I just wanted to write a fun blog encouraging you to go for a run and not stress about finals for a bit. As it turns out maybe that was overambitious. My last handful of blogs have been fairly uncontroversial; the research I encountered generally pointed to one solid answer and –besides having to manage my tendency to get off on tangential stories about myself– all went smoothly with the writing. Writing this blog, however, has been simultaneously awkward and very interesting.
To explain, as I began my research on exercise I encountered two categories of scientific writing on the topic. The first category felt very familiar; it consisted of studies which suggested different health benefits associated with exercise. The second presented a new challenge for me. In this second category I found a group of papers which grouped studies from the first category together and tore into their validity. The second category caused me to question the reliability of the first.
And honestly, I am surprised this did not happen sooner.
Scientists face a big challenge studying people. People present immense complexity. Massive individual differences between humans make study design highly important. How scientific teams create controls, manage data, and draw conclusions from data can harm the validity of their outcomes.
I (re)discovered this while researching the effects of exercise on mood and memory. Studies that suggest exercise positively affect the body are widespread. Some claim decreased likelihood of mental-disorder, better conflict management, decreased anxiety, and even increases in some kinds of memory (1,2). And all of these things are probably true.
But we have to exercise some caution. Because, as I mentioned, the results of studies on this topic have been called into question. Failure to create adequate controls and clarify cause and effect relationships have created ambiguous results for many studies. Good study controls help sharpen predictive power of study conclusions. Bad study controls result in unclear outcomes. For instance, let’s say a study wants to demonstrate exercise prevents depression. The study must make sure not to include participants who are already depressed in order to have meaningful outcomes. Similarly, just having fit individuals self report whether they are depressed hurts predictive power by failing to reveal cause and effect. You can see how a chicken or the egg situation would develop quickly. Do people exercise because they are not depressed? Or are they not depressed because they exercise? Questions like these led Andreas Strohle (from Campus Charité Mitte in Berlin) to conclude that “the majority of published studies [relating exercise to anxiety and depression] have substantial methodological shortcomings”(4).
A British Medical Journal review of 72 studies related to exercise and depression found most of the studies to be of poor quality due to brief follow up and intake of nonclinical volunteers. The review lobbed a variety of critiques ranging from some studies failing to randomize properly to outright missing data and methodology. I highly recommend giving it a read or at least looking over the figures; it is only seven pages long and an easy read as far as studies go. (2)
As a result, many studies related to the topic have been heavily questioned. But please do not go throw your running shoes in the trash. It seems obvious that physical activity makes people healthier. I know I feel better when I make a point of getting to Rimac a few times a week. The issue here lies in scientists’ ability to confirm a well known truth, not in the obvious truth’s existence.
Now, scientists pointing out flawed methodology in other studies feels as close to drama as I have yet seen in science. And it raises some good questions, such as: how do we confirm the benefits of exercise?
Well, meta-analyses of current research allow an overview of a large number of studies. The goal here lies in finding a trend in outcomes of research. In the case of controlling depression, a statistical assessment of a handful of meta analyses found treatment level response to exercise. This indicates a high level of effectiveness in exercise decreasing depression symptoms. Similarly, meta analyses of studies correlating exercise and anxiety find moderate reduction with exercise. In both cases, these meta-analyses look at studies which work with a control group and with individuals already suffering from depression and anxiety. So, generally speaking they gather a large quantity of data which circumvents the above criticisms. These outcomes can be trusted (4).
These studies give the takeaway that exercising can help control anxiety and depression.
Additionally, well-designed studies – those with adequate controls and good tracking of beginning and end results – provide meaningful information. In regards to memory, one study found that four weeks of exercise increased object-recognition memory. The study looked at genes encoding specific neurotrophic factors which assist in development and control of neurons. The findings actually showed that the tracked neurotrophic factor heavily influenced object-recognition improvement (3). This indicates that, as some level, our genes may determine if exercise improves our memory. So, if you are looking for a way to get any edge you can in upcoming finals, this would be worth a shot.
Ultimately, we find we can trust results when looking at well designed studies. You still have plenty of good reasons to exercise. If you are anything like me approaching finals week, you will embrace anything that can decrease anxiety and simultaneously promote better memory with open arms. After all, I need all the help I can get.
Luckily, at least for those of us at UC San Diego, we already pay a gym membership tied right in with our tuition. Main Gym provides a few basketball courts and a small upstairs weightlifting and cardio area, as well as a basement combat room with free boxing gloves to check out by showing student ID. Rimac has more full access to weightlifting and cardio, as well as additional basketball courts. All of these are free options for getting a workout on campus. If you are looking for something a little more guided, UC San Diego Recreation classes are offered offer discounts for students. Visiting the website gives you the chance to sign up for classes ranging from Surfing to Wushu Weapons.
So start forming the habit of exercising however you can. Science says so. Good luck with finals, everybody!. Study hard and try not to stress too much. The learning itself is the reward, and good grades are just an added bonus. Also, if you sign up for the Wushu Weapons class, go ahead and email me about it at firstname.lastname@example.org. I have so many questions.
(1) Hillman, Charles H., et al. “Be Smart, Exercise Your Heart: Exercise Effects on Brain and Cognition.” Nature Reviews Neuroscience, vol. 9, no. 1, Jan. 2008, pp. 58—65., doi:10.1038/nrn2298.
(2) Hopkins, M.E., et al. “Differential Effects of Acute and Regular Physical Exercise on Cognition and Affect.” Neuroscience, vol. 215, 30 Apr. 2012, pp. 59—68., doi:10.1016/j.neuroscience.2012.04.056.
(3) Lawlor, D. A, and Stephen W. Hopker. “The Effectiveness of Exercise as an Intervention in the Management of Depression: Systematic Review and Meta-Regression Analysis of Randomised Controlled Trials.” BMJ, vol. 322, no. 7289, 2001, pp. 763—763., doi:10.1136/bmj.322.7289.763.
(4) StrÃ¶hle, Andreas. “Physical Activity, Exercise, Depression and Anxiety Disorders.” Journal of Neural Transmission, vol. 116, no. 6, 2008, pp. 777—784., doi:10.1007/s00702-008-0092-x.