013,
2. Craig Freudenrich, “How Exercise Works,” Discovery Fit & Health, accessed April 27, 2013,
3. Apart from the tiny muscles that form goosebumps.
4. Barbara Herrnstein Smith, “Contingencies of Value,” The Norton Anthology of Theory and Criticism, 2nd ed, ed. Vincent B. Leitch (New York: Norton, 2010), 1810.