Why Do You Exercise?
I have a younger brother who avoids working out at all costs. I even tried to bribe him once, but even that didn’t work. His reason is simple: he says it makes him tired and he doesn’t enjoy it, so why bother? To him, working out feels too much like… well, work.
Meanwhile, I have a great time working out. I feel way better after working out. Working out feels fun to me.
Is he a wimp? Does he just need to suck it up for a few days or weeks until he likes it, or does he respond to exercise differently?
Ultramarathoning in the Sahara: fun or crazy?
How about extreme exercisers? I mean people like ultramarathon runners. Races that can go on for days, rather than hours. How about those people? Are they just crazy or do they get something different out of exercising than everybody else?
The researchers in this week’s review wanted to know whether a single session of aerobic exercise would change the mood of the participants — with a catch: Did everybody have the same mood changes or did regular exercisers have a more positive response than “non-exercisers”?
Hoffman MD, Hoffman DR. Exercisers achieve greater acute exercise-induced mood enhancement than nonexercisers. Arch Phys Med Rehabil. 2008 Feb;89(2):358-63.
Methods
The experiment was pretty straightforward. Three groups, each with 8 men and 8 women, for a total of 48 participants in the study.
The groups were:
- Non-exercisers: less than 5 workouts/month for the last 6 months
- Moderate exercisers: 30-60 minutes of aerobic exercise, 3-6 times/week
- Ultramarathon runners: must have completed 2 ultramarathons of a least 50 km in the last 2 years and at least 45 minutes of aerobic exercise, 4 days/week for the last 12 months
Profile of Mood States
Everybody was asked to fill out a questionnaire known as the Profile of Mood States before and after running on a treadmill.
The PoMS questionnaire examines six dimensions (areas) of mood: tension, depression, anger, vigor, fatigue and confusion.
Exercise and the Borg…
…Scale that is. not the meanies in Star Trek.
Everybody ran on the treadmill for 30 minutes. That broke down to 5 minutes warm-up and cool down, plus 20 minutes of “somewhat hard” running.
Since everybody had such a different fitness background, it would have made no sense to use the same speed or even percentage of maximum aerobic capacity, because aerobically trained people can run longer at a higher percent of their max.
So what to do? The researchers decided to use a “rating of perceived exertion” or RPE.
This scale is a subjective method of how hard people feel they’re working. There are different versions of this rating system; researchers used the 15 point Borg 6 to 20 point scale (1). This scale is nearly in every gym next to the cardio equipment. Borg decided that 6 would be the lowest, because he tried to match 6 with 60 beats per minute (rest), 13 with 130 beats per minute, etc. The idea is that the scale would approximately reflect heart rate for a 30-50 year old (2).
The warm-up and cool down was set at an RPE of 9 (very light — basically a leisurely stroll) and the exercise was 13 RPE (somewhat hard — it takes some effort but you’re not pushing yourself).
When 1% is 0%: Lies your treadmill told you
For this study, the treadmill was set to a 2% incline. This is important for anybody who steps on a treadmill.
Have you ever wondered why you can run so much faster on a treadmill than outside? 0% incline in the gym isn’t the same as 0% incline outside. If you run on a treadmill at 0% grade (incline) you are doing less work than 0% incline outside, because the treadmill belt/motor pulls your foot/leg back and so you don’t have to. Voila, you run faster.
So where should you set the incline on your treadmill? To be the closest to 0% grade outside, set it to a 1% incline (3), but I personally think running at a minimum of 5% incline makes things more fun and challenging.
Results
Average age of the participants was about 42 years old, so a little older than the usual participant, who’s usually a university or college student of 20.
The BMI of the moderate exercisers and ultra-marathoners was lower (about 23) than the non-exercisers (30.5). So regular exercise lowers BMI! Good, but not exactly a cutting edge finding.
Exercise decreases tension, depression, anger and confusion
Based on how the participants answered the questionnaire before and after exercise, the researchers figured out that exercise improved most of the moods (as defined by the questionnaire) regardless of whether they exercised regularly before the test.
Everybody had moderately less tension, depression, anger and confusion after they ran. So these moods are unlikely to determine people’s exercise. Based on this everybody would want to exercise, because they felt better.
Exercise increases the vigor of exercisers, but not non-exercisers
The exercisers (moderate & ultra-marathon runners) had an increase in “vigor” score, but the non-exercisers had no change after exercising. So the exercisers felt more energetic after exercise, but the non-exercisers didn’t feel any different.
Another difference in mood between exercisers and non-exercisers was fatigue. No group felt more fatigued after exercise, but the exercisers felt less fatigued. Even after running for 20 minutes at a somewhat hard pace, they felt less tired. Non-exercisers felt the same as before — neither more nor less tired.
No mood differences between regular exercisers and ultra-marathon runners
Part of the reason the researchers included ultramarathon runners in this study was to figure out if more was better… more exercise, that is. The answer is yes and no. The ultramarathoners improved their vigor slightly, but there were no other differences compared to the moderate exercise group.
And I’m sure the regular exercisers had more money because they didn’t have to buy new running shoes as often as the ultramarathoners (did I mention ultramarathoners run up to 100 miles or more?).
Conclusion
Why do exercisers exercise and why do non-exercisers not exercise?
Why do people exercise… or not exercise? That’s the million dollar question. Do exercisers exercise because they feel more vigorous and less fatigued? Or is it because regular exercise causes them to respond better to exercise?
Nature versus nurture
If exercise came in a bottle.
It could be that after a while, consistent exercise would make the non-exercisers feel the same way as the exercisers feel. So one possibility is that all the exercisers are former non-exercisers who’ve actually converted to feeling more energetic and less tired after exercise. After all, everybody starts at the same place and consistency makes the difference.
The nurture possibility means that in the right environment, everybody can become an exerciser with exerciser feelings of more vigor and less fatigue after exercise.
The other possibility is you are either born an exerciser or a non-exerciser (3). Some studies have found links between how people respond to exercise and what versions of the genes they have.
For example if you have the “sports car” version of the gene, you’ll respond well to sprint and power training, which leads you to become a good sprinter. If you have the “economy car” version then sprinting is not your thing, but long distance running would be. Researchers have also found a link between “exercise intolerance” and certain genes.
The nature possibility suggests that you are what you are, and if you’re a non-exerciser, no amount of exercise will make you feel like an exerciser. You won’t feel post-exercise vigor or less fatigue regardless of what you do.
Bottom line
We don’t yet know the answer to the nature vs nurture question. We don’t know whether exercisers are made or born.
Nevertheless, exercise comes in a lot of different forms. I suggest that any non-exerciser try different activities until they find one that they enjoy. Running, swimming, weight training, team sports, martial arts, etc. are traditional physical activities, but things like dancing, mall walking, gardening, and hiking can be physically demanding. So find something you enjoy and start there. Over time, you may find something more challenging enjoyable.
References
- Borg G. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med. 1970;2(2):92-8.
- Borg GA. Psychophysical bases of perceived exertion. Med Sci Sports Exerc. 1982;14(5):377-81.
- Jones AM, Doust JH. A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. J Sports Sci. 1996 Aug;14(4):321-7.
- Bray MS, Hagberg JM, Pérusse L, Rankinen T, Roth SM, Wolfarth B, Bouchard C. The human gene map for performance and health-related fitness phenotypes: the 2006-2007 update. Med Sci Sports Exerc. 2009 Jan;41(1):35-73. Review.